EFFECTS OF LARVAL STOCKING DENSITY ON LABORATORY-SCALE AND COMMERICAL-SCALE PRODUCTION OF SUMMER FLOUNDER, PARALICHTHYS DENTATUS

EPA Science Inventory

Three experiments investigating larval stocking densities of summer flounder from hatch to metamorphosis, Paralichthys dentatus, were conducted at laboratory-scale (75-L aquaria) and at commercial scale (1,000-L tanks). Experiments 1 and 2 at commercial scale tested the densities...

Parasitism of Megacopta cribraria (Hemiptera: Plataspidae)by Paratelenomus saccharalis (Hymenoptera: Platygastridae) in organic soybean plots in Georgia, USA

USDA-ARS?s Scientific Manuscript database

The kudzu bug, Megacopta cribraria (F.) (Hemiptera: Plataspidae), is a newly-invasive exotic pest of soybean in the southeastern US. In 2013, the exotic egg parasitoid Paratelenomus saccharalis (Hymenoptera: Platygastridae) (Dodd) was discovered parasitizing eggs of this pest in kudzu and soybean in...

Diet and density dependent competition affect larval performance and oviposition site selection in the mosquito species Aedes albopictus (Diptera: Culicidae)

PubMed Central

2012-01-01

Background Oviposition-site choice is an essential component of the life history of all mosquito species. According to the oviposition-preference offspring-performance (P-P) hypothesis, if optimizing offspring performance and fitness ensures high overall reproductive fitness for a given species, the female should accurately assess details of the heterogeneous environment and lay her eggs preferentially in sites with conditions more suitable to offspring. Methods We empirically tested the P-P hypothesis using the mosquito species Aedes albopictus by artificially manipulating two habitat conditions: diet (measured as mg of food added to a container) and conspecific density (CD; number of pre-existing larvae of the same species). Immature development (larval mortality, development time to pupation and time to emergence) and fitness (measured as wing length) were monitored from first instar through adult emergence using a factorial experimental design over two ascending gradients of diet (2.0, 3.6, 7.2 and 20 mg food/300 ml water) and CD (0, 20, 40 and 80 larvae/300 ml water). Treatments that exerted the most contrasting values of larval performance were recreated in a second experiment consisting of single-female oviposition site selection assay. Results Development time decreased as food concentration increased, except from 7.2 mg to 20.0 mg (Two-Way CR ANOVA Post-Hoc test, P > 0.1). Development time decreased also as conspecific density increased from zero to 80 larvae (Two-Way CR ANOVA Post-Hoc test, P < 0.5). Combined, these results support the role of density-dependent competition for resources as a limiting factor for mosquito larval performance. Oviposition assays indicated that female mosquitoes select for larval habitats with conspecifics and that larval density was more important than diet in driving selection for oviposition sites. Conclusions This study supports predictions of the P-P hypothesis and provides a mechanistic understanding of the

Evolution of increased larval competitive ability in Drosophila melanogaster without increased larval feeding rate.

PubMed

Sarangi, Manaswini; Nagarajan, Archana; Dey, Snigdhadip; Bose, Joy; Joshi, Amitabh

2016-09-01

Multiple experimental evolution studies on Drosophila melanogaster in the 1980s and 1990s indicated that enhanced competitive ability evolved primarily through increased larval tolerance to nitrogenous wastes and increased larval feeding and foraging rate, at the cost of efficiency of food conversion to biomass, and this became the widely accepted view of how adaptation to larval crowding evolves in fruitflies.We recently showed that populations of D. ananassae and D. n. nasuta subjected to extreme larval crowding evolved greater competitive ability without evolving higher feeding rates, primarily through a combination of reduced larval duration, faster attainment of minimum critical size for pupation, greater efficiency of food conversion to biomass, increased pupation height and, perhaps, greater urea/ammonia tolerance. This was a very different suite of traits than that seen to evolve under similar selection in D. melanogaster and was closer to the expectations from the theory of K-selection. At that time, we suggested two possible reasons for the differences in the phenotypic correlates of greater competitive ability seen in the studies with D. melanogaster and the other two species. First, that D. ananassae and D. n. nasuta had a very different genetic architecture of traits affecting competitive ability compared to the long-term laboratory populations of D. melanogaster used in the earlier studies, either because the populations of the former two species were relatively recently wild-caught, or by virtue of being different species. Second, that the different evolutionary trajectories in D. ananassae and D. n. nasuta versus D. melanogaster were a reflection of differences in the manner in which larval crowding was imposed in the two sets of selection experiments. The D. melanogaster studies used a higher absolute density of eggs per unit volume of food, and a substantially larger total volume of food, than the studies on D. ananassae and D. n. nasuta. Here, we

The effects of food level and conspecific density on biting and cannibalism in larval long-toed salamanders, Ambystoma macrodactylum.

PubMed

Wildy, Erica L; Chivers, Douglas P; Kiesecker, Joseph M; Blaustein, Andrew R

2001-07-01

Previous studies have examined abiotic and biotic factors that facilitate agonistic behavior. For larval amphibians, food availability and conspecific density have been suggested as important factors influencing intraspecific aggression and cannibalism. In this study, we examined the separate and combined effects of food availability and density on the agonistic behavior and life history of larval long-toed salamanders, Ambystoma macrodactylum. We designed a 2×2 factorial experiment in which larvae were raised with either a high or low density of conspecifics and fed either a high or low level of food. For each treatment, we quantified the amount of group size variation, biting, and cannibalism occurring. Additionally, we examined survival to, time to and size at metamorphosis for all larvae. Results indicated that differences in both density and food level influenced all three life history traits measured. Moreover, differences in food level at which larvae were reared resulted in higher within-group size variation and heightened intraspecific biting while both density and food level contributed to increased cannibalism. We suggest that increased hunger levels and an uneven size structure promoted biting among larvae in the low food treatments. Moreover, these factors combined with a higher encounter rate with conspecifics in the high density treatments may have prompted larger individuals to seek an alternative food source in the form of smaller conspecifics.

Exploring variable patterns of density-dependent larval settlement among corals with distinct and shared functional traits

NASA Astrophysics Data System (ADS)

Doropoulos, Christopher; Gómez-Lemos, Luis A.; Babcock, Russell C.

2018-03-01

Coral settlement is a key process for the recovery and maintenance of coral reefs, yet interspecific variations in density-dependent settlement are unknown. Settlement of the submassive Goniastrea retiformis and corymbose Acropora digitifera and A. millepora was quantified at densities ranging from 1 to 50 larvae per 20 mL from 110 to 216 h following spawning. Settlement patterns were distinct for each species. Goniastrea settlement was rapid and increased linearly with time, whereas both Acropora spp. hardly settled until crustose coralline algae was provided. Both Goniastrea and A. digitifera showed positive density-dependent settlement, but the relationship was exponential for Goniastrea but linear for A. digitifera. Settlement was highest but density independent in A. millepora. Our results suggest that larval density can have significant effects on settler replenishment, and highlight variability in density-dependent settlement among corals with distinct functional traits as well as those with similar functional forms.

Evolution of increased adult longevity in Drosophila melanogaster populations selected for adaptation to larval crowding.

PubMed

Shenoi, V N; Ali, S Z; Prasad, N G

2016-02-01

In holometabolous animals such as Drosophila melanogaster, larval crowding can affect a wide range of larval and adult traits. Adults emerging from high larval density cultures have smaller body size and increased mean life span compared to flies emerging from low larval density cultures. Therefore, adaptation to larval crowding could potentially affect adult longevity as a correlated response. We addressed this issue by studying a set of large, outbred populations of D. melanogaster, experimentally evolved for adaptation to larval crowding for 83 generations. We assayed longevity of adult flies from both selected (MCUs) and control populations (MBs) after growing them at different larval densities. We found that MCUs have evolved increased mean longevity compared to MBs at all larval densities. The interaction between selection regime and larval density was not significant, indicating that the density dependence of mean longevity had not evolved in the MCU populations. The increase in longevity in MCUs can be partially attributed to their lower rates of ageing. It is also noteworthy that reaction norm of dry body weight, a trait probably under direct selection in our populations, has indeed evolved in MCU populations. To the best of our knowledge, this is the first report of the evolution of adult longevity as a correlated response of adaptation to larval crowding. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

Cross-resistance between the Mexican Rice Borer and the Sugarcane Borer (Lepidoptera: Crambidae): A Case Study Using Sugarcane Breeding Populations

USDA-ARS?s Scientific Manuscript database

The sugarcane borer (SCB) (Diatraea saccharalis) and Mexican rice borer (MRB) (Eoreuma loftini) are two economically important pests of sugarcane in the USA. Because of similarities in larval feeding behavior, selecting for resistance to one species could provide resistance to the other, a phenomeno...

A two-agent model applied to the biological control of the sugarcane borer (Diatraea saccharalis) by the egg parasitoid Trichogramma galloi and the larvae parasitoid Cotesia flavipes.

PubMed

Molnár, Sándor; López, Inmaculada; Gámez, Manuel; Garay, József

2016-03-01

The paper is aimed at a methodological development in biological pest control. The considered one pest two-agent system is modelled as a verticum-type system. Originally, linear verticum-type systems were introduced by one of the authors for modelling certain industrial systems. These systems are hierarchically composed of linear subsystems such that a part of the state variables of each subsystem affect the dynamics of the next subsystem. Recently, verticum-type system models have been applied to population ecology as well, which required the extension of the concept a verticum-type system to the nonlinear case. In the present paper the general concepts and technics of nonlinear verticum-type control systems are used to obtain biological control strategies in a two-agent system. For the illustration of this verticum-type control, these tools of mathematical systems theory are applied to a dynamic model of interactions between the egg and larvae populations of the sugarcane borer (Diatraea saccharalis) and its parasitoids: the egg parasitoid Trichogramma galloi and the larvae parasitoid Cotesia flavipes. In this application a key role is played by the concept of controllability, which means that it is possible to steer the system to an equilibrium in given time. In addition to a usual linearization, the basic idea is a decomposition of the control of the whole system into the control of the subsystems, making use of the verticum structure of the population system. The main aim of this study is to show several advantages of the verticum (or decomposition) approach over the classical control theoretical model (without decomposition). For example, in the case of verticum control the pest larval density decreases below the critical threshold value much quicker than without decomposition. Furthermore, it is also shown that the verticum approach may be better even in terms of cost effectiveness. The presented optimal control methodology also turned out to be an efficient

Optimizing larval assessment to support sea lamprey control in the Great Lakes

USGS Publications Warehouse

Hansen, Michael J.; Adams, Jean V.; Cuddy, Douglas W.; Richards, Jessica M.; Fodale, Michael F.; Larson, Geraldine L.; Ollila, Dale J.; Slade, Jeffrey W.; Steeves, Todd B.; Young, Robert J.; Zerrenner, Adam

2003-01-01

Elements of the larval sea lamprey (Petromyzon marinus) assessment program that most strongly influence the chemical treatment program were analyzed, including selection of streams for larval surveys, allocation of sampling effort among stream reaches, allocation of sampling effort among habitat types, estimation of daily growth rates, and estimation of metamorphosis rates, to determine how uncertainty in each element influenced the stream selection program. First, the stream selection model based on current larval assessment sampling protocol significantly underestimated transforming sea lam-prey abundance, transforming sea lampreys killed, and marginal costs per sea lamprey killed, compared to a protocol that included more years of data (especially for large streams). Second, larval density in streams varied significantly with Type-I habitat area, but not with total area or reach length. Third, the ratio of larval density between Type-I and Type-II habitat varied significantly among streams, and that the optimal allocation of sampling effort varied with the proportion of habitat types and variability of larval density within each habitat. Fourth, mean length varied significantly among streams and years. Last, size at metamorphosis varied more among years than within or among regions and that metamorphosis varied significantly among streams within regions. Study results indicate that: (1) the stream selection model should be used to identify streams with potentially high residual populations of larval sea lampreys; (2) larval sampling in Type-II habitat should be initiated in all streams by increasing sampling in Type-II habitat to 50% of the sampling effort in Type-I habitat; and (3) methods should be investigated to reduce uncertainty in estimates of sea lamprey production, with emphasis on those that reduce the uncertainty associated with larval length at the end of the growing season and those used to predict metamorphosis.

Predictions of adult Anopheles albimanus densities in villages based on distances to remotely sensed larval habitats

NASA Technical Reports Server (NTRS)

Rejmankova, E.; Roberts, D. R.; Pawley, A.; Manguin, S.; Polanco, J.

1995-01-01

Remote sensing is particularly helpful for assessing the location and extent of vegetation formations, such as herbaceous wetlands, that are difficult to examine on the ground. Marshes that are sparsely populated with emergent macrophytes and dense cyanobacterial mats have previously been identified as very productive Anopheles albimanus larval habitats. This type of habitat was detectable on a classified multispectral System Probatoire d'Observation de la Terre image of northern Belize as a mixture of two isoclasses. A similar spectral signature is characteristic for vegetation of river margins consisting of aquatic grasses and water hyacinth, which constitutes another productive larval habitat. Based on the distance between human settlements (sites) of various sizes and the nearest marsh/river exhibiting this particular class combination, we selected two groups of sites: those located closer than 500 m and those located more than 1,500 m from such habitats. Based on previous adult collections near larval habitats, we defined a landing rate of 0.5 mosquitoes/human/min from 6:30 PM to 8:00 PM as the threshold for high (> or = 0.5 mosquitoes/human/min) versus low (< 0.5 mosquitoes/human/min) densities of An. albimanus. Sites located less than 500 m from the habitat were predicted as having values higher than this threshold, while lower values were predicted for sites located greater than 1,500 m from the habitat. Predictions were verified by collections of mosquitoes landing on humans. The predictions were 100% accurate for sites in the > 1,500-m category and 89% accurate for sites in the < 500-m category.

Inorganic elements in the fat bodies of Diatraea saccharalis (Lepidoptera: Crambidae) larvae parasitized by Cotesia flavipes (Hymenoptera: Braconidae).

PubMed

Pinheiro, D O; Zucchi, T D; Zucchi, O L A D; Nascimento Filho, V F; Almeida, E; Cônsoli, F L

2010-08-01

Koinobiont parasitoids use several strategies to regulate the host's physiological processes during parasitism. Although many aspects of host-parasitoid interactions have been explored, studies that attempted to assess the effects of parasitism on the availability of inorganic elements in the host are virtually nonexistent. Therefore, we aimed to evaluate the effects of parasitism on the concentrations of inorganic elements in the fat bodies of larvae of Diatraea saccharalis (Lepidoptera: Crambidae) during the development of the parasitoid Cotesia flavipes (Hymenoptera: Braconidae), by using total reflection X-ray fluorescence (TXRF). TXRF analysis allowed comparisons of the changes in the availability of the elements P, S, K, Ca, Cr, Fe, Ni, Cu, and Zn in the fat body tissues of D. saccharalis larvae parasitized by C. flavipes. Overall, the concentration of inorganic elements was higher early in parasitoid development (1 and 3days after parasitism) compared to non-parasitized larvae, but much lower towards the end of parasitoid development (7 and 9days after parasitism). Ca, K, and S were reduced after the fifth day of parasitism, which affected the total abundance of inorganic elements observed in the fat bodies of the parasitized hosts. The regulatory mechanisms or pathological effects related to the observed variation of the host inorganic elements induced by the parasitoid remain unknown, but there might be a strategy to make these elements available to the parasitoid larvae at the end of their development, when higher metabolic activity of the host fat body is required to sustain parasitoid growth. The observed variation of the host's inorganic elements could also be related to the known effects of parasitism on the host's immune response. 2010 Elsevier Inc. All rights reserved.

Diel variation of larval fish abundance in the Amazon and Rio Negro.

PubMed

Araujo-Lima, C A; da Silva, V V; Petry, P; Oliveira, E C; Moura, S M

2001-08-01

Many streams and large rivers present higher ichthyoplankton densities at night. However, in some rivers this does not occur and larvae are equally abundant during the day. Larval drift diel variation is an important information for planning sampling programs for evaluating larval distribution and production. The aim of this study was to test whether the abundance of larval fish was different at either period. We tested it by comparing day and night densities of characiform, clupeiform and siluriform larvae during five years in the Amazon and one year in Rio Negro. We found that larvae of three species of characiform and larvae of siluriform were equally abundant during day and night in the Amazon. Conversely, the catch of Pellona spp. larvae was significantly higher during the day. In Rio Negro, however, larval abundance was higher during the night. These results imply that day samplings estimate adequately the abundance of these characiform and siluriform larvae in the Amazon, but not Pellona larvae. Evaluations of larved densities of Rio Negro will have to consider night sampling.

Sampling uncharted waters: Examining rearing habitat of larval Longfin Smelt (Spirinchus thaleichthys) in the upper San Francisco Estuary

USGS Publications Warehouse

Grimaldo, Lenny; Feyrer, Frederick; Burns, Jillian; Maniscalco, Donna

2017-01-01

The southern-most reproducing Longfin Smelt population occurs in the San Francisco Estuary, California, USA. Long-term monitoring of estuarine habitat for this species has generally only considered deep channels, with little known of the role shallow waters play in supporting their early life stage. To address the need for focused research on shallow-water habitat, a targeted study of Longfin Smelt larvae in littoral habitat was conducted to identify potential rearing habitats during 2013 and 2014. Our study objectives were to (1) determine if larval densities vary between littoral habitats (tidal slough vs. open-water shoal), (2) determine how larval densities in littoral habitats vary with physicochemical and biological attributes, (3) determine if larval densities vary between littoral habitats and long-term monitoring channel collections, and (4) determine what factors predict larval rearing distributions from the long-term monitoring channel collections. Larval densities did not vary between littoral habitats but they did vary between years. Water temperature, salinity, and chlorophyll a were found important in predicting larval densities in littoral habitats. Larval densities do not vary between littoral and channel surveys; however, the analysis based on channel data suggests that Longfin Smelt are hatching and rearing in a much broader region and under higher salinities (∼2–12 psu) than previously recognized. Results of this study indicate that conservation efforts should consider how freshwater flow, habitat, climate, and food webs interact as mechanisms that influence Longfin Smelt recruitment in estuarine environments.

Juvenile frogs compensate for small metamorph size with terrestrial growth: Overcoming the effects of larval density and insecticide exposure

USGS Publications Warehouse

Boone, M.D.

2005-01-01

I reared four species of anurans (Rana sphenocephala [Southern Leopard Frog], Rana blairi [Plains Leopard Frog], Rana clamitans [Green Frog], and Bufo woodhousii [Woodhouse's Toad]) for seven to 12 months in small, outdoor terrestrial enclosures (1 x 2 m) to examine the consequences of larval competition (via density) and contaminant exposure (via the insecticide carbaryl). I added six Rana clamitans, eight Rana sphenocephala, eight Rana blairi, and 10 Bufo woodhousii to terrestrial enclosures shortly after metamorphosis and recaptured them during the following spring. All anurans from low-density ponds were significantly larger than those from high-density ponds, but these size differences did not significantly affect survival to or size at spring emergence. However, R. sphenocephala, R. blairi, and R. clamitans that survived to spring had been larger at metamorphosis on average than those that did not survive; in contrast, B. woodhousii that survived the winter were smaller at metamorphosis on average than those that did not survive. Carbaryl exposure affected mass at metamorphosis of R. clamitans and B. woodhousii that were added to enclosures, but this difference disappeared or did not increase by spring emergence. Overall, exposure to carbaryl during the larval period did not have any apparent effects on survival or growth during the terrestrial phase. In my study, anurans were able to offset small size at metamorphosis with terrestrial growth, although there was a trend of reduced overwinter survival for ranid species that metamorphosed at a smaller size. Copyright 2005 Society for the Study of Amphibians and Reptiles.

Morphological and molecular characterization of Brazilian populations of Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) and the evolutionary relationship among species of Diatraea Guilding

PubMed Central

Francischini, Fabricio J. B.; de Campos, Jaqueline Bueno; Alves-Pereira, Alessandro; Gomes Viana, João Paulo; Grinter, Christopher C.; Clough, Steven J.

2017-01-01

The sugarcane borer or corn stalk borer, Diatraea Guilding is polyphagous insect pest of many important crops such as corn, sorghum and sugarcane. Losses arising from the attack of Diatraea species have been a serious problem, which may cause loss in sugarcane production around 0.25% in sugar, 0.20% in alcohol and 0.77% of body weight for every 1% infestation and up to 21% in corn production fields. In Brazil, the most commonly reported species are Diatraea saccharalis (Fabricius, 1794) and Diatraea impersonatella (Walker, 1863) (= D. flavipennella). However, multiple other species of Diatraea have been identified in Brazil according to the literature. Currently, little information exists on the presence of the other species causing injury to sugarcane and corn. The objectives of this study were to improve the accuracy of species assignment, evaluate the population genetic structure, and address many of the outstanding questions of systematics and evolution of Brazilian populations of D. saccharalis. To address these main questions, classical taxonomic methods were used, focused on morphological characterization of the reproductive organs, especially the male genitalia. In addition, genetic studies were performed using simple sequence repeats (SSR) and a fragment of cytochrome C oxidase subunit I (COI) gene. The data and findings from this research will contribute to the understanding of evolutionary aspects of insect pests in order to develop more effective and sustainable population management practices. PMID:29145390

Larval gizzard shad characteristics in Lake Oahe, South Dakota: A species at the northern edge of its range

USGS Publications Warehouse

Fincel, Mark J.; Chipps, Steven R.; Graeb, Brian D. S.; Edwards, Kris R.

2013-01-01

Gizzard shad, Dorosoma cepedianum, have generally been restricted to the lower Missouri River impoundments in South Dakota. In recent years, gizzard shad numbers have increased in Lake Oahe, marking the northern-most natural population. These increases could potentially affect recreational fishes. Specifically, questions arise about larval gizzard shad growth dynamics and if age-0 gizzard shad in Lake Oahe will exhibit fast or slow growth, both of which can have profound effects on piscivore populations in this reservoir. In this study, we evaluated larval gizzard shad hatch timing, growth, and density in Lake Oahe. We collected larval gizzard shad from six sites from May to July 2008 and used sagittal otoliths to estimate the growth and back-calculate the hatch date. We found that larval gizzard shad hatched earlier in the upper part of the reservoir compared to the lower portion and that hatch date appeared to correspond to warming water temperatures. The peak larval gizzard shad density ranged from 0.6 to 33.6 (#/100 m3) and varied significantly among reservoir sites. Larval gizzard shad growth ranged from 0.24 to 0.57 (mm/d) and differed spatially within the reservoir. We found no relationship between the larval gizzard shad growth or density and small- or large-bodied zooplankton density (p > 0.05). As this population exhibits slow growth and low densities, gizzard shad should remain a suitable forage option for recreational fishes in Lake Oahe.

Does White Clover (Trifolium repens) Abundance in Temperate Pastures Determine Sitona obsoletus (Coleoptera: Curculionidae) Larval Populations?

PubMed

McNeill, Mark R; van Koten, Chikako; Cave, Vanessa M; Chapman, David; Hodgson, Hamish

2016-01-01

To determine if host plant abundance determined the size of clover root weevil (CRW) Sitona obsoletus larval populations, a study was conducted over 4 years in plots sown in ryegrass ( Lolium perenne ) (cv. Nui) sown at either 6 or 30 kg/ha and white clover ( Trifolium repens ) sown at a uniform rate of 8 kg/ha. This provided a range of % white clover content to investigate CRW population establishment and impacts on white clover survival. Larval sampling was carried out in spring (October) when larval densities are near their spring peak at Lincoln (Canterbury, New Zealand) with % clover measured in autumn (April) and spring (September) of each year. Overall, mean larval densities measured in spring 2012-2015 were 310, 38, 59, and 31 larvae m -2 , respectively. There was a significant decline in larval populations between 2012 and 2013, but spring populations were relatively uniform thereafter. The mean % white clover measured in autumns of 2012 to 2015 was 17, 10, 3, and 11%, respectively. In comparison, mean spring % white clover from 2012 to 2015, averaged c. 5% each year. Analysis relating spring (October) larval populations to % white clover measured in each plot in autumn (April) found the 2012 larval population to be statistically significantly larger in the ryegrass 6 kg/ha plots than 30 kg/ha plots. Thereafter, sowing rate had no significant effect on larval populations. From 2013 to 2015, spring larval populations had a negative relationship with the previous autumn % white clover with the relationship highly significant for the 2014 data. When CRW larval populations in spring 2013 to 2015 were predicted from the 2013 to 2015 autumn % white clover, respectively, based on their positive relationship in 2012, the predicted densities were substantially larger than those observed. Conversely, when 2015 spring larval data and % clover was regressed against 2012-2014 larval populations, observed densities tended to be higher than predicted, but the numbers

Rapid Effects of Marine Reserves via Larval Dispersal

PubMed Central

Cudney-Bueno, Richard; Lavín, Miguel F.; Marinone, Silvio G.; Raimondi, Peter T.; Shaw, William W.

2009-01-01

Marine reserves have been advocated worldwide as conservation and fishery management tools. It is argued that they can protect ecosystems and also benefit fisheries via density-dependent spillover of adults and enhanced larval dispersal into fishing areas. However, while evidence has shown that marine reserves can meet conservation targets, their effects on fisheries are less understood. In particular, the basic question of if and over what temporal and spatial scales reserves can benefit fished populations via larval dispersal remains unanswered. We tested predictions of a larval transport model for a marine reserve network in the Gulf of California, Mexico, via field oceanography and repeated density counts of recently settled juvenile commercial mollusks before and after reserve establishment. We show that local retention of larvae within a reserve network can take place with enhanced, but spatially-explicit, recruitment to local fisheries. Enhancement occurred rapidly (2 yrs), with up to a three-fold increase in density of juveniles found in fished areas at the downstream edge of the reserve network, but other fishing areas within the network were unaffected. These findings were consistent with our model predictions. Our findings underscore the potential benefits of protecting larval sources and show that enhancement in recruitment can be manifested rapidly. However, benefits can be markedly variable within a local seascape. Hence, effects of marine reserve networks, positive or negative, may be overlooked when only focusing on overall responses and not considering finer spatially-explicit responses within a reserve network and its adjacent fishing grounds. Our results therefore call for future research on marine reserves that addresses this variability in order to help frame appropriate scenarios for the spatial management scales of interest. PMID:19129910

Larval habitats of the Anopheles farauti and Anopheles lungae complexes in the Solomon Islands.

PubMed

Russell, Tanya L; Burkot, Thomas R; Bugoro, Hugo; Apairamo, Allan; Beebe, Nigel W; Chow, Weng K; Cooper, Robert D; Collins, Frank H; Lobo, Neil F

2016-03-15

There is an urgent need for vector control tools to supplement long-lasting insecticidal nets (LLINs) and indoor residual spraying; particularly in the Solomon Islands where the primary vector, Anopheles farauti, is highly anthropophagic and feeds mainly outdoors and early in the evening. Currently, the only supplementary tool recommended by the World Health Organization is larval source management (LSM). The feasibility and potential effectiveness of LSM requires information on the distribution of anophelines, the productivity of larval habitats and the potential impacts of larval control on adult fitness. The distribution of anophelines in Central and Western Provinces in the Solomon Islands was mapped from cross-sectional larval habitat surveys. The composition and micro-distribution of larval instars within a large permanent river-mouth lagoon was examined with a longitudinal survey. Density-dependent regulation of An. farauti larvae was investigated by longitudinally following the development and survival of different densities of first instars in floating cages in a river-mouth lagoon. Five anopheline species were molecularly identified from a range of fresh and brackish water habitats: An. farauti s.s., An. hinesorum, An. lungae, An. nataliae and An. solomonis. The most common habitats used by the primary malaria vector, An. farauti, were coastal lagoons and swamps. In the detailed study of lagoon micro-productivity, An. farauti was non-uniformly distributed with highest densities found at collections sites most proximal and distal to the mouth of the lagoon. The survival of An. farauti larvae was more than twofold lower when larvae were held at the highest experimental density (1 larva per 3.8 cm(2)) when compared with the lowest density (1 larva per 38 cm(2)). The only documented major malaria vector collected in larval surveys in both Central and Western Provinces was An. farauti. Lagoons and swamps, the most common, largest and (potentially) most

Drosophila adult and larval pheromones modulate larval food choice

PubMed Central

Farine, Jean-Pierre; Cortot, Jérôme; Ferveur, Jean-François

2014-01-01

Insects use chemosensory cues to feed and mate. In Drosophila, the effect of pheromones has been extensively investigated in adults, but rarely in larvae. The colonization of natural food sources by Drosophila buzzatii and Drosophila simulans species may depend on species-specific chemical cues left in the food by larvae and adults. We identified such chemicals in both species and measured their influence on larval food preference and puparation behaviour. We also tested compounds that varied between these species: (i) two larval volatile compounds: hydroxy-3-butanone-2 and phenol (predominant in D. simulans and D. buzzatii, respectively), and (ii) adult cuticular hydrocarbons (CHs). Drosophila buzzatii larvae were rapidly attracted to non-CH adult conspecific cues, whereas D. simulans larvae were strongly repulsed by CHs of the two species and also by phenol. Larval cues from both species generally reduced larval attraction and pupariation on food, which was generally—but not always—low, and rarely reflected larval response. As these larval and adult pheromones specifically influence larval food search and the choice of a pupariation site, they may greatly affect the dispersion and survival of Drosophila species in nature. PMID:24741012

Location Isn’t Everything: Timing of Spawning Aggregations Optimizes Larval Replenishment

PubMed Central

Donahue, Megan J.; Karnauskas, Mandy; Toews, Carl; Paris, Claire B.

2015-01-01

Many species of reef fishes form large spawning aggregations that are highly predictable in space and time. Prior research has suggested that aggregating fish derive fitness benefits not just from mating at high density but, also, from oceanographic features of the spatial locations where aggregations occur. Using a probabilistic biophysical model of larval dispersal coupled to a fine resolution hydrodynamic model of the Florida Straits, we develop a stochastic landscape of larval fitness. Tracking virtual larvae from release to settlement and incorporating changes in larval behavior through ontogeny, we found that larval success was sensitive to the timing of spawning. Indeed, propagules released during the observed spawning period had higher larval success rates than those released outside the observed spawning period. In contrast, larval success rates were relatively insensitive to the spatial position of the release site. In addition, minimum (rather than mean) larval survival was maximized during the observed spawning period, indicating a reproductive strategy that minimizes the probability of recruitment failure. Given this landscape of larval fitness, we take an inverse optimization approach to define a biological objective function that reflects a tradeoff between the mean and variance of larval success in a temporally variable environment. Using this objective function, we suggest that the length of the spawning period can provide insight into the tradeoff between reproductive risk and reward. PMID:26103162

Variation in food availability mediate the impact of density on cannibalism, growth, and survival in larval yellow spotted mountain newts (Neurergus microspilotus): Implications for captive breeding programs.

PubMed

Vaissi, Somaye; Sharifi, Mozafar

2016-11-01

In this study, we examined cannibalistic behavior, growth, metamorphosis, and survival in larval and post-metamorph endangered yellow spotted mountain newts Neurergus microspilotus hatched and reared in a captive breeding facility. We designed a 2 × 2 factorial experiment, crossing two levels of food with two levels of density including high food/high density, high food/low density, low food/high density, and low food/low density. The level of cannibalistic behavior (including the loss of fore and hind limbs, missing toes, tail, gills, body damage, and whole body consumption) changed as the larvae grew, from a low level during the first 4 weeks, peaking from weeks 7 to 12, and then dropped during weeks 14-52. Both food level and density had a significant effect on cannibalism. The highest frequency of cannibalism was recorded for larvae reared in the low food/high density and lowest in high food/low density treatments. Growth, percent of larval metamorphosed, and survival were all highest in the high food/low density and lowest in low food/high density treatment. Food level had a significant effect on growth, metamorphosis, and survival. However, the two levels of density did not influence growth and metamorphosis but showed a significant effect on survival. Similarly, combined effects of food level and density showed significant effects on growth, metamorphosis, and survival over time. Information obtained from current experiment could improve productivity of captive breeding facilities to ensure the release of adequate numbers of individuals for reintroduction programs. Zoo Biol. 35:513-521, 2016. © 2016 The Authors. Zoo Biology published by Wiley Periodicals, Inc. © 2016 The Authors. Zoo Biology published by Wiley Periodicals, Inc.

Parental care masks a density-dependent shift from cooperation to competition among burying beetle larvae.

PubMed

Schrader, Matthew; Jarrett, Benjamin J M; Kilner, Rebecca M

2015-04-01

Studies of siblings have focused mainly on their competitive interactions and to a lesser extent on their cooperation. However, competition and cooperation are at opposite ends on a continuum of possible interactions and the nature of these interactions may be flexible with ecological factors tipping the balance toward competition in some environments and cooperation in others. Here we show that the presence of parental care and the density of larvae on the breeding carcass change the outcome of sibling interactions in burying beetle broods. With full parental care there was a strong negative relationship between larval density and larval mass, consistent with sibling competition for resources. In the absence of care, initial increases in larval density had beneficial effects on larval mass but further increases in larval density reduced larval mass. This likely reflects a density-dependent shift between cooperation and competition. In a second experiment, we manipulated larval density and removed parental care. We found that the ability of larvae to penetrate the breeding carcass increased with larval density and that feeding within the carcass resulted in heavier larvae than feeding outside the carcass. However, larval density did not influence carcass decay. © 2015 The Author(s). Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

Zooplankton variability and larval striped bass foraging: Evaluating potential match/mismatch regulation

USGS Publications Warehouse

Chick, J.H.; Van Den Avyle, M.J.

1999-01-01

We quantified temporal and spatial variability of zooplankton in three potential nursery sites (river, transition zone, lake) for larval striped bass (Morone saxatilis) in Lake Marion, South Carolina, during April and May 1993-1995. In two of three years, microzooplankton (rotifers and copepod nauplii) density was significantly greater in the lake site than in the river or transition zone. Macrozooplankton (>200 ??m) composition varied among the three sites in all years with adult copepods and cladocerans dominant at the lake, and juvenile Corbicula fluminea dominant at the river and transition zone. Laboratory feeding experiments, simulating both among-site (site treatments) and within-site (density treatments) variability, were conducted in 1995 to quantify the effects of the observed zooplankton variability on foraging success of larval striped bass. A greater proportion of larvae fed in the lake than in the river or transition-zone treatments across all density treatments: mean (x), 10x and 100x. Larvae also ingested significantly more dry mass of prey in the lake treatment in both the mean and 10x density treatments. Field zooplankton and laboratory feeding data suggest that both spatial and temporal variability of zooplankton influence larval striped bass foraging. Prey density levels that supported successful foraging in our feeding experiments occurred in the lake during late April and May in 1994 and 1995 but were never observed in the river or transition zone. Because the rivers flowing into Lake Marion are regulated, it may be possible to devise flow management schemes that facilitate larval transport to the lake and thereby increase the proportion of larvae matched to suitable prey resources.

Observations on the reproductive and larval biology of Blennius pavo (Pisces: Teleostei)

NASA Astrophysics Data System (ADS)

Westernhagen, H.

1983-09-01

Social behaviour and spawning of adult Blennius pavo kept in the laboratory are described. Eggs are deposited in batches on the walls of artificial spawning places (PVC pipes). One male guards and tends the eggs of different females in one spawning place. Larval hatching occurs in groups according to oviposition. Minimum incubation temperature is around 14 15°C. Larval survival in 1-1 rearing jars is not related to larval total length but to density of larval stock. An experimental population of laboratory reared juvenile and adolescent B. pavo displays a male to female ratio of 1:1.4. Factors possibly influencing the sex ratio of this littoral fish are discussed in view of the situation in its natural environment.

A Marriage Of Larval Modeling And Empirical Data: Linking Adult, Larval And Juvenile Scallops In An Estuary

NASA Astrophysics Data System (ADS)

Bayer, S.; Wahle, R.; Brooks, D. A.; Brady, D. C.

2016-02-01

The giant sea scallop, Placopecten magellanicus, is a commercially valuable sedentary broadcast spawner that occupies offshore banks and coastal bays and estuaries in the Northwest Atlantic. Although area closures have helped repopulate depleted scallop populations, little is known about whether populations at densities that yield larvae supply local or distant populations. Surveying scallop populations in the Damariscotta River estuary in Maine during the 2013 and 2014 spawning seasons, and settling out spat bags to collect settling larvae along the gradient of the estuary, we were able to compare adult densities to newly settled juvenile (`spat') abundance. Using the location where we found a high density of adults, we incorporated previously published behavior, pelagic larval duration, wind and current data into a particle dispersal model within the estuary to determine likely sinks for larvae from the 2013 and 2014 spawning seasons. Preliminary model simulations demonstrate where in the estuary swimming is effective in affecting water column position for larvae, and that most larvae are retained much closer to the mouth of the estuary than previously expected. Combining larval dispersal modeling with empirical data on adult densities and spat settlement on the scale of an embayment or estuary may be helpful in determining sources, sinks and areas that are both sources and sinks for shellfish species that are endangered or economically critical. This may aid in determining small area closures or Marine Protected Areas along coastal regions in the Gulf of Maine and beyond.

DENSITY-DEPENDENT EVOLUTION OF LIFE-HISTORY TRAITS IN DROSOPHILA MELANOGASTER.

PubMed

Bierbaum, Todd J; Mueller, Laurence D; Ayala, Francisco J

1989-03-01

Populations of Drosophila melanogaster were maintained for 36 generations in r- and K-selected environments in order to test the life-history predictions of theories on density-dependent selection. In the r-selection environment, populations were reduced to low densities by density-independent adult mortality, whereas populations in the K-selection environment were maintained at their carrying capacity. Some of the experimental results support the predictions or r- and K-selection theory; relative to the r-selected populations, the K-selected populations evolved an increased larval-to-adult viability, larger body size, and longer development time at high larval densities. Mueller and Ayala (1981) found that K-selected populations also have a higher rate of population growth at high densities. Other predictions of the thoery are contradicted by the lack of differences between the r and K populations in adult longevity and fecundity and a slower rate of development for r-selected individuals at low densities. The differences between selected populations in larval survivorship, larval-to-adult development time, and adult body size are strongly dependent on larval density, and there is a significant interaction between populations and larval density for each trait. This manifests an inadequacy of the theory on r- and K-selection, which does not take into account such interactions between genotypes and environments. We describe mechanisms that may explain the evolution of preadult life-history traits in our experiment and discuss the need for changes in theories of density-dependent selection. © 1989 The Society for the Study of Evolution.

Hydrodynamic starvation in first-feeding larval fishes

PubMed Central

China, Victor; Holzman, Roi

2014-01-01

Larval fishes suffer prodigious mortality rates, eliminating 99% of the brood within a few days after first feeding. Hjort (1914) famously attributed this “critical period” of low survival to the larvae’s inability to obtain sufficient food [Hjort (1914) Rapp P-v Réun Cons Int Explor Mer 20:1–228]. However, the cause of this poor feeding success remains to be identified. Here, we show that hydrodynamic constraints on the ubiquitous suction mechanism in first-feeding larvae limit their ability to capture prey, thereby reducing their feeding rates. Dynamic-scaling experiments revealed that larval size is the primary determinant of feeding rate, independent of other ontogenetic effects. We conclude that first-feeding larvae experience “hydrodynamic starvation,” in which low Reynolds numbers mechanistically limit their feeding performance even under high prey densities. Our results provide a hydrodynamic perspective on feeding of larval fishes that focuses on the physical properties of the larvae and prey, rather than on prey concentration and the rate of encounters. PMID:24843180

Within-Host Competition between Two Entomopathogenic Fungi and a Granulovirus in Diatraea saccharalis (Lepidoptera: Crambidae).

PubMed

Pauli, Giuliano; Moura Mascarin, Gabriel; Eilenberg, Jørgen; Delalibera Júnior, Italo

2018-06-13

We provide insights into how the interactions of two entomopathogenic fungi and a virus play a role in virulence, disease development, and pathogen reproduction for an economically important insect crop pest, the sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae). In our model system, we highlight the antagonistic effects of the co-inoculation of Beauveria bassiana and granulovirus (DisaGV) on virulence, compared to their single counterparts. By contrast, combinations of Metarhizium anisopliae and B. bassiana , or M. anisopliae and DisaGV, have resulted in additive effects against the insect. Intriguingly, most cadavers that were derived from dual or triple infections, produced signs/symptoms of only one species after the death of the infected host. In the combination of fungi and DisaGV, there was a trend where a higher proportion of viral infection bearing conspicuous symptoms occurred, except when the larvae were inoculated with M. anisopliae and DisaGV at the two highest inoculum rates. Co-infections with B. bassiana and M. anisopliae did not affect pathogen reproduction, since the sporulation from co-inoculated larvae did not differ from their single counterparts.

Larval competition of Chrysomya megacephala and Chrysomya rufifacies (Diptera: Calliphoridae): behavior and ecological studies of two blow fly species of forensic significance.

PubMed

Shiao, Shiuh-Feng; Yeh, Ta-Chuan

2008-07-01

Chrysomya megacephala and Chrysomya rufifacies are two predominant necrophagous species in Taiwan. Larvae of the latter can prey on other maggots, including that of their own species as facultative food. This facultative characteristic of C. rufifacies may enhance its competitive advantage over other maggots and could also change the situation of other coexisting colonies. In this study, these two species were colonized in the laboratory, and the main objective was to try to understand the effect of competition on larval development. According to our results, intraspecific competition mostly occurred as competition for food; when the rearing density was increased, larvae pupated earlier, resulting in a lighter adult dry weight. The tendencies were similar in both species, but C. megacephala developed smaller viable adults and had higher survivorship at high densities. Although C. rufifacies could use the food resource of cannibalism, its survivorship was still low. Our results also showed there were significant interactions between intraspecific competition and the density factor. However, with interspecific competition, the first-instar larvae of C. rufifacies invaded maggot masses of C. megacephala to feed together. The third instars of C. rufifacies were able to expel C. megacephala larvae from food by using a fleshy protrusion on their body surface; C. megacephala was usually forced to pupate earlier by shortening its larval stages. The results indicated that a temporary competitive advantage could only be obtained by C. rufifacies under a proper larval density. In addition, the effects on different larval stages, the responses to different competition intensities, and the temperature-dependent effects on interspecific competition are also discussed. In general, under mixed-species rearing at different temperatures and densities, larval duration, adult dry weight, and survivorship of both species decreased. However, our results did not completely agree with

Larval crowding accelerates C. elegans development and reduces lifespan.

PubMed

Ludewig, Andreas H; Gimond, Clotilde; Judkins, Joshua C; Thornton, Staci; Pulido, Dania C; Micikas, Robert J; Döring, Frank; Antebi, Adam; Braendle, Christian; Schroeder, Frank C

2017-04-01

Environmental conditions experienced during animal development are thought to have sustained impact on maturation and adult lifespan. Here we show that in the model organism C. elegans developmental rate and adult lifespan depend on larval population density, and that this effect is mediated by excreted small molecules. By using the time point of first egg laying as a marker for full maturity, we found that wildtype hermaphrodites raised under high density conditions developed significantly faster than animals raised in isolation. Population density-dependent acceleration of development (Pdda) was dramatically enhanced in fatty acid β-oxidation mutants that are defective in the biosynthesis of ascarosides, small-molecule signals that induce developmental diapause. In contrast, Pdda is abolished by synthetic ascarosides and steroidal ligands of the nuclear hormone receptor DAF-12. We show that neither ascarosides nor any known steroid hormones are required for Pdda and that another chemical signal mediates this phenotype, in part via the nuclear hormone receptor NHR-8. Our results demonstrate that C. elegans development is regulated by a push-pull mechanism, based on two antagonistic chemical signals: chemosensation of ascarosides slows down development, whereas population-density dependent accumulation of a different chemical signal accelerates development. We further show that the effects of high larval population density persist through adulthood, as C. elegans larvae raised at high densities exhibit significantly reduced adult lifespan and respond differently to exogenous chemical signals compared to larvae raised at low densities, independent of density during adulthood. Our results demonstrate how inter-organismal signaling during development regulates reproductive maturation and longevity.

Larval crowding accelerates C. elegans development and reduces lifespan

PubMed Central

Ludewig, Andreas H.; Gimond, Clotilde; Judkins, Joshua C.; Thornton, Staci; Pulido, Dania C.; Micikas, Robert J.; Döring, Frank; Antebi, Adam; Braendle, Christian; Schroeder, Frank C.

2017-01-01

Environmental conditions experienced during animal development are thought to have sustained impact on maturation and adult lifespan. Here we show that in the model organism C. elegans developmental rate and adult lifespan depend on larval population density, and that this effect is mediated by excreted small molecules. By using the time point of first egg laying as a marker for full maturity, we found that wildtype hermaphrodites raised under high density conditions developed significantly faster than animals raised in isolation. Population density-dependent acceleration of development (Pdda) was dramatically enhanced in fatty acid β-oxidation mutants that are defective in the biosynthesis of ascarosides, small-molecule signals that induce developmental diapause. In contrast, Pdda is abolished by synthetic ascarosides and steroidal ligands of the nuclear hormone receptor DAF-12. We show that neither ascarosides nor any known steroid hormones are required for Pdda and that another chemical signal mediates this phenotype, in part via the nuclear hormone receptor NHR-8. Our results demonstrate that C. elegans development is regulated by a push-pull mechanism, based on two antagonistic chemical signals: chemosensation of ascarosides slows down development, whereas population-density dependent accumulation of a different chemical signal accelerates development. We further show that the effects of high larval population density persist through adulthood, as C. elegans larvae raised at high densities exhibit significantly reduced adult lifespan and respond differently to exogenous chemical signals compared to larvae raised at low densities, independent of density during adulthood. Our results demonstrate how inter-organismal signaling during development regulates reproductive maturation and longevity. PMID:28394895

Intra-instar larval cannibalism in Anopheles gambiae (s.s.) and Anopheles stephensi (Diptera: Culicidae).

PubMed

Porretta, Daniele; Mastrantonio, Valentina; Crasta, Graziano; Bellini, Romeo; Comandatore, Francesco; Rossi, Paolo; Favia, Guido; Bandi, Claudio; Urbanelli, Sandra

2016-11-02

Cannibalism has been observed in a wide range of animal taxa and its importance in persistence and stability of populations has been documented. In anopheline malaria vectors the inter-instar cannibalism between fourth- and first-instar larvae (L4-L1) has been shown in several species, while intra-instar cannibalism remains poorly investigated. In this study we tested the occurrence of intra-instar cannibalism within larvae of second-, third- and fourth-instar (L2, L3 and L4) of Anopheles gambiae (s.s.) and An. stephensi. Experiments were set up under laboratory conditions and the effects of larval density, duration of the contact period among larvae and the presence of an older larva (i.e. a potential cannibal of bigger size) on cannibalism rate were analysed. Cannibalism was assessed by computing the number of missing larvae after 24 and 48 h from the beginning of the experiments and further documented by records with a GoPro videocamera. Intra-instar cannibalism was observed in all larval instars of both species with higher frequency in An. gambiae (s.s.) than in An. stephensi. In both species the total number of cannibalistic events increased from 0-24 to 0-48 h. The density affected the cannibalism rate, but its effect was related to the larval instar and to the presence of older larvae. Interestingly, the lower cannibalism rate between L4 larvae was observed at the highest density and the cannibalism rate between L3 larvae decreased when one L4 was added. The present study provides experimental evidence of intra-instar cannibalism in the malaria vectors An. gambiae (s.s.) and An. stephensi and highlights the possible occurrence of complex interactions between all larval instars potentially present in the breeding sites. We hypothesize that the high density and the presence of a potential cannibal of bigger size could affect the readiness to attack conspecifics, resulting into low risk larval behavior and lower cannibalism rate. The understanding of

Soundscapes and Larval Settlement: Larval Bivalve Responses to Habitat-Associated Underwater Sounds.

PubMed

Eggleston, David B; Lillis, Ashlee; Bohnenstiehl, DelWayne R

2016-01-01

We quantified the effects of habitat-associated sounds on the settlement response of two species of bivalves with contrasting habitat preferences: (1) Crassostrea virginicia (oyster), which prefers to settle on other oysters, and (2) Mercenaria mercenaria (clam), which settles on unstructured habitats. Oyster larval settlement in the laboratory was significantly higher when exposed to oyster reef sound compared with either off-reef or no-sound treatments. Clam larval settlement did not vary according to sound treatments. Similar to laboratory results, field experiments showed that oyster larval settlement in "larval housings" suspended above oyster reefs was significantly higher compared with off-reef sites.

Bioenergetics models to estimate numbers of larval lampreys consumed by smallmouth bass in Elk Creek, Oregon

USGS Publications Warehouse

Schultz, Luke; Heck, Michael; Kowalski, Brandon M; Eagles-Smith, Collin A.; Coates, Kelly C.; Dunham, Jason B.

2017-01-01

Nonnative fishes have been increasingly implicated in the decline of native fishes in the Pacific Northwest. Smallmouth Bass Micropterus dolomieu were introduced into the Umpqua River in southwest Oregon in the early 1960s. The spread of Smallmouth Bass throughout the basin coincided with a decline in counts of upstream-migrating Pacific Lampreys Entosphenus tridentatus. This suggested the potential for ecological interactions between Smallmouth Bass and Pacific Lampreys, as well as freshwater-resident Western Brook Lampreys Lampetra richardsoni. To evaluate the potential effects of Smallmouth Bass on lampreys, we sampled diets of Smallmouth Bass and used bioenergetics models to estimate consumption of larval lampreys in a segment of Elk Creek, a tributary to the lower Umpqua River. We captured 303 unique Smallmouth Bass (mean: 197 mm and 136 g) via angling in July and September. We combined information on Smallmouth Bass diet and energy density with other variables (temperature, body size, growth, prey energy density) in a bioenergetics model to estimate consumption of larval lampreys. Larval lampreys were found in 6.2% of diet samples, and model estimates indicated that the Smallmouth Bass we captured consumed 925 larval lampreys in this 2-month study period. When extrapolated to a population estimate of Smallmouth Bass in this segment, we estimated 1,911 larval lampreys were consumed between July and September. Although the precision of these estimates was low, this magnitude of consumption suggests that Smallmouth Bass may negatively affect larval lamprey populations.

Soundscapes and Larval Settlement: Characterizing the Stimulus from a Larval Perspective.

PubMed

Lillis, Ashlee; Eggleston, David B; Bohnenstiehl, DelWayne R

2016-01-01

There is growing evidence that underwater sounds serve as a cue for the larvae of marine organisms to locate suitable settlement habitats; however, the relevant spatiotemporal scales of variability in habitat-related sounds and how this variation scales with larval settlement processes remain largely uncharacterized, particularly in estuarine habitats. Here, we provide an overview of the approaches we have developed to characterize an estuarine soundscape as it relates to larval processes, and a conceptual framework is provided for how habitat-related sounds may influence larval settlement, using oyster reef soundscapes as an example.

Validation of a New Larval Rearing Unit for Aedes albopictus (Diptera: Culicidae) Mass Rearing

PubMed Central

Gilles, Jérémie R. L.; Bellini, Romeo

2014-01-01

The mosquito larval rearing unit developed at the Insect Pest Control Laboratory (IPCL) of the FAO/IAEA Joint Division was evaluated for its potential use for Aedes albopictus (Skuse, 1895) mass rearing in support of the development of a sterile insect technique (SIT) package for this species. The use of the mass rearing trays and rack did not adversely affect larval development, pupation and survival rates and allowed the management of large larval rearing colonies with reduced space requirements in comparison with classical individual trays. The effects of larval density, water temperature and diet composition on pupal production and size differentiation for sex separation efficacy were analyzed for individual mass rearing trays as well as multiple trays stacked within the dedicated rack unit. Best results were obtained using eighteen thousand larvae per tray at a density of 3 larvae per ml of deionized water at a temperature of 28°C on a diet consisting of 50% tuna meal, 36% bovine liver powder, 14% brewer's yeast and, as an additive, 0.2 gr of Vitamin Mix per 100 ml of diet solution. Pupae were harvested on the sixth day from larval introduction at L1 stage and males were separated out by the use of a 1400 µm sieve with 99.0% accuracy with a recovery rate of ca. 25% of the total available males. With the use of this larval rearing unit, an average production of 100,000 male pupae per week can be achieved in just 2 square meter of laboratory space. Compared to previous laboratory rearing method, the same pupal production and sex separation efficacy could only be achieved by use of ca. 200 plastic trays which required the space of two 5 square meter climatic-controlled rooms. PMID:24647347

Anopheline larval habitats seasonality and species distribution: a prerequisite for effective targeted larval habitats control programmes.

PubMed

Kweka, Eliningaya J; Zhou, Guofa; Munga, Stephen; Lee, Ming-Chieh; Atieli, Harrysone E; Nyindo, Mramba; Githeko, Andrew K; Yan, Guiyun

2012-01-01

Larval control is of paramount importance in the reduction of malaria vector abundance and subsequent disease transmission reduction. Understanding larval habitat succession and its ecology in different land use managements and cropping systems can give an insight for effective larval source management practices. This study investigated larval habitat succession and ecological parameters which influence larval abundance in malaria epidemic prone areas of western Kenya. A total of 51 aquatic habitats positive for anopheline larvae were surveyed and visited once a week for a period of 85 weeks in succession. Habitats were selected and identified. Mosquito larval species, physico-chemical parameters, habitat size, grass cover, crop cycle and distance to nearest house were recorded. Polymerase chain reaction revealed that An. gambiae s.l was the most dominant vector species comprised of An.gambiae s.s (77.60%) and An.arabiensis (18.34%), the remaining 4.06% had no amplification by polymerase chain reaction. Physico-chemical parameters and habitat size significantly influenced abundance of An. gambiae s.s (P = 0.024) and An. arabiensis (P = 0.002) larvae. Further, larval species abundance was influenced by crop cycle (P≤0.001), grass cover (P≤0.001), while distance to nearest houses significantly influenced the abundance of mosquito species larvae (r = 0.920;P≤0.001). The number of predator species influenced mosquito larval abundance in different habitat types. Crop weeding significantly influenced with the abundance of An.gambiae s.l (P≤0.001) when preceded with fertilizer application. Significantly higher anopheline larval abundance was recorded in habitats in pasture compared to farmland (P = 0.002). When habitat stability and habitat types were considered, hoof print were the most productive followed by disused goldmines. These findings suggest that implementation of effective larval control programme should be targeted with larval habitats

Dynamics of population densities and vegetation associations of Anopheles albimanus larvae in a coastal area of southern Chiapas, Mexico.

PubMed

Rodríguez, A D; Rodríguez, M H; Meza, R A; Hernández, J E; Rejmankova, E; Savage, H M; Roberts, D R; Pope, K O; Legters, L

1993-03-01

Spatial and seasonal variations on Anopheles albimanus larval densities and their plant associations were investigated in larval habitats in southern Mexico between April 1989 and May 1990. Thirty-four plant groups were dominant in larval habitats. Dense larval populations were associated with 3 genera of plants, Cynodon, Echinocloa and Fimbristylis and no larvae were found in habitats with Salvinia and Rhizophora. Low significant positive or negative associations were documented with the other 12 plant genera. Larval habitats were classified according to the morphology of their dominant plants. Higher larval densities were observed in the groups characterized by relatively short emergent vegetation. The distribution of habitat-types within 5 identified vegetation units showed a significantly dependent relationship. For the entire study period, highest larval densities were detected in flooded pasture/grassland vegetation units. For all vegetation units, higher larval densities were found when the dominant plant type covered between 25-50% of the breeding site. The integration of data from habitat-types into vegetation units did not result in loss of information.

Experimental studies on the larval development of the shrimps Crangon crangon and C. allmanni

NASA Astrophysics Data System (ADS)

Criales, M. M.; Anger, K.

1986-09-01

Larvae of the shrimps Crangon crangon L. and C. allmanni Kinahan were reared in the laboratory from hatching through metamorphosis. Effects of rearing methods (larval density, application of streptomycin, food) and of salinity on larval development were tested only in C. crangon, influence of temperature was studied in both species. Best results were obtained when larvae were reared individually, with a mixture of Artemia sp. and the rotifer Brachionus plicatilis as food. Streptomycin had partly negative effects and was thus not adopted for standard rearing techniques. All factors tested in this study influenced not only the rates of larval survival and moulting, but also morphogenesis. In both species, in particular in C. crangon, a high degree of variability in larval morphology and in developmental pathways was observed. Unsuitable conditions, e.g. crowding in mass culture, application of antibiotics, unsuitable food (rotifers, phytoplankton), extreme temperatures and salinities, tend to increase the number of larval instars and of morphological forms. The frequency of moulting is controlled mainly by temperature. Regression equations describing the relations between the durations of larval instars and temperature are given for both Crangon species. The number of moults is a linear function of larval age and a power function of temperature. There is high variation in growth (measured as carapace length), moulting frequency, morphogenesis, and survival among hatches originating from different females. The interrelations between these different measures of larval development in shrimps and prawns are discussed.

Larval settlement and metamorphosis of the mussel Mytilus coruscus in response to monospecific bacterial biofilms.

PubMed

Yang, Jin-Long; Shen, Pei-Jing; Liang, Xiao; Li, Yi-Feng; Bao, Wei-Yang; Li, Jia-Le

2013-01-01

The effects of bacterial biofilms (BFs) on larval settlement and metamorphosis of the mussel, Mytilus coruscus, were investigated in the laboratory. Of nine different isolates, Shewanella sp.1 BF induced the highest percentage of larval settlement and metamorphosis, whereas seven other isolates had a moderate inducing activity and one isolate, Pseudoalteromonas sp. 4, had a no inducing activity. The inducing activity of individual bacterial isolates was not correlated either with their phylogenetic relationship or with the surfaces from which they were isolated. Among the eight bacterial species that demonstrated inducing activity, bacterial density was significantly correlated with the inducing activity for each strain, with the exception of Vibrio sp. 1. The Shewanella sp. 1 BF cue that was responsible for inducing larval settlement and metamorphosis was further investigated. Treatment of the BFs with formalin, antibiotics, ultraviolet irradiation, heat, and ethanol resulted in a significant decrease in their inducing activities and cell survival. BF-conditioned water (CW) did not induce larval metamorphosis, but it triggered larval settlement behavior. A synergistic effect of CW with formalin-fixed Shewanella sp. 1 BF significantly promoted larval metamorphosis. Thus, a cocktail of chemical cues derived from bacteria may be necessary to stimulate larval settlement and metamorphosis in this species.

Regulation of Aedes aegypti Population Dynamics in Field Systems: Quantifying Direct and Delayed Density Dependence

PubMed Central

Walsh, Rachael K.; Aguilar, Cristobal L.; Facchinelli, Luca; Valerio, Laura; Ramsey, Janine M.; Scott, Thomas W.; Lloyd, Alun L.; Gould, Fred

2013-01-01

Transgenic strains of Aedes aegypti have been engineered to help control transmission of dengue virus. Although resources have been invested in developing the strains, we lack data on the ecology of mosquitoes that could impact the success of this approach. Although studies of intra-specific competition have been conducted using Ae. aegypti larvae, none of these studies examine mixed age cohorts at densities that occur in the field, with natural nutrient levels. Experiments were conducted in Mexico to determine the impact of direct and delayed density dependence on Ae. aegypti populations. Natural water, food, and larval densities were used to estimate the impacts of density dependence on larval survival, development, and adult body size. Direct and delayed density-dependent factors had a significant impact on larval survival, larval development, and adult body size. These results indicate that control methods attempting to reduce mosquito populations may be counteracted by density-dependent population regulation. PMID:23669230

Composition and diversity of larval fish in the mangrove estuarine area of Marudu Bay, Sabah, Malaysia.

PubMed

Rezagholinejad, Sadaf; Arshad, Aziz; Amin, S M Nurul; Ara, Roushon

2016-07-01

The composition of fish larvae and their diversity in different habitats are very important for fisheries management. Larval fishes were investigated in a mangrove estuary of Marudu Bay, Sabah, Malaysia from October 2012 to September 2013 at five different sites. Monthly samples of fish larvae were collected at five sampling sites by a plankton net with a mouth opening of 40.5 cm in diameter. In total, 3879 larval fish were caught in the investigated area. The mean density of ichthyoplankton at this area was 118 larvae/100 m(3). The fish larval assemblage comprised of 20 families whereas 13 families occurred at St1, 16 at St2, 16 at St3, 12 at St4 and 16 at St5. The top major families were Sillaginidae, Engraulidae, Mugilidae and Sparidae with Sillaginidae consisted 44% of total larval composition. St3 with 143 larvae/100 m(3) had the highest density amongst the stations which was due to higher abundance of Sillaginidae. Shannon-Wiener diversity index represented significant variation during monsoon and inter-monsoon seasons, peaking in the months December-January and May-June. However, Shannon-Wiener index, evenness and family richness showed significant differences among stations and months (p < 0.05).

Foraging and predation risk for larval cisco (Coregonus artedi) in Lake Superior: a modelling synthesis of empirical survey data

USGS Publications Warehouse

Myers, Jared T.; Yule, Daniel L.; Jones, Michael L.; Quinlan, Henry R.; Berglund, Eric K.

2014-01-01

The relative importance of predation and food availability as contributors to larval cisco (Coregonus artedi) mortality in Lake Superior were investigated using a visual foraging model to evaluate potential predation pressure by rainbow smelt (Osmerus mordax) and a bioenergetic model to evaluate potential starvation risk. The models were informed by observations of rainbow smelt, larval cisco, and zooplankton abundance at three Lake Superior locations during the period of spring larval cisco emergence and surface-oriented foraging. Predation risk was highest at Black Bay, ON, where average rainbow smelt densities in the uppermost 10 m of the water column were >1000 ha−1. Turbid conditions at the Twin Ports, WI-MN, affected larval cisco predation risk because rainbow smelt remained suspended in the upper water column during daylight, placing them alongside larval cisco during both day and night hours. Predation risk was low at Cornucopia, WI, owing to low smelt densities (<400 ha−1) and deep light penetration, which kept rainbow smelt near the lakebed and far from larvae during daylight. In situ zooplankton density estimates were low compared to the values used to develop the larval coregonid bioenergetics model, leading to predictions of negative growth rates for 10 mm larvae at all three locations. The model predicted that 15 mm larvae were capable of attaining positive growth at Cornucopia and the Twin Ports where low water temperatures (2–6 °C) decreased their metabolic costs. Larval prey resources were highest at Black Bay but warmer water temperatures there offset the benefit of increased prey availability. A sensitivity analysis performed on the rainbow smelt visual foraging model showed that it was relatively insensitive, while the coregonid bioenergetics model showed that the absolute growth rate predictions were highly sensitive to input parameters (i.e., 20% parameter perturbation led to order of magnitude differences in model estimates). Our

Density-dependent coral recruitment displays divergent responses during distinct early life-history stages

PubMed Central

Evensen, Nicolas R.; Gómez-Lemos, Luis A.; Babcock, Russell C.

2017-01-01

Population growth involves demographic bottlenecks that regulate recruitment success during various early life-history stages. The success of each early life-history stage can vary in response to population density, interacting with intrinsic (e.g. behavioural) and environmental (e.g. competition, predation) factors. Here, we used the common reef-building coral Acropora millepora to investigate how density-dependence influences larval survival and settlement in laboratory experiments that isolated intrinsic effects, and post-settlement survival in a field experiment that examined interactions with environmental factors. Larval survival was exceptionally high (greater than 80%) and density-independent from 2.5 to 12 days following spawning. By contrast, there was a weak positive effect of larval density on settlement, driven by gregarious behaviour at the highest density. When larval supply was saturated, settlement was three times higher in crevices compared with exposed microhabitats, but a negative relationship between settler density and post-settlement survival in crevices and density-independent survival on exposed surfaces resulted in similar recruit densities just one month following settlement. Moreover, a negative relationship was found between turf algae and settler survival in crevices, whereas gregarious settlement improved settler survival on exposed surfaces. Overall, our findings reveal divergent responses by coral larvae and newly settled recruits to density-dependent regulation, mediated by intrinsic and environmental interactions. PMID:28573015

Fisheries Closed Areas Strengthen Scallop Larval Settlement and Connectivity Among Closed Areas and Across International Open Fishing Grounds: A Model Study.

PubMed

Davies, Kimberley T A; Gentleman, W C; DiBacco, C; Johnson, C L

2015-09-01

This study examined whether a measured increase in average body size of adult sea scallops inside three fishery closed areas on Georges Bank (GB), United States (US), was sufficient to increase larval supply to closed areas and open fishing areas in both US and Canadian areas of the Bank. The effects of adult scallop density-at-size and fecundity-at-size on egg production were compared among open and closed fishery areas, countries, and time periods before and after the closed areas were established. Estimated egg production was then used to define spawning conditions in a coupled biological-physical larval tracking model that simulated larval development, mortality, and dispersal. Results showed that order of magnitude increases in larval settlement after closure were facilitated by increases in size-dependant egg production inside and dispersal from Closed Areas I and II, but not Nantucket Lightship Closed Area. The distributions of both egg production and larval settlement became more uniform across the Bank, causing the relative contribution of Canadian larvae to US scallop aggregations to decrease after establishment of Closed Areas I and II. Decreases in small and medium-sized scallop density in Canada and decreases in large scallops over the US-Southern Flank after closure caused local declines in egg production but were not sufficient to negatively affect larval settlement at the regional scale. Our model suggests that the establishment of fishery closed areas on GB considerably strengthened larval supply and settlement within and among several adult scallop aggregations.

Fisheries Closed Areas Strengthen Scallop Larval Settlement and Connectivity Among Closed Areas and Across International Open Fishing Grounds: A Model Study

NASA Astrophysics Data System (ADS)

Davies, Kimberley T. A.; Gentleman, W. C.; DiBacco, C.; Johnson, C. L.

2015-09-01

This study examined whether a measured increase in average body size of adult sea scallops inside three fishery closed areas on Georges Bank (GB), United States (US), was sufficient to increase larval supply to closed areas and open fishing areas in both US and Canadian areas of the Bank. The effects of adult scallop density-at-size and fecundity-at-size on egg production were compared among open and closed fishery areas, countries, and time periods before and after the closed areas were established. Estimated egg production was then used to define spawning conditions in a coupled biological-physical larval tracking model that simulated larval development, mortality, and dispersal. Results showed that order of magnitude increases in larval settlement after closure were facilitated by increases in size-dependant egg production inside and dispersal from Closed Areas I and II, but not Nantucket Lightship Closed Area. The distributions of both egg production and larval settlement became more uniform across the Bank, causing the relative contribution of Canadian larvae to US scallop aggregations to decrease after establishment of Closed Areas I and II. Decreases in small and medium-sized scallop density in Canada and decreases in large scallops over the US-Southern Flank after closure caused local declines in egg production but were not sufficient to negatively affect larval settlement at the regional scale. Our model suggests that the establishment of fishery closed areas on GB considerably strengthened larval supply and settlement within and among several adult scallop aggregations.

Elucidating Mechanisms by which Invertebrate Larval Settlement is Affected by Biofilm Ciliates

NASA Astrophysics Data System (ADS)

Shimeta, J.; Watson, M. G.; Zalizniak, L.; Scardino, A. J.

2016-02-01

Despite extensive studies of benthic invertebrate larvae responding to settlement cues from bacteria and microalgae in biofilms, the roles of protozoa have been largely ignored. We recently showed that an assemblage of biofilm ciliates affected larval settlement and survival rates among two polychaetes, a mussel, and a bryozoan, being inhibitory to some and facilitative to others. Here we investigated settlement inhibition further for the serpulid worm, Galeolaria caespitosa, and the mussel, Mytilus galloprovincialis. Single species of ciliates were capable of inhibiting settlement by up to 68%. The effects were density dependent, with the strength of inhibition being directly related to ciliate abundance. The strength of inhibition also differed significantly among ciliate species, suggesting that both the abundance and makeup of ciliate assemblages could be an important variable determining settlement rates in the field. We studied the mechanisms of inhibition further with G. caespitosa and the ciliate, Euplotes minuta. Filtrate from ciliate cultures failed to inhibit settlement, indicating that dissolved chemicals were not the inhibiting factor. Physical presence of ciliates was inhibitory, as demonstrated by video analysis of larval search behavior. Following contact with a ciliate, larval swimming was disrupted, including retreat from the substratum and significant changes in swimming angles. Ciliates may also have influenced settlement indirectly by altering cues from biofilm bacteria. Although bacterial densities were unaffected by ciliate grazing during the assays, bacterial distributions were significantly more clumped in the presence of ciliates, which could perhaps affect the suitability of the biofilm for larvae. These organism-scale interactions at the biofilm boundary could produce significant constraints on larval recruitment patterns and suggest that further studies are needed on the roles of protozoans in boundary layer processes.

Spatial distribution of larval Ixodes scapularis (Acari:Ixodidae) on Peromyscus leucopus and Microtus pennsylvanicus at two island sites

USGS Publications Warehouse

Markowski, D.; Hyland, K.E.; Ginsberg, H.S.

1997-01-01

Larval blacklegged ticks, Ixodes scapularis, were collected from white-footed mice, Peromyscus leucopus, on Prudence Island (where Microtus pennsylavanicus were not captured) and from meadow voles, M. pennsylvanicus, on Patience Island (where P. leucopus was absent) in Narragansett Bay, Rhode Island from June to October 1992. Ixodes scapularis larvae were also collected by flagging in the vicinity of host captures. On both islands, the relative density of larvae changed from July to September in samples from hosts, but not in flagging samples. Consequently, different sampling techniques can give different assessments of tick populations. Larvae were highly aggregated on both of the host species throughout the sampling period. As the mean relative density of larvae increased in the environment (based on flagging samples), larvae on the hosts became more dense and more crowded. Increased densities of larvae in the environment were not correlated with increased patchiness in the distribution of larvae among host animals on either island. Changes in the spatial distribution of larval I. scapularis on each host species had similar trends as larval densities and distributions within the environment. These results suggest that M. pennsylvanicus can serve as an alternative host for immature I. scapularis in a P. leucopus-free environment and have similar distributional characteristics.

Foraging characteristics of larval bluegill sunfish and larval longear sunfish in the Kanawha River, West Virginia

USGS Publications Warehouse

Rider, S.J.; Margraf, F.J.

1998-01-01

We determined spatial and temporal foraging characteristics of larval bluegill sunfish (Lepomis macrochirus) and longear sunfish (Lepomis megalotis) in the upper Kanawha River, West Virginia during the summer of 1989. Stomach contents were examined among habitat types (i.e., main channel, main-channel border, and shoreline habitats) and depth (surface, middle, and bottom). Diet of larval bluegill sunfish was dominated by Chironomidae, temporally and spatially. Chironomidae dominated larval longear sunfish diet in main channel and main-channel border collections from all three depths. However, along the shoreline, larval longear sunfish diet was dominated by Cladocera.

Anopheles larval abundance and diversity in three rice agro-village complexes Mwea irrigation scheme, central Kenya.

PubMed

Mwangangi, Joseph M; Shililu, Josephat; Muturi, Ephantus J; Muriu, Simon; Jacob, Benjamin; Kabiru, Ephantus W; Mbogo, Charles M; Githure, John; Novak, Robert J

2010-08-09

The diversity and abundance of Anopheles larvae has significant influence on the resulting adult mosquito population and hence the dynamics of malaria transmission. Studies were conducted to examine larval habitat dynamics and ecological factors affecting survivorship of aquatic stages of malaria vectors in three agro-ecological settings in Mwea, Kenya. Three villages were selected based on rice husbandry and water management practices. Aquatic habitats in the 3 villages representing planned rice cultivation (Mbui Njeru), unplanned rice cultivation (Kiamachiri) and non-irrigated (Murinduko) agro-ecosystems were sampled every 2 weeks to generate stage-specific estimates of mosquito larval densities, relative abundance and diversity. Records of distance to the nearest homestead, vegetation coverage, surface debris, turbidity, habitat stability, habitat type, rice growth stage, number of rice tillers and percent Azolla cover were taken for each habitat. Captures of early, late instars and pupae accounted for 78.2%, 10.9% and 10.8% of the total Anopheles immatures sampled (n = 29,252), respectively. There were significant differences in larval abundance between 3 agro-ecosystems. The village with 'planned' rice cultivation had relatively lower Anopheles larval densities compared to the villages where 'unplanned' or non-irrigated. Similarly, species composition and richness was higher in the two villages with either 'unplanned' or limited rice cultivation, an indication of the importance of land use patterns on diversity of larval habitat types. Rice fields and associated canals were the most productive habitat types while water pools and puddles were important for short periods during the rainy season. Multiple logistic regression analysis showed that presence of other invertebrates, percentage Azolla cover, distance to nearest homestead, depth and water turbidity were the best predictors for Anopheles mosquito larval abundance. These results suggest that agricultural

Survival and metamorphosis of low-density populations of larval sea lampreys (Petromyzon marinus) in streams following lampricide treatment

USGS Publications Warehouse

Johnson, Nicholas S.; Swink, William D.; Brenden, Travis O.; Slade, Jeffrey W.; Steeves, Todd B.; Fodale, Michael F.; Jones, Michael L.

2014-01-01

Sea lamprey Petromyzon marinus control in the Great Lakes primarily involves application of lampricides to streams where larval production occurs to kill larvae prior to their metamorphosing and entering the lakes as parasites (juveniles). Because lampricides are not 100% effective, larvae that survive treatment maymetamorphose before streams are again treated. Larvae that survive treatment have not beenwidely studied, so their dynamics are notwell understood.Wetagged and released larvae in six Great Lake tributaries following lampricide treatment and estimated vital demographic rates using multistate tag-recovery models. Model-averaged larval survivals ranged from 56.8 to 57.6%. Model-averaged adult recovery rates, which were the product of juvenile survivals and adult capture probabilities, ranged from 6.8 to 9.3%. Using stochastic simulations, we estimated production of juvenile sea lampreys from a hypothetical population of treatment survivors under different growth conditions based on parameter estimates from this research. For fast-growing populations, juvenile production peaked 2 years after treatment. For slow-growing populations, juvenile production was approximately one-third that of fast-growing populations,with production not peaking until 4 years after treatment. Our results suggest that dynamics (i.e., survival, metamorphosis) of residual larval populations are very similar to those of untreated larval populations. Consequently, residual populations do not necessarily warrant special consideration for the purpose of sea lamprey control and can be ranked for treatment along with other populations. Consecutive lampricide treatments, which are under evaluation by the sea lamprey control program, would bemost effective for reducing juvenile production in large, fast-growing populations.

Phylogenetic analyses of mode of larval development.

PubMed

Hart, M

2000-12-01

Phylogenies based on morphological or molecular characters have been used to provide an evolutionary context for analysis of larval evolution. Studies of gastropods, bivalves, tunicates, sea stars, sea urchins, and polychaetes have revealed massive parallel evolution of similar larval forms. Some of these studies were designed to test, and have rejected, the species selection hypothesis for evolutionary trends in the frequency of derived larvae or life history traits. However, the lack of well supported models of larval character evolution leave some doubt about the quality of inferences of larval evolution from phylogenies of living taxa. Better models based on maximum likelihood methods and known prior probabilities of larval character state changes will improve our understanding of the history of larval evolution. Copyright 2000 Academic Press.

Effect of Larval Competition on Extrinsic Incubation Period and Vectorial Capacity of Aedes albopictus for Dengue Virus.

PubMed

Bara, Jeffrey; Rapti, Zoi; Cáceres, Carla E; Muturi, Ephantus J

2015-01-01

Despite the growing awareness that larval competition can influence adult mosquito life history traits including susceptibility to pathogens, the net effect of larval competition on human risk of exposure to mosquito-borne pathogens remains poorly understood. We examined how intraspecific larval competition affects dengue-2 virus (DENV-2) extrinsic incubation period and vectorial capacity of its natural vector Aedes albopictus. Adult Ae. albopictus from low and high-larval density conditions were orally challenged with DENV-2 and then assayed for virus infection and dissemination rates following a 6, 9, or 12-day incubation period using real-time quantitative reverse transcription PCR. We then modeled the effect of larval competition on vectorial capacity using parameter estimates obtained from peer-reviewed field and laboratory studies. Larval competition resulted in significantly longer development times, lower emergence rates, and smaller adults, but did not significantly affect the extrinsic incubation period of DENV-2 in Ae. albopictus. Our vectorial capacity models suggest that the effect of larval competition on adult mosquito longevity likely has a greater influence on vectorial capacity relative to any competition-induced changes in vector competence. Furthermore, we found that large increases in the viral dissemination rate may be necessary to compensate for small competition-induced reductions in daily survivorship. Our results indicate that mosquito populations that experience stress from larval competition are likely to have a reduced vectorial capacity, even when susceptibility to pathogens is enhanced.

Effect of Larval Competition on Extrinsic Incubation Period and Vectorial Capacity of Aedes albopictus for Dengue Virus

PubMed Central

Bara, Jeffrey; Rapti, Zoi; Cáceres, Carla E.; Muturi, Ephantus J.

2015-01-01

Despite the growing awareness that larval competition can influence adult mosquito life history traits including susceptibility to pathogens, the net effect of larval competition on human risk of exposure to mosquito-borne pathogens remains poorly understood. We examined how intraspecific larval competition affects dengue-2 virus (DENV-2) extrinsic incubation period and vectorial capacity of its natural vector Aedes albopictus. Adult Ae. albopictus from low and high-larval density conditions were orally challenged with DENV-2 and then assayed for virus infection and dissemination rates following a 6, 9, or 12-day incubation period using real-time quantitative reverse transcription PCR. We then modeled the effect of larval competition on vectorial capacity using parameter estimates obtained from peer-reviewed field and laboratory studies. Larval competition resulted in significantly longer development times, lower emergence rates, and smaller adults, but did not significantly affect the extrinsic incubation period of DENV-2 in Ae. albopictus. Our vectorial capacity models suggest that the effect of larval competition on adult mosquito longevity likely has a greater influence on vectorial capacity relative to any competition-induced changes in vector competence. Furthermore, we found that large increases in the viral dissemination rate may be necessary to compensate for small competition-induced reductions in daily survivorship. Our results indicate that mosquito populations that experience stress from larval competition are likely to have a reduced vectorial capacity, even when susceptibility to pathogens is enhanced. PMID:25951173

Exploration of the "larval pool": development and ground-truthing of a larval transport model off leeward Hawai'i.

PubMed

Wren, Johanna L K; Kobayashi, Donald R

2016-01-01

Most adult reef fish show site fidelity thus dispersal is limited to the mobile larval stage of the fish, and effective management of such species requires an understanding of the patterns of larval dispersal. In this study, we assess larval reef fish distributions in the waters west of the Big Island of Hawai'i using both in situ and model data. Catches from Cobb midwater trawls off west Hawai'i show that reef fish larvae are most numerous in offshore waters deeper than 3,000 m and consist largely of pre-settlement Pomacanthids, Acanthurids and Chaetodontids. Utilizing a Lagrangian larval dispersal model, we were able to replicate the observed shore fish distributions from the trawl data and we identified the 100 m depth strata as the most likely depth of occupancy. Additionally, our model showed that for larval shore fish with a pelagic larval duration longer than 40 days there was no significant change in settlement success in our model. By creating a general additive model (GAM) incorporating lunar phase and angle we were able to explain 67.5% of the variance between modeled and in situ Acanthurid abundances. We took steps towards creating a predictive larval distribution model that will greatly aid in understanding the spatiotemporal nature of the larval pool in west Hawai'i, and the dispersal of larvae throughout the Hawaiian archipelago.

Establishment of a medium-scale mosquito facility: optimization of the larval mass-rearing unit for Aedes albopictus (Diptera: Culicidae).

PubMed

Zhang, Dongjing; Zhang, Meichun; Wu, Yu; Gilles, Jeremie R L; Yamada, Hanano; Wu, Zhongdao; Xi, Zhiyong; Zheng, Xiaoying

2017-11-13

Standardized larval rearing units for mosquito production are essential for the establishment of a mass-rearing facility. Two larval rearing units, developed respectively by the Guangzhou Wolbaki Biotech Co. Ltd. (Wolbaki) and Insect Pest Control Laboratory, Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture (FAO/IAEA-IPCL), are tested to assess their potential uses to mass-rear the larval stages of Aedes albopictus in support of the establishment of a medium-scale mosquito facility for the application of mosquito genetic control strategies. The triple Wolbachia-infected Ae. albopictus strain (HC strain) was used in this study. The effects of larval densities of two larval rearing trays (corresponding to 2.4, 3.0 and 3.6 larvae/cm 2 ) and tray size/position (top, middle and bottom layers) on the pupae production and larval survival were assessed when trays were stacked within the larval rearing units. The male pupae production, female pupae contamination after sex separation, and male mating competitiveness were also studied by using both larval rearing units in their entirety. The optimal larval rearing density for Wolbaki-tray (Wol-tray) was 6,600 larvae (equal to 3.0 larvae/cm 2 ) and 18,000 larvae (3.6 larvae/cm 2 ) for the FAO/IAEA-IPCL tray (IAEA-tray). No significant difference in pupae production was observed when trays were stacked within top, middle or bottom layers for both units. At thirty-four hours after the first pupation, the average male pupae production was (0.89 × 10 5 ) for the Wol-unit and (3.16 × 10 5 ) for the IAEA-unit. No significant difference was observed in female pupae contamination between these two units. The HC males showed equal male mating competitiveness to wild type males for mating with wild type females in large cages, regardless of whether they were reared in the Wol-unit or IAEA-unit. The current study has indicated that both the Wol-unit and IAEA-unit are suitable for larvae mass-rearing for Ae

Spatial and temporal variation in distribution of larval lake whitefish in eastern Lake Ontario: signs of recovery?

USGS Publications Warehouse

McKenna, J.E.; Johnson, J. H.

2009-01-01

The lake whitefish (Coregonus clupeaformis) is one of the native Lake Ontario fishes that declined severely over the past century. Recent evidence of larval lake whitefish production in a historic spawning area (Chaumont Bay) might signal a recovery of this species in New York waters. We surveyed coastal and open water areas to evaluate densities and estimate total abundance of larval lake whitefish in Chaumont Bay. Other historic spawning areas and embayments with appropriate spawning and nursery habitat were also surveyed, but only a few larvae were found outside of Chaumont Bay. Lake whitefish larvae were found in every embayment sampled within Chaumont Bay, with larval densities of nearly 600/1000 m2 in some samples. Greatest abundances occurred in the northern sectors and near the mouth of the bay. Open water densities were generally less than half that of nearshore sites. The total bay-wide estimate for 2005 was approximately 644,000 lake whitefish larvae, but dropped to 230,000–400,000 in 2006 and 2007, respectively. Mean larval growth rates (0.36 mm/day) did not differ by year, but were consistently higher in early May than in late April. Lake whitefish production in Chaumont Bay is encouraging for this species, but the cause and persistence of the decline after 2005 can be determined only by continued monitoring. Other possible bottlenecks of survival may exist at juvenile and adult stages and could significantly affect recruitment dynamics. This species is sensitive to normal climatic fluctuations and increased variability associated with global climatic change could make winter nursery conditions unfavorable for this species.

Analyzing the spatio-temporal relationship between dengue vector larval density and land-use using factor analysis and spatial ring mapping

PubMed Central

2012-01-01

Background Dengue, a mosquito-borne febrile viral disease, is found in tropical and sub-tropical regions and is now extending its range to temperate regions. The spread of the dengue viruses mainly depends on vector population (Aedes aegypti and Aedes albopictus), which is influenced by changing climatic conditions and various land-use/land-cover types. Spatial display of the relationship between dengue vector density and land-cover types is required to describe a near-future viral outbreak scenario. This study is aimed at exploring how land-cover types are linked to the behavior of dengue-transmitting mosquitoes. Methods Surveys were conducted in 92 villages of Phitsanulok Province Thailand. The sampling was conducted on three separate occasions in the months of March, May and July. Dengue indices, i.e. container index (C.I.), house index (H.I.) and Breteau index (B.I.) were used to map habitats conducible to dengue vector growth. Spatial epidemiological analysis using Bivariate Pearson’s correlation was conducted to evaluate the level of interdependence between larval density and land-use types. Factor analysis using principal component analysis (PCA) with varimax rotation was performed to ascertain the variance among land-use types. Furthermore, spatial ring method was used as to visualize spatially referenced, multivariate and temporal data in single information graphic. Results Results of dengue indices showed that the settlements around gasoline stations/workshops, in the vicinity of marsh/swamp and rice paddy appeared to be favorable habitat for dengue vector propagation at highly significant and positive correlation (p = 0.001) in the month of May. Settlements around the institutional areas were highly significant and positively correlated (p = 0.01) with H.I. in the month of March. Moreover, dengue indices in the month of March showed a significant and positive correlation (p <= 0.05) with deciduous forest. The H.I. of people living around horticulture

Analyzing the spatio-temporal relationship between dengue vector larval density and land-use using factor analysis and spatial ring mapping.

PubMed

Sarfraz, Muhammad Shahzad; Tripathi, Nitin K; Tipdecho, Taravudh; Thongbu, Thawisak; Kerdthong, Pornsuk; Souris, Marc

2012-10-09

Dengue, a mosquito-borne febrile viral disease, is found in tropical and sub-tropical regions and is now extending its range to temperate regions. The spread of the dengue viruses mainly depends on vector population (Aedes aegypti and Aedes albopictus), which is influenced by changing climatic conditions and various land-use/land-cover types. Spatial display of the relationship between dengue vector density and land-cover types is required to describe a near-future viral outbreak scenario. This study is aimed at exploring how land-cover types are linked to the behavior of dengue-transmitting mosquitoes. Surveys were conducted in 92 villages of Phitsanulok Province Thailand. The sampling was conducted on three separate occasions in the months of March, May and July. Dengue indices, i.e. container index (C.I.), house index (H.I.) and Breteau index (B.I.) were used to map habitats conducible to dengue vector growth. Spatial epidemiological analysis using Bivariate Pearson's correlation was conducted to evaluate the level of interdependence between larval density and land-use types. Factor analysis using principal component analysis (PCA) with varimax rotation was performed to ascertain the variance among land-use types. Furthermore, spatial ring method was used as to visualize spatially referenced, multivariate and temporal data in single information graphic. Results of dengue indices showed that the settlements around gasoline stations/workshops, in the vicinity of marsh/swamp and rice paddy appeared to be favorable habitat for dengue vector propagation at highly significant and positive correlation (p = 0.001) in the month of May. Settlements around the institutional areas were highly significant and positively correlated (p = 0.01) with H.I. in the month of March. Moreover, dengue indices in the month of March showed a significant and positive correlation (p <= 0.05) with deciduous forest. The H.I. of people living around horticulture land were significantly and

Non-additive effects of intra- and interspecific competition between two larval salamanders.

PubMed

Anderson, Thomas L; Whiteman, Howard H

2015-05-01

Assessment of the relative strengths of intra- and interspecific competition has increased in recent years and is critical to understanding the importance of competition. Yet, whether intra- and interspecific competition can have non-additive effects has rarely been tested. The resulting fitness consequences of such non-additive interactions are important to provide the context necessary to advance our understanding of competition theory. We compared the strength of additive and non-additive intra- and interspecific competition by manipulating densities of a pair of larval salamanders (Ambystoma talpoideum and A. maculatum) in experimental mesocosms within a response surface design. Intraspecific density had the strongest effect on the strength of competition for both species, and few observed comparisons indicated interspecific competition was an important factor in predicting body size, growth or larval period length of either species. Non-additive effects of intra- and interspecific competition influenced some response variables, including size and mass at metamorphosis in A. maculatum, but at a reduced strength compared to intraspecific effects alone. Intraspecific competition was thus the dominant biotic interaction, but non-additive effects also impact the outcome of competition in these species, validating the importance of testing for and incorporating non-additive density effects into competition models. © 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.

Weak Larval Competition Between Two Invasive Mosquitoes Aedes koreicus and Aedes albopictus (Diptera: Culicidae).

PubMed

Baldacchino, Frédéric; Arnoldi, Daniele; Lapère, Charlotte; Rosà, Roberto; Montarsi, Fabrizio; Capelli, Gioia; Rizzoli, Annapaola

2017-09-01

Aedes (Hulecoeteomyia) koreicus (Edwards) and Aedes (Stegomyia) albopictus (Skuse) are two invasive mosquito species well established in northeastern Italy, and these two species may co-occur in artificial larval habitats such as tires, buckets, drums, and catch basins. Because Ae. albopictus has been shown experimentally to be a superior competitor to several mosquito species, we investigated larval competition between Ae. koreicus and Ae. albopictus using two diet levels (low level and high level) and 10 Ae. albopictus: Ae. koreicus density combination levels (30:0, 60:0, 15:15, 30:30, 10:20, 20:10, 20:40, 40:20, 0:60, and 0:30). A multivariate analysis (MANOVA) demonstrated a significant effect of the density combination on Ae. koreicus survivorship, female development time, and female wing length considered simultaneously in low-level diet and high-level diet treatments. Pairwise comparisons across low-level diet treatments showed a significant reduction of Ae. koreicus survivorship in 20:10 combination treatments (i.e. 20 Ae. albopictus and 10 Ae. koreicus larvae) compared to 10:20, 20:40, and 30:30 combination treatments, while no difference was detected for Ae. albopictus between density combination treatments. Furthermore, Ae. albopictus developed faster than Ae. koreicus regardless of diet and density combination treatments. Our results show weak larval competition between Ae. koreicus and Ae. albopictus with a slight advantage of the latter species. On the other hand, the presence of Ae. albopictus seems to favor the emergence of larger Ae. koreicus females. We suggest that factors such as habitats preferences or seasonal distributions may be determinant for the invasion success of Ae. koreicus. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Larval Connectivity and the International Management of Fisheries

PubMed Central

Kough, Andrew S.; Paris, Claire B.; Butler, Mark J.

2013-01-01

Predicting the oceanic dispersal of planktonic larvae that connect scattered marine animal populations is difficult, yet crucial for management of species whose movements transcend international boundaries. Using multi-scale biophysical modeling techniques coupled with empirical estimates of larval behavior and gamete production, we predict and empirically verify spatio-temporal patterns of larval supply and describe the Caribbean-wide pattern of larval connectivity for the Caribbean spiny lobster (Panulirus argus), an iconic coral reef species whose commercial value approaches $1 billion USD annually. Our results provide long sought information needed for international cooperation in the management of marine resources by identifying lobster larval connectivity and dispersal pathways throughout the Caribbean. Moreover, we outline how large-scale fishery management could explicitly recognize metapopulation structure by considering larval transport dynamics and pelagic larval sanctuaries. PMID:23762273

Detecting larval export from marine reserves

PubMed Central

Pelc, R. A.; Warner, R. R.; Gaines, S. D.; Paris, C. B.

2010-01-01

Marine reserve theory suggests that where large, productive populations are protected within no-take marine reserves, fished areas outside reserves will benefit through the spillover of larvae produced in the reserves. However, empirical evidence for larval export has been sparse. Here we use a simple idealized coastline model to estimate the expected magnitude and spatial scale of larval export from no-take marine reserves across a range of reserve sizes and larval dispersal scales. Results suggest that, given the magnitude of increased production typically found in marine reserves, benefits from larval export are nearly always large enough to offset increased mortality outside marine reserves due to displaced fishing effort. However, the proportional increase in recruitment at sites outside reserves is typically small, particularly for species with long-distance (on the order of hundreds of kilometers) larval dispersal distances, making it very difficult to detect in field studies. Enhanced recruitment due to export may be detected by sampling several sites at an appropriate range of distances from reserves or at sites downcurrent of reserves in systems with directional dispersal. A review of existing empirical evidence confirms the model's suggestion that detecting export may be difficult without an exceptionally large differential in production, short-distance larval dispersal relative to reserve size, directional dispersal, or a sampling scheme that encompasses a broad range of distances from the reserves. PMID:20181570

Growth and development of larval green frogs (Rana clamitans) exposed to multiple doses of an insecticide

USGS Publications Warehouse

Boone, M.D.; Bridges, C.M.; Rothermel, B.B.

2001-01-01

Our objective was to determine how green frogs (Rana clamitans) are affected by multiple exposures to a sublethal level of the carbamate insecticide, carbaryl, in outdoor ponds. Tadpoles were added to 1,000-1 ponds at a low or high density which were exposed to carbaryl 0, 1, 2, or 3 times. Length of the larval period, mass, developmental stage, tadpole survival, and proportion metamorphosed were used to determine treatment effects. The frequency of dosing affected the proportion of green frogs that reached metamorphosis and the developmental stage of tadpoles. Generally, exposure to carbaryl increased rates of metamorphosis and development. The effect of the frequency of carbaryl exposure on development varied with the density treatment; the majority of metamorphs and the most developed tadpoles came from high-density ponds exposed to carbaryl 3 times. This interaction suggests that exposure to carbaryl later in the larval period stimulated metamorphosis, directly or indirectly, under high-density conditions. Our study indicates that exposure to a contaminant can lead to early initiation of metamorphosis and that natural biotic factors can mediate the effects of a contaminant in the environment.

Induction of Larval Metamorphosis of the Coral Acropora millepora by Tetrabromopyrrole Isolated from a Pseudoalteromonas Bacterium

PubMed Central

Tebben, Jan; Tapiolas, Dianne M.; Motti, Cherie A.; Abrego, David; Negri, Andrew P.; Blackall, Linda L.; Steinberg, Peter D.; Harder, Tilmann

2011-01-01

The induction of larval attachment and metamorphosis of benthic marine invertebrates is widely considered to rely on habitat specific cues. While microbial biofilms on marine hard substrates have received considerable attention as specific signals for a wide and phylogenetically diverse array of marine invertebrates, the presumed chemical settlement signals produced by the bacteria have to date not been characterized. Here we isolated and fully characterized the first chemical signal from bacteria that induced larval metamorphosis of acroporid coral larvae (Acropora millepora). The metamorphic cue was identified as tetrabromopyrrole (TBP) in four bacterial Pseudoalteromonas strains among a culture library of 225 isolates obtained from the crustose coralline algae Neogoniolithon fosliei and Hydrolithon onkodes. Coral planulae transformed into fully developed polyps within 6 h, but only a small proportion of these polyps attached to the substratum. The biofilm cell density of the four bacterial strains had no influence on the ratio of attached vs. non-attached polyps. Larval bioassays with ethanolic extracts of the bacterial isolates, as well as synthetic TBP resulted in consistent responses of coral planulae to various doses of TBP. The lowest bacterial density of one of the Pseudoalteromonas strains which induced metamorphosis was 7,000 cells mm−2 in laboratory assays, which is on the order of 0.1 –1% of the total numbers of bacteria typically found on such surfaces. These results, in which an actual cue from bacteria has been characterized for the first time, contribute significantly towards understanding the complex process of acroporid coral larval settlement mediated through epibiotic microbial biofilms on crustose coralline algae. PMID:21559509

Microhabitat influence on larval fish assemblages within ...

EPA Pesticide Factsheets

We examined larval and juvenile fish assemblage structure in relation to microhabitat variables within the St. Louis River estuary, a drowned river mouth of Lake Superior. Fish were sampled in vegetated beds throughout the estuary, across a gradient of vegetation types and densities (including disturbed, preserved and post-restoration sites). Canonical correspondence analysis, relating species abundances to environmental variables revealed that plant species richness, turbidity and aquatic plant cover were most influential in structuring assemblages. Results from this microhabitat analysis at this crucial life stage has potential to inform wetland restoration efforts within the St. Louis River and other Great Lake coastal wetlands. not applicable

The influence of larval migration and dispersal depth on potential larval trajectories of a deep-sea bivalve

NASA Astrophysics Data System (ADS)

McVeigh, Doreen M.; Eggleston, David B.; Todd, Austin C.; Young, Craig M.; He, Ruoying

2017-09-01

Many fundamental questions in marine ecology require an understanding of larval dispersal and connectivity, yet direct observations of larval trajectories are difficult or impossible to obtain. Although biophysical models provide an alternative approach, in the deep sea, essential biological parameters for these models have seldom been measured empirically. In this study, we used a biophysical model to explore the role of behaviorally mediated migration from two methane seep sites in the Gulf of Mexico on potential larval dispersal patterns and population connectivity of the deep-sea mussel ;Bathymodiolus; childressi, a species for which some biological information is available. Three possible larval dispersal strategies were evaluated for larvae with a Planktonic Larval Duration (PLD) of 395 days: (1) demersal drift, (2) dispersal near the surface early in larval life followed by an extended demersal period before settlement, and (3) dispersal near the surface until just before settlement. Upward swimming speeds varied in the model based on the best data available. Average dispersal distances for simulated larvae varied between 16 km and 1488 km. Dispersal in the upper water column resulted in the greatest dispersal distance (1173 km ± 2.00), followed by mixed dispersal depth (921 km ± 2.00). Larvae originating in the Gulf of Mexico can potentially seed most known seep metapopulations on the Atlantic continental margin, whereas larvae drifting demersally cannot (237 km ± 1.43). Depth of dispersal is therefore shown to be a critical parameter for models of deep-sea connectivity.

Impact of physical and chemical characteristics of breeding sites on mosquito larval abundance at Ismailia Governorate, Egypt.

PubMed

Bahgat, Iman Mohamed

2013-08-01

The distribution and monthly abundance of mosquito larvae in released water, drainage canals and sewage water tanks in Ismailia governorate were investigated. The results obtained indicated the presence of five culicine (Culex. pipiens, Cx. pusillus, Cx. perexiguus, Cx. theleri and Ochlerotatus. caspius) and two anopheline (Anopheles. multicolor and An. pharoensis) mosquito species. Significantly higher larval density was recorded in sewage water (n= 5534; 46.08%) as compared with released water (n = 2903; 24.17%) and drainage water (n= 3573; 29.75%). Culex pipiens was the most dominant mosquito species in the three habitats. The effects of environmental parameters including pH, biological and chemical oxygen demands, day time water temperature, plant growth, salinity, total organic matter and concentrations of heavy metals on larval population density were investigated. The positive correlations observed between heavy metals concentrations in the three habitats suggested relative uniformity of the sources of metal pollutants. Culex pipiens larvae demonstrated high tolerance to elevated levels of heavy metals in sewage water and compensatory effects of high nutrient levels generally associated with sewage or domestic waste. High densities of culicine larvae were accompanied by low density of anopheline larvae. This was attributed to water chemistry & competitive interactions.

Larval Dispersal Modeling of Pearl Oyster Pinctada margaritifera following Realistic Environmental and Biological Forcing in Ahe Atoll Lagoon

PubMed Central

Thomas, Yoann; Dumas, Franck; Andréfouët, Serge

2014-01-01

Studying the larval dispersal of bottom-dwelling species is necessary to understand their population dynamics and optimize their management. The black-lip pearl oyster (Pinctada margaritifera) is cultured extensively to produce black pearls, especially in French Polynesia's atoll lagoons. This aquaculture relies on spat collection, a process that can be optimized by understanding which factors influence larval dispersal. Here, we investigate the sensitivity of P. margaritifera larval dispersal kernel to both physical and biological factors in the lagoon of Ahe atoll. Specifically, using a validated 3D larval dispersal model, the variability of lagoon-scale connectivity is investigated against wind forcing, depth and location of larval release, destination location, vertical swimming behavior and pelagic larval duration (PLD) factors. The potential connectivity was spatially weighted according to both the natural and cultivated broodstock densities to provide a realistic view of connectivity. We found that the mean pattern of potential connectivity was driven by the southwest and northeast main barotropic circulation structures, with high retention levels in both. Destination locations, spawning sites and PLD were the main drivers of potential connectivity, explaining respectively 26%, 59% and 5% of the variance. Differences between potential and realistic connectivity showed the significant contribution of the pearl oyster broodstock location to its own dynamics. Realistic connectivity showed larger larval supply in the western destination locations, which are preferentially used by farmers for spat collection. In addition, larval supply in the same sectors was enhanced during summer wind conditions. These results provide new cues to understanding the dynamics of bottom-dwelling populations in atoll lagoons, and show how to take advantage of numerical models for pearl oyster management. PMID:24740288

Diatom diet selectivity by early post-larval abalone Haliotis diversicolor supertexta under hatchery conditions

NASA Astrophysics Data System (ADS)

Zhang, Yuyu; Gao, Yahui; Liang, Junrong; Chen, Changping; Zhao, Donghai; Li, Xuesong; Li, Yang; Wu, Wenzhong

2010-11-01

Benthic diatoms constitute the primary diet of abalone during their early stages of development. To evaluate the dietary preferences of early post-larval abalone, Haliotis diversicolor supertexta, we analyzed the gut contents of post-larvae that settled on diatom films. We compared the abundance and species diversity of diatom assemblages in the gut to those of the epiphytic diatom assemblages on the attachment films, and identified 40 benthic diatom species in the gut contents of post-larvae 12 to 24 d after settlement. The most abundant taxa in the gut contents were Navicula spp., Amphora copulate, and Amphora coffeaeformis. Navicula spp. accounted for 64.0% of the cell density. In the attachment films, we identified 110 diatom species belonging to 38 genera. Pennate diatoms were the dominant members including the species Amphiprora alata, Cocconeis placentula var. euglypta, Cylindrotheca closterium, Navicula sp. 2, and A. coffeaeformis. Nano-diatoms (<20 μm in length) accounted for a considerable proportion of the total species number and cell density of the diatom assemblages in the gut contents and on the films. This suggests that nano-diatoms are important to the efficient production of abalone seed. The difference of the composition and abundance of diatoms between in the guts and on the biofilms suggests that early post-larval grazing was selective. An early post-larval abalone preferred nano-diatoms and the genera Navicula and Amphora during the month after settlement.

Modeling larval connectivity of the Atlantic surfclams within the Middle Atlantic Bight: Model development, larval dispersal and metapopulation connectivity

NASA Astrophysics Data System (ADS)

Zhang, Xinzhong; Haidvogel, Dale; Munroe, Daphne; Powell, Eric N.; Klinck, John; Mann, Roger; Castruccio, Frederic S.

2015-02-01

To study the primary larval transport pathways and inter-population connectivity patterns of the Atlantic surfclam, Spisula solidissima, a coupled modeling system combining a physical circulation model of the Middle Atlantic Bight (MAB), Georges Bank (GBK) and the Gulf of Maine (GoM), and an individual-based surfclam larval model was implemented, validated and applied. Model validation shows that the model can reproduce the observed physical circulation patterns and surface and bottom water temperature, and recreates the observed distributions of surfclam larvae during upwelling and downwelling events. The model results show a typical along-shore connectivity pattern from the northeast to the southwest among the surfclam populations distributed from Georges Bank west and south along the MAB shelf. Continuous surfclam larval input into regions off Delmarva (DMV) and New Jersey (NJ) suggests that insufficient larval supply is unlikely to be the factor causing the failure of the population to recover after the observed decline of the surfclam populations in DMV and NJ from 1997 to 2005. The GBK surfclam population is relatively more isolated than populations to the west and south in the MAB; model results suggest substantial inter-population connectivity from southern New England to the Delmarva region. Simulated surfclam larvae generally drift for over one hundred kilometers along the shelf, but the distance traveled is highly variable in space and over time. Surfclam larval growth and transport are strongly impacted by the physical environment. This suggests the need to further examine how the interaction between environment, behavior, and physiology affects inter-population connectivity. Larval vertical swimming and sinking behaviors have a significant net effect of increasing larval drifting distances when compared with a purely passive model, confirming the need to include larval behavior.

Monitoring larval populations of the Douglas-fir tussock moth and the western spruce budworm on permanent plots: sampling methods and statistical properties of data

Treesearch

A.R. Mason; H.G. Paul

1994-01-01

Procedures for monitoring larval populations of the Douglas-fir tussock moth and the western spruce budworm are recommended based on many years experience in sampling these species in eastern Oregon and Washington. It is shown that statistically reliable estimates of larval density can be made for a population by sampling host trees in a series of permanent plots in a...

Spatial distribution of the larval indices of Aedes aegypti in Guadalupe, Nuevo León, Mexico, with circular distribution analysis.

PubMed

Mercado-Hernandez, Roberto; Fernández-Salas, Ildefonso; Villarreal-Martinez, Homero

2003-03-01

A census of all outdoor larval breeding sites (951) present in 361 dwellings in a neighborhood of Guadalupe in northeastern Mexico was conducted in October 1997 to determine larval indices of Aedes aegypti, and their relationship to human population density and vegetation type. Here we present a method that allows finding the direction and extrapolar flight range of vectors, as parameters in the dynamics of dengue transmission. By using circular statistics applied to each block of data, ranges (quartiles) were computed for larval index type, adult-child (a/c) relationship, and vegetation. Eight angles between 37 and 300 degrees were used. Circular distribution was determined by using mean angle (a) and argument (r) from the sum of ranges for each variable. Arguments corresponding to the mean angle of house (260 degrees), recipient (265 degrees), and Breteau (247 degrees) indices were 0.2321, 0.2331, and 0.2225, respectively. In addition, arguments for the mean angle of herbaceous (277 degrees), shrub (318 degrees), and arboreal (333 degrees) vegetation were 0.2589, 0.1984, and 0.2367, respectively, and the 3 were located in the 4th quadrant. The a/c relationship was in 282 degrees, with an argument of 0.2466, which indicates that in this neighborhood in southern Guadalupe, both the human population density and the larval indices were higher than in other areas.

Effects of biotic and abiotic factors on the distribution and abundance of larval two-lined salamanders (Eurycea bislineata) across spatial scales.

PubMed

Barr, Garrett E; Babbitt, Kimberly J

2002-10-01

We sampled eight streams in the White Mountain National Forest, New Hampshire, throughout their elevational reach for larval salamanders and predatory fish to examine the effects of abiotic factors and predation on the distribution and abundance of larval salamanders. Eurycea bislineata (two-lined salamander) and Salvelinus fontinalis (brook trout) abundance varied among and within streams. Eurycea bislineata showed a negative association with S. fontinalis across spatial scales (micro-scale, among quadrats; meso-scale, among pool/riffle pairs; macro-scale, among streams). At the smallest scale, the average density of larval E. bislineata was greatest in microhabitats with relatively high boulder cover and low sand and bare rock cover only in the presence of S. fontinalis; no such relationship was observed in the absence of S. fontinalis. In a mesocosm experiment, larval salamander survival was higher in enclosures containing cobbles than enclosures containing a gravel mix, illustrating the advantage of coarse substrates with interstitial spaces that are inaccessible to predatory fish. At the meso-scale, E. bislineata larvae were less abundant in stream sections with S. fontinalis than those without. Among streams, those with many S. fontinalis had fewer E. bislineata. Of the abiotic parameters measured, water temperature and pH were positively related to E. bislineata presence, and elevation, water temperature, pH, canopy cover, and gradient were positively related to E. bislineata abundance. Larval Plethodontid salamanders can reach high densities and appear to have strong interactions with stream biota, thus their functional role in stream communities deserves further attention.

Similarities and Differences for Swimming in Larval and Adult Lampreys.

PubMed

McClellan, Andrew D; Pale, Timothée; Messina, J Alex; Buso, Scott; Shebib, Ahmad

2016-01-01

The spinal locomotor networks controlling swimming behavior in larval and adult lampreys may have some important differences. As an initial step in comparing the locomotor systems in lampreys, in larval animals the relative timing of locomotor movements and muscle burst activity were determined and compared to those previously published for adults. In addition, the kinematics for free swimming in larval and adult lampreys was compared in detail for the first time. First, for swimming in larval animals, the neuromechanical phase lag between the onsets or terminations of muscle burst activity and maximum concave curvature of the body increased with increasing distance along the body, similar to that previously shown in adults. Second, in larval lampreys, but not adults, absolute swimming speed (U; mm s(-1)) increased with animal length (L). In contrast, normalized swimming speed (U'; body lengths [bl] s(-1)) did not increase with L in larval or adult animals. In both larval and adult lampreys, U' and normalized wave speed (V') increased with increasing tail-beat frequency. Wavelength and mechanical phase lag did not vary significantly with tail-beat frequency but were significantly different in larval and adult animals. Swimming in larval animals was characterized by a smaller U/V ratio, Froude efficiency, and Strouhal number than in adults, suggesting less efficient swimming for larval animals. In addition, during swimming in larval lampreys, normalized lateral head movements were larger and normalized lateral tail movements were smaller than for adults. Finally, larval animals had proportionally smaller lateral surface areas of the caudal body and fin areas than adults. These differences are well suited for larval sea lampreys that spend most of the time buried in mud/sand, in which swimming efficiency is not critical, compared to adults that would experience significant selection pressure to evolve higher-efficiency swimming to catch up to and attach to fish for

Explaining variation in adult Anopheles indoor resting abundance: the relative effects of larval habitat proximity and insecticide-treated bed net use.

PubMed

McCann, Robert S; Messina, Joseph P; MacFarlane, David W; Bayoh, M Nabie; Gimnig, John E; Giorgi, Emanuele; Walker, Edward D

2017-07-17

Spatial determinants of malaria risk within communities are associated with heterogeneity of exposure to vector mosquitoes. The abundance of adult malaria vectors inside people's houses, where most transmission takes place, should be associated with several factors: proximity of houses to larval habitats, structural characteristics of houses, indoor use of vector control tools containing insecticides, and human behavioural and environmental factors in and near houses. While most previous studies have assessed the association of larval habitat proximity in landscapes with relatively low densities of larval habitats, in this study these relationships were analysed in a region of rural, lowland western Kenya with high larval habitat density. 525 houses were sampled for indoor-resting mosquitoes across an 8 by 8 km study area using the pyrethrum spray catch method. A predictive model of larval habitat location in this landscape, previously verified, provided derivations of indices of larval habitat proximity to houses. Using geostatistical regression models, the association of larval habitat proximity, long-lasting insecticidal nets (LLIN) use, house structural characteristics (wall type, roof type), and peridomestic variables (cooking in the house, cattle near the house, number of people sleeping in the house) with mosquito abundance in houses was quantified. Vector abundance was low (mean, 1.1 adult Anopheles per house). Proximity of larval habitats was a strong predictor of Anopheles abundance. Houses without an LLIN had more female Anopheles gambiae s.s., Anopheles arabiensis and Anopheles funestus than houses where some people used an LLIN (rate ratios, 95% CI 0.87, 0.85-0.89; 0.84, 0.82-0.86; 0.38, 0.37-0.40) and houses where everyone used an LLIN (RR, 95% CI 0.49, 0.48-0.50; 0.39, 0.39-0.40; 0.60, 0.58-0.61). Cooking in the house also reduced Anopheles abundance across all species. The number of people sleeping in the house, presence of cattle near the house

Socioeconomic status affects mosquito (Diptera: Culicidae) larval habitat type availability and infestation level.

PubMed

Dowling, Zara; Ladeau, Shannon L; Armbruster, Peter; Biehler, Dawn; Leisnham, Paul T

2013-07-01

Mosquito populations are largely regulated by processes occurring at the larval stage. We sampled mosquito larval microhabitats (mostly water-holding containers) in six neighborhoods in the Washington, DC, area that varied in socioeconomic status (SES) and housing structure (row houses vs. stand-alone houses) to test associations among these neighborhood characteristics, microhabitat abundance and parameters, and mosquito occurrence and densities. Thirty-four percent (33.9%) of sampled microhabitats contained mosquito larvae, and 93.1% of larvae were Aedes albopictus Skuse or Culex pipiens L. Five specific container types (drains, corrugated flexible drainpipes, planters, garbage cans, and buckets) accounted for the majority of water-holding (56.0%) and mosquito-positive (50.6%) microhabitats sampled. We found no associations between SES or housing structure with total microhabitat abundance per yard, mosquito occurrence or mosquito densities per microhabitat. In contrast, container purpose varied with SES, with low SES neighborhoods having greater numbers of disused containers and lower numbers of functional containers than low and medium SES neighborhoods. Ae. albopictus were 83% more abundant in disused containers, whereas Cx. pipiens were more abundant in structural and functional containers, possibly owing to species-specific oviposition and development related to water quality. Ae. albopictus densities increased over the summer, whereas Cx. pipiens densities remained constant. Ae. albopictus is usually the dominant pest in urban areas in the eastern United States; therefore, integrated mosquito management programs should incorporate the elimination of disused containers to reduce its infestation and adult production, especially in low SES neighborhoods where they occur most frequently.

Novel methodologies in marine fish larval nutrition.

PubMed

Conceição, Luis E C; Aragão, Cláudia; Richard, Nadège; Engrola, Sofia; Gavaia, Paulo; Mira, Sara; Dias, Jorge

2010-03-01

Major gaps in knowledge on fish larval nutritional requirements still remain. Small larval size, and difficulties in acceptance of inert microdiets, makes progress slow and cumbersome. This lack of knowledge in fish larval nutritional requirements is one of the causes of high mortalities and quality problems commonly observed in marine larviculture. In recent years, several novel methodologies have contributed to significant progress in fish larval nutrition. Others are emerging and are likely to bring further insight into larval nutritional physiology and requirements. This paper reviews a range of new tools and some examples of their present use, as well as potential future applications in the study of fish larvae nutrition. Tube-feeding and incorporation into Artemia of (14)C-amino acids and lipids allowed studying Artemia intake, digestion and absorption and utilisation of these nutrients. Diet selection by fish larvae has been studied with diets containing different natural stable isotope signatures or diets where different rare metal oxides were added. Mechanistic modelling has been used as a tool to integrate existing knowledge and reveal gaps, and also to better understand results obtained in tracer studies. Population genomics may assist in assessing genotype effects on nutritional requirements, by using progeny testing in fish reared in the same tanks, and also in identifying QTLs for larval stages. Functional genomics and proteomics enable the study of gene and protein expression under various dietary conditions, and thereby identify the metabolic pathways which are affected by a given nutrient. Promising results were obtained using the metabolic programming concept in early life to facilitate utilisation of certain nutrients at later stages. All together, these methodologies have made decisive contributions, and are expected to do even more in the near future, to build a knowledge basis for development of optimised diets and feeding regimes for

Larval dispersion of the estuarine crab Neohelice granulata in coastal marine waters of the Southwest Atlantic

NASA Astrophysics Data System (ADS)

Bas, Claudia; Luppi, Tomás; Spivak, Eduardo; Schejter, Laura

2009-08-01

The estuarine brachyuran crab Neohelice granulata export their larvae from the parental intertidal population of the Mar Chiquita coastal lagoon, and probably other populations, to marine waters. The degree of larval dispersion or self-recruitment of populations is unknown. We evaluated the presence of all larval stages of N. granulata in coastal waters of Argentina between 37.9° and 35.8° S, at two different spatial scales: a broad scale of tens to hundreds of kilometers from the Río de la Plata estuary in the north, to Mar Chiquita lagoon in the south, and a small scale of hundreds of meters to some kilometers around the mouth of Mar Chiquita, during spring and summer. Additionally, we registered the larval composition and density at San Clemente creek population, in Samborombon Bay (Río de la Plata estuary), every 3 h along a 30-hour period. Evidence indicates that larval release of N. granulata is temporally synchronized with nocturnal ebb tides and all development from Zoea I to Zoea IV occur in areas close to the parental population, even with very different oceanographic characteristics. A possible mechanism based on salinity selection and wind-driven transport is proposed for such behavior, and some considerations related to the connectivity of present populations are made.

Toxicity of hydrolyzed vicilins toward Callosobruchus maculatus and phytopathogenic fungi.

PubMed

Uchôa, Adriana Ferreira; de Miranda, Maria Raquel Alcântara; de Souza, Amanda Jardim; Gomes, Valdirene Moreira; Fernandes, Kátia Valevski Sales; Lemos, Francisco José Alves; Oliveira, Antonia Elenir Amancio; Xavier-Filho, José

2009-09-09

Studies have shown that vicilins (7S storage proteins) from seeds were able to bind to the surface of the Callosobruchus maculatus larval midgut and to the peritrophic matrices of the midguts of Diatraea saccharalis and Tenebrio molitor , inhibiting larval development. Vicilins were also shown to inhibit yeast growth and bind to yeast cells through the association with chitin-containing structures. The present work studies the association of peptides from vicilins of genotypes of Vigna unguiculata (susceptible and resistant to bruchid) with acetylated chitin and the toxicity of vicilin fragments and chitin-binding vicilin fragments to C. maculatus and phytopathogenic fungi. Hydrolysis of vicilins with alpha-chymotrypsin results in a complex mixture of fragments that were separated by chitin-affinity chromatography. Chitin-binding peptides from both genotypes were toxic to C. maculatus larvae, and alpha-chymotrypsin-hydrolyzed vicilins were deleterious to the above insect and to Fusarium oxysporum , Colletotrichum musae , and Saccharomyces cerevisiae fungi.

Patterns of larval sucker emigration from the Sprague and lower Williamson Rivers of the Upper Klamath Basin, Oregon, after the removal of Chiloquin Dam - 2009-10 Annual Report

USGS Publications Warehouse

Ellsworth, Craig M.; Martin, Barbara A.

2012-01-01

Data presented in this report is a continuation of a research project that began in 2004. Larval drift parameters measured in 2009 and 2010 were similar to those measured from 2004 to 2008. Most larvae and eggs were collected at the two drift sites downstream of the former Chiloquin Dam (river kilometer 0.7 on the Sprague River and river kilometer 7.4 on the Williamson River). Mean and peak sample densities increased with proximity to Upper Klamath Lake. Peak larval densities continued to be collected between 1 and 3 hours after sunset at Chiloquin, which is the drift site nearest a known spawning area. Catch distribution of larvae and eggs in the lower Sprague and Williamson Rivers suggests that most SNS and LRS spawning continues to occur downstream of the site of the former Chiloquin Dam. The sizes and growth stages indicate that larval emigration from spawning areas resulting from drift occurs within a few days after swim-up. Larval suckers appear to move downstream quickly until they reach suitable rearing habitat.

Hydrodynamics of larval settlement: The influence of turbulent stress events at potential recruitment sites

USGS Publications Warehouse

Crimaldi, John P.; Thompson, Janet K.; Rosman, Johanna H.; Lowe, Ryan J.; Koseff, Jeffrey R.

2002-01-01

We describe a laboratory investigation into the effect of turbulent hydrodynamic stresses on clam larvae in the settlement phase of the recruitment process. A two-component laser-Doppler anemometer (LDA) was used to measure time histories of the instantaneous turbulence structure at potential recruitment sites within reconstructed beds of the adult Asian clam, Potamocorbula amurensis. Measurements were made for two flow speeds over beds with three different clam densities and two different clam heights. We analyze the statistical effect of the turbulence on the larval flux to the bed and on the probability of successful anchoring to the substrate. It is shown that the anchoring probability depends on the nature of the instantaneous stress events rather than on mean stresses. The instantaneous turbulence structure near the bed is altered by the flow rate and the spacing and height of adult clams living in the substrate. The ability to anchor quickly is therefore extremely important, since the time sequence of episodic turbulent stress events influences larval settlement success. The probability of successful larval settlement is predicted to decrease as the spacing between adults decreases, implying that the hydrodynamics impose negative feedback on clam bed aggregation dynamics.

Using spatial, seasonal, and diel drift patterns of larval Lost River suckers Deltistes luxatus (Cypriniformes: Catostomidae) and shortnose suckers Chasmistes brevirostris (Cypriniformes: Catostomidae) to help identify a site for a water withdrawal structure on the Williamson River, Oregon

USGS Publications Warehouse

Ellsworth, Craig M.; Tyler, Torrey J.; VanderKooi, Scott P.

2010-01-01

A small irrigation diversion dam near Chiloquin, Oregon, was removed and replaced with a pump station to improve fish passage for Lost River suckers (Deltistes luxatus) and shortnose suckers (Chasmistes brevirostris) entering the Sprague River on their spawning migrations. During the developmental phase of the pump station, a need was identified to better understand the larval drift characteristics of these endangered catostomids in order to reduce entrainment into the irrigation system. The spatial, seasonal, and diel distribution of drifting larvae was measured during the 2004 spawning season at two proposed sites on the Williamson River where the pump station could be located. Larval drift for both species coincided with the irrigation season making them subject to entrainment into the irrigation system. Drift occurred almost exclusively at night with larvae entering the drift at sunset and exiting the drift at sunrise. Nighttime larval densities were concentrated near the surface and at midchannel at both sites. Densities were generally greater on the side of mid-channel with greater flow. During early morning sampling we detected a general shift in larval drift from surface to subsurface drift. We also observed an increase in larval densities towards the shore opposite from the proposed pump station at the upper site whereas larval densities remained high at midchannel at the lower site. During daytime sampling, the few larvae that were collected were distributed throughout the water column at both pump sites. This study found that larvae drifting during all time periods were generally distributed further across the cross section, deeper in the water column, and closer to where the proposed water withdrawal structure would be built at the downstream site when compared to the upstream site. Recommendations were provided to locate the withdrawal facility at the upstream site and operate it in a manner such that larval entrainment would likely be minimized.

Patterns of Larval Sucker Emigration from the Sprague and Lower Williamson Rivers of the Upper Klamath Basin, Oregon, Prior to the Removal of Chiloquin Dam - 2006 Annual Report

USGS Publications Warehouse

Ellsworth, Craig M.; Tyler, Torrey J.; VanderKooi, Scott P.; Markle, Douglas F.

2009-01-01

In 2006, we collected larval Lost River sucker Deltistes luxatus (LRS), shortnose sucker Chasmistes brevirostris (SNS), and Klamath largescale sucker Catostomus snyderi (KLS) emigrating from spawning areas in the Williamson and Sprague Rivers. This work is part of a multi-year effort to characterize the relative abundance, drift timing, and length frequencies of larval suckers in this watershed prior to the removal of Chiloquin Dam on the lower Sprague River. Additional larval drift samples were collected from the Fremont Bridge on Lakeshore Drive on the south end of Upper Klamath Lake near its outlet to the Link River. Because of difficulties in distinguishing KLS larvae from SNS larvae, individuals identified as either of these two species were grouped together and reported as KLS-SNS in this report. We found that larval densities varied by site with the highest densities being collected at the most upstream site on the Sprague River at river kilometer (rkm) 108.0 near Beatty, Oregon (Beatty), and the most downstream sites near Chiloquin, Oregon; one site on the Sprague River at rkm 0.7 (Chiloquin) and the other site on the Williamson River at rkm 7.4 (Williamson). Larval catches were relatively small and sporadic at two other sites on the Sprague River located between Chiloquin and Beatty (Power Station at rkm 9.5 and Lone Pine at rkm 52.7) and one site on the Sycan River at rkm 4.7. Most larvae (79 percent) collected in 2006 were identified as LRS. More larvae and eggs were collected at Chiloquin than at any other site. The seasonal timing of larval drift varied by location; larvae generally were captured earlier at upstream sites than at downstream sites. Cumulative catch percentages of drifting larvae suggest that larval LRS emigrated earlier than KLS-SNS larvae at every site. Drift of LRS larvae at Beatty began 3 to 4 weeks earlier than at Chiloquin or Williamson. At Chiloquin, peak larval catches occurred 3 and 5 weeks after peak egg catches. The daily peak

Dry season refugia for anopheline larvae and mapping of the seasonal distribution in mosquito larval habitats in Kandi, northeastern Benin.

PubMed

Govoetchan, Renaud; Gnanguènon, Virgile; Ogouwalé, Euloge; Oké-Agbo, Frédéric; Azondékon, Roseric; Sovi, Arthur; Attolou, Roseline; Badirou, Kefilath; Youssouf, Ramziyath Agbanrin; Ossè, Razaki; Akogbéto, Martin

2014-03-31

The dynamics of mosquito populations depends on availability of suitable surface water for oviposition. It is well known that suitable management of mosquito larval habitats in the sub-Saharan countries, particularly during droughts, could help to suppress vector densities and malaria transmission. We conducted a field survey to investigate the spatial and seasonal distribution of mosquito larval habitats and identify drought-refugia for anopheline larvae. A GIS approach was used to identify, geo-reference and follow up longitudinally from May 2012 to May 2013, all mosquito breeding sites in two rural sites (Yondarou and Thui), one urban (Kossarou), and one peri-urban (Pèdè) site at Kandi, a municipality in northeastern Benin. In Kandi, droughts are excessive with no rain for nearly six months and a lot of sunshine. A comprehensive record of mosquito larval habitats was conducted periodically in all sites for the identification of drought-refugia of anopheline larval stages. With geospatialisation data, seasonal larval distribution maps were generated for each study site with the software ArcGIS version 10.2. Overall, 187 mosquito breeding sites were identified of which 29.95% were recorded during drought. In rural, peri-urban and urban sites, most of the drought-refugia of anopheline larvae were domestic in nature (61.54%). Moreover, in rural settings, anopheline larvae were also sampled in cisterns and wells (25% of larval habitats sampled during drought in Yondarou and 20% in Thui). The mapping showed a significant decrease in the spatial distribution of mosquito larval habitats in rural, peri-urban and urban sites during drought, except in Yondarou (rural) where the aridity did not seem to influence the distribution of larval habitats. Our data showed that the main drought-refugia of anopheline larvae were of a domestic nature as well as wells and cisterns. A suitable management of mosquito larvae in sub-Saharan countries, particularly during droughts, should

Stock-specific advection of larval walleye (Sander vitreus) in western Lake Erie: Implications for larval growth, mixing, and stock discrimination

USGS Publications Warehouse

Fraker, Michael E.; Anderson, Eric J.; May, Cassandra J.; Chen, Kuan-Yu; Davis, Jeremiah J.; DeVanna, Kristen M.; DuFour, Mark R.; Marschall, Elizabeth A.; Mayer, Christine M.; Miner, Jeffery G.; Pangle, Kevin L.; Pritt, Jeremy J.; Roseman, Edward F.; Tyson, Jeffrey T.; Zhao, Yingming; Ludsin, Stuart A

2015-01-01

Physical processes can generate spatiotemporal heterogeneity in habitat quality for fish and also influence the overlap of pre-recruit individuals (e.g., larvae) with high-quality habitat through hydrodynamic advection. In turn, individuals from different stocks that are produced in different spawning locations or at different times may experience dissimilar habitat conditions, which can underlie within- and among-stock variability in larval growth and survival. While such physically-mediated variation has been shown to be important in driving intra- and inter-annual patterns in recruitment in marine ecosystems, its role in governing larval advection, growth, survival, and recruitment has received less attention in large lake ecosystems such as the Laurentian Great Lakes. Herein, we used a hydrodynamic model linked to a larval walleye (Sander vitreus) individual-based model to explore how the timing and location of larval walleye emergence from several spawning sites in western Lake Erie (Maumee, Sandusky, and Detroit rivers; Ohio reef complex) can influence advection pathways and mixing among these local spawning populations (stocks), and how spatiotemporal variation in thermal habitat can influence stock-specific larval growth. While basin-wide advection patterns were fairly similar during 2011 and 2012, smaller scale advection patterns and the degree of stock mixing varied both within and between years. Additionally, differences in larval growth were evident among stocks and among cohorts within stocks which were attributed to spatiotemporal differences in water temperature. Using these findings, we discuss the value of linked physical–biological models for understanding the recruitment process and addressing fisheries management problems in the world's Great Lakes.

A simple approximation for larval retention around reefs

NASA Astrophysics Data System (ADS)

Cetina-Heredia, Paulina; Connolly, Sean R.

2011-09-01

Estimating larval retention at individual reefs by local scale three-dimensional flows is a significant problem for understanding, and predicting, larval dispersal. Determining larval dispersal commonly involves the use of computationally demanding and expensively calibrated/validated hydrodynamic models that resolve reef wake eddies. This study models variation in larval retention times for a range of reef shapes and circulation regimes, using a reef-scale three-dimensional hydrodynamic model. It also explores how well larval retention time can be estimated based on the "Island Wake Parameter", a measure of the degree of flow turbulence in the wake of reefs that is a simple function of flow speed, reef dimension, and vertical diffusion. The mean residence times found in the present study (0.48-5.64 days) indicate substantial potential for self-recruitment of species whose larvae are passive, or weak swimmers, for the first several days after release. Results also reveal strong and significant relationships between the Island Wake Parameter and mean residence time, explaining 81-92% of the variability in retention among reefs across a range of unidirectional flow speeds and tidal regimes. These findings suggest that good estimates of larval retention may be obtained from relatively coarse-scale characteristics of the flow, and basic features of reef geomorphology. Such approximations may be a valuable tool for modeling connectivity and meta-population dynamics over large spatial scales, where explicitly characterizing fine-scale flows around reef requires a prohibitive amount of computation and extensive model calibration.

Effect of diet processing method and ingredient substitution on feed characteristics and survival of larval walleye, Sander vitreus

USGS Publications Warehouse

Barrows, F.T.; Lellis, W.A.

2006-01-01

Two methods were developed for the production of larval fish diets. The first method, microextrusion marumerization (MEM), has been tested in laboratory feeding trials for many years and produces particles that are palatable and water stable. The second method, particle-assisted rotational agglomeration (PARA), produced diets that have lower density than diets produced by MEM. Each method was used to produce diets in the 250- to 400- and 400- to 700-??m range and compared with a reference diet (Fry Feed Kyowa* [FFK]) for feeding larval walleye in two experiments. The effect of substituting 4% of the fish meal with freeze-dried artemia fines was also investigated. In the first experiment, 30-d survival was greater (P < 0.05) for fish fed a diet produced by PARA without Artemia (49.1.0%) than for fish fed the same diet produced by MEM (27.6%). The addition of Artemia to a diet produced by MEM did not increase survival of larval walleye. Fish fed the reference diet had 24.4% survival. In the second experiment, there was an effect of both processing method and Artemia supplementation, and an interaction of these effects, on survival. Fish fed a diet produced by PARA without Artemia supplementation had 48.4% survival, and fish fed the same diet produced by MEM had only 19.6% survival. Inclusion of 4% freeze-dried Artemia improved (P < 0.04) survival of fish fed MEM particles but not those fed PARA particles. Fish fed FFK had greater weight gain than fish fed other diets in both experiments. Data indicate that the PARA method of diet processing produces smaller, lower density particles than the MEM process and that diets produced by the PARA process support higher survival of larval walleye with low capital and operating costs. ?? Copyright by the World Aquaculture Society 2006.

Dissection and staining of Drosophila larval ovaries.

PubMed

Maimon, Iris; Gilboa, Lilach

2011-05-13

Many organs depend on stem cells for their development during embryogenesis and for maintenance or repair during adult life. Understanding how stem cells form, and how they interact with their environment is therefore crucial for understanding development, homeostasis and disease. The ovary of the fruit fly Drosophila melanogaster has served as an influential model for the interaction of germ line stem cells (GSCs) with their somatic support cells (niche) (1, 2). The known location of the niche and the GSCs, coupled to the ability to genetically manipulate them, has allowed researchers to elucidate a variety of interactions between stem cells and their niches (3-12). Despite the wealth of information about mechanisms controlling GSC maintenance and differentiation, relatively little is known about how GSCs and their somatic niches form during development. About 18 somatic niches, whose cellular components include terminal filament and cap cells (Figure 1), form during the third larval instar (13-17). GSCs originate from primordial germ cells (PGCs). PGCs proliferate at early larval stages, but following the formation of the niche a subgroup of PGCs becomes GSCs (7, 16, 18, 19). Together, the somatic niche cells and the GSCs make a functional unit that produces eggs throughout the lifetime of the organism. Many questions regarding the formation of the GSC unit remain unanswered. Processes such as coordination between precursor cells for niches and stem cell precursors, or the generation of asymmetry within PGCs as they become GSCs, can best be studied in the larva. However, a methodical study of larval ovary development is physically challenging. First, larval ovaries are small. Even at late larval stages they are only 100μm across. In addition, the ovaries are transparent and are embedded in a white fat body. Here we describe a step-by-step protocol for isolating ovaries from late third instar (LL3) Drosophila larvae, followed by staining with fluorescent

Fitness consequences of larval traits persist across the metamorphic boundary.

PubMed

Crean, Angela J; Monro, Keyne; Marshall, Dustin J

2011-11-01

Metamorphosis is thought to provide an adaptive decoupling between traits specialized for each life-history stage in species with complex life cycles. However, an increasing number of studies are finding that larval traits can carry-over to influence postmetamorphic performance, suggesting that these life-history stages may not be free to evolve independently of each other. We used a phenotypic selection framework to compare the relative and interactive effects of larval size, time to hatching, and time to settlement on postmetamorphic survival and growth in a marine invertebrate, Styela plicata. Time to hatching was the only larval trait found to be under directional selection, individuals that took more time to hatch into larvae survived better after metamorphosis but grew more slowly. Nonlinear selection was found to act on multivariate trait combinations, once again acting in opposite directions for selection acting via survival and growth. Individuals with above average values of larval traits were most likely to survive, but surviving individuals with intermediate larval traits grew to the largest size. These results demonstrate that larval traits can have multiple, complex fitness consequences that persist across the metamorphic boundary; and thus postmetamorphic selection pressures may constrain the evolution of larval traits. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

GROWTH AND BEHAVIOR OF LARVAL ZEBRAFISH Danio ...

EPA Pesticide Factsheets

Because Zebrafish (Danio rerio) have become a popular and important model for scientific research, the capability to rear larval zebrafish to adulthood is of great importance. Recently research examining the effects of diet (live versus processed) have been published. In the current study we examined whether the larvae can be reared on a processed diet alone, live food alone, or the combination while maintaining normal locomotor behavior, and acceptable survival, length and weight at 14 dpf in a static system. A 14 day feeding trial was conducted in glass crystallizing dishes containing 500 ml of 4 ppt Instant Ocean. On day 0 pdf 450 embryos were selected as potential study subjects and placed in a 26○C incubator on a 14:10 (light:dark) light cycle. At 4 dpf 120 normally developing embryos were selected per treatment and divided into 3 bowls of 40 embryos (for an n=3 per treatment; 9 bowls total). Treatment groups were: G (Gemma Micro 75 only), R (L-type marine rotifers (Brachionus plicatilis) only) or B (Gemma and rotifers). Growth (length), survival, water quality and rotifer density were monitored on days 5-14. On day 14, weight of larva in each bowl was measured and 8 larva per bowl were selected for use in locomotor testing. This behavior paradigm tests individual larval zebrafish under both light and dark conditions in a 24-well plate.After 14 dpf, survival among the groups was not different (92-98%). By days 7 -14 R and B larvae were ~2X longer

Soundscape manipulation enhances larval recruitment of a reef-building mollusk

PubMed Central

Bohnenstiehl, DelWayne R.; Eggleston, David B.

2015-01-01

Marine seafloor ecosystems, and efforts to restore them, depend critically on the influx and settlement of larvae following their pelagic dispersal period. Larval dispersal and settlement patterns are driven by a combination of physical oceanography and behavioral responses of larvae to a suite of sensory cues both in the water column and at settlement sites. There is growing evidence that the biological and physical sounds associated with adult habitats (i.e., the “soundscape”) influence larval settlement and habitat selection; however, the significance of acoustic cues is rarely tested. Here we show in a field experiment that the free-swimming larvae of an estuarine invertebrate, the eastern oyster, respond to the addition of replayed habitat-related sounds. Oyster larval recruitment was significantly higher on larval collectors exposed to oyster reef sounds compared to no-sound controls. These results provide the first field evidence that soundscape cues may attract the larval settlers of a reef-building estuarine invertebrate. PMID:26056624

Larval fish distribution in the St. Louis River estuary

EPA Science Inventory

Our objective was to determine what study design, environmental, and habitat variables contribute to the distribution and abundance of larval fish in the St. Louis River estuary. Larval fish habitat associations are poorly understood in Great Lakes coastal wetlands, yet critical ...

Effects of arginine vasotocin and mesotocin on the activation and development of amiloride-blockable short-circuit current across larval, adult, and cultured larval bullfrog skins.

PubMed

Takada, Makoto; Fujimaki-Aoba, Kayo; Hokari, Shigeru

2010-03-01

Amphibian skin has osmoregulatory functions, with Na(+) crossing from outside to inside. Na(+) transport can be measured as the short-circuit current (SCC). We investigated the short-term and long-term effects of arginine vasotocin (AVT) and mesotocin (MT) (which modulate Na(+) transport) on the activation and development of an amiloride-blockable SCC (adult-type feature) in larval, adult, and corticoid-cultured larval bullfrog skins. We found: (1) AVT-receptor (AVT-R) and MT-receptor (MT-R) mRNAs could be detected in both larval and adult skins, (2) in the short term (within 60 min), the larval SCC (amiloride-stimulated SCC) was increased by AVT, forskolin, and MT, suggesting that AVT and MT did not activate the inactive ENaC (epithelial sodium channel) protein thought to be expressed in larval skin, (3) in the short term (within 90 min), AVT, forskolin, and MT stimulated the adult SCC (amiloride-blockable SCC), (4) AVT and MT increased both the larval and adult SCC via receptors insensitive to OPC-21268 (an antagonist of the V(1)-type receptor), OPC-31260 (an antagonist of the V(2)-type receptor), and ([d(CH(2))(5),Tyr(Me)(2),Thr(4),Orn(8),des-Gly-NH (2) (9) ]VT) (an antagonist of the oxytocin receptor), (5) culturing EDTA-treated larval skin with corticoids supplemented with AVT (1 microM) or MT (1 microM) for 2 weeks (long-term effects of AVT and MT) did not alter the corticoid-induced development of an amiloride-blockable SCC (adult-type feature). AVT and MT thus have the potential to stimulate SCC though channels that are already expressed, but they may not influence the development of the amiloride-blockable SCC (an adult-type feature) in larval skin.

The influence of a severe reservoir drawdown on springtime zooplankton and larval fish assemblages in Red Willow Reservoir, Nebraska

USGS Publications Warehouse

DeBoer, Jason A.; Webber, Christa M.; Dixon, Taylor A.; Pope, Kevin L.

2016-01-01

Reservoirs can be dynamic systems, often prone to unpredictable and extreme water-level fluctuations, and can be environments where survival is difficult for zooplankton and larval fish. Although numerous studies have examined the effects of extreme reservoir drawdown on water quality, few have examined extreme drawdown on both abiotic and biotic characteristics. A fissure in the dam at Red Willow Reservoir in southwest Nebraska necessitated an extreme drawdown; the water level was lowered more than 6 m during a two-month period, reducing reservoir volume by 76%. During the subsequent low-water period (i.e., post-drawdown), spring sampling (April–June) showed dissolved oxygen concentration was lower, while turbidity and chlorophyll-a concentration were greater, relative to pre-drawdown conditions. Additionally, there was an overall increase in zooplankton density, although there were differences among taxa, and changes in mean size among taxa, relative to pre-drawdown conditions. Zooplankton assemblage composition had an average dissimilarity of 19.3% from pre-drawdown to post-drawdown. The ratio of zero to non-zero catches was greater post-drawdown for larval common carp and for all larval fishes combined, whereas we observed no difference for larval gizzard shad. Larval fish assemblage composition had an average dissimilarity of 39.7% from pre-drawdown to post-drawdown. Given the likelihood that other dams will need repair or replacement in the near future, it is imperative for effective reservoir management that we anticipate the likely abiotic and biotic responses of reservoir ecosystems as these management actions will continue to alter environmental conditions in reservoirs.

Trait-based Modeling of Larval Dispersal in the Gulf of Maine

NASA Astrophysics Data System (ADS)

Jones, B.; Richardson, D.; Follows, M. J.; Hill, C. N.; Solow, A.; Ji, R.

2016-02-01

Population connectivity of marine species is the inter-generational movement of individuals among geographically separated subpopulations and is a crucial determinant of population dynamics, community structure, and optimal management strategies. For many marine species, population connectivity is largely determined by the dispersal patterns that emerge from a pelagic larval phase. These dispersal patterns are a result of interactions between the physical environment, adult spawning strategy, and larval ecology. Using a generalized trait-based model that represents the adult spawning strategy as a distribution of larval releases in time and space and the larval trait space with the pelagic larval duration, vertical swimming behavior, and settlement habitat preferences, we simulate dispersal patterns in the Gulf of Maine and surrounding regions. We implement this model as an individual-based simulation that tracks Lagrangian particles on a graphics processing unit as they move through hourly archived output from the Finite-Volume Community Ocean Model. The particles are released between the Hudson Canyon and Nova Scotia and the release distributions are determined using a novel method that minimizes the number of simulations required to achieve a predetermined level of precision for the connectivity matrices. The simulated larvae have a variable pelagic larval duration and exhibit multiple forms of dynamic depth-keeping behavior. We describe how these traits influence the dispersal trajectories and connectivity patterns among regions in the northwest Atlantic. Our description includes the probability of successful recruitment, patchiness of larval distributions, and the variability of these properties in time and space under a variety of larval dispersal strategies.

A Simple Ground-Based Trap For Estimating Densities of Arboreal Leaf Insects

Treesearch

Robert A. Haack; Richard W. Blank

1991-01-01

Describes a trap design to use in collecting larval frass or head capsules for estimating densities of aboveground arthropods. The trap is light, compact, durable, and easily constructed from common inexpensive items.

Effects of moisture content of food waste on residue separation, larval growth and larval survival in black soldier fly bioconversion.

PubMed

Cheng, Jack Y K; Chiu, Sam L H; Lo, Irene M C

2017-09-01

In order to foster sustainable management of food waste, innovations in food waste valorization technologies are crucial. Black soldier fly (BSF) bioconversion is an emerging technology that can turn food waste into high-protein fish feed through the use of BSF larvae. The conventional method of BSF bioconversion is to feed BSF larvae with food waste directly without any moisture adjustment. However, it was reported that difficulty has been experienced in the separation of the residue (larval excreta and undigested material) from the insect biomass due to excessive moisture. In addition to the residue separation problem, the moisture content of the food waste may also affect the growth and survival aspects of BSF larvae. This study aims to determine the most suitable moisture content of food waste that can improve residue separation as well as evaluate the effects of the moisture content of food waste on larval growth and survival. In this study, pre-consumer and post-consumer food waste with different moisture content (70%, 75% and 80%) was fed to BSF larvae in a temperature-controlled rotary drum reactor. The results show that the residue can be effectively separated from the insect biomass by sieving using a 2.36mm sieve, for both types of food waste at 70% and 75% moisture content. However, sieving of the residue was not feasible for food waste at 80% moisture content. On the other hand, reduced moisture content of food waste was found to slow down larval growth. Hence, there is a trade-off between the sieving efficiency of the residue and the larval growth rate. Furthermore, the larval survival rate was not affected by the moisture content of food waste. A high larval survival rate of at least 95% was achieved using a temperature-controlled rotary drum reactor for all treatment groups. The study provides valuable insights for the waste management industry on understanding the effects of moisture content when employing BSF bioconversion for food waste recycling

The importance of accounting for larval detectability in mosquito habitat-association studies.

PubMed

Low, Matthew; Tsegaye, Admasu Tassew; Ignell, Rickard; Hill, Sharon; Elleby, Rasmus; Feltelius, Vilhelm; Hopkins, Richard

2016-05-04

Mosquito habitat-association studies are an important basis for disease control programmes and/or vector distribution models. However, studies do not explicitly account for incomplete detection during larval presence and abundance surveys, with potential for significant biases because of environmental influences on larval behaviour and sampling efficiency. Data were used from a dip-sampling study for Anopheles larvae in Ethiopia to evaluate the effect of six factors previously associated with larval sampling (riparian vegetation, direct sunshine, algae, water depth, pH and temperature) on larval presence and detectability. Comparisons were made between: (i) a presence-absence logistic regression where samples were pooled at the site level and detectability ignored, (ii) a success versus trials binomial model, and (iii) a presence-detection mixture model that separately estimated presence and detection, and fitted different explanatory variables to these estimations. Riparian vegetation was consistently highlighted as important, strongly suggesting it explains larval presence (-). However, depending on how larval detectability was estimated, the other factors showed large variations in their statistical importance. The presence-detection mixture model provided strong evidence that larval detectability was influenced by sunshine and water temperature (+), with weaker evidence for algae (+) and water depth (-). For larval presence, there was also some evidence that water depth (-) and pH (+) influenced site occupation. The number of dip-samples needed to determine if larvae were likely present at a site was condition dependent: with sunshine and warm water requiring only two dips, while cooler water and cloud cover required 11. Environmental factors influence true larval presence and larval detectability differentially when sampling in field conditions. Researchers need to be more aware of the limitations and possible biases in different analytical approaches used to

Correlated evolution between mode of larval development and habitat in muricid gastropods.

PubMed

Pappalardo, Paula; Rodríguez-Serrano, Enrique; Fernández, Miriam

2014-01-01

Larval modes of development affect evolutionary processes and influence the distribution of marine invertebrates in the ocean. The decrease in pelagic development toward higher latitudes is one of the patterns of distribution most frequently discussed in marine organisms (Thorson's rule), which has been related to increased larval mortality associated with long pelagic durations in colder waters. However, the type of substrate occupied by adults has been suggested to influence the generality of the latitudinal patterns in larval development. To help understand how the environment affects the evolution of larval types we evaluated the association between larval development and habitat using gastropods of the Muricidae family as a model group. To achieve this goal, we collected information on latitudinal distribution, sea water temperature, larval development and type of substrate occupied by adults. We constructed a molecular phylogeny for 45 species of muricids to estimate the ancestral character states and to assess the relationship between traits using comparative methods in a Bayesian framework. Our results showed high probability for a common ancestor of the muricids with nonpelagic (and nonfeeding) development, that lived in hard bottoms and cold temperatures. From this ancestor, a pelagic feeding larva evolved three times, and some species shifted to warmer temperatures or sand bottoms. The evolution of larval development was not independent of habitat; the most probable evolutionary route reconstructed in the analysis of correlated evolution showed that type of larval development may change in soft bottoms but in hard bottoms this change is highly unlikely. Lower sea water temperatures were associated with nonpelagic modes of development, supporting Thorson's rule. We show how environmental pressures can favor a particular mode of larval development or transitions between larval modes and discuss the reacquisition of feeding larva in muricids gastropods.

Horizontal Trends in Larval Fish Diversity and Abundance Along an Ocean-Estuarine Gradient on the Northern KwaZulu-Natal Coast, South Africa

NASA Astrophysics Data System (ADS)

Harris, S. A.; Cyrus, D. P.; Beckley, L. E.

2001-08-01

The structure of the larval fish assemblages along an ocean-estuarine gradient in the St Lucia region on the northern KwaZulu-Natal coast of South Africa was examined using a combination of univariate, distributional and multivariate techniques. The data was comprised of a full annual set of ichthyoplankton samples taken from three types of environment: nearshore coastal waters, surf zone and within the St Lucia Estuary itself. The mean monthly densities of each species in each environment were used in the species matrix, and the mean monthly values of salinity, temperature and turbidity were used in the physical variables matrix. The mean species diversity and eveness index was significantly higher in the nearshore waters than the surf zone and estuary. The patterns of relative species abundances in each environment (K-dominance curves) showed that the estuarine environment was dominated by a few species in large numbers, the surf zone was intermediate, and the nearshore coast was the most diverse. Classification and multidimensional scaling (MDS) ordination analyses of larval fish densities grouped together into three main clusters based on the three different environments. The species similarity matrix (inverse analysis) clustered into four groups at the 10% similarity level. The MDS analysis of the same matrix showed that the groups separated out more or less according to the type of environment they occur in, and hence the level of estuarine dependence of the various species. Species belonging to each assemblage showed similarities with regards to their reproduction modes and/or preference to a particular physical condition. Some species were restricted to one environment, whilst others were common to two or all three environments. The occurrence of partially estuarine-dependent species in all three environments suggests that ocean-estuarine coupling is an important process for the recruitment success of these species. The ' best fitting ' physical variable

Horizontal and vertical distributions of larval fishes around an isolated oceanic island in the tropical Pacific

NASA Astrophysics Data System (ADS)

Boehlert, George W.; Watson, William; Sun, L. Charles

1992-04-01

Ichthyoplankton and oceanographic sampling was conducted in November 1984 in waters surrounding Johnston Atoll (16°44'N, 169°32'W), a small, isolated atoll in the central Pacific Ocean. The typical flow pattern in this region is westward; the nearest island is in the Hawaiian Archipelago, 760 km away. Most collections were dominated by oceanic taxa. In the 0-50 m stratum, larval densities were relatively uniform horizontally, but densities down-current of the island tended to be higher, and fish eggs were concentrated there. In the 50-100 m stratum, larval abundance on the down-current side of the island was markedly higher than either up-current or farther down-current. Oceanic taxa did not display this pattern, while marked areas of very high abundance characterized the island-related taxa, the most abundant including the gobiid Eviota epiphanes and the apogonid Pseudamiops sp. Estimates of geostrophic flow indicate that the region down-current of the atoll was one of return flow associated with apparent mesoscale eddies or meanders north and west of the island. This region may serve as a down-current retention area for the pelagic larvae of island-related taxa and may facilitate recruitment back to the source populations.

Modelling larval transport in a axial convergence front

NASA Astrophysics Data System (ADS)

Robins, P.

2010-12-01

Marine larvae exhibit different vertical swimming behaviours, synchronised by factors such as tidal currents and daylight, in order to aid retention near the parent populations and hence promote production, avoid predation, or to stimulate digestion. This paper explores two types of larval migration in an estuarine axial convergent front which is an important circulatory mechanism in many coastal regions where larvae are concentrated. A parallelised, three-dimensional, ocean model was applied to an idealised estuarine channel which was parameterised from observations of an axial convergent front which occurs in the Conwy Estuary, U.K. (Nunes and Simpson, 1985). The model successfully simulates the bilateral cross-sectional recirculation of an axial convergent front, which has been attributed to lateral density gradients established by the interaction of the lateral shear of the longitudinal currents with the axial salinity gradients. On the flood tide, there is surface axial convergence whereas on the ebb tide, there is (weaker) surface divergence. Further simulations with increased/decreased tidal velocities and with stronger/weaker axial salinity gradients are planned so that the effects of a changing climate on the secondary flow can be understood. Three-dimensional Lagrangian Particle Tracking Models (PTMs) have been developed which use the simulated velocity fields to track larvae in the estuarine channel. The PTMs take into account the vertical migrations of two shellfish species that are commonly found in the Conwy Estuary: (i) tidal migration of the common shore crab (Carcinus maenas) and (ii), diel (daily) migration of the Great scallop (Pecten maximus). These migration behaviours are perhaps the most widespread amongst shellfish larvae and have been compared with passive (drifting) particles in order to assess their relative importance in terms of larval transport. Preliminary results suggest that the net along-estuary dispersal over a typical larval

Effect of small-scale turbulence on feeding rates of larval cod and haddock in stratified water on Georges Bank

NASA Astrophysics Data System (ADS)

Gregory Lough, R.; Mountain, David G.

A set of vertically stratified MOCNESS tows made on the southern flank of Georges Bank in spring 1981 and 1983 was analyzed to examine the relationship between larval cod and haddock feeding success and turbulent dissipation in a stratified water column. Observed feeding ratios (mean no. prey larval gut -1) for three size classes of larvae were compared with estimated ingestion rates using the Rothschild and Osborn ( Journal of Plankton Research, 10, 1988, 465-474) predator-prey encounter rate model. Simulation of contact rates requires parameter estimates of larval fish and their prey cruising speeds, density of prey, and turbulent velocity of the water column. Turbulent dissipation was estimated from a formulation by James ( Estuarine and Coastal Marine Science, 5, 1977, 339-353) incorporating both a wind a tidal component. Larval ingestion rates were based on swallowing probabilities derived from calm-water laboratory observations. Model-predicted turbulence profiles generally showed that dissipation rates were low to moderate (10 -11-10 -7 W kg -1). Turbulence was minimal at or below the pycnocline (≈ 25 m) with higher values(1-2 orders of magnitude) near the surface due to wind mixing and at depth due to shear in the tidal current near bottom. In a stratified water column during the day, first-feeding larvae (5-6 mm) were located mostly within or above the pycnocline coincident with their copepod prey (nauplii and copepodites). The 7-8 mm larvae were most abundant within the pycnocline, whereas the 9-10 mm larvae were found within and below the pycnocline. Feeding ratios were relatively low in early morning following darkness when the wind speed was low, but increased by a factor of 2-13 by noon and evening when the wind speed doubled. Comparison of depth-specific feeding ratios with estimated ingestion rates, derived from turbulence-affected contact rates, generally were reasonable after allowing for an average gut evacuation time (4 h), and in many cases

'Peer pressure' in larval Drosophila?

PubMed

Niewalda, Thomas; Jeske, Ines; Michels, Birgit; Gerber, Bertram

2014-06-06

Understanding social behaviour requires a study case that is simple enough to be tractable, yet complex enough to remain interesting. Do larval Drosophila meet these requirements? In a broad sense, this question can refer to effects of the mere presence of other larvae on the behaviour of a target individual. Here we focused in a more strict sense on 'peer pressure', that is on the question of whether the behaviour of a target individual larva is affected by what a surrounding group of larvae is doing. We found that innate olfactory preference of a target individual was neither affected (i) by the level of innate olfactory preference in the surrounding group nor (ii) by the expression of learned olfactory preference in the group. Likewise, learned olfactory preference of a target individual was neither affected (iii) by the level of innate olfactory preference of the surrounding group nor (iv) by the learned olfactory preference the group was expressing. We conclude that larval Drosophila thus do not take note of specifically what surrounding larvae are doing. This implies that in a strict sense, and to the extent tested, there is no social interaction between larvae. These results validate widely used en mass approaches to the behaviour of larval Drosophila. © 2014. Published by The Company of Biologists Ltd.

Density of Emerald Ash Borer (Coleoptera: Buprestidae) Adults and Larvae at Three Stages of the Invasion Wave.

PubMed

Burr, Stephen J; McCullough, Deborah G; Poland, Therese M

2018-02-08

Emerald ash borer (EAB) (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae), an invasive phloem-feeding buprestid, has killed hundreds of millions of ash (Fraxinus spp.) trees in the United States and two Canadian provinces. We evaluated EAB persistence in post-invasion sites and compared EAB adult captures and larval densities in 24 forested sites across an east-west gradient in southern Michigan representing the Core (post-invasion), Crest (high EAB populations), and Cusp (recently infested areas) of the EAB invasion wave. Condition of green ash (Fraxinus pennsylvanica Marsh) trees were recorded in fixed radius plots and linear transects in each site. Ash mortality was highest in Core sites in the southeast, moderate in Crest sites in central southern Michigan, and low in Cusp sites in the southwest. Traps and trap trees in Crest sites accounted for 75 and 60% of all EAB beetles captured in 2010 and 2011, respectively. Populations of EAB were present in all Core sites and traps in these sites captured 13% of all beetles each year. Beetle captures and larval densities at Cusp sites roughly doubled between 2010 and 2011, reflecting the increasing EAB populations. Sticky bands on girdled trees captured the highest density of EAB beetles per m2 of area, while baited double-decker traps had the highest detection rates and captured the most beetles. Larval densities were higher on girdled ash than on similar ungirdled trees and small planted trees. Woodpecker predation and a native larval parasitoid were present in all three invasion regions but had minor effects on ash survival and EAB densities. © The Author(s) 2018. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Cyanobacteria associated with Anopheles albimanus (Diptera: Culicidae) larval habitats in southern Mexico.

PubMed

Vázquez-Martínez, M Guadalupe; Rodríguez, Mario H; Arredondo-Jiménez, Juan I; Méndez-Sanchez, José D; Bond-Compeán, J Guillermo; Cold-Morgan, Michelle

2002-11-01

Cyanobacteria associated with Anopheles albimanus Wiedemann larval habitats from southern Chiapas, Mexico, were isolated and identified from water samples and larval midguts using selective medium BG-11. Larval breeding sites were classified according to their hydrology and dominant vegetation. Cyanobacteria isolated in water samples were recorded and analyzed according to hydrological and vegetation habitat breeding types, and mosquito larval abundance. In total, 19 cyanobacteria species were isolated from water samples. Overall, the most frequently isolated cyanobacterial taxa were Phormidium sp., Oscillatoria sp., Aphanocapsa cf. littoralis, Lyngbya lutea, P. animalis, and Anabaena cf. spiroides. Cyanobacteria were especially abundant in estuaries, irrigation canals, river margins and mangrove lagoons, and more cyanobacteria were isolated from Brachiaria mutica, Ceratophyllum demersum, and Hymenachne amplexicaulis habitats. Cyanobacteria were found in habitats with low to high An. albimanus larval abundance, but Aphanocapsa cf. littoralis was associated with habitats of low larval abundance. No correlation was found between water chemistry parameters and the presence of cyanobacteria, however, water temperature (29.2-29.4 degrees C) and phosphate concentration (79.8-136.5 ppb) were associated with medium and high mosquito larvae abundance. In An. albimanus larval midguts, only six species of cyanobacteria were isolated, the majority being from the most abundant cyanobacteria in water samples.

Adaptation to larval crowding in Drosophila ananassae leads to the evolution of population stability.

PubMed

Dey, Snigdhadip; Bose, Joy; Joshi, Amitabh

2012-05-01

Density-dependent selection is expected to lead to population stability, especially if r and K tradeoff. Yet, there is no empirical evidence of adaptation to crowding leading to the evolution of stability. We show that populations of Drosophila ananassae selected for adaptation to larval crowding have higher K and lower r, and evolve greater stability than controls. We also show that increased population growth rates at high density can enhance stability, even in the absence of a decrease in r, by ensuring that the crowding adapted populations do not fall to very low sizes. We discuss our results in the context of traits known to have diverged between the selected and control populations, and compare our results with previous work on the evolution of stability in D. melanogaster. Overall, our results suggest that density-dependent selection may be an important factor promoting the evolution of relatively stable dynamics in natural populations.

Interspecific Larval Competition Between Aedes albopictus and Aedes japonicus (Diptera: Culicidae) in Northern Virginia

PubMed Central

Armistead, J. S.; Arias, J. R.; Nishimura, N.; Lounibos, L. P.

2008-01-01

Aedes albopictus (Skuse) and Aedes japonicus (Theobald) are two of the most recent and widespread invasive mosquito species to have become established in the United States. The two species co-occur in water-filled artificial containers, where crowding and limiting resources are likely to promote inter- or intraspecific larval competition. The performance of northern Virginia populations of Ae. japonicus and Ae. albopictus competing as larvae under field conditions was evaluated. Per capita rates of population increase for each species were estimated, and the effects of species composition and larval density were determined. In water-containing cups provided with oak leaves, Ae. albopictus larvae exhibited a competitive advantage over Ae. japonicus as a consequence of higher survivorship, shorter developmental time, and a significantly higher estimated population growth rate under conditions of interspecific competition. Intraspecific competition constrained population performance of Ae. albopictus significantly more than competition with Ae. japonicus. In the context of the Lotka-Volterra model of competition, these findings suggest competitive exclusion of Ae. japonicus in those habitats where this species co-occurs with Ae. albopictus. PMID:18714861

Interspecific larval competition between Aedes albopictus and Aedes japonicus (Diptera: Culicidae) in northern Virginia.

PubMed

Armistead, J S; Arias, J R; Nishimura, N; Lounibos, L P

2008-07-01

Aedes albopictus (Skuse) and Aedes japonicus (Theobald) are two of the most recent and widespread invasive mosquito species to have become established in the United States. The two species co-occur in water-filled artificial containers, where crowding and limiting resources are likely to promote inter- or intraspecific larval competition. The performance of northern Virginia populations of Ae. japonicus and Ae. albopictus competing as larvae under field conditions was evaluated. Per capita rates of population increase for each species were estimated, and the effects of species composition and larval density were determined. In water-containing cups provided with oak leaves, Ae. albopictus larvae exhibited a competitive advantage over Ae. japonicus as a consequence of higher survivorship, shorter developmental time, and a significantly higher estimated population growth rate under conditions of interspecific competition. Intraspecific competition constrained population performance of Ae. albopictus significantly more than competition with Ae. japonicus. In the context of the Lotka-Volterra model of competition, these findings suggest competitive exclusion of Ae. japonicus in those habitats where this species co-occurs with Ae. albopictus.

Role of large- and fine-scale variables in predicting catch rates of larval Pacific lamprey in the Willamette Basin, Oregon

USGS Publications Warehouse

Schultz, Luke; Mayfield, Mariah P.; Sheoships, Gabe T.; Wyss, Lance A.; Clemens, Benjamin J.; Whitlock, Steven L.; Schreck, Carl B.

2016-01-01

Pacific lamprey Entosphenus tridentatus is an anadromous fish native to the Pacific Northwest of the USA. That has declined substantially over the last 40 years. Effective conservation of this species will require an understanding of the habitat requirements for each life history stage. Because its life cycle contains extended freshwater rearing (3–8 years), the larval stage may be a critical factor limiting abundance of Pacific lamprey. The objective of our study was to estimate the influence of barriers and habitat characteristics on the catch-per-unit-effort (CPUE) of larval Pacific lamprey in the Willamette River Basin, Oregon, USA. We sampled lampreys at multiple locations in wadeable streams throughout the basin in 2011–13 and used an information theoretic approach to examine the relative influence of fine- and large-scale predictors of CPUE. Pacific lamprey was observed across the basin, but its relative abundance appeared to be limited by the presence of natural and artificial barriers in some sub-basins. Lower velocity habitats such as off-channel areas and pools contained higher densities of larval lamprey; mean Pacific lamprey CPUE in off-channel habitats was 4 and 32 times greater than in pools and riffles respectively. Restoration and conservation strategies that improve fish passage, enhance natural hydrologic and depositional processes and increase habitat heterogeneity will likely benefit larval Pacific lamprey.

Larval fish dynamics in spring pools in middle Tennessee

USGS Publications Warehouse

Bettoli, Phillip William; Goldsworthy, C.A.

2011-01-01

We used lighted larval traps to assess reproduction by fishes inhabiting nine spring pools in the Barrens Plateau region of middle Tennessee between May and September 2004. The traps (n = 162 deployments) captured the larval or juvenile forms of Etheostoma crossopterum (Fringed Darter) (n = 188), Gambusia affinis (Western Mosquitofish) (n = 139), Hemitremia flammea (Flame Chub) (n = 55), the imperiled Fundulus julisia (Barrens Topminnow) (n = 10), and Forbesichthys agassizii (Spring Cavefish) (n = 1). The larval forms of four other species (Families Centrarchidae, Cyprinidae, and Cottidae) were not collected, despite the presence of adults. Larval Barrens Topminnow hatched over a protracted period (early June through late September); in contrast, hatching intervals were much shorter for Fringed Darter (mid-May through early June). Flame Chub hatching began before our first samples in early May and concluded by late-May. Juvenile Western Mosquitofish were collected between early June and late August. Our sampling revealed that at least two species (Flame Chub and Fringed Darter) were able to reproduce and recruit in habitats harboring the invasive Western Mosquitofish, while Barrens Topminnow could not.

A sampler for capturing larval and juvenile Atlantic menhaden

USGS Publications Warehouse

Hedrick, J.D.; Hedrick, L.R.; Margraf, F.J.

2005-01-01

Interest in capturing larval and juvenile Atlantic menhaden Brevoortia tyrannus for use in laboratory studies required the design and construction of a sampling device that would allow us to make collections of live fish from open-water areas. Our device for capturing 1-2.5-in larval-juvenile fish was constructed of a stainless steel frame that supported a 9.84-ft-long (3-m-long)5 cone plankton net with a 3.28-ft-diameter (1-m-diameter) opening and a 0.04-in (1-mm) mesh size. Although the plankton net was similar to that used during typical larval fish collections, the cod end was constructed of Plexiglas and was nearly watertight; this prevented impingement and injury to larval fish and provided a calm-water environment. The cod end was designed for quick release from the plankton net, and the entire cod end could be submerged into a 75-gal onboard holding tank. This design and technique obviated the netting or emerging of fish from the water until they were returned to the laboratory. ?? Copyright by the American Fisheries Society 2005.

Larval fish assemblages across an upwelling front: Indication for active and passive retention

NASA Astrophysics Data System (ADS)

Tiedemann, Maik; Brehmer, Patrice

2017-03-01

In upwelling areas, enrichment, concentration and retention are physical processes that have major consequences for larval fish survival. While these processes generally increase larval survival, strong upwelling can also increase mortality due to an offshore transport of larvae towards unfavorable habitats. In 2013 a survey was conducted along the Senegalese coast to investigate the upwelling effect with regard to larval fish assemblages and possible larval fish retention. According to water column characteristics two distinct habitats during an upwelling event were discriminated, i.e. the inshore upwelled water and the transition area over the deepest part of the Senegalese shelf. Along the two areas 42,162 fish larvae were collected representing 133 species within 40 families. Highest larval fish abundances were observed in the inshore area and decreasing abundances towards the transition, indicating that certain fish species make use of the retentive function of the inner shelf area as spawning grounds. Two larval fish assemblages overlap both habitats, which are sharply delimited by a strong upwelling front. One assemblage inhabited the inshore/upwelling area characterized by majorly neritic and pelagic species (Sparidae spp., Sardinella aurita), that seem to take the advantage of a passive retention on the shelf. The second assemblage consisted of a mix of pelagic and mesopelagic species (Engraulis encrasicolus, Carangidae spp. and Myctophidae spp.). Some species of the second assemblage, e.g. horse mackerels (Trachurus trachurus and Trachurus trecae), large finned-lantern fish (Hygophum macrochir) and foureyed sole (Microchirus ocellatus), revealed larval peak occurrences at intermediate and deep water layers, where the near-ground upwelling layer is able to transport larvae back to the shelf. This indicates active larval retention for species that are dominant in the transition area. Diel vertical migration patterns of S. aurita, E. encrasicolus and M

Comparison of Intrinsic Rate of Different House Fly Densities in a Simulated Condition: A Prediction for House Fly Population and Control Threshold.

PubMed

Ong, Song-Quan; Ahmad, Hamdan; Jaal, Zairi; Rus, Adanan; Fadzlah, Fadhlina Hazwani Mohd

2017-01-01

Determining the control threshold for a pest is common prior to initiating a pest control program; however, previous studies related to the house fly control threshold for a poultry farm are insufficient for determining such a threshold. This study aimed to predict the population changes of house fly population by comparing the intrinsic rate of increase (r m ) for different house fly densities in a simulated system. This study first defined the knee points of a known population growth curve as a control threshold by comparing the r m of five densities of house flies in a simulated condition. Later, to understand the interactions between the larval and adult populations, the correlation between larval and adult capacity rate (r c ) was studied. The r m values of 300- and 500-fly densities were significantly higher compared with the r m values at densities of 50 and 100 flies. This result indicated their representative indices as candidates for a control threshold. The r c of larval and adult populations were negatively correlated with densities of fewer than 300 flies; this implicated adult populations with fewer than 300 flies as declining while the larval population was growing; therefore, control approaches should focus on the immature stages. The results in the present study suggest a control threshold for house fly populations. Future works should focus on calibrating the threshold indices in field conditions. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Effects of climate change on the survival of larval cod

NASA Astrophysics Data System (ADS)

Kristiansen, T.; Stock, C. A.; Drinkwater, K. F.; Curchitser, E. N.

2011-12-01

Understanding how climate change may impact important commercial fisheries is critical for developing sustainable fisheries management strategies. In this study, we used simulations from an Earth System Model (NOAA GFDL ESM2.1) coupled with an individual-based model (IBM) for larval fish to provide a first assessment of the potential importance of climate-change driven changes in primary productivity and temperature on cod recruitment in the North Atlantic to the year 2100. ESM model output was averaged for 5 regions, each with an area of 5x5 on a latitude-longitude grid, and representing the geographic boundaries of the current cod range. The physical and environmental data were incorporated into a mechanistic IBM used to simulate the critical early phases in the life of larval fish (e.g. cod) in a changing environment. Large phytoplankton production was predicted to decrease in most regions, thereby lowering the number of meso-zooplankton in the water column. Meso-zooplankton is the most important prey item for larval cod and a reduction in their numbers have strong impacts on larval cod survival. The combination of lowered prey abundance with increased energy requirement for growth and metabolism through increased temperature had a negative impact on cod recruitment in all modeled regions of the North Atlantic. The probability of survival past the larval stages was reduced with 20-30% at all five spawning grounds by the year 2100. Together, these results suggest climate change could have significant impacts on the survival of larval cod in the North Atlantic.

Larval Transport on the Atlantic Continental Shelf of North America: a Review

NASA Astrophysics Data System (ADS)

Epifanio, C. E.; Garvine, R. W.

2001-01-01

This review considers transport of larval fish and crustaceans on the continental shelf. Previous reviews have contained only limited treatments of the physical processes involved. The present paper provides a physical background that is considerably more comprehensive. It includes a discussion of three principal forcing agents: (1) wind stress; (2) tides propagating from the deep ocean; and (3) differences in density associated with the buoyant outflow of estuaries, surface heat flux, or the interaction of coastal and oceanic water masses at the seaward margin of the shelf. The authors discuss the effects of these forcing agents on transport of larvae in the Middle Atlantic and South Atlantic Bights along the east coast of North America. The discussion concentrates on three species (blue crab, menhaden, bluefish) that have been the subject of a very recent multi-disciplinary study. Taken as a whole, the reproductive activities of these three species span the entire year and utilize the entire shelf, from the most seaward margin to the estuarine nursery. The blue crab is representative of species affected by physical processes occurring during summer and early autumn on the inner and mid-shelf. Menhaden are impacted by processes occurring in winter on the outer and mid-shelf. Bluefish are influenced primarily by processes occurring during early spring at the outer shelf margin near the western boundary current. The authors conclude that alongshore wind stress and density differences, i.e. buoyancy-driven flow, are the primary agents of larval transport in the region. Circulation associated with the western boundary current is only important at the shelf margin and tidally driven processes are generally inconsequential.

Fitness consequences of larval exposure to Beauveria bassiana on adults of the malaria vector Anopheles stephensi.

PubMed

Vogels, Chantal B F; Bukhari, Tullu; Koenraadt, Constantianus J M

2014-06-01

Entomopathogenic fungi have shown to be effective in biological control of both larval and adult stages of malaria mosquitoes. However, a small fraction of mosquitoes is still able to emerge after treatment with fungus during the larval stage. It remains unclear whether fitness of these adults is affected by the treatment during the larval stage and whether they are still susceptible for another treatment during the adult stage. Therefore, we tested the effects of larval exposure to the entomopathogenic fungus Beauveria bassiana on fitness of surviving Anopheles stephensi females. Furthermore, we tested whether larval exposed females were still susceptible to re-exposure to the fungus during the adult stage. Sex ratio, survival and reproductive success were compared between non-exposed and larval exposed A. stephensi. Comparisons were also made between survival of non-exposed and larval exposed females that were re-exposed to B. bassiana during the adult stage. Larval treatment did not affect sex ratio of emerging mosquitoes. Larval exposed females that were infected died significantly faster and laid equal numbers of eggs from which equal numbers of larvae hatched, compared to non-exposed females. Larval exposed females that were uninfected had equal survival, but laid a significantly larger number of eggs from which a significantly higher number of larvae hatched, compared to non-exposed females. Larval exposed females which were re-exposed to B. bassiana during the adult stage had equal survival as females exposed only during the adult stage. Our results suggest that individual consequences for fitness of larval exposed females depended on whether a fungal infection was acquired during the larval stage. Larval exposed females remained susceptible to re-exposure with B. bassiana during the adult stage, indicating that larval and adult control of malaria mosquitoes with EF are compatible. Copyright © 2014. Published by Elsevier Inc.

Mosquito larval productivity in rice-fields infested with Azolla in Mvomero District, Tanzania.

PubMed

Mwingira, V S; Mayala, B K; Senkoro, K P; Rumisha, S F; Shayo, E H; Mlozi, M R S; Mboera, L E G

2009-01-01

Azolla (Salviniales: Azollaceae) is known to reduce oviposition and adult emergence of a number of mosquito species. Several species of Azolla are reportedly indigenous to Tanzania. However, the potential of Azolla as a biocontrol agent against malaria mosquitoes has not been evaluated in the country. This cross-sectional study was carried out to assess mosquito larval productivity in irrigated rice-fields infested with Azolla in Mvomero District, Tanzania. A systematic larval sampling covering all open water bodies along designed transect was carried in rice-fields. Larval density was estimated by dipping water bodies with or without Azolla. The degree of Azolla coverage was categorized as 0%, <50%, 50%, and >80%. Larvae densities were categorised as low (<50/m2), medium (50-500/m2) and high (> or = 500/m2) productivity. A total of 120 water bodies were surveyed and 105 (87.5%) had Azolla microphyla and A. pinnata at varying degrees of coverage. Of the total 105 water bodies with Azolla, 80 (76.2%) had a green Azolla mat, and 25 (23.8%) a brown Azolla mat. Eighty-eight (73.3%) of the sites were infested with anophelines and 109 (90.8%) with culicine larvae. Seventy percent of all water bodies contained anophelines and culicines in sympatric breeding, while 20.8% and 3.3% had only culicines and anophelines, respectively. The majority (82%) of mosquito breeding sites were found in area with Azolla substrate. Mosquito larva productivity was low in sites with highest (>80%) Azolla coverage. Seventy-two (81.8%) of the anopheline and 90 (82.6%) culicine breeding sites were infested with Azolla. Water bodies infested with green Azolla were more productive than those covered by brown coloured Azolla substrates for both culicines (13%) and anophelines (8%). Of the 1537 field collected larvae that hatched to adult stage, 646 (42.03%) were Anopheles gambiae s.l., 42 (2.73%) were An. funestus and 769 (50.03%) were Culex quinquefasciatus. These findings suggest that the

Identification of mosquito larval habitats in high resolution satellite data

NASA Astrophysics Data System (ADS)

Kiang, Richard K.; Hulina, Stephanie M.; Masuoka, Penny M.; Claborn, David M.

2003-09-01

Mosquito-born infectious diseases are a serious public health concern, not only for the less developed countries, but also for developed countries like the U.S. Larviciding is an effective method for vector control and adverse effects to non-target species are minimized when mosquito larval habitats are properly surveyed and treated. Remote sensing has proven to be a useful technique for large-area ground cover mapping, and hence, is an ideal tool for identifying potential larval habitats. Locating small larval habitats, however, requires data with very high spatial resolution. Textural and contextual characteristics become increasingly evident at higher spatial resolution. Per-pixel classification often leads to suboptimal results. In this study, we use pan-sharpened Ikonos data, with a spatial resolution approaching 1 meter, to classify potential mosquito larval habitats for a test site in South Korea. The test site is in a predominantly agricultural region. When spatial characteristics were used in conjunction with spectral data, reasonably good classification accuracy was obtained for the test site. In particular, irrigation and drainage ditches are important larval habitats but their footprints are too small to be detected with the original spectral data at 4-meter resolution. We show that the ditches are detectable using automated classification on pan-sharpened data.

Granulomatous responses in larval taeniid infections.

PubMed

Díaz, Á; Sagasti, C; Casaravilla, C

2018-05-01

Granulomas are responses to persistent nonliving bodies or pathogens, centrally featuring specialized macrophage forms called epithelioid and multinucleated giant cells. The larval stages of the cestode parasites of the Taeniidae family (Taenia, Echinococcus) develop for years in fixed tissue sites in mammals. In consequence, they are targets of granulomatous responses. The information on tissue responses to larval taeniids is fragmented among host and parasite species and scattered over many decades. We attempt to draw an integrated picture of these responses in solid tissues. The intensity of inflammation around live parasites spans a spectrum from minimal to high, parasite vitality correlating with low inflammation. The low end of the inflammatory spectrum features collagen capsules proximal to the parasites and moderate distal infiltration. The middle of the spectrum is dominated by classical granulomatous responses, whereas the high end features massive eosinophil invasions. Across the range of parasite species, much observational evidence suggests that eosinophils are highly effective at killing larval taeniids in solid tissues, before and during chronic granulomatous responses. The evidence available also suggests that these parasites are adapted to inhibit host granulomatous responses, in part through the exacerbation of host regulatory mechanisms including regulatory T cells and TGF-β. © 2018 John Wiley & Sons Ltd.

‘Peer pressure’ in larval Drosophila?

PubMed Central

Niewalda, Thomas; Jeske, Ines; Michels, Birgit; Gerber, Bertram

2014-01-01

ABSTRACT Understanding social behaviour requires a study case that is simple enough to be tractable, yet complex enough to remain interesting. Do larval Drosophila meet these requirements? In a broad sense, this question can refer to effects of the mere presence of other larvae on the behaviour of a target individual. Here we focused in a more strict sense on ‘peer pressure’, that is on the question of whether the behaviour of a target individual larva is affected by what a surrounding group of larvae is doing. We found that innate olfactory preference of a target individual was neither affected (i) by the level of innate olfactory preference in the surrounding group nor (ii) by the expression of learned olfactory preference in the group. Likewise, learned olfactory preference of a target individual was neither affected (iii) by the level of innate olfactory preference of the surrounding group nor (iv) by the learned olfactory preference the group was expressing. We conclude that larval Drosophila thus do not take note of specifically what surrounding larvae are doing. This implies that in a strict sense, and to the extent tested, there is no social interaction between larvae. These results validate widely used en mass approaches to the behaviour of larval Drosophila. PMID:24907371

Mechanistic insights into the effects of climate change on larval cod.

PubMed

Kristiansen, Trond; Stock, Charles; Drinkwater, Kenneth F; Curchitser, Enrique N

2014-05-01

Understanding the biophysical mechanisms that shape variability in fisheries recruitment is critical for estimating the effects of climate change on fisheries. In this study, we used an Earth System Model (ESM) and a mechanistic individual-based model (IBM) for larval fish to analyze how climate change may impact the growth and survival of larval cod in the North Atlantic. We focused our analysis on five regions that span the current geographical range of cod and are known to contain important spawning populations. Under the SRES A2 (high emissions) scenario, the ESM-projected surface ocean temperatures are expected to increase by >1 °C for 3 of the 5 regions, and stratification is expected to increase at all sites between 1950-1999 and 2050-2099. This enhanced stratification is projected to decrease large (>5 μm ESD) phytoplankton productivity and mesozooplankton biomass at all 5 sites. Higher temperatures are projected to increase larval metabolic costs, which combined with decreased food resources will reduce larval weight, increase the probability of larvae dying from starvation and increase larval exposure to visual and invertebrate predators at most sites. If current concentrations of piscivore and invertebrate predators are maintained, larval survival is projected to decrease at all five sites by 2050-2099. In contrast to past observed responses to climate variability in which warm anomalies led to better recruitment in cold-water stocks, our simulations indicated that reduced prey availability under climate change may cause a reduction in larval survival despite higher temperatures in these regions. In the lower prey environment projected under climate change, higher metabolic costs due to higher temperatures outweigh the advantages of higher growth potential, leading to negative effects on northern cod stocks. Our results provide an important first large-scale assessment of the impacts of climate change on larval cod in the North Atlantic. © 2013 John

Effects of pulsed, high-velocity water flow on larval robust redhorse and V-lip redhorse

USGS Publications Warehouse

Weyers, R.S.; Jennings, C.A.; Freeman, Mary C.

2003-01-01

The pulsed, high-velocity water flow characteristic of water-flow patterns downstream from hydropower-generating dams has been implicated in the declining abundance of both aquatic insects and fishes in dam-regulated rivers. This study examined the effects of 0, 4, and 12 h per day of pulsed, high-velocity water flow on the egg mortality, hatch length, final length, and survival of larval robust redhorse Moxostoma robusturn, a presumedly extinct species that was rediscovered in the 1990s, and V-lip redhorse M. collapsum (previously synonomized with the silver redhorse M. anisurum) over a 3-5 week period in three separate experiments. Twelve 38.0-L aquaria (four per treatment) were modified to simulate pulsed, high-velocity water flow (>35 cm/s) and stable, low-velocity water flow (<10 cm/s). Temperature, dissolved oxygen, zooplankton density, and water quality variables were kept the same across treatments. Fertilized eggs were placed in gravel nests in each aquarium. Hatch success was estimated visually at greater than 90%, and the mean larval length at 24 h posthatch was similar in each experiment. After emergence from the gravel nest, larvae exposed to 4 and 12 h of pulsed, high-velocity water flow grew significantly more slowly and had lower survival than those in the 0-h treatment. These results demonstrate that the altered water-flow patterns that typically occur when water is released during hydropower generation can have negative effects on the growth and survival of larval catostomid suckers.

The effects of exposure in sandy beach surf zones on larval fishes.

PubMed

Pattrick, P; Strydom, N A

2014-05-01

The influence of wind and wave exposure on larval fish assemblages within a large bay system was investigated. Larval fishes were sampled from two areas with vastly different exposure to waves and wind, namely the windward and leeward sectors of Algoa Bay. In total, 5702 larval fishes were collected using a modified larval seine. Of these, 4391 were collected in the leeward and 1311 in the windward sector of the bay, representing a total of 23 families and 57 species. Dominant fish families included Clinidae, Engraulidae, Kyphosidae, Mugilidae, Soleidae and Sparidae, similar to the situation elsewhere, highlighting continuity in the composition of larval fish assemblages and the utilization of surf zones by a specific group of larval fishes. Nineteen estuary-associated marine species occurred within the surf zones of Algoa Bay and dominated catches (86·7%) in terms of abundance. Postflexion larvae comprised > 80% of the catch, indicating the importance of the seemingly inhospitable surf zone environment for the early life stages of many fish species. The greatest species diversity was observed within the windward sector of the bay. Distance-based linear modelling identified wave period as the environmental variable explaining the largest proportion of the significant variation in the larval fish assemblage. The physical disturbance generated by breaking waves could create a suitable environment for fish larvae, sheltered from predators and with an abundance of food resources. © 2014 The Fisheries Society of the British Isles.

Hypothalamic Projections to the Optic Tectum in Larval Zebrafish.

PubMed

Heap, Lucy A; Vanwalleghem, Gilles C; Thompson, Andrew W; Favre-Bulle, Itia; Rubinsztein-Dunlop, Halina; Scott, Ethan K

2017-01-01

The optic tectum of larval zebrafish is an important model for understanding visual processing in vertebrates. The tectum has been traditionally viewed as dominantly visual, with a majority of studies focusing on the processes by which tectal circuits receive and process retinally-derived visual information. Recently, a handful of studies have shown a much more complex role for the optic tectum in larval zebrafish, and anatomical and functional data from these studies suggest that this role extends beyond the visual system, and beyond the processing of exclusively retinal inputs. Consistent with this evolving view of the tectum, we have used a Gal4 enhancer trap line to identify direct projections from rostral hypothalamus (RH) to the tectal neuropil of larval zebrafish. These projections ramify within the deepest laminae of the tectal neuropil, the stratum album centrale (SAC)/stratum griseum periventriculare (SPV), and also innervate strata distinct from those innervated by retinal projections. Using optogenetic stimulation of the hypothalamic projection neurons paired with calcium imaging in the tectum, we find rebound firing in tectal neurons consistent with hypothalamic inhibitory input. Our results suggest that tectal processing in larval zebrafish is modulated by hypothalamic inhibitory inputs to the deep tectal neuropil.

Synchronized Oviposition Triggered by Migratory Flight Intensifies Larval Outbreaks of Beet Webworm

PubMed Central

Cheng, Yun Xia; Luo, Li Zhi; Jiang, Xing Fu; Sappington, Thomas W.

2012-01-01

Identifying the reproductive consequences of insect migration is critical to understanding its ecological and evolutionary significance. However, many empirical studies are seemingly contradictory, making recognition of unifying themes elusive and controversial. The beet webworm, Loxostege sticticalis L. is a long-range migratory pest of many crops in the northern temperate zone from 36°N to 55°N, with larval populations often exploding in regions receiving immigrants. In laboratory experiments, we examined (i) the reproductive costs of migratory flight by tethered flight, and (ii) the reproductive traits contributing to larval outbreaks of immigrant populations. Our results suggest that the beet webworm does not initiate migratory flight until the 2nd or 3rd night after emergence. Preoviposition period, lifetime fecundity, mating capacity, and egg hatch rate for adults that experienced prolonged flight after the 2nd night did not differ significantly from unflown moths, suggesting these traits are irrelevant to the severity of beet webworm outbreaks after migration. However, the period of first oviposition, a novel parameter developed in this paper measuring synchrony of first egg-laying by cohorts of post-migratory females, for moths flown on d 3 and 5 of adulthood was shorter than that of unflown moths, indicating a tightened time-window for onset of oviposition after migration. The resulting synchrony of egg-laying will serve to increase egg and subsequent larval densities. A dense population offers potential selective advantages to the individual larvae comprising it, whereas the effect from the human standpoint is intensification of damage by an outbreak population. The strategy of synchronized oviposition may be common in other migratory insect pests, such as locust and armyworm species, and warrants further study. PMID:22347494

Effects of beach morphology and waves on onshore larval transport

NASA Astrophysics Data System (ADS)

Fujimura, A.; Reniers, A.; Paris, C. B.; Shanks, A.; MacMahan, J.; Morgan, S.

2015-12-01

Larvae of intertidal species grow offshore, and migrate back to the shore when they are ready to settle on their adult substrates. In order to reach the habitat, they must cross the surf zone, which is characterized as a semi-permeable barrier. This is accomplished through physical forcing (i.e., waves and current) as well as their own behavior. Two possible scenarios of onshore larval transport are proposed: Negatively buoyant larvae stay in the bottom boundary layer because of turbulence-dependent sinking behavior, and are carried toward the shore by streaming of the bottom boundary layer; positively buoyant larvae move to the shore during onshore wind events, and sink to the bottom once they encounter high turbulence (i.e., surf zone edge), where they are carried by the bottom current toward the shore (Fujimura et al. 2014). Our biophysical Lagrangian particle tracking model helps to explain how beach morphology and wave conditions affect larval distribution patterns and abundance. Model results and field observations show that larval abundance in the surf zone is higher at mildly sloped, rip-channeled beaches than at steep pocket beaches. Beach attributes are broken up to examine which and how beach configuration factors affect larval abundance. Modeling with alongshore uniform beaches with variable slopes reveal that larval populations in the surf zone are negatively correlated with beach steepness. Alongshore variability enhances onshore larval transport because of increased cross-shore water exchange by rip currents. Wave groups produce transient rip currents and enhance cross-shore exchange. Effects of other wave components, such as wave height and breaking wave rollers are also considered.

Remotely Sensing Larval Population Dynamics of Rice Field Anophelines

NASA Technical Reports Server (NTRS)

Beck, Louisa R.; Dister, Sheri W.; Wood, Byron L.; Washino, Robert K.

1997-01-01

The primary objective of both studies was to determine if RS and GIS techniques could be used to distinguish between high and low larval-producing rice fields in California. Results of the first study suggested that early-season green-up and proximity to livestock pastures were positively correlated with high larval abundance. Based on the early-season spectral differences between high and low larval-producing fields, it appeared that canopy development and tillering influenced mosquito habitat quality. At that time, rice fields consisted of a mixture of plants and water, a combination that allowed An. freeborni females to lay eggs in partial sunlight, protected from both predators and wind. This established a population earlier in the season than in other, 'less-green' fields where tillering and plant emergence was too minimal for ovipositioning. The study also indicated the importance of the distance that a mosquito would have to fly in order to take a bloodmeal prior to ovipositing. These associations were fully explored in an expanded study two years later. The second study confirmed the positive relationship between early season canopy development and larval abundance, and also demonstrated the relationship between abundance and distance-to-pasture. The association between greenness (as measured using NDVI), distance-to-pasture, and abundance is illustrated. The second study also indicated the siginificance of the landscape context of rice fields for larval production. Fields that included opportunities for feeding and resting within the flight range of the mosquito had higher abundances than did fields that were in a homogeneous rice area.

Exposure to 2,4-decadienal negatively impacts upon marine invertebrate larval fitness.

PubMed

Caldwell, Gary S; Lewis, Ceri; Olive, Peter J W; Bentley, Matthew G

2005-06-01

Diatoms liberate volatile, biologically active unsaturated aldehydes following cell damage, which negatively impact upon invertebrate reproductive processes such as fertilization, embryogenesis and larval survival. 2,4-Decadienal is frequently identified among the aldehydes produced and is one of the more biologically active. The majority of studies which have examined the toxic effects of diatom aldehydes to invertebrate reproduction have scored egg production and/or hatching success as indicators of biological impacts. There are very few studies which have dealt specifically with the impacts of diatom-derived aldehydes on larval fitness. Larval stages of the polychaetes Arenicola marina and Nereis virens and the echinoderms Asterias rubens and Psammechinus miliaris exposed to 2,4-decadienal at sub 1 microg ml(-1) concentrations suffered reduced survival over the incubation period (day 1-8 post fertilization) with detectable differences for the polychates at a concentration of 0.005 and 0.01-0.1 microg ml(-1) for the echinoderms. Susceptibility of larval N. virens was investigated using stage specific 24 h exposures at 2,4-decadienal concentrations up to 1.5 microg ml(-1). A clear stage specific effect was found, with earlier larval stages most vulnerable. Nectochaete larvae (9-10 d) showed no reduction in survival at the concentrations assayed. Fluctuating asymmetry (FA), defined as random deviations from perfect bilateral symmetry, was used to analyse fitness of larval P. miliaris exposed to 2,4-decadienal at concentrations of 0.1, 0.5 and 1 microg ml(-1). The degree and frequency of asymmetrical development increased with increasing 2,4-decadienal concentration. Equally, as FA increased larval survival decreased. These results provide further support for the teratogenic nature of 2,4-decadienal and its negative impact on invertebrate larval fitness.

Larval descriptions of the family Porcellanidae: A worldwide annotated compilation of the literature (Crustacea, Decapoda)

PubMed Central

Vela, María José; González-Gordillo, Juan Ignacio

2016-01-01

Abstract For most of the family Porcellanidae, which comprises 283 species, larval development remains to be described. Full development has been only described for 52 species, while part of the larval cycle has been described for 45 species. The importance of knowing the complete larval development of a species goes beyond allowing the identification of larval specimens collected in the plankton. Morphological larval data also constitute a support to cladistic techniques used in the establishment of the phylogenetic status (see Hiller et al. 2006, Marco-Herrero et al. 2013). Nevertheless, the literature on the larval development of this family is old and widely dispersed and in many cases it is difficult to collect the available information on a particular taxon. Towards the aim of facilitating future research, all information available on the larval development of porcellanids has been compiled. Following the taxonomic checklist of Porcellanidae proposed by Osawa and McLaughlin (2010), a checklist has been prepared that reflects the current knowledge about larval development of the group including larval stages and the method used to obtain the larvae, together with references. Those species for which the recognised names have been changed according to Osawa and McLaughlin (2010) are indicated. PMID:27081332

Vegetative substrates used by larval northern pike in Rainy and Kabetogama Lakes, Minnesota

Treesearch

Anne L. Timm; Rodney B. Pierce

2015-01-01

Our objective was to identify characteristics of aquatic vegetative communities used as larval northern pike nursery habitat in Rainy and Kabetogama lakes, glacial shield reservoirs in northern Minnesota. Quatrefoil light traps fished at night were used to sample larval northern pike in 11 potential nursery areas. Larval northern pike were most commonly sampled among...

Feeding ecology of pelagic larval Burbot in Northern Lake Huron, Michigan

USGS Publications Warehouse

George, Ellen M.; Roseman, Edward F.; Davis, Bruce M.; O'Brien, Timothy P.

2013-01-01

Burbot Lota lota are a key demersal piscivore across the Laurentian Great Lakes whose populations have declined by about 90% in recent decades. Larval Burbot typically hatch in the early spring and rely on abundant crustacean zooplankton prey. We examined the stomach contents of larval Burbot from inshore (≤15 m) and offshore sites (37 and 91 m) in northern Lake Huron, Michigan. Concurrent zooplankton vertical tows at the same sites showed that the prey community was dominated by calanoid copepods, dreissenid mussel veligers, and rotifers. Burbot consumed mostly cyclopoid copepods, followed by copepod nauplii and calanoid copepods. Chesson's index of selectivity was calculated and compared among sites and months for individual Burbot. According to this index, larval Burbot exhibited positive selection for cyclopoid copepods and copepod nauplii and negative selection for calanoid copepods, cladocerans, rotifers, and dreissenid veligers. This selectivity was consistent across sites and throughout the sampling period. Burbot displayed little variation in their prey preferences during the larval stage, which suggests that the recent shifts in zooplankton abundance due to the invasion of the predatory zooplankter Bythotrephes longimanus and competition from invasive Rainbow Smelt Osmerus mordax could negatively impact larval Burbot populations.

Is mosquito larval source management appropriate for reducing malaria in areas of extensive flooding in The Gambia? A cross-over intervention trial.

PubMed

Majambere, Silas; Pinder, Margaret; Fillinger, Ulrike; Ameh, David; Conway, David J; Green, Clare; Jeffries, David; Jawara, Musa; Milligan, Paul J; Hutchinson, Robert; Lindsay, Steven W

2010-02-01

Larviciding to control malaria was assessed in rural areas with extensive seasonal flooding. Larval and adult mosquitoes and malaria incidence were surveyed routinely in four 100-km(2) areas either side of the Gambia River. Baseline data were collected in 2005. Microbial larvicide was applied to all water bodies by hand application with water-dispersible granular formulations and corn granules weekly from May to November in two areas in 2006 and in the other two areas in 2007 in a cross-over design. The intervention was associated with a reduction in habitats with late stage anopheline larvae and an 88% reduction in larval densities (P < 0.001). The effect of the intervention on mosquito densities was not pronounced and was confounded by the distance of villages to the major breeding sites and year (P = 0.002). There was no reduction in clinical malaria or anemia. Ground applications of non-residual larvicides with simple equipment are not effective in riverine areas with extensive flooding, where many habitats are poorly demarcated, highly mobile, and inaccessible on foot.

Evolved differences in larval social behavior mediated by novel pheromones

PubMed Central

Mast, Joshua D; De Moraes, Consuelo M; Alborn, Hans T; Lavis, Luke D; Stern, David L

2014-01-01

Pheromones, chemical signals that convey social information, mediate many insect social behaviors, including navigation and aggregation. Several studies have suggested that behavior during the immature larval stages of Drosophila development is influenced by pheromones, but none of these compounds or the pheromone-receptor neurons that sense them have been identified. Here we report a larval pheromone-signaling pathway. We found that larvae produce two novel long-chain fatty acids that are attractive to other larvae. We identified a single larval chemosensory neuron that detects these molecules. Two members of the pickpocket family of DEG/ENaC channel subunits (ppk23 and ppk29) are required to respond to these pheromones. This pheromone system is evolving quickly, since the larval exudates of D. simulans, the sister species of D. melanogaster, are not attractive to other larvae. Our results define a new pheromone signaling system in Drosophila that shares characteristics with pheromone systems in a wide diversity of insects. DOI: http://dx.doi.org/10.7554/eLife.04205.001 PMID:25497433

Phormidium animalis (Cyanobacteria: Oscillatoriaceae) supports larval development of Anopheles albimanus.

PubMed

Vázquez-Martínez, M Guadalupe; Rodríguez, Mario H; Arredondo-Jiménez, Juan I; Méndez-Sánchez, José D

2003-06-01

The capability of Phormidium animalis, a cyanobacterium commonly found in larval habitats of Anopheles albimanus in southern Mexico, to support larval development of this mosquito was investigated. First-stage larvae were reared under insectary conditions with P. animalis ad libitum and their development was compared with larvae fed with wheat germ. The time of pupation and adult mosquito size, assessed by wing length, were similar in both groups, but fewer adult mosquitoes were obtained from larvae fed with the cyanobacteria. Nevertheless, these observations indicate that P. animalis is ingested and assimilated by larval An. albimanus, making this cyanobacterium a good candidate for genetic engineering for the introduction of mosquitocidal toxins for malaria control in the region.

Swimming behavior of larval Medaka fish under microgravity

NASA Astrophysics Data System (ADS)

Furukawa, R.; Ijiri, K.

Fish exhibit looping and rolling behaviors when subjected to short periods of microgravity during parabolic flight. Strain-differences in the behavioral response of adult Medaka fish ( Oryzias latipes) were reported previously, however, there have been few studies of larval fish behavior under microgravity. In the present study, we investigated whether microgravity affects the swimming behavior of larvae at various ages (0 to 20 days after hatching), using different strains: HNI-II, HO5, ha strain, and variety of different strains (variety). The preliminary experiments were done in the ground laboratory: the development of eyesight was examined using optokinetic response for the different strains. The visual acuity of larvae improved drastically during 20 days after hatching. Strain differences of response were noted for the development of their visual acuity. In microgravity, the results were significantly different from those of adult Medaka. The larval fish appeared to maintain their orientation, except that a few of them exhibited looping and rolling behavior. Further, most larvae swam normally with their backs turning toward the light source (dorsal light response, DLR), and the rest of them stayed with their abdomen touching the surface of the container (ventral substrate response, VSR). For larval stages, strain-differences and age-differences in behavior were observed, but less pronounced than with adult fish under microgravity. Our observations suggest that adaptability of larval fish to the gravitational change and the mechanism of their postural control in microgravity are more variable than in adult fish.

Hypothalamic Projections to the Optic Tectum in Larval Zebrafish

PubMed Central

Heap, Lucy A.; Vanwalleghem, Gilles C.; Thompson, Andrew W.; Favre-Bulle, Itia; Rubinsztein-Dunlop, Halina; Scott, Ethan K.

2018-01-01

The optic tectum of larval zebrafish is an important model for understanding visual processing in vertebrates. The tectum has been traditionally viewed as dominantly visual, with a majority of studies focusing on the processes by which tectal circuits receive and process retinally-derived visual information. Recently, a handful of studies have shown a much more complex role for the optic tectum in larval zebrafish, and anatomical and functional data from these studies suggest that this role extends beyond the visual system, and beyond the processing of exclusively retinal inputs. Consistent with this evolving view of the tectum, we have used a Gal4 enhancer trap line to identify direct projections from rostral hypothalamus (RH) to the tectal neuropil of larval zebrafish. These projections ramify within the deepest laminae of the tectal neuropil, the stratum album centrale (SAC)/stratum griseum periventriculare (SPV), and also innervate strata distinct from those innervated by retinal projections. Using optogenetic stimulation of the hypothalamic projection neurons paired with calcium imaging in the tectum, we find rebound firing in tectal neurons consistent with hypothalamic inhibitory input. Our results suggest that tectal processing in larval zebrafish is modulated by hypothalamic inhibitory inputs to the deep tectal neuropil. PMID:29403362

Measuring larval nematode contamination on cattle pastures: Comparing two herbage sampling methods.

PubMed

Verschave, S H; Levecke, B; Duchateau, L; Vercruysse, J; Charlier, J

2015-06-15

Assessing levels of pasture larval contamination is frequently used to study the population dynamics of the free-living stages of parasitic nematodes of livestock. Direct quantification of infective larvae (L3) on herbage is the most applied method to measure pasture larval contamination. However, herbage collection remains labour intensive and there is a lack of studies addressing the variation induced by the sampling method and the required sample size. The aim of this study was (1) to compare two different sampling methods in terms of pasture larval count results and time required to sample, (2) to assess the amount of variation in larval counts at the level of sample plot, pasture and season, respectively and (3) to calculate the required sample size to assess pasture larval contamination with a predefined precision using random plots across pasture. Eight young stock pastures of different commercial dairy herds were sampled in three consecutive seasons during the grazing season (spring, summer and autumn). On each pasture, herbage samples were collected through both a double-crossed W-transect with samples taken every 10 steps (method 1) and four random located plots of 0.16 m(2) with collection of all herbage within the plot (method 2). The average (± standard deviation (SD)) pasture larval contamination using sampling methods 1 and 2 was 325 (± 479) and 305 (± 444)L3/kg dry herbage (DH), respectively. Large discrepancies in pasture larval counts of the same pasture and season were often seen between methods, but no significant difference (P = 0.38) in larval counts between methods was found. Less time was required to collect samples with method 2. This difference in collection time between methods was most pronounced for pastures with a surface area larger than 1 ha. The variation in pasture larval counts from samples generated by random plot sampling was mainly due to the repeated measurements on the same pasture in the same season (residual variance

Hydrodynamic Constraints of Suction Feeding in Low Reynolds Numbers, and the Critical Period of Larval Fishes.

PubMed

Holzman, Roi; China, Victor; Yaniv, Sarit; Zilka, Miri

2015-07-01

Larval fishes suffer prodigious mortality rates, eliminating 99% of the cohort within a few days after their first feeding. Hjort (1914) famously attributed this "critical period" of low survival to larval inability to obtain sufficient food. We discuss recent experimental and modeling work, suggesting that the viscous hydrodynamic regime have marked effects on the mechanism of suction feeding in larval fish. As larvae grow, the size of the gape and associated volume of the mouth increase. At the same time, larvae swim faster and can generate faster suction flows, thus transiting to a hydrodynamic regime of higher Reynolds numbers. This hydrodynamic regime further leads to changes in the spatio-temporal patterns of flow in front of the mouth, and an increasing ability in larger larvae to exert suction forces on the prey. Simultaneously, the increase in swimming speed and the distance from which the prey is attacked result in higher rates of encountering prey by larger (older) larvae. In contrast, during the first few days after feeding commence the lower rates of encounter and success in feeding translate to low feeding rates. We conclude that young larvae experience "hydrodynamic starvation," in which low Reynolds numbers mechanically limit their feeding performance even under high densities of prey. © The Author 2015. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

Potential exposure of larval and juvenile delta smelt to dissolved pesticides in the Sacramento-San Joaquin Delta, California

USGS Publications Warehouse

Kuivila, K.M.; Moon, G.E.

2004-01-01

The San Francisco Estuary is critical habitat for delta smelt Hypomesus transpacificus, a fish whose abundance has declined greatly since 1983 and is now listed as threatened. In addition, the estuary receives drainage from the Central Valley, an urban and agricultural region with intense and diverse pesticide usage. One possible factor of the delta smelt population decline is pesticide toxicity during vulnerable larval and juvenile stages, but pesticide concentrations are not well characterized in delta smelt spawning and nursery habitat. The objective of this study was to estimate the potential exposure of delta smelt during their early life stages to dissolved pesticides. For 3 years (1998-2000), water samples from the Sacramento-San Joaquin Delta were collected during April-June in coordination with the California Department of Fish and Game's delta smelt early life stage monitoring program. Samples were analyzed for pesticides using solid-phase extraction and gas chromatography/mass spectrometry. Water samples contained multiple pesticides, ranging from 2 to 14 pesticides in each sample. In both 1999 and 2000, elevated concentrations of pesticides overlapped in time and space with peak densities of larval and juvenile delta smelt. In contrast, high spring outflows in 1998 transported delta smelt away from the pesticide sampling sites so that exposure could not be estimated. During 2 years, larval and juvenile delta smelt were potentially exposed to a complex mixture of pesticides for a minimum of 2-3 weeks. Although the measured concentrations were well below short-term (96-h) LC50 values for individual pesticides, the combination of multiple pesticides and lengthy exposure duration could potentially have lethal or sublethal effects on delta smelt, especially during early larval development.

Chronic toxicity of azo and anthracenedione dyes to embryo-larval fathead minnow.

PubMed

Parrott, Joanne L; Bartlett, Adrienne J; Balakrishnan, Vimal K

2016-03-01

The toxicity of selected azo and anthracenedione dyes was studied using chronic exposures of embryo-larval fathead minnows (Pimephales promelas). Newly fertilized fathead minnow embryos were exposed through the egg stage, past hatching, through the larval stage (until 14 days post-hatch), with dye solutions renewed daily. The anthracenedione dyes Acid Blue 80 (AB80) and Acid Blue 129 (AB129) caused no effects in larval fish at the highest measured concentrations tested of 7700 and 6700 μg/L, respectively. Both azo dyes Disperse Yellow 7 (DY7) and Sudan Red G (SRG) decreased survival of larval fish, with LC50s (based on measured concentrations of dyes in fish exposure water) of 25.4 μg/L for DY7 and 16.7 μg/L for SRG. Exposure to both azo dyes caused a delayed response, with larval fish succumbing 4-10 days after hatch. If the exposures were ended at the embryo stage or just after hatch, the potency of these two dyes would be greatly underestimated. Concentrations of dyes that we measured entering the Canadian environment were much lower than those that affected larval fish survival in the current tests. In a total of 162 samples of different municipal wastewater effluents from across Canada assessed for these dyes, all were below detection limits. The similarities of the structures and larval fish responses for the two azo and two anthracenedione dyes in this study support the use of read-across data for risk assessment of these classes of compounds. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

LABORATORY EVOLUTION OF LIFE-HISTORY TRAITS IN THE BEAN WEEVIL (ACANTHOSCELIDES OBTECTUS): THE EFFECTS OF DENSITY-DEPENDENT AND AGE-SPECIFIC SELECTION.

PubMed

Tucić, Nikola; Stojković, Oliver; Gliksman, Ivana; Milanović, Agana; Šešlija, Darka

1997-12-01

Four types of laboratory populations of the bean weevil (Acanthoscelides obtectus) have been developed to study the effects of density-dependent and age-specific selection. These populations have been selected at high (K) and low larval densities (r) as well as for reproduction early (Y) and late (O) in life. The results presented here suggest that the r- and K-populations (density-dependent selection regimes) have differentiated from each other with respect to the following life-history traits: egg-to-adult viability at high larval density (K > r), preadult developmental time (r > K), body weight (r > K), late fecundity (K > r), total realized fecundity (r > K), and longevity of males (r > K). It was also found that the following traits responded in statistically significant manner in populations subjected to different age-specific selection regimes: egg-to-adult viability (O > Y), body weight (O > Y), early fecundity (Y > O), late fecundity (O > Y), and longevity of females and males (O > Y). Although several life-history traits (viability, body weight, late fecundity) responded in similar manner to both density-dependent and age-specific selection regimes, it appears that underlying genetic and physiological mechanisms responsible for differentiation of the r/K and Y/O populations are different. We have also tested quantitative genetic basis of the bean weevil life-history traits in the populations experiencing density-dependent and age-specific selection. Among the traits traded-off within age-specific selection regimes, only early fecundity showed directional dominance, whereas late fecundity and longevity data indicated additive inheritance. In contrast to age-specific selecton regimes, three life-history traits (developmental time, body size, total fecundity) in the density-sependent regimes exhibited significant dominance effects. Lastly, we have tested the congruence between short-term and long-term effects of larval densities. The comparisons of the

Effects of open marsh water management on numbers of larval salt marsh mosquitoes

USGS Publications Warehouse

James-Pirri, Mary-Jane; Ginsberg, Howard S.; Erwin, R. Michael; Taylor, Janith

2009-01-01

Open marsh water management (OMWM) is a commonly used approach to manage salt marsh mosquitoes than can obviate the need for pesticide application and at the same time, partially restore natural functions of grid-ditched marshes. OMWM includes a variety of hydrologic manipulations, often tailored to the specific conditions on individual marshes, so the overall effectiveness of this approach is difficult to assess. Here, we report the results of controlled field trials to assess the effects of two approaches to OMWM on larval mosquito production at National Wildlife Refuges (NWR). A traditional OMWM approach, using pond construction and radial ditches was used at Edwin B. Forsythe NWR in New Jersey, and a ditch-plugging approach was used at Parker River NWR in Massachusetts. Mosquito larvae were sampled from randomly placed stations on paired treatment and control marshes at each refuge. The proportion of sampling stations that were wet declined after OMWM at the Forsythe site, but not at the Parker River site. The proportion of samples with larvae present and mean larval densities, declined significantly at the treatment sites on both refuges relative to the control marshes. Percentage of control for the 2 yr posttreatment, compared with the 2 yr pretreatment, was >90% at both treatment sites.

Growing Pains: Development of the Larval Nocifensive Response in Drosophila

PubMed Central

SULKOWSKI, MIKOLAJ J.; KUROSAWA, MATHIEU S.; OX, DANIEL N.

2014-01-01

The ability to perceive and avoid harmful substances or stimuli is key to an organism’s survival. The neuronal cognate of the perception of pain is known as nociception, and the reflexive motion to avoid pain is termed the nocifensive response. As the nocifensive response is an ancient and evolutionarily conserved behavioral response to nociceptive stimuli, it is amenable to study in relatively simple and genetically tractable model systems such as Drosophila. Recent studies have taken advantage of the useful properties of Drosophila larvae to begin elucidating the neuronal connectivity and molecular machinery underlying the nocifensive response. However, these studies have primarily utilized the third-instar larval stage, and many mutations that potentially influence nociception survive only until earlier larval stages. Here we characterize the nocifensive responses of Drosophila throughout larval development and find dramatic changes in the nature of the behavior. Notably, we find that prior to the third instar, larvae are unable to perform the characteristic “corkscrew-like roll” behavior. Also, we identify an avoidance behavior consistent with a nocifensive response that is present immediately after larval hatching, representing a paradigm that may be useful in examining mutations with an early lethal phenotype. PMID:22186918

Do larval fishes exhibit diel drift patterns in a large, turbid river?

USGS Publications Warehouse

Reeves, K.S.; Galat, D.L.

2010-01-01

Previous research suggested larval fishes do not exhibit a diel drift cycle in turbid rivers (transparency <30 cm). We evaluated this hypothesis in the turbid, lower Missouri River, Missouri. We also reviewed diel patterns of larval drift over a range of transparencies in rivers worldwide. Larval fishes were collected from the Missouri River primary channel every 4 h per 24-h period during spring-summer 2002. Water transparency was measured during this period and summarized for previous years. Diel drift patterns were analyzed at the assemblage level and lower taxonomic levels for abundant groups. Day and night larval fish catch-per-unit-effort (CPUE) was compared for the entire May through August sampling period and spring (May - June) and summer (July - August) seasons separately. There were no significant differences between day and night CPUE at the assemblage level for the entire sampling period or for the spring and summer seasons. However, Hiodon alosoides, Carpiodes/Ictiobus spp. and Macrhybopsis spp. exhibited a diel cycle of abundance within the drift. This pattern was evident although mean Secchi depth (transparency) ranged from 4 to 25 cm during the study and was <30 cm from May through August over the previous nine years. Larval diel drift studies from 48 rivers excluding the Missouri River indicated the primary drift period for larval fishes was at night in 38 rivers and during the day for five, with the remaining rivers showing no pattern. Water transparency was reported for 10 rivers with six being <30 cm or 'low'. Two of these six turbid rivers exhibited significant diel drift patterns. The effect of water transparency on diel drift of larval fishes appears taxa-specific and patterns of abundant taxa could mask patterns of rare taxa when analyzed only at the assemblage level. ?? 2010 Blackwell Verlag, Berlin.

Environmental factors limiting fertilisation and larval success in corals

NASA Astrophysics Data System (ADS)

Woods, Rachael M.; Baird, Andrew H.; Mizerek, Toni L.; Madin, Joshua S.

2016-12-01

Events in the early life history of reef-building corals, including fertilisation and larval survival, are susceptible to changes in the chemical and physical properties of sea water. Quantifying how changes in water quality affect these events is therefore important for understanding and predicting population establishment in novel and changing environments. A review of the literature identified that levels of salinity, temperature, pH, suspended sediment, nutrients and heavy metals affect coral early life-history stages to various degrees. In this study, we combined published experimental data to determine the relative importance of sea water properties for coral fertilisation success and larval survivorship. Of the water properties manipulated in experiments, fertilisation success was most sensitive to suspended sediment, copper, salinity, phosphate and ammonium. Larval survivorship was sensitive to copper, lead and salinity. A combined model was developed that estimated the joint probability of both fertilisation and larval survivorship in sea water with different chemical and physical properties. We demonstrated the combined model using water samples from Sydney and Lizard Island in Australia to estimate the likelihood of larvae surviving through both stages of development to settlement competency. Our combined model could be used to recommend targets for water quality in coastal waterways as well as to predict the potential for species to expand their geographical ranges in response to climate change.

Investigating phenology of larval fishes in St. Louis River ...

EPA Pesticide Factsheets

As part of the development of an early detection monitoring strategy for non-native fishes, larval fish surveys have been conducted since 2012 in the St. Louis River estuary. Survey data demonstrates there is considerable variability in fish abundance and species assemblages across different habitats and at multiple temporal scales. To optimize early detection monitoring we need to understand temporal and spatial patterns of larval fishes related to their development and dispersion, as well as the environmental factors that influence them. In 2016 we designed an experiment to assess the phenological variability in larval fish abundance and assemblages amongst shallow water habitats. Specifically, we sought to contrast different thermal environments and turbidity levels, as well as assess the importance of vegetation in these habitats. To evaluate phenological differences we sampled larval fish bi-weekly at nine locations from mid-May to mid-July. Sampling locations were split between upper estuary and lower estuary to contrast river versus seiche influenced habitats. To assess differences in thermal environments, temperature was monitored every 15 minutes at each sampling location throughout the study, beginning in early April. Our design also included sampling at both vegetated (or pre-vegetated) and non-vegetated stations within each sampling location throughout the study to assess the importance of this habitat variable. Hydroacoustic surveys (Biosonics) were

Larval nematodes found in amphibians from northeastern Argentina.

PubMed

González, C E; Hamann, M I

2010-11-01

Five species of amphibians, Leptodactylus podicipinus, Scinax acuminatus, S. nasicus, Rhinella fernandezae and Pseudis paradoxa, were collected in Corrientes province, Argentina and searched for larval nematodes. All larval nematodes were found as cysts in the serous of the stomach of hosts. Were identified one superfamily, Seuratoidea; one genus, Spiroxys (Superfamily Gnathostomatoidea) and one family, Rhabdochonidae (Superfamily Thelazioidea). We present a description and illustrations of these taxa. These nematodes have an indirect life cycle and amphibians are infected by consuming invertebrate, the intermediate hosts. The genus Spiroxys and superfamily Seuratoidea were reported for the first time for Argentinean amphibians.

Behavorial assessments of larval zebrafish neurotoxicology

EPA Science Inventory

Fishes have long been a popular organism in ecotoxicology research, and are increasingly used in human health research as an alternative animal model for chemical screening. Our laboratory incorporates a zebrafish (Danio rerio) embryo/larval assay to screen chemicals for developm...

Experimental Examination of Intraspecific Density-Dependent Competition during the Breeding Period in Monarch Butterflies (Danaus plexippus)

PubMed Central

Flockhart, D. T. Tyler; Martin, Tara G.; Norris, D. Ryan

2012-01-01

A central goal of population ecology is to identify the factors that regulate population growth. Monarch butterflies (Danaus plexippus) in eastern North America re-colonize the breeding range over several generations that result in population densities that vary across space and time during the breeding season. We used laboratory experiments to measure the strength of density-dependent intraspecific competition on egg laying rate and larval survival and then applied our results to density estimates of wild monarch populations to model the strength of density dependence during the breeding season. Egg laying rates did not change with density but larvae at high densities were smaller, had lower survival, and weighed less as adults compared to lower densities. Using mean larval densities from field surveys resulted in conservative estimates of density-dependent population reduction that varied between breeding regions and different phases of the breeding season. Our results suggest the highest levels of population reduction due to density-dependent intraspecific competition occur early in the breeding season in the southern portion of the breeding range. However, we also found that the strength of density dependence could be almost five times higher depending on how many life-stages were used as part of field estimates. Our study is the first to link experimental results of a density-dependent reduction in vital rates to observed monarch densities in the wild and show that the effects of density dependent competition in monarchs varies across space and time, providing valuable information for developing robust, year-round population models in this migratory organism. PMID:22984614

Passive larval transport explains recent gene flow in a Mediterranean gorgonian

NASA Astrophysics Data System (ADS)

Padrón, Mariana; Costantini, Federica; Baksay, Sandra; Bramanti, Lorenzo; Guizien, Katell

2018-06-01

Understanding the patterns of connectivity is required by the Strategic Plan for Biodiversity 2011-2020 and will be used to guide the extension of marine protection measures. Despite the increasing accuracy of ocean circulation modelling, the capacity to model the population connectivity of sessile benthic species with dispersal larval stages can be limited due to the potential effect of filters acting before or after dispersal, which modulates offspring release or settlement, respectively. We applied an interdisciplinary approach that combined demographic surveys, genetic methods (assignment tests and coalescent-based analyses) and larval transport simulations to test the relative importance of demographics and ocean currents in shaping the recent patterns of gene flow among populations of a Mediterranean gorgonian ( Eunicella singularis) in a fragmented rocky habitat (Gulf of Lion, NW Mediterranean Sea). We show that larval transport is a dominant driver of recent gene flow among the populations, and significant correlations were found between recent gene flow and larval transport during an average single dispersal event when the pelagic larval durations (PLDs) ranged from 7 to 14 d. Our results suggest that PLDs that efficiently connect populations distributed over a fragmented habitat are filtered by the habitat layout within the species competency period. Moreover, a PLD ranging from 7 to 14 d is sufficient to connect the fragmented rocky substrate of the Gulf of Lion. The rocky areas located in the centre of the Gulf of Lion, which are currently not protected, were identified as essential hubs for the distribution of migrants in the region. We encourage the use of a range of PLDs instead of a single value when estimating larval transport with biophysical models to identify potential connectivity patterns among a network of Marine Protected Areas or even solely a seascape.

Microbial composition affects the performance of an artificial Tephritid larval diet.

PubMed

Rempoulakis, P; Sela Saldinger, S; Nemny-Lavy, E; Pinto, R; Birke, A; Nestel, D

2017-09-20

The present study investigated the patterns of microorganisms in an artificial larval diet during Dacus ciliatus (Diptera; Tephritidae) larval development. Microbial population contents in the diet of total heterotrophic bacteria, yeast and molds, coliform and lactobacilli, and their dynamics during development, were monitored. Initially, the microbial composition in diet trays failing to produce viable pupae and in trays successfully producing pupae and adult flies was characterized. The failing diet trays contained large populations of lactobacilli that increased during larval development, and low populations of coliforms. In contrast, the successful diet showed an increasing population of coliforms and a low, or undetected, population of lactobacilli. To study the hypothesis that lactobacilli affect D. ciliatus larval development, we conducted controlled inoculation experiments in which Lactobacillus plantarum was added into fresh diet at the time of egg seeding. L. plantarum inoculated trays showed no production of D. ciliatus. Control trays without lactobacilli inoculation showed variable results. One tray successfully produced viable pupae and adults, and showed a slight and slow increase in the indigenous populations of lactobacilli. The second tray, however, failed to produce pupae and showed a fast increase of the indigenous lactobacilli to very high levels. Monitored pH trends in L. plantarum-inoculated diet showed a sharp pH decrease during the first 4 days of larval development from 5 to less than 4 units, while successful diet, producing viable D. ciliatus pupae and adults, showed a moderate pH drop during most of the larval development period. The paper discusses the possible ecological interactions between D. ciliatus larvae, the microbial content of the diet and the physical properties of the diet. The discussion also points out at the usefulness of this approach in understanding and managing mass production parameters of tephritid fruit flies

Larval Chigger Mites Collected from Small Mammals in 3 Provinces, Korea

PubMed Central

Lee, In-Yong; Song, Hyeon-Je; Choi, Yeon-Joo; Shin, Sun-Hye; Choi, Min-Kyung; Kwon, So-Hyun; Shin, E-Hyun; Park, Chan; Kim, Heung-Chul; Klein, Terry A.; Park, Kyung-Hee

2014-01-01

A total of 9,281 larval chigger mites were collected from small mammals captured at Hwaseong-gun, Gyeonggi-do (Province) (2,754 mites from 30 small mammals), Asan city, Chungcheongnam-do (3,358 mites from 48 mammals), and Jangseong-gun, Jeollanam-do (3,169 for 62 mammals) from April-November 2009 in the Republic of Korea (= Korea) and were identified to species. Leptotrombidium pallidum was the predominant species in Hwaseong (95.8%) and Asan (61.2%), while Leptotrombidium scutellare was the predominant species collected from Jangseong (80.1%). Overall, larval chigger mite indices decreased from April (27.3) to June (4.9), then increased in September (95.2) and to a high level in November (169.3). These data suggest that L. pallidum and L. scutellare are the primary vectors of scrub typhus throughout their range in Korea. While other species of larval chigger mites were also collected with some implications in the transmission of Orientia tsutsugamushi, they only accounted for 11.2% of all larval chigger mites collected from small mammals. PMID:24850971

How Metamorphosis Is Different in Plethodontids: Larval Life History Perspectives on Life-Cycle Evolution

PubMed Central

Beachy, Christopher K.; Ryan, Travis J.; Bonett, Ronald M.

2017-01-01

Plethodontid salamanders exhibit biphasic, larval form paedomorphic, and direct developing life cycles. This diversity of developmental strategies exceeds that of any other family of terrestrial vertebrate. Here we compare patterns of larval development among the three divergent lineages of biphasic plethodontids and other salamanders. We discuss how patterns of life-cycle evolution and larval ecology might have produced a wide array of larval life histories. Compared with many other salamanders, most larval plethodontids have relatively slow growth rates and sometimes exceptionally long larval periods (up to 60 mo). Recent phylogenetic analyses of life-cycle evolution indicate that ancestral plethodontids were likely direct developers. If true, then biphasic and paedomorphic lineages might have been independently derived through different developmental mechanisms. Furthermore, biphasic plethodontids largely colonized stream habitats, which tend to have lower productivity than seasonally ephemeral ponds. Consistent with this, plethodontid larvae grow very slowly, and metamorphic timing does not appear to be strongly affected by growth history. On the basis of this, we speculate that feeding schedules and stress hormones might play a comparatively reduced role in governing the timing of metamorphosis of stream-dwelling salamanders, particularly plethodontids. PMID:29269959

Complex life cycles and density dependence: assessing the contribution of egg mortality to amphibian declines.

PubMed

Vonesh, James R; De la Cruz, Omar

2002-11-01

In the last decade there has been increasing evidence of amphibian declines from relatively pristine areas. Some declines are hypothesized to be the result of egg mortality caused by factors such as elevated solar UV-B irradiation, chemical pollutants, pathogenic fungi, and climate change. However, the population-level consequences of egg mortality have not been examined explicitly, and may be complicated by density dependence in intervening life-history stages. Here we develop a demographic model for two amphibians with contrasting life-history strategies, Bufo boreas and Ambystoma macrodactylum. We then use the complementary approaches of elasticity and limitation to examine the relationships among stage-specific survival rates, larval-stage density dependence and amphibian population dynamics. Elasticity analyses showed that for a range of density dependence scenarios both species were more sensitive to changes in post-embryonic survival parameters, particularly juvenile survival, than to egg survival, suggesting that mortality of later stages may play an important role in driving declines. Limitation analyses revealed that larval density dependence can dramatically alter the consequences of early mortality, reducing or even reversing the expected population-level effects of egg mortality. Thus, greater focus on later life stages and density dependence is called for to accurately assess how stressors are likely to affect amphibian populations of conservation concern.

Effects of metal and predator stressors in larval southern toads (Anaxyrus terrestris).

PubMed

Rumrill, Caitlin T; Scott, David E; Lance, Stacey L

2016-08-01

Natural and anthropogenic stressors typically do not occur in isolation; therefore, understanding ecological risk of contaminant exposure should account for potential interactions of multiple stressors. Realistically, common contaminants can also occur chronically in the environment. Because parental exposure to stressors may cause transgenerational effects on offspring, affecting their ability to cope with the same or novel environmental stressors, the exposure histories of generations preceding that being tested should be considered. To examine multiple stressor and parental exposure effects we employed a 2 × 2 × 2 factorial design in outdoor 1000-L mesocosms (n = 24). Larval southern toads (Anaxyrus terrestris), bred from parents collected from reference and metal-contaminated sites, were exposed to two levels of both an anthropogenic (copper-0, 30 µg/L Cu) and natural (predator cue - present/absent) stressor and reared to metamorphosis. Toads from the metal-contaminated parental source population were smaller at metamorphosis and had delayed development; i.e., a prolonged larval period. Similarly, larval Cu exposure also reduced size at metamorphosis and prolonged the larval period. We, additionally, observed a significant interaction between larval Cu and predator-cue exposure on larval period, wherein delayed emergence was only present in the 30-µg/L Cu treatments in the absence of predator cues. The presence of parental effects as well as an interaction between aquatic stressors on commonly measured endpoints highlight the importance of conducting multistressor studies across generations to obtain data that are more relevant to field conditions in order to determine population-level effects of contaminant exposure.

Influences of acid mine drainage and thermal enrichment on stream fish reproduction and larval survival

USGS Publications Warehouse

Hafs, Andrew W.; Horn, C.D.; Mazik, P.M.; Hartman, K.J.

2010-01-01

Potential effects of acid mine drainage (AMD) and thermal enrichment on the reproduction of fishes were investigated through a larval-trapping survey in the Stony River watershed, Grant County, WV. Trapping was conducted at seven sites from 26 March to 2 July 2004. Overall larval catch was low (379 individuals in 220 hours of trapping). More larval White Suckers were captured than all other species. Vectors fitted to nonparametric multidimensional scaling ordinations suggested that temperature was highly correlated to fish communities captured at our sites. Survival of larval Fathead Minnows was examined in situ at six sites from 13 May to 11 June 2004 in the same system. Larval survival was lower, but not significantly different between sites directly downstream of AMD-impacted tributaries (40% survival) and non-AMD sites (52% survival). The lower survival was caused by a significant mortality event at one site that coincided with acute pH depression in an AMD tributary immediately upstream of the site. Results from a Cox proportional hazard test suggests that low pH is having a significant negative influence on larval fish survival in this system. The results from this research indicate that the combination of low pH events and elevated temperature are negatively influencing the larval fish populations of the Stony River watershed. Management actions that address these problems would have the potential to substantially increase both reproduction rates and larval survival, therefore greatly enhancing the fishery.

Adaptive Locomotor Behavior in Larval Zebrafish

PubMed Central

Portugues, Ruben; Engert, Florian

2011-01-01

In this study we report that larval zebrafish display adaptive locomotor output that can be driven by unexpected visual feedback. We develop a new assay that addresses visuomotor integration in restrained larval zebrafish. The assay involves a closed-loop environment in which the visual feedback a larva receives depends on its own motor output in a way that resembles freely swimming conditions. The experimenter can control the gain of this closed feedback loop, so that following a given motor output the larva experiences more or less visual feedback depending on whether the gain is high or low. We show that increases and decreases in this gain setting result in adaptive changes in behavior that lead to a generalized decrease or increase of motor output, respectively. Our behavioral analysis shows that both the duration and tail beat frequency of individual swim bouts can be modified, as well as the frequency with which bouts are elicited. These changes can be implemented rapidly, following an exposure to a new gain of just 175 ms. In addition, modifications in some behavioral parameters accumulate over tens of seconds and effects last for at least 30 s from trial to trial. These results suggest that larvae establish an internal representation of the visual feedback expected from a given motor output and that the behavioral modifications are driven by an error signal that arises from the discrepancy between this expectation and the actual visual feedback. The assay we develop presents a unique possibility for studying visuomotor integration using imaging techniques available in the larval zebrafish. PMID:21909325

Adaptive locomotor behavior in larval zebrafish.

PubMed

Portugues, Ruben; Engert, Florian

2011-01-01

In this study we report that larval zebrafish display adaptive locomotor output that can be driven by unexpected visual feedback. We develop a new assay that addresses visuomotor integration in restrained larval zebrafish. The assay involves a closed-loop environment in which the visual feedback a larva receives depends on its own motor output in a way that resembles freely swimming conditions. The experimenter can control the gain of this closed feedback loop, so that following a given motor output the larva experiences more or less visual feedback depending on whether the gain is high or low. We show that increases and decreases in this gain setting result in adaptive changes in behavior that lead to a generalized decrease or increase of motor output, respectively. Our behavioral analysis shows that both the duration and tail beat frequency of individual swim bouts can be modified, as well as the frequency with which bouts are elicited. These changes can be implemented rapidly, following an exposure to a new gain of just 175 ms. In addition, modifications in some behavioral parameters accumulate over tens of seconds and effects last for at least 30 s from trial to trial. These results suggest that larvae establish an internal representation of the visual feedback expected from a given motor output and that the behavioral modifications are driven by an error signal that arises from the discrepancy between this expectation and the actual visual feedback. The assay we develop presents a unique possibility for studying visuomotor integration using imaging techniques available in the larval zebrafish.

Managing Ammonia Emissions From Screwworm Larval Rearing Media.

PubMed

Sagel, Agustin; Phillips, Pamela; Chaudhury, Muhammad; Skoda, Steven

2016-02-01

Mass production, sterilization, and release of screwworms (Cochliomyia hominivorax (Coquerel)) that were competitive in the field significantly contributed to the successful application of the sterile insect technique for eradication of screwworms from continental North America. Metabolic byproducts resulting from protein-rich diets required for larval screwworms lead to ammonia liberation, sometimes at high levels, within the mass rearing facility. Until recently a sodium polyacrylate gel bulking agent was used for the larval media and adsorbed much of the ammonia. A need to replace the gel with an environmentally "friendly" bulking agent, while not increasing ammonia levels in the rearing facility, led to a series of experiments with the objective of developing procedures to reduce ammonia emissions from the larval media bulked with cellulose fiber. Additives of ammonia-converting bacteria, potassium permanganate, and Yucca schidigera Roezl ex Otrgies powder extract, previously reported to reduce ammonia levels in organic environments, were evaluated. Ammonia-converting bacteria did not have a positive effect. Addition of Y. schidigera powder extract (∼1% of total volume), potassium permanganate (∼250 ppm), and a combination of these two additives (at these same concentrations) kept ammonia at equivalent levels as when larval media was bulked with gel. Potassium permanganate also had sufficient antimicrobial properties that the use of formaldehyde in the diet was not necessary. Further testing is needed, at a mass rearing level, before full implementation into the screwworm eradication program. Published by Oxford University Press on behalf of Entomological Society of America 2015. This work is written by US Government employees and is in the public domain in the US.

Synergism and Antagonism between Bacillus thuringiensis Vip3A and Cry1 Proteins in Heliothis virescens, Diatraea saccharalis and Spodoptera frugiperda

PubMed Central

Lemes, Ana Rita Nunes; Davolos, Camila Chiaradia; Legori, Paula Cristina Brunini Crialesi; Fernandes, Odair Aparecido; Ferré, Juan; Lemos, Manoel Victor Franco; Desiderio, Janete Apparecida

2014-01-01

Second generation Bt crops (insect resistant crops carrying Bacillus thuringiensis genes) combine more than one gene that codes for insecticidal proteins in the same plant to provide better control of agricultural pests. Some of the new combinations involve co-expression of cry and vip genes. Because Cry and Vip proteins have different midgut targets and possibly different mechanisms of toxicity, it is important to evaluate possible synergistic or antagonistic interactions between these two classes of toxins. Three members of the Cry1 class of proteins and three from the Vip3A class were tested against Heliothis virescens for possible interactions. At the level of LC50, Cry1Ac was the most active protein, whereas the rest of proteins tested were similarly active. However, at the level of LC90, Cry1Aa and Cry1Ca were the least active proteins, and Cry1Ac and Vip3A proteins were not significantly different. Under the experimental conditions used in this study, we found an antagonistic effect of Cry1Ca with the three Vip3A proteins. The interaction between Cry1Ca and Vip3Aa was also tested on two other species of Lepidoptera. Whereas antagonism was observed in Spodoptera frugiperda, synergism was found in Diatraea saccharalis. In all cases, the interaction between Vip3A and Cry1 proteins was more evident at the LC90 level than at the LC50 level. The fact that the same combination of proteins may result in a synergistic or an antagonistic interaction may be an indication that there are different types of interactions within the host, depending on the insect species tested. PMID:25275646

Effect of corticosterone on larval growth, antipredator behaviour and metamorphosis of Hylarana indica.

PubMed

Kulkarni, P S; Gramapurohit, N P

2017-09-15

Corticosterone (CORT), a principal glucocorticoid in amphibians, is known to regulate diverse physiological processes including growth and metamorphosis of anuran tadpoles. Environmental stressors activate the neuroendocrine stress axis (hypothalamus-pituitary-interrenal axis, HPI) leading to an acute increase in CORT, which in turn, helps in coping with particular stress. However, chronic increase in CORT can negatively affect other physiological processes such as growth and metamorphosis. Herein, we studied the effect of exogenous CORT on larval growth, antipredator behaviour and metamorphic traits of Hylarana indica. Embryonic exposure to 5 or 20μg/L CORT did not affect their development, hatching duration as well as larval growth and metamorphosis. Exposure of tadpoles to 10 or 20μg/L CORT throughout larval development caused slower growth and development leading to increased body mass at stage 37. However, body and tail morphology of tadpoles was not affected. Interestingly, larval exposure to 5, 10 or 20μg/L CORT enhanced their antipredator response against kairomones in a concentration-dependent manner. Further, larval exposure to increasing concentrations of CORT resulted in the emergence of heavier froglets at 10 and 20μg/L while, delaying metamorphosis at all concentrations. Interestingly, the heavier froglets had shorter hindlimbs and consequently shorter jump distances. Tadpoles exposed to 20μg/L CORT during early, mid or late larval stages grew and developed slowly but tadpole morphology was not altered. Interestingly, exposure during early or mid-larval stages resulted in an enhanced antipredator response. These individuals metamorphosed later but at higher body mass while SVL was unaffected. Copyright © 2016 Elsevier Inc. All rights reserved.

Larval diet affects mosquito development and permissiveness to Plasmodium infection.

PubMed

Linenberg, Inbar; Christophides, George K; Gendrin, Mathilde

2016-12-02

The larval stages of malaria vector mosquitoes develop in water pools, feeding mostly on microorganisms and environmental detritus. Richness in the nutrient supply to larvae influences the development and metabolism of larvae and adults. Here, we investigated the effects of larval diet on the development, microbiota content and permissiveness to Plasmodium of Anopheles coluzzii. We tested three fish diets often used to rear mosquitoes in the laboratory, including two pelleted diets, Dr. Clarke's Pool Pellets and Nishikoi Fish Pellets, and one flaked diet, Tetramin Fish-Flakes. Larvae grow and develop faster and produce bigger adults when feeding on both types of pellets compared with flakes. This correlates with a higher microbiota load in pellet-fed larvae, in agreement with the known positive effect of the microbiota on mosquito development. Larval diet also significantly influences the prevalence and intensity of Plasmodium berghei infection in adults, whereby Nishikoi Fish Pellets-fed larvae develop into adults that are highly permissive to parasites and survive longer after infection. This correlates with a lower amount of Enterobacteriaceae in the midgut microbiota. Together, our results shed light on the influence of larval feeding on mosquito development, microbiota and vector competence; they also provide useful data for mosquito rearing.

Detecting critical periods in larval flatfish populations

NASA Astrophysics Data System (ADS)

Chambers, R. Christopher; Witting, David A.; Lewis, Stephen J.

2001-06-01

We evaluate the time-course of deaths and evidence of periods of increased mortality (i.e., critical periods) in laboratory populations of larval flatfish. First, we make the distinction between age-at-death and abundance-at-time data for fish larvae, the latter being typical in studies of natural populations. Next, we describe an experimental investigation of age- and temperature-dependent mortality in larval winter flounder, Pseudopleuronectes americanus. The survivorship curves of these populations differed significantly in both the magnitude and time-course of mortality among the four water temperatures evaluated (7, 10, 13, and 16°C). Mortality was highest in the cooler temperatures and concentrated in the third quarter of larval life, largely concurrent with settlement of surviving members of the cohort. Among the statistical methods for analysing survival data, the proportional-hazards model with time-varying covariates proved best at capturing the patterns of age-specific mortalities. We conclude that fair appraisals of recruitment hypotheses which are predicated on periods of high, age-specific mortality that vary with environmental conditions (e.g., Hjort's critical period hypothesis) will require: (1) data that are based on age, not time; (2) data that are of higher temporal resolution than commonly available at present and (3) analytical methods that are sensitive to irregularities in survivorship curves. We suggest four research approaches for evaluating critical periods in nature.

Developmental transitions in C. elegans larval stages.

PubMed

Rougvie, Ann E; Moss, Eric G

2013-01-01

Molecular mechanisms control the timing, sequence, and synchrony of developmental events in multicellular organisms. In Caenorhabditis elegans, these mechanisms are revealed through the analysis of mutants with "heterochronic" defects: cell division or differentiation patterns that occur in the correct lineage, but simply at the wrong time. Subsets of cells in these mutants thus express temporal identities normally restricted to a different life stage. A seminal finding arising from studies of the heterochronic genes was the discovery of miRNAs; these tiny miRNAs are now a defining feature of the pathway. A series of sequentially expressed miRNAs guide larval transitions through stage-specific repression of key effector molecules. The wild-type lineage patterns are executed as discrete modules programmed between temporal borders imposed by the molting cycles. How these successive events are synchronized with the oscillatory molting cycle is just beginning to come to light. Progression through larval stages can be specifically, yet reversibly, halted in response to environmental cues, including nutrient availability. Here too, heterochronic genes and miRNAs play key roles. Remarkably, developmental arrest can, in some cases, either mask or reveal timing defects associated with mutations. In this chapter, we provide an overview of how the C. elegans heterochronic gene pathway guides developmental transitions during continuous and interrupted larval development. © 2013 Elsevier Inc. All rights reserved.

Identification of Essential Containers for Aedes Larval Breeding to Control Dengue in Dhaka, Bangladesh.

PubMed

Ferdousi, Farhana; Yoshimatsu, Shoji; Ma, Enbo; Sohel, Nazmul; Wagatsuma, Yukiko

2015-12-01

Dengue fever (DF), one of the most important emerging arboviral diseases, is transmitted through the bite of container breeding mosquitoes Aedes aegypti and Aedes albopictus. A household entomological survey was conducted in Dhaka from August through October 2000 to inspect water-holding containers in indoor, outdoor, and rooftop locations for Aedes larvae. The objective of this study was to determine mosquito productivity of each container type and to identify some risk factors of households infested with Aedes larvae. Of 9,222 households inspected, 1,306 (14.2%) were positive for Aedes larvae. Of 38,777 wet containers examined, 2,272 (5.8%) were infested with Aedes larvae. Containers used to hold water, such as earthen jars, tanks, and drums were the most common containers for larval breeding. Tires in outdoor and rooftop locations of the households were also important for larval breeding. Although present in abundance, buckets were of less importance. Factors such as independent household, presence of a water storage system in the house, and fully/partly shaded outdoors were found to be significantly associated with household infestation of Aedes larvae. Identification and subsequent elimination of the most productive containers in a given area may potentially reduce mosquito density to below a level at which dengue transmission may be halted.

Identification of Essential Containers for Aedes Larval Breeding to Control Dengue in Dhaka, Bangladesh

PubMed Central

Ferdousi, Farhana; Yoshimatsu, Shoji; Ma, Enbo; Sohel, Nazmul; Wagatsuma, Yukiko

2015-01-01

Dengue fever (DF), one of the most important emerging arboviral diseases, is transmitted through the bite of container breeding mosquitoes Aedes aegypti and Aedes albopictus. A household entomological survey was conducted in Dhaka from August through October 2000 to inspect water-holding containers in indoor, outdoor, and rooftop locations for Aedes larvae. The objective of this study was to determine mosquito productivity of each container type and to identify some risk factors of households infested with Aedes larvae. Of 9,222 households inspected, 1,306 (14.2%) were positive for Aedes larvae. Of 38,777 wet containers examined, 2,272 (5.8%) were infested with Aedes larvae. Containers used to hold water, such as earthen jars, tanks, and drums were the most common containers for larval breeding. Tires in outdoor and rooftop locations of the households were also important for larval breeding. Although present in abundance, buckets were of less importance. Factors such as independent household, presence of a water storage system in the house, and fully/partly shaded outdoors were found to be significantly associated with household infestation of Aedes larvae. Identification and subsequent elimination of the most productive containers in a given area may potentially reduce mosquito density to below a level at which dengue transmission may be halted. PMID:26865829

Embryogenesis and Larval Biology of the Cold-Water Coral Lophelia pertusa

PubMed Central

Strömberg, Susanna M.; Dahl, Mikael P.; Lundälv, Tomas; Brooke, Sandra

2014-01-01

Cold-water coral reefs form spectacular and highly diverse ecosystems in the deep sea but little is known about reproduction, and virtually nothing about the larval biology in these corals. This study is based on data from two locations of the North East Atlantic and documents the first observations of embryogenesis and larval development in Lophelia pertusa, the most common framework-building cold-water scleractinian. Embryos developed in a more or less organized radial cleavage pattern from ∼160 µm large neutral or negatively buoyant eggs, to 120–270 µm long ciliated planulae. Embryogenesis was slow with cleavage occurring at intervals of 6–8 hours up to the 64-cell stage. Genetically characterized larvae were sexually derived, with maternal and paternal alleles present. Larvae were active swimmers (0.5 mm s−1) initially residing in the upper part of the water column, with bottom probing behavior starting 3–5 weeks after fertilization. Nematocysts had developed by day 30, coinciding with peak bottom-probing behavior, and possibly an indication that larvae are fully competent to settle at this time. Planulae survived for eight weeks under laboratory conditions, and preliminary results indicate that these planulae are planktotrophic. The late onset of competency and larval longevity suggests a high dispersal potential. Understanding larval biology and behavior is of paramount importance for biophysical modeling of larval dispersal, which forms the basis for predictions of connectivity among populations. PMID:25028936

Acidification reduced growth rate but not swimming speed of larval sea urchins.

PubMed

Chan, Kit Yu Karen; García, Eliseba; Dupont, Sam

2015-05-15

Swimming behaviors of planktonic larvae impact dispersal and population dynamics of many benthic marine invertebrates. This key ecological function is modulated by larval development dynamics, biomechanics of the resulting morphology, and behavioral choices. Studies on ocean acidification effects on larval stages have yet to address this important interaction between development and swimming under environmentally-relevant flow conditions. Our video motion analysis revealed that pH covering present and future natural variability (pH 8.0, 7.6 and 7.2) did not affect age-specific swimming of larval green urchin Strongylocentrotus droebachiensis in still water nor in shear, despite acidified individuals being significantly smaller in size (reduced growth rate). This maintenance of speed and stability in shear was accompanied by an overall change in size-corrected shape, implying changes in swimming biomechanics. Our observations highlight strong evolutionary pressure to maintain swimming in a varying environment and the plasticity in larval responses to environmental change.

Land use and land cover changes and spatiotemporal dynamics of anopheline larval habitats during a four-year period in a highland community of Africa.

PubMed

Munga, Stephen; Yakob, Laith; Mushinzimana, Emmanuel; Zhou, Guofa; Ouna, Tom; Minakawa, Noboru; Githeko, Andrew; Yan, Guiyun

2009-12-01

Spatial and temporal variations in the distribution of anopheline larval habitats and land use and land cover (LULC) changes can influence malaria transmission intensity. This information is important for understanding the environmental determinants of malaria transmission heterogeneity, and it is critical to the study of the effects of environmental changes on malaria transmission. In this study, we investigated the spatial and temporal variations in the distribution of anopheline larval habitats and LULC changes in western Kenya highlands over a 4-year period. Anopheles gambiae complex larvae were mainly confined to valley bottoms during both the dry and wet seasons. Although An. gambiae larvae were located in man-made habitats where riparian forests and natural swamps had been cleared, Anopheles funestus larvae were mainly found in permanent habitats in pastures. The association between land cover type and occurrence of anopheline larvae was statistically significant. The distribution of anopheline positive habitats varied significantly between months, during the survey. In 2004, the mean density of An. gambiae was significantly higher during the month of May, whereas the density of An. funestus peaked significantly in February. Over the study period, major LULC changes occurred mostly in the valley bottoms. Overall, farmland increased by 3.9%, whereas both pastures and natural swamps decreased by 8.9% and 20.9%, respectively. The area under forest cover was decreased by 5.8%. Land-use changes in the study area are favorable to An. gambiae larval development, thereby risking a more widespread distribution of malaria vector habitats and potentially increasing malaria transmission in western Kenya highlands.

Condition of larval red snapper (Lutjanus campechanus) relative to environmental variability and the Deepwater Horizon oil spill

NASA Astrophysics Data System (ADS)

Hernandez, F. J., Jr.; Filbrun, J. E.; Fang, J.; Ransom, J. T.

2016-09-01

The Deepwater Horizon oil spill (DWHOS) spatially and temporally overlapped with the spawning of many fish species, including Red Snapper, one of the most economically important reef fish in the Gulf of Mexico. To investigate potential impacts of the DWHOS on larval Red Snapper, data from a long-term ichthyoplankton survey off the coast of Alabama were used to examine: (1) larval abundances among pre-impact (2007-2009), impact (2010), and post-impact (2011, 2013) periods; (2) proxies for larval condition (size-adjusted morphometric relationships and dry weight) among the same periods; and (3) the effects of background environmental variation on larval condition. We found that larval Red Snapper were in poorer body condition during 2010, 2011, and 2013 as compared to the 2007-2009 period, a trend that was strongly (and negatively) related to variation in Mobile Bay freshwater discharge. However, larvae collected during and after 2010 were in relatively poor condition even after accounting for variation in freshwater discharge and other environmental variables. By contrast, no differences in larval abundance were detected during these survey years. Taken together, larval supply did not change relative to the timing of the DWHOS, but larval condition was negatively impacted. Even small changes in condition can affect larval survival, so these trends may have consequences for recruitment of larvae to juvenile and adult life stages.

Efficiency of selection methods for increased ratio of pupal-larval to adult-larval weight gains in Tribolium.

PubMed

Campo, J L; Cobos, P

1994-01-12

Four lines of Tribolium castaneum were selected in each of three replicates for increased ratio of (pupal-larval) to (adult-larval) weight gains, using selection for increased (pupal-larval) weight gain (PL), selection for decreased (adult-larval) weight gain (AL), direct selection for the ratio (R) and linear selection index of larval, pupal and adult weights (I), respectively, for four generations. Linear index was calculated with economic weights of m(2) -m(3) , m(3) -m(1) and m(1) -m(2) , respectively, with m(1) , m(2) and m(3) being the means for larval, pupal and adult weights. Selection to increase the ratio is considered to be a method to maximize the mean response in (adult-larval) weight while controlling the response in (pupal-adult) weight, and as a form of antagonistic selection to increase the weight gain during a given age period relative to the gain at another age period. Larval, pupal and adult weights were measured at 14, 21 and 28 days after adult emergence, respectively. The selected proportion was 20 % in all lines. The response observed for the ratio differed significantly among lines (p < 0.01), with the I and AL lines having the greatest responses. Line R was less effective in improving the objective of selection, while line PL appeared to be inappropriate. The observed responses for the numerator and denominator weight gains were positive in line PL, and negative in the AL, R and I lines. All lines apart from line PL decreased the (adult-larval) weight, holding (pupal-adult) weight constant. Larval weight showed the greatest influence on the response for the objective of selection. The results for this greater than 1 ratio are compared with results of others for smaller than 1 ratios, in which indirect selection for increased numerator is the more efficient alternative to the selection index. ZUSAMMENFASSUNG: Effizienz Selektionsverfahren zur Verbesserung des Quotienten der Gewichtsentwicklung zwischen Puppe/Larve und Käfer/Larve bei

Oyster larval transport in coastal Alabama: Dominance of physical transport over biological behavior in a shallow estuary

NASA Astrophysics Data System (ADS)

Kim, Choong-Ki; Park, Kyeong; Powers, Sean P.; Graham, William M.; Bayha, Keith M.

2010-10-01

Among the various factors affecting recruitment of marine invertebrates and fish, larval transport may produce spatial and temporal patterns of abundance that are important determinants of management strategies. Here we conducted a field and modeling study to investigate the larval transport of eastern oyster, Crassostrea virginica, in Mobile Bay and eastern Mississippi Sound, Alabama. A three-dimensional larval transport model accounting for physical transport, biological movement of larvae, and site- and larval-specific conditions was developed. A hydrodynamic model was used to simulate physical transport, and biological movement was parameterized as a function of swimming and sinking velocity of oyster larvae. Site- and larval-specific conditions, including spawning location, spawning stock size, spawning time, and larval period, were determined based on the previous studies. The model reasonably reproduced the observed gradient in oyster spat settlement and bivalve larval concentration, although the model results were less dynamic than the data, probably owing to the simplified biological conditions employed in the model. A persistent gradient decreasing from west to east in the model results at time scales of overall average, season, and each survey in 2006 suggests that the larval supply may be responsible for the corresponding gradient in oyster spat settlement observed over the past 40 years. Biological movement increased larval retention near the spawning area, thus providing a favorable condition for local recruitment of oysters. Inclusion of biological movement, however, caused little change in the overall patterns of larval transport and still resulted in a west-east gradient, presumably because of frequent destratification in the shallow Mobile Bay system.

Redescription of the early larval stages of the pandalid shrimp Chlorotocus crassicornis (Decapoda: Caridea: Pandalidae).

PubMed

Landeira, Jose M; Jiang, Guo-Chen; Chan, Tin-Yam; Shih, Tung-Wei; Gozález-Gordillo, J Ignacio

2015-09-07

The first four larval stages of the pandalid shrimp Chlorotocus crassicornis (A. Costa, 1871) are described and illustrated from laboratory-reared material obtained from ovigerous females collected in the southwestern Spain and south Taiwan. The second to fourth larval stages of this species are reported for the first time to science. Detailed examination of the first larval stages reveals that previous description misidentified some key larval characters which have prevented its identification in plankton samples. It is found that the zoeal morphology of Chlorotocus is not very different from other pandalid larvae, and in fact closely resembles Plesionika and Heterocarpus.

The structure and timescales of heat perception in larval zebrafish.

PubMed

Haesemeyer, Martin; Robson, Drew N; Li, Jennifer M; Schier, Alexander F; Engert, Florian

2015-11-25

Avoiding temperatures outside the physiological range is critical for animal survival, but how temperature dynamics are transformed into behavioral output is largely not understood. Here, we used an infrared laser to challenge freely swimming larval zebrafish with "white-noise" heat stimuli and built quantitative models relating external sensory information and internal state to behavioral output. These models revealed that larval zebrafish integrate temperature information over a time-window of 400 ms preceding a swimbout and that swimming is suppressed right after the end of a bout. Our results suggest that larval zebrafish compute both an integral and a derivative across heat in time to guide their next movement. Our models put important constraints on the type of computations that occur in the nervous system and reveal principles of how somatosensory temperature information is processed to guide behavioral decisions such as sensitivity to both absolute levels and changes in stimulation.

Interspecific larval competition between invasive Aedes japonicus and native Aedes triseriatus (Diptera: Culicidae) and adult longevity.

PubMed

Alto, Barry W

2011-03-01

The Asian rock pool mosquito Aedes japonicus (Theobald) inhabits natural and artificial container habitats, some of which are occupied by the native treehole mosquitoAedes triseriatus (Say), a vector of LaCrosse encephalitis virus. A laboratory experiment was used to evaluate the effects of nutrient limitation and interspecific interactions between these species. The goal was to address two related hypotheses. First, interspecific interactions between these species show competitive asymmetry with the invasive mosquito Ae. japonicus being favored over Ae. triseriatus. Second, competitive stress at the larval stage alters adult longevity. There was minimal evidence for competitive asymmetry between these two species. Mosquito and population performance showed clear negative density-dependent effects with similar effects of intra- and interspecific interactions. Only Ae. japonicus development time showed competitive asymmetry over Ae. triseriatus, providing weak support for the first hypothesis. For both species, competition resulted in lower adult longevity compared with low competition, providing support for the second hypothesis. These results suggest both species are similarly affected by intra- and interspecific competition and underscore the importance of the effects of larval competition that continue into adulthood and alter parameters important to transmission of vector-borne diseases.

Reverse osmosis and ultrafiltration for recovery and reuse of larval rearing water in Anopheles arabiensis mass production: Effect of water quality on larval development and fitness of emerging adults.

PubMed

Mamai, Wadaka; Hood-Nowotny, Rebecca; Maiga, Hamidou; Ali, Adel Barakat; Bimbile-Somda, Nanwintoun S; Soma, Diloma Dieudonné; Yamada, Hanano; Lees, Rosemary Susan; Gilles, Jeremie R L

2017-06-01

Countries around the world are showing increased interest in applying the sterile insect technique against mosquito disease vectors. Many countries in which mosquitoes are endemic, and so where vector control using the sterile insect technique may be considered, are located in arid zones where water provision can be costly or unreliable. Water reuse provides an alternate form of water supply. In order to reduce the cost of mass rearing of Anopheles arabiensis mosquitoes, the possibility of recycling and reusing larval rearing water was explored. The used rearing water ('dirty water') was collected after the tilting of rearing trays for collection of larvae/pupae, and larvae/pupae separation events and underwent treatment processes consisting of ultrafiltration and reverse osmosis. First-instar An. arabiensis larvae were randomly assigned to different water-type treatments, 500 larvae per laboratory rearing tray: 'clean' dechlorinated water, routinely used in rearing; dirty water; and 'recycled' dirty water treated using reverse osmosis and ultrafiltration. Several parameters of insect quality were then compared: larval development, pupation rate, adult emergence, body size and longevity. Water quality of the samples was analyzed in terms of ammonia, nitrite, nitrate, sulphate, dissolved oxygen, chloride, and phosphate concentrations after the larvae had all pupated or died. Surface water temperatures were also recorded continuously during larval development. Pupation rates and adult emergence were similar in all water treatments. Adult body sizes of larvae reared in recycled water were similar to those reared in clean water, but larger than those reared in the dirty larval water treatment, whereas the adult longevity of larvae reared in recycled water was significantly increased relative to both 'clean' and 'dirty' water. Dirty larval water contained significantly higher concentrations of ammonium, sulfate, phosphate and chloride and lower levels of dissolved

Contributions of Anopheles larval control to malaria suppression in tropical Africa: review of achievements and potential.

PubMed

Walker, K; Lynch, M

2007-03-01

Malaria vector control targeting the larval stages of mosquitoes was applied successfully against many species of Anopheles (Diptera: Culicidae) in malarious countries until the mid-20th Century. Since the introduction of DDT in the 1940s and the associated development of indoor residual spraying (IRS), which usually has a more powerful impact than larval control on vectorial capacity, the focus of malaria prevention programmes has shifted to the control of adult vectors. In the Afrotropical Region, where malaria is transmitted mainly by Anopheles funestus Giles and members of the Anopheles gambiae Giles complex, gaps in information on larval ecology and the ability of An. gambiae sensu lato to exploit a wide variety of larval habitats have discouraged efforts to develop and implement larval control strategies. Opportunities to complement adulticiding with other components of integrated vector management, along with concerns about insecticide resistance, environmental impacts, rising costs of IRS and logistical constraints, have stimulated renewed interest in larval control of malaria vectors. Techniques include environmental management, involving the temporary or permanent removal of anopheline larval habitats, as well as larviciding with chemical or biological agents. This present review covers large-scale trials of anopheline larval control methods, focusing on field studies in Africa conducted within the past 15 years. Although such studies are limited in number and scope, their results suggest that targeting larvae, particularly in human-made habitats, can significantly reduce malaria transmission in appropriate settings. These approaches are especially suitable for urban areas, where larval habitats are limited, particularly when applied in conjunction with IRS and other adulticidal measures, such as the use of insecticide treated bednets.

Social coercion of larval development in an ant species

NASA Astrophysics Data System (ADS)

Villalta, Irene; Amor, Fernando; Cerdá, Xim; Boulay, Raphaël

2016-04-01

Ants provide one of the best examples of the division of labor in animal societies. While the queens reproduce, workers generally refrain from laying eggs and dedicate themselves exclusively to domestic tasks. In many species, the small diploid larvae are bipotent and can develop either into workers or queens depending mostly on environmental cues. This generates a conflicting situation between the adults that tend to rear a majority of larvae into workers and the larvae whose individual interest may be to develop into reproductive queens. We tested the social regulation of larval caste fate in the fission-performing ant Aphaenogaster senilis. We first observed interactions between resident workers and queen- and worker-destined larvae in presence/absence of the queen. The results show that workers tend to specifically eliminate queen-destined larvae when the queen is present but not when she is absent or imprisoned in a small cage allowing for volatile pheromone exchanges. In addition, we found that the presence of already developed queen-destined larvae does not inhibit the development of younger still bipotent larvae into queens. Finally, we analyzed the cuticular hydrocarbon profiles of queen- and worker-destined larvae and found no significant quantitative or qualitative difference. Interestingly, the total amount of hydrocarbons on both larval castes is extremely low, which lends credence on the chemical insignificance hypothesis of larval ants. Overall, our results suggest that workers control larval development and police larvae that would develop into queens instead of workers. Such policing behavior is similar in many aspects to what is known of worker policing among adults.

Social coercion of larval development in an ant species.

PubMed

Villalta, Irene; Amor, Fernando; Cerdá, Xim; Boulay, Raphaël

2016-04-01

Ants provide one of the best examples of the division of labor in animal societies. While the queens reproduce, workers generally refrain from laying eggs and dedicate themselves exclusively to domestic tasks. In many species, the small diploid larvae are bipotent and can develop either into workers or queens depending mostly on environmental cues. This generates a conflicting situation between the adults that tend to rear a majority of larvae into workers and the larvae whose individual interest may be to develop into reproductive queens. We tested the social regulation of larval caste fate in the fission-performing ant Aphaenogaster senilis. We first observed interactions between resident workers and queen- and worker-destined larvae in presence/absence of the queen. The results show that workers tend to specifically eliminate queen-destined larvae when the queen is present but not when she is absent or imprisoned in a small cage allowing for volatile pheromone exchanges. In addition, we found that the presence of already developed queen-destined larvae does not inhibit the development of younger still bipotent larvae into queens. Finally, we analyzed the cuticular hydrocarbon profiles of queen- and worker-destined larvae and found no significant quantitative or qualitative difference. Interestingly, the total amount of hydrocarbons on both larval castes is extremely low, which lends credence on the chemical insignificance hypothesis of larval ants. Overall, our results suggest that workers control larval development and police larvae that would develop into queens instead of workers. Such policing behavior is similar in many aspects to what is known of worker policing among adults.

Larval traits carry over to affect post-settlement behaviour in a common coral reef fish.

PubMed

Dingeldein, Andrea L; White, J Wilson

2016-07-01

Most reef fishes begin life as planktonic larvae before settling to the reef, metamorphosing and entering the benthic adult population. Different selective forces determine survival in the planktonic and benthic life stages, but traits established in the larval stage may carry over to affect post-settlement performance. We tested the hypothesis that larval traits affect two key post-settlement fish behaviours: social group-joining and foraging. Certain larval traits of reef fishes are permanently recorded in the rings in their otoliths. In the bluehead wrasse (Thalassoma bifasciatum), prior work has shown that key larval traits recorded in otoliths (growth rate, energetic condition at settlement) carry over to affect post-settlement survival on the reef, with higher-larval-condition fish experiencing less post-settlement mortality. We hypothesized that this selective mortality is mediated by carry-over effects on post-settlement antipredator behaviours. We predicted that better-condition fish would forage less and be more likely to join groups, both behaviours that would reduce predation risk. We collected 550 recently settled bluehead wrasse (Thalassoma bifasciatum) from three reef sites off St. Croix (USVI) and performed two analyses. First, we compared each settler's larval traits to the size of its social group to determine whether larval traits influenced group-joining behaviour. Secondly, we observed foraging behaviour in a subset of grouped and solitary fish (n = 14) for 1-4 days post-settlement. We then collected the fish and tested whether larval traits influenced the proportion of time spent foraging. Body length at settlement, but not condition, affected group-joining behaviour; smaller fish were more likely to remain solitary or in smaller groups. However, both greater length and better condition were associated with greater proportions of time spent foraging over four consecutive days post-settlement. Larval traits carry over to affect post

Circatrigintan instead of lunar periodicity of larval release in a brooding coral species.

PubMed

Linden, Bart; Huisman, Jef; Rinkevich, Baruch

2018-04-04

Larval release by brooding corals is often assumed to display lunar periodicity. Here, we show that larval release of individual Stylophora pistillata colonies does not comply with the assumed tight entrainment by the lunar cycle, and can better be classified as a circatrigintan pattern. The colonies exhibited three distinct reproductive patterns, characterized by short intervals, long intervals and no periodicity between reproductive peaks, respectively. Cross correlation between the lunar cycle and larval release of the periodic colonies revealed an approximately 30-day periodicity with a variable lag of 5 to 10 days after full moon. The observed variability indicates that the lunar cycle does not provide a strict zeitgeber. Other factors such as water temperature and solar radiation did not correlate significantly with the larval release. The circatrigintan patterns displayed by S. pistillata supports the plasticity of corals and sheds new light on discussions on the fecundity of brooding coral species.

Density, Viability Conidia And Symptoms of Metarhizium anisopliae infection on Oryctes rhinoceros larvae

NASA Astrophysics Data System (ADS)

Indriyanti, D. R.; Putri, R. I. P.; Widiyaningrum, P.; Herlina, L.

2017-04-01

M. anisopliae is parasitic fungus on insect pests; it is used as a biocontrol agent. M. anisopliae can be propagated on maize or rice substrate. M. anisopliae is currently sold in the form of kaolin powder formulations. Before it is used to check the density, viability and pathogenicity of M. anisopliae. However the problem is the kaolin powder very soft, so it difficult to distinguish between kaolin and conidia. This article gives information on how to calculate conidia density, viability and symptoms of M. anisopliae infection on Oryctes rhinoceros larvae. The study was conducted in the laboratory to determine the density and viability. The pathogenicity testing was done using pots. The Pot is containing soil substrate mixed with M. Anispoliae and ten tails O. Rhinoceros larvae per pot. The results showed that the density of M. anisopliae conidia was 1.81 x 108 conidia mL-1 and the viability was 94% within 24 hours. The larval mortality began to emerge in the 1st week, and all larvae died at the sixth week. The symptom of M. anisopliae infection on Oryctes rhinoceros larvae, there was a black spot on the larval integument. The larvae movements become slow and poor appetite; it will die within 3-7 days. The larvae die hard, and the white hyphae grow on the body surface that turns green.

A review of postfeeding larval dispersal in blowflies: implications for forensic entomology

NASA Astrophysics Data System (ADS)

Gomes, Leonardo; Godoy, Wesley Augusto Conde; von Zuben, Claudio José

2006-05-01

Immature and adult stages of blowflies are one of the primary invertebrate consumers of decomposing animal organic matter. When the food supply is consumed or when the larvae complete their development and migrate prior to the total removal of the larval substrate, they disperse to find adequate places for pupation, a process known as postfeeding larval dispersal. Several important ecological and physiological aspects of this process were studied since the work by Green (Ann Appl Biol 38:475, 1951) 50 years ago. An understanding of postfeeding larval dispersal can be useful for determining the postmortem interval (PMI) of human cadavers in legal medicine, particularly because this interval may be underestimated if older dispersing larvae or those that disperse longer, faster, and deeper are not taken into account. In this article, we review the process of postfeeding larval dispersal and its implications for legal medicine, in particular showing that aspects such as burial behavior and competition among species of blowflies can influence this process and consequently, the estimation of PMI.

Short-term developmental effects and potential mechanisms of azoxystrobin in larval and adult zebrafish (Danio rerio).

PubMed

Cao, Fangjie; Wu, Peizhuo; Huang, Lan; Li, Hui; Qian, Le; Pang, Sen; Qiu, Lihong

2018-05-01

Previous study indicated that azoxystrobin had high acute toxicity to zebrafish, and larval zebrafish were more sensitive to azoxystrobin than adult zebrafish. The objective of the present study was to investigate short-term developmental effects and potential mechanisms of azoxystrobin in larval and adult zebrafish. After zebrafish embryos and adults were exposed to 0.01, 0.05 and 0.20 mg/L azoxystrobin (equal to 25, 124 and 496 nM azoxystrobin, respectively) for 8 days, the lethal effect, physiological responses, liver histology, mitochondrial ultrastructure, and expression alteration of genes related to mitochondrial respiration, oxidative stress, cell apoptosis and innate immune response were determined. The results showed that there was no significant effect on larval and adult zebrafish after exposure to 0.01 mg/L azoxystrobin. However, increased ROS, MDA concentration and il1b in larval zebrafish, as well as increased il1b, il8 and cxcl-c1c in adult zebrafish were induced after exposure to 0.05 mg/L azoxystrobin. Reduced mitochondrial complex III activity and ATP concentration, increased SOD activity, ROS and MDA concentration, decreased cytb, as well as increased sod1, sod2, cat, il1b, il8 and cxcl-c1c were observed both in larval and adult zebrafish after exposure to 0.20 mg/L azoxystrobin; meanwhile, increased p53, bax, apaf1 and casp9, alteration of liver histology and mitochondrial ultrastructure in larval zebrafish, and alteration of mitochondrial ultrastructure in adult zebrafish were also induced. The results demonstrated that azoxytrobin induced short-term developmental effects on larval zebrafish and adult zebrafish, including mitochondrial dysfunction, oxidative stress, cell apoptosis and innate immune response. Statistical analysis indicated that azoxystrobin induced more negative effects on larval zebrafish, which might be the reason for the differences of developmental toxicity between larval and adult zebrafish caused by

Bacterial microbiota assemblage in Aedes albopictus mosquitoes and its impacts on larval development.

PubMed

Wang, Xiaoming; Liu, Tong; Wu, Yang; Zhong, Daibin; Zhou, Guofa; Su, Xinghua; Xu, Jiabao; Sotero, Charity F; Sadruddin, Adnan A; Wu, Kun; Chen, Xiao-Guang; Yan, Guiyun

2018-05-30

Interactions between bacterial microbiota and mosquitoes play an important role in mosquitoes' capacity to transmit pathogens. However, microbiota assemblages within mosquitoes and the impact of microbiota in environments on mosquito development and survival remain unclear. This study examined microbiota assemblages and the effects of aquatic environment microbiota on the larval development of the Aedes albopictus mosquito, an important dengue virus vector. Life table studies have found that reducing bacterial load in natural aquatic habitats through water filtering and treatment with antibiotics significantly reduced the larva-to-adult emergence rate. This finding was consistent in two types of larval habitats examined-discarded tires and flowerpots, suggesting that bacteria play a crucial role in larval development. Pyrosequencing of the bacterial 16S rRNA gene was used to determine the diversity of bacterial communities in larval habitats and the resulting numbers of mosquitoes under both laboratory and field conditions. The microbiota profiling identified common shared bacteria among samples from different years; further studies are needed to determine whether these bacteria represent a core microbiota. The highest microbiota diversity was found in aquatic habitats, followed by mosquito larvae, and the lowest in adult mosquitoes. Mosquito larvae ingested their bacterial microbiota and nutrients from aquatic habitats of high microbiota diversity. Taken together, the results support the observation that Ae. albopictus larvae are able to utilize diverse bacteria from aquatic habitats and that live bacteria from aquatic habitats play an important role in larval mosquito development and survival. These findings provide new insights into bacteria's role in mosquito larval ecology. © 2018 John Wiley & Sons Ltd.

Dispersal of larval suckers at the Williamson River Delta, Upper Klamath Lake, Oregon, 2006-09

USGS Publications Warehouse

Wood, Tamara M.; Hendrixson, Heather A.; Markle, Douglas F.; Erdman, Charles S.; Burdick, Summer M.; Ellsworth, Craig M.; Buccola, Norman L.

2012-01-01

An advection/diffusion modeling approach was used to simulate the transport of larval suckers from spawning areas in the Williamson River, through the newly restored Williamson River Delta, to Upper Klamath Lake. The density simulations spanned the years of phased restoration, from 2006/2007 prior to any levee breaching, to 2008 when the northern part of the delta was reconnected to the lake, and 2009 when levees on both sides of the delta had been breached. Model simulation results from all four years were compared to field data using rank correlation. Spearman ρ correlation coefficients were usually significant and in the range 0.30 to 0.60, providing moderately strong validation of the model. The correlation coefficients varied with fish size class in a way that suggested that the model best described the distribution of smaller fish near the Williamson River channel, and larger fish away from the channel. When Lost River and shortnose/Klamath largescale suckers were simulated independently, the correlation results suggested that the model better described the transport and dispersal of the latter species. The incorporation of night-time-only drift behavior in the Williamson River channel neither improved nor degraded correlations with field data. The model showed that advection by currents is an important factor in larval dispersal.

Environmental characteristics of anopheline mosquito larval habitats in a malaria endemic area in Iran.

PubMed

Soleimani-Ahmadi, Moussa; Vatandoost, Hassan; Hanafi-Bojd, Ahmad-Ali; Zare, Mehdi; Safari, Reza; Mojahedi, Abdolrasul; Poorahmad-Garbandi, Fatemeh

2013-07-01

To determine the effects of environmental parameters of larval habitats on distribution and abundance of anopheline mosquitoes in Rudan county of Iran. This cross-sectional study was conducted during the mosquito breeding season from February 2010 to October 2011. The anopheline larvae were collected using the standard dipping method. The specimens were identified using a morphological-based key. Simultaneously with larval collection, environmental parameters of the larval habitats including water current and turbidity, sunlight situation, and substrate type of habitats were recorded. Water samples were taken from breeding sites during larval collection. Before collection of samples, the water temperature was measured. The water samples were analysed for turbidity, conductivity, total alkalinity, total dissolved solid, pH and ions including chloride, sulphate, calcium, and magnesium. Statistical correlation analysis and ANOVA test were used to analyze the association between environmental parameters and larval mosquito abundance. In total 2 973 larvae of the genus Anopheles were collected from 25 larval habitats and identified using morphological characters. They comprised of six species: An. dthali (53.21%), An. stephensi (24.22%), An. culicifacies (14.06%), An. superpictus (4.07%), An. turkhudi (3.30%), and An. apoci (1.14%). The most abundant species was An. dthali which were collected from all of the study areas. Larvae of two malaria vectors, An. dthali and An. stephensi, co-existed and collected in a wide range of habitats with different physico-chemical parameters. The most common larval habitats were man-made sites such as sand mining pools with clean and still water. The anopheline mosquitoes also preferred permanent habitats in sunlight with sandy substrates. The results indicated that there was a significant relationship between mean physico-chemical parameters such as water temperature, conductivity, total alkalinity, sulphate, chloride, and mosquito

Seasonal Occurrence and Interspecific Interactions of Egg Parasitoids of Megacopta cribraria (Heteroptera: Plataspidae) in Japan.

PubMed

Hoshino, Keisuke; Adati, Tarô; Olson, Dawn M; Takasu, Keiji

2017-06-01

We conducted a field study to determine seasonal egg parasitism rates of the kudzu bug Megacopta cribraria (F.) on the kudzu plant, Pueraria montana (Lour.) Merr. var. lobata (Willd.) Maesen et Almeida ex Sanjappa and Pradeep, in Tokyo, Japan, during the period from May 2014 to September 2014. The eggs of M. cribraria per 1 m2 of kudzu at four locations in Tokyo were collected weekly and parasitism rates were assessed. Eggs of M. cribraria were laid on the kudzu plant from May to September. Megacopta cribraria eggs were parasitized by two parasitoid species, Paratelenomus saccharalis (Dodd) and Ooencyrtus nezarae Ishii. Paratelenomus saccharalis first appeared in May, and its parasitism rates peaked in July and September. Ooencyrtus nezarae first appeared in June and its parasitism rates peaked in July. Except for one location which could not be statistically analyzed because of the small sample size, occurrence of parasitism by P. saccharalis and O. nezarae in M. cribraria egg masses was independent at one location and positively associated at two locations, suggesting that the use of host egg masses by P. saccharalis and O. nezarae is not mutually exclusive. Parasitism rates by P. saccharalis and O. nezarae were significantly lower for egg masses parasitized by both species than for those parasitized by a single species. The proportion of males among O. nezarae progeny was significantly higher for egg masses parasitized by O. nezarae together with P. saccharalis than for those parasitized by O. nezarae alone. These results suggest that parasitism of host egg masses by the two species is influenced by their interspecific interactions. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Fast versus slow larval growth in an invasive marine mollusc: does paternity matter?

PubMed

Le Cam, Sabrina; Pechenik, Jan A; Cagnon, Mathilde; Viard, Frédérique

2009-01-01

Reproductive strategies and parental effects play a major role in shaping early life-history traits. Although polyandry is a common reproductive strategy, its role is still poorly documented in relation to paternal effects. Here, we used as a case study the invasive sessile marine gastropod Crepidula fornicata, a mollusc with polyandry and extreme larval growth variation among sibling larvae. Based on paternity analyses, the relationships between paternal identity and the variations in a major early life-history trait in marine organisms, that is, larval growth, were investigated. Using microsatellite markers, paternities of 437 fast- and slow-growing larvae from 6 broods were reliably assigned to a set of 20 fathers. No particular fathers were found responsible for the specific growth performances of their offspring. However, the range of larval growth rates within a brood was significantly correlated to 1) an index of sire diversity and 2) the degree of larvae relatedness within broods. Multiple paternity could thus play an important role in determining the extent of pelagic larval duration and consequently the range of dispersal distances achieved during larval life. This study also highlighted the usefulness of using indices based on fathers' relative contribution to the progeny in paternity studies.

Effects of Larval Density on Gene Regulation in Caenorhabditis elegans During Routine L1 Synchronization.

PubMed

Chan, Io Long; Rando, Oliver J; Conine, Colin C

2018-05-04

Bleaching gravid C. elegans followed by a short period of starvation of the L1 larvae is a routine method performed by worm researchers for generating synchronous populations for experiments. During the process of investigating dietary effects on gene regulation in L1 stage worms by single-worm RNA-Seq, we found that the density of resuspended L1 larvae affects expression of many mRNAs. Specifically, a number of genes related to metabolism and signaling are highly expressed in worms arrested at low density, but are repressed at higher arrest densities. We generated a GFP reporter strain based on one of the most density-dependent genes in our dataset - lips-15 - and confirmed that this reporter was expressed specifically in worms arrested at relatively low density. Finally, we show that conditioned media from high density L1 cultures was able to downregulate lips-15 even in L1 animals arrested at low density, and experiments using daf-22 mutant animals demonstrated that this effect is not mediated by the ascaroside family of signaling pheromones. Together, our data implicate a soluble signaling molecule in density sensing by L1 stage C. elegans , and provide guidance for design of experiments focused on early developmental gene regulation. Copyright © 2018 Chan et al.

[BIO-INSECTICIDAL ACTIVITY OF ALPINIA GALANGA (L.) ON LARVAL DEVELOPMENT OF SPODOPTERA LITURA (LEPIDOPTERA: NOCTUIDAE).

PubMed

Pumchan, A; Puangsomchit, A; Temyarasilp, P; Pluempanupat, W; Bullangpoti, V

2015-01-01

The aim of the study was to assess the bio-efficacy of four Alpinia galanga rhizome crude extracts against the second and third instars of Spodoptera litura, an important field pest. The growth of younger larvae was significantly affected while that of the older larval stage was less influenced. In both stages, the methanol crude extract showed the greatest efficiency which caused the highest number of abnormal adults to occur and produced a large LD₅₀ value (12.816 µg/ larvae) pupicidal percentage after treatment, whereas, hexane extract caused the highest mortality during the larval-pupal stage after treatment with an LD₅₀ value of 6.354 µg/ larvae. However, the larval development was not significantly different among all treated larvae compared to the control. This study suggests that secondary larval instars of S. litura are more susceptible to the larval growth inhibitory action of Alpinia galanga extracts and these extracts could also be applied for use in the management of pests.

Temperature during larval development and adult maintenance influences the survival of Anopheles gambiae s.s.

PubMed

Christiansen-Jucht, Céline; Parham, Paul E; Saddler, Adam; Koella, Jacob C; Basáñez, María-Gloria

2014-11-05

Malaria transmission depends on vector life-history parameters and population dynamics, and particularly on the survival of adult Anopheles mosquitoes. These dynamics are sensitive to climatic and environmental factors, and temperature is a particularly important driver. Data currently exist on the influence of constant and fluctuating adult environmental temperature on adult Anopheles gambiae s.s. survival and on the effect of larval environmental temperature on larval survival, but none on how larval temperature affects adult life-history parameters. Mosquito larvae and pupae were reared individually at different temperatures (23 ± 1°C, 27 ± 1°C, 31 ± 1°C, and 35 ± 1°C), 75 ± 5% relative humidity. Upon emergence into imagoes, individual adult females were either left at their larval temperature or placed at a different temperature within the range above. Survival was monitored every 24 hours and data were analysed using non-parametric and parametric methods. The Gompertz distribution fitted the survivorship data better than the gamma, Weibull, and exponential distributions overall and was adopted to describe mosquito mortality rates. Increasing environmental temperature during the larval stages decreased larval survival (p < 0.001). Increases of 4°C (from 23°C to 27°C, 27°C to 31°C, and 31°C to 35°C), 8°C (27°C to 35°C) and 12°C (23°C to 35°C) statistically significantly increased larval mortality (p < 0.001). Higher environmental temperature during the adult stages significantly lowered adult survival overall (p < 0.001), with increases of 4°C and 8°C significantly influencing survival (p < 0.001). Increasing the larval environment temperature also significantly increased adult mortality overall (p < 0.001): a 4°C increase (23°C to 27°C) did not significantly affect adult survival (p > 0.05), but an 8°C increase did (p < 0.05). The effect of a 4°C increase in larval temperature from 27

Live Cell Imaging of Butterfly Pupal and Larval Wings In Vivo

PubMed Central

Ohno, Yoshikazu; Otaki, Joji M.

2015-01-01

Butterfly wing color patterns are determined during the late larval and early pupal stages. Characterization of wing epithelial cells at these stages is thus critical to understand how wing structures, including color patterns, are determined. Previously, we successfully recorded real-time in vivo images of developing butterfly wings over time at the tissue level. In this study, we employed similar in vivo fluorescent imaging techniques to visualize developing wing epithelial cells in the late larval and early pupal stages 1 hour post-pupation. Both larval and pupal epithelial cells were rich in mitochondria and intracellular networks of endoplasmic reticulum, suggesting high metabolic activities, likely in preparation for cellular division, polyploidization, and differentiation. Larval epithelial cells in the wing imaginal disk were relatively large horizontally and tightly packed, whereas pupal epithelial cells were smaller and relatively loosely packed. Furthermore, larval cells were flat, whereas pupal cells were vertically elongated as deep as 130 μm. In pupal cells, many endosome-like or autophagosome-like structures were present in the cellular periphery down to approximately 10 μm in depth, and extensive epidermal feet or filopodia-like processes were observed a few micrometers deep from the cellular surface. Cells were clustered or bundled from approximately 50 μm in depth to deeper levels. From 60 μm to 80 μm in depth, horizontal connections between these clusters were observed. The prospective eyespot and marginal focus areas were resistant to fluorescent dyes, likely because of their non-flat cone-like structures with a relatively thick cuticle. These in vivo images provide important information with which to understand processes of epithelial cell differentiation and color pattern determination in butterfly wings. PMID:26107809

Live Cell Imaging of Butterfly Pupal and Larval Wings In Vivo.

PubMed

Ohno, Yoshikazu; Otaki, Joji M

2015-01-01

Butterfly wing color patterns are determined during the late larval and early pupal stages. Characterization of wing epithelial cells at these stages is thus critical to understand how wing structures, including color patterns, are determined. Previously, we successfully recorded real-time in vivo images of developing butterfly wings over time at the tissue level. In this study, we employed similar in vivo fluorescent imaging techniques to visualize developing wing epithelial cells in the late larval and early pupal stages 1 hour post-pupation. Both larval and pupal epithelial cells were rich in mitochondria and intracellular networks of endoplasmic reticulum, suggesting high metabolic activities, likely in preparation for cellular division, polyploidization, and differentiation. Larval epithelial cells in the wing imaginal disk were relatively large horizontally and tightly packed, whereas pupal epithelial cells were smaller and relatively loosely packed. Furthermore, larval cells were flat, whereas pupal cells were vertically elongated as deep as 130 μm. In pupal cells, many endosome-like or autophagosome-like structures were present in the cellular periphery down to approximately 10 μm in depth, and extensive epidermal feet or filopodia-like processes were observed a few micrometers deep from the cellular surface. Cells were clustered or bundled from approximately 50 μm in depth to deeper levels. From 60 μm to 80 μm in depth, horizontal connections between these clusters were observed. The prospective eyespot and marginal focus areas were resistant to fluorescent dyes, likely because of their non-flat cone-like structures with a relatively thick cuticle. These in vivo images provide important information with which to understand processes of epithelial cell differentiation and color pattern determination in butterfly wings.

Larval Settlement: The Role of Surface Topography for Sessile Coral Reef Invertebrates

PubMed Central

Whalan, Steve; Abdul Wahab, Muhammad A.; Sprungala, Susanne; Poole, Andrew J.; de Nys, Rocky

2015-01-01

For sessile marine invertebrates with complex life cycles, habitat choice is directed by the larval phase. Defining which habitat-linked cues are implicated in sessile invertebrate larval settlement has largely concentrated on chemical cues which are thought to signal optimal habitat. There has been less effort establishing physical settlement cues, including the role of surface microtopography. This laboratory based study tested whether surface microtopography alone (without chemical cues) plays an important contributing role in the settlement of larvae of coral reef sessile invertebrates. We measured settlement to tiles, engineered with surface microtopography (holes) that closely matched the sizes (width) of larvae of a range of corals and sponges, in addition to surfaces with holes that were markedly larger than larvae. Larvae from two species of scleractinian corals (Acropora millepora and Ctenactis crassa) and three species of coral reef sponges (Luffariella variabilis, Carteriospongia foliascens and Ircinia sp.,) were used in experiments. L. variabilis, A. millepora and C. crassa showed markedly higher settlement to surface microtopography that closely matched their larval width. C. foliascens and Ircinia sp., showed no specificity to surface microtopography, settling just as often to microtopography as to flat surfaces. The findings of this study question the sole reliance on chemical based larval settlement cues, previously established for some coral and sponge species, and demonstrate that specific physical cues (surface complexity) can also play an important role in larval settlement of coral reef sessile invertebrates. PMID:25671562

Larval settlement: the role of surface topography for sessile coral reef invertebrates.

PubMed

Whalan, Steve; Wahab, Muhammad A Abdul; Sprungala, Susanne; Poole, Andrew J; de Nys, Rocky

2015-01-01

For sessile marine invertebrates with complex life cycles, habitat choice is directed by the larval phase. Defining which habitat-linked cues are implicated in sessile invertebrate larval settlement has largely concentrated on chemical cues which are thought to signal optimal habitat. There has been less effort establishing physical settlement cues, including the role of surface microtopography. This laboratory based study tested whether surface microtopography alone (without chemical cues) plays an important contributing role in the settlement of larvae of coral reef sessile invertebrates. We measured settlement to tiles, engineered with surface microtopography (holes) that closely matched the sizes (width) of larvae of a range of corals and sponges, in addition to surfaces with holes that were markedly larger than larvae. Larvae from two species of scleractinian corals (Acropora millepora and Ctenactis crassa) and three species of coral reef sponges (Luffariella variabilis, Carteriospongia foliascens and Ircinia sp.,) were used in experiments. L. variabilis, A. millepora and C. crassa showed markedly higher settlement to surface microtopography that closely matched their larval width. C. foliascens and Ircinia sp., showed no specificity to surface microtopography, settling just as often to microtopography as to flat surfaces. The findings of this study question the sole reliance on chemical based larval settlement cues, previously established for some coral and sponge species, and demonstrate that specific physical cues (surface complexity) can also play an important role in larval settlement of coral reef sessile invertebrates.

Unimodal relationship between small-scale barnacle recruitment and the density of pre-existing barnacle adults.

PubMed

Scrosati, Ricardo A; Ellrich, Julius A

2017-01-01

Recruitment is a key demographic process for population persistence. This paper focuses on barnacle ( Semibalanus balanoides ) recruitment. In rocky intertidal habitats from the Gulf of St. Lawrence coast of Nova Scotia (Canada), ice scour is common during the winter. At the onset of intertidal barnacle recruitment in early May (after sea ice has fully melted), mostly only adult barnacles and bare substrate are visible at high elevations in wave-exposed habitats. We conducted a multiannual study to investigate if small-scale barnacle recruitment could be predicted from the density of pre-existing adult barnacles. In a year that exhibited a wide adult density range (ca. 0-130 individuals dm -2 ), the relationship between adult density and recruit density (scaled to the available area for recruitment, which excluded adult barnacles) was unimodal. In years that exhibited a lower adult density range (ca. 0-40/50 individuals dm -2 ), the relationship between adult and recruit density was positive and resembled the lower half of the unimodal relationship. Overall, adult barnacle density was able to explain 26-40% of the observed variation in recruit density. The unimodal adult-recruit relationship is consistent with previously documented intraspecific interactions. Between low and intermediate adult densities, the positive nature of the relationship relates to the previously documented fact that settlement-seeking larvae are chemically and visually attracted to adults, which might be important for local population persistence. Between intermediate and high adult densities, where population persistence may be less compromised and the abundant adults may limit recruit growth and survival, the negative nature of the relationship suggests that adult barnacles at increasingly high densities stimulate larvae to settle elsewhere. The unimodal pattern may be especially common on shores with moderate rates of larval supply to the shore, because high rates of larval supply may

Larval cannibalism and pupal defense against cannibalism in two species of tenebrionid beetles.

PubMed

Ichikawa, Toshio; Kurauchi, Toshiaki

2009-08-01

Cannibalism of pupae by larvae has been documented In many species of Insects, but the features of larval cannibalism and pupal defensive mechanisms against larval cannibalism have been largely Ignored. Pupae of tenebrionld beetles rotate their abdominal segments in a circular motion in response to the tactile stimulation of appendages, including legs, antennae, maxillary pulps, and wings. When the pupal abdominal rotation responses of Tenebrio molitor and Zophobas atratus were completely blocked by transecting the ventral nerve cord (VNC) of the pupae, the appendages of the paralytic pupae became initial, major targets for attack by larval cannibals. The majority of 20 paralytic pupae was cannibalized by 100 larvae within 6 h, and almost all the pupae were killed within 2-3 days. In contrast, only a few pupae of Z. atratus and several pupae of T. molitor were cannibalized when the VNC was Intact. The abdominal rotation response of the pupae thus functions as an effective defense against larval cannibalism.

Larval connectivity of pearl oyster through biophysical modelling; evidence of food limitation and broodstock effect

NASA Astrophysics Data System (ADS)

Thomas, Yoann; Dumas, Franck; Andréfouët, Serge

2016-12-01

The black-lip pearl oyster (Pinctada margaritifera) is cultured extensively to produce black pearls, especially in French Polynesia atoll lagoons. This aquaculture relies on spat collection, a process that experiences spatial and temporal variability and needs to be optimized by understanding which factors influence recruitment. Here, we investigate the sensitivity of P. margaritifera larval dispersal to both physical and biological factors in the lagoon of Ahe atoll. Coupling a validated 3D larval dispersal model, a bioenergetics larval growth model following the Dynamic Energy Budget (DEB) theory, and a population dynamics model, the variability of lagoon-scale connectivity patterns and recruitment potential is investigated. The relative contribution of reared and wild broodstock to the lagoon-scale recruitment potential is also investigated. Sensitivity analyses pointed out the major effect of the broodstock population structure as well as the sensitivity to larval mortality rate and inter-individual growth variability to larval supply and to the subsequent settlement potential. The application of the growth model clarifies how trophic conditions determine the larval supply and connectivity patterns. These results provide new cues to understand the dynamics of bottom-dwelling populations in atoll lagoons, their recruitment, and discuss how to take advantage of these findings and numerical models for pearl oyster management.

Larval biology of the crab Rhithropanopeus harrisii (Gould): a synthesis.

PubMed

Forward, Richard B

2009-06-01

This synthesis reviews the physiological ecology and behavior of larvae of the benthic crab Rhithropanopeus harrisii, which occurs in low-salinity areas of estuaries. Larvae are released rhythmically around the time of high tide in tidal estuaries and in the 2-h interval after sunset in nontidal estuaries. As in most subtidal crustaceans, the timing of larval release is controlled by the developing embryos, which release peptide pheromones that stimulate larval release behavior by the female to synchronize the time of egg hatching. Larvae pass through four zoeal stages and a postlarval or megalopal stage that are planktonic before metamorphosis. They are retained near the adult population by means of an endogenous tidal rhythm in vertical migration. Larvae have several safeguards against predation: they undergo nocturnal diel vertical migration (DVM) and have a shadow response to avoid encountering predators, and they bear long spines as a deterrent. Photoresponses during DVM and the shadow response are enhanced by exposure to chemical cues from the mucus of predator fishes and ctenophores. The primary visual pigment has a spectral sensitivity maximum at about 500 nm, which is typical for zooplankton and matches the ambient spectrum at twilight. Larvae can detect vertical gradients in temperature, salinity, and hydrostatic pressure, which are used for depth regulation and avoidance of adverse environmental conditions. Characteristics that are related to the larval habitat and are common to other crab larval species are considered.

Maternal effects and larval survival of marbled sole Pseudopleuronectes yokohamae

NASA Astrophysics Data System (ADS)

Higashitani, Tomomi; Takatsu, Tetsuya; Nakaya, Mitsuhiro; Joh, Mikimasa; Takahashi, Toyomi

2007-07-01

Maternal effects of animals are the phenotypic influences of age, size, and condition of spawners on the survival and phenotypic traits of offspring. To clarify the maternal effects for marbled sole Pseudopleuronectes yokohamae, we investigated the effects of body size, nutrient condition, and growth history of adult females on egg size, larval size, and starvation tolerance, growth, and feeding ability of offspring. The fecundity of adult females was strongly dependent on body size. Path analysis revealed that the mother's total length positively affected mean egg diameter, meaning that large females spawned large eggs. In contrast, the relative growth rate of adult females negatively affected egg diameter. Egg diameters positively affected both notochord length and yolk sac volume of the larvae at hatching. Under starvation conditions, notochord length at hatching strongly and positively affected days of survival at 14 °C but not at 9 °C. Under adequate food conditions (1000 rotifers L - 1 ), the notochord length of larvae 5 days after hatching positively affected feeding rate, implying that large larvae have high feeding ability. In addition, the mean growth rate of larvae between 0 and 15 days increased with increasing egg diameter under homogenous food conditions, suggesting that larvae hatched from large eggs might have a growth advantage for at least to 15 days after hatching. In marbled sole, these relationships (i.e., mother's body size-egg size-larval size-larval resistance to starvation-larval feeding ability) may help explain recruitment variability.

Oceanography promotes self-recruitment in a planktonic larval disperser.

PubMed

Teske, Peter R; Sandoval-Castillo, Jonathan; van Sebille, Erik; Waters, Jonathan; Beheregaray, Luciano B

2016-09-30

The application of high-resolution genetic data has revealed that oceanographic connectivity in marine species with planktonic larvae can be surprisingly limited, even in the absence of major barriers to dispersal. Australia's southern coast represents a particularly interesting system for studying planktonic larval dispersal, as the hydrodynamic regime of the wide continental shelf has potential to facilitate onshore retention of larvae. We used a seascape genetics approach (the joint analysis of genetic data and oceanographic connectivity simulations) to assess population genetic structure and self-recruitment in a broadcast-spawning marine gastropod that exists as a single meta-population throughout its temperate Australian range. Levels of self-recruitment were surprisingly high, and oceanographic connectivity simulations indicated that this was a result of low-velocity nearshore currents promoting the retention of planktonic larvae in the vicinity of natal sites. Even though the model applied here is comparatively simple and assumes that the dispersal of planktonic larvae is passive, we find that oceanography alone is sufficient to explain the high levels of genetic structure and self-recruitment. Our study contributes to growing evidence that sophisticated larval behaviour is not a prerequisite for larval retention in the nearshore region in planktonic-developing species.

Carryover effects of larval exposure to different environmental bacteria drive adult trait variation in a mosquito vector

PubMed Central

Dickson, Laura B.; Jiolle, Davy; Minard, Guillaume; Moltini-Conclois, Isabelle; Volant, Stevenn; Ghozlane, Amine; Bouchier, Christiane; Ayala, Diego; Paupy, Christophe; Moro, Claire Valiente; Lambrechts, Louis

2017-01-01

Conditions experienced during larval development of holometabolous insects can affect adult traits, but whether differences in the bacterial communities of larval development sites contribute to variation in the ability of insect vectors to transmit human pathogens is unknown. We addressed this question in the mosquito Aedes aegypti, a major arbovirus vector breeding in both sylvatic and domestic habitats in Sub-Saharan Africa. Targeted metagenomics revealed differing bacterial communities in the water of natural breeding sites in Gabon. Experimental exposure to different native bacterial isolates during larval development resulted in significant differences in pupation rate and adult body size but not life span. Larval exposure to an Enterobacteriaceae isolate resulted in decreased antibacterial activity in adult hemolymph and reduced dengue virus dissemination titer. Together, these data provide the proof of concept that larval exposure to different bacteria can drive variation in adult traits underlying vectorial capacity. Our study establishes a functional link between larval ecology, environmental microbes, and adult phenotypic variation in a holometabolous insect vector. PMID:28835919

Organization of the Drosophila larval visual circuit

PubMed Central

Gendre, Nanae; Neagu-Maier, G Larisa; Fetter, Richard D; Schneider-Mizell, Casey M; Truman, James W; Zlatic, Marta; Cardona, Albert

2017-01-01

Visual systems transduce, process and transmit light-dependent environmental cues. Computation of visual features depends on photoreceptor neuron types (PR) present, organization of the eye and wiring of the underlying neural circuit. Here, we describe the circuit architecture of the visual system of Drosophila larvae by mapping the synaptic wiring diagram and neurotransmitters. By contacting different targets, the two larval PR-subtypes create two converging pathways potentially underlying the computation of ambient light intensity and temporal light changes already within this first visual processing center. Locally processed visual information then signals via dedicated projection interneurons to higher brain areas including the lateral horn and mushroom body. The stratified structure of the larval optic neuropil (LON) suggests common organizational principles with the adult fly and vertebrate visual systems. The complete synaptic wiring diagram of the LON paves the way to understanding how circuits with reduced numerical complexity control wide ranges of behaviors.

Using larval fish community structure to guide long-term monitoring of fish spawning activity

USGS Publications Warehouse

Pritt, Jeremy J.; Roseman, Edward F.; Ross, Jason E.; DeBruyne, Robin L.

2015-01-01

Larval fishes provide a direct indication of spawning activity and may therefore be useful for long-term monitoring efforts in relation to spawning habitat restoration. However, larval fish sampling can be time intensive and costly. We sought to understand the spatial and temporal structure of larval fish communities in the St. Clair–Detroit River system, Michigan–Ontario, to determine whether targeted larval fish sampling can be made more efficient for long-term monitoring. We found that larval fish communities were highly nested, with lower river segments and late-spring samples containing the highest genus richness of larval fish. We created four sampling scenarios for each river system: (1) using all available data, (2) limiting temporal sampling to late spring, (3) limiting spatial sampling to lower river segments only, and (4) limiting both spatial and temporal sampling. By limiting the spatial extent of sampling to lower river sites and/or limiting the temporal extent to the late-spring period, we found that effort could be reduced by more than 50% while maintaining over 75% of the observed and estimated total genus richness. Similarly, limiting the sampling effort to lower river sites and/or the late-spring period maintained between 65% and 93% of the observed richness of lithophilic-spawning genera and invasive genera. In general, community composition remained consistent among sampling scenarios. Targeted sampling offers a lower-cost alternative to exhaustive spatial and temporal sampling and may be more readily incorporated into long-term monitoring.

Muscle organizers in Drosophila: the role of persistent larval fibers in adult flight muscle development

NASA Technical Reports Server (NTRS)

Farrell, E. R.; Fernandes, J.; Keshishian, H.

1996-01-01

In many organisms muscle formation depends on specialized cells that prefigure the pattern of the musculature and serve as templates for myoblast organization and fusion. These include muscle pioneers in insects and muscle organizing cells in leech. In Drosophila, muscle founder cells have been proposed to play a similar role in organizing larval muscle development during embryogenesis. During metamorphosis in Drosophila, following histolysis of most of the larval musculature, there is a second round of myogenesis that gives rise to the adult muscles. It is not known whether muscle founder cells organize the development of these muscles. However, in the thorax specific larval muscle fibers do not histolyze at the onset of metamorphosis, but instead serve as templates for the formation of a subset of adult muscles, the dorsal longitudinal flight muscles (DLMs). Because these persistent larval muscle fibers appear to be functioning in many respects like muscle founder cells, we investigated whether they were necessary for DLM development by using a microbeam laser to ablate them singly and in combination. We found that, in the absence of the larval muscle fibers, DLMs nonetheless develop. Our results show that the persistent larval muscle fibers are not required to initiate myoblast fusion, to determine DLM identity, to locate the DLMs in the thorax, or to specify the total DLM fiber volume. However, they are required to regulate the number of DLM fibers generated. Thus, while the persistent larval muscle fibers are not obligatory for DLM fiber formation and differentiation, they are necessary to ensure the development of the correct number of fibers.

The neural basis of visual behaviors in the larval zebrafish

PubMed Central

Portugues, Ruben; Engert, Florian

2015-01-01

We review visually guided behaviors in larval zebrafish and summarise what is known about the neural processing that results in these behaviors, paying particular attention to the progress made in the last 2 years. Using the examples of the optokinetic reflex, the optomotor response, prey tracking and the visual startle response, we illustrate how the larval zebrafish presents us with a very promising model vertebrate system that allows neurocientists to integrate functional and behavioral studies and from which we can expect illuminating insights in the near future. PMID:19896836

The neural basis of visual behaviors in the larval zebrafish.

PubMed

Portugues, Ruben; Engert, Florian

2009-12-01

We review visually guided behaviors in larval zebrafish and summarise what is known about the neural processing that results in these behaviors, paying particular attention to the progress made in the last 2 years. Using the examples of the optokinetic reflex, the optomotor response, prey tracking and the visual startle response, we illustrate how the larval zebrafish presents us with a very promising model vertebrate system that allows neurocientists to integrate functional and behavioral studies and from which we can expect illuminating insights in the near future. Copyright 2009 Elsevier Ltd. All rights reserved.

A trypsin inhibitor from Sapindus saponaria L. seeds: purification, characterization, and activity towards pest insect digestive enzyme.

PubMed

Macedo, Maria Lígia R; Diz Filho, Eduardo B S; Freire, Mariadas Graças M; Oliva, Maria Luiza V; Sumikawa, Joana T; Toyama, Marcos H; Marangoni, Sérgio

2011-01-01

The present paper describes the purification, characterization and determination of the partial primary structure of the first trypsin inhibitor isolated from the family Sapindaceae. A highly stable, potent trypsin inhibitor (SSTI) was purified to homogeneity. SDS-PAGE analysis revealed that the protein consists of a two-polypeptide chain with molecular masses of approximately 15 and 3 kDa. The purified inhibitor inhibited bovine trypsin at a 1:1 M ratio. Kinetic analysis revealed that the protein is a competitive inhibitor with an equilibrium dissociation constant of 10⁻⁹ M for trypsin. The partial NH₂- terminal sequence of 36 amino acids in SSTI indicates homology with other members of the trypsin-inhibitor family from different sources. This inhibitor is highly stable in the presence of denaturing agents. SSTI showed significant inhibitory activity against trypsin-like proteases present in the larval midgut on Anagasta kuehniella, Corcyra cephalonica, Diatreae saccharalis and Anticarsia gemmatalis.

Morphology-flow interactions lead to stage-selective vertical transport of larval sand dollars in shear flow.

PubMed

Clay, T W; Grünbaum, D

2010-04-01

Many larvae and other plankton have complex and variable morphologies of unknown functional significance. We experimentally and theoretically investigated the functional consequences of the complex morphologies of larval sand dollars, Dendraster excentricus (Eschscholtz), for hydrodynamic interactions between swimming and turbulent water motion. Vertical shearing flows (horizontal gradients of vertical flow) tilt organisms with simple geometries (e.g. spheres, ellipsoids), causing these organisms to move horizontally towards downwelling water and compromising their abilities to swim upwards. A biomechanical model of corresponding hydrodynamic interactions between turbulence-induced shear and the morphologically complex four-, six- and eight-armed stages of sand dollar larvae suggests that the movements of larval morphologies differ quantitatively and qualitatively across stages and shear intensities: at shear levels typical of calm conditions in estuarine and coastal environments, all modeled larval stages moved upward. However, at higher shears, modeled four- and eight-armed larvae moved towards downwelling, whereas six-armed larvae moved towards upwelling. We also experimentally quantified larval movement by tracking larvae swimming in low-intensity shear while simultaneously mapping the surrounding flow fields. Four- and eight-armed larvae moved into downwelling water, but six-armed larvae did not. Both the model and experiments suggest that stage-dependent changes to larval morphology lead to differences in larval movement: four- and eight-armed stages are more prone than the six-armed stage to moving into downwelling water. Our results suggest a mechanism by which differences can arise in the vertical distribution among larval stages. The ability to mitigate or exploit hydrodynamic interactions with shear is a functional consequence that potentially shapes larval evolution and development.

Quantification of larval resistance to Cypermethrin in tobacco budworm (Lepidoptera: Noctuidae) and the effects of larval weight

Treesearch

Michael J. Firko; Janes Leslie Hayes

1990-01-01

We examined relationships between larval weight and degree of resistance to cypermethrin in tobacco budworm, Heliothis virescens (F.). Laboratory-reared larvae (9.0-175.4 mg) were treated with either 0.1 or 1.0 mg cypermethrin in acetone. Degree of debilitation of each larva was assessed at intervals from 0.5 h to 5 d after treatment cumulative...

Larval retention and connectivity among populations of corals and reef fishes: history, advances and challenges

NASA Astrophysics Data System (ADS)

Jones, G. P.; Almany, G. R.; Russ, G. R.; Sale, P. F.; Steneck, R. S.; van Oppen, M. J. H.; Willis, B. L.

2009-06-01

The extent of larval dispersal on coral reefs has important implications for the persistence of coral reef metapopulations, their resilience and recovery from an increasing array of threats, and the success of protective measures. This article highlights a recent dramatic increase in research effort and a growing diversity of approaches to the study of larval retention within (self-recruitment) and dispersal among (connectivity) isolated coral reef populations. Historically, researchers were motivated by alternative hypotheses concerning the processes limiting populations and structuring coral reef assemblages, whereas the recent impetus has come largely from the need to incorporate dispersal information into the design of no-take marine protected area (MPA) networks. Although the majority of studies continue to rely on population genetic approaches to make inferences about dispersal, a wide range of techniques are now being employed, from small-scale larval tagging and paternity analyses, to large-scale biophysical circulation models. Multiple approaches are increasingly being applied to cross-validate and provide more realistic estimates of larval dispersal. The vast majority of empirical studies have focused on corals and fishes, where evidence for both extremely local scale patterns of self-recruitment and ecologically significant connectivity among reefs at scales of tens of kilometers (and in some cases hundreds of kilometers) is accumulating. Levels of larval retention and the spatial extent of connectivity in both corals and fishes appear to be largely independent of larval duration or reef size, but may be strongly influenced by geographic setting. It is argued that high levels of both self-recruitment and larval import can contribute to the resilience of reef populations and MPA networks, but these benefits will erode in degrading reef environments.

Diel periodicity of drift of larval fishes in tributaries of Lake Ontario

USGS Publications Warehouse

Johnson, J. H.; McKenna, J.E.

2007-01-01

Diel patterns of downstream drift were examined during mid-June in three tributaries of Lake Ontario. Larval fishes were collected in drift nets that were set in each stream for 72 consecutive hours and emptied at 4-h intervals. Fantail darter (Ethostoma flabellare) and blacknose dace (Rhinichthys atractulus) were the two most abundant native stream fishes and were two of the three species collected in the ichthyoplankton drift. Fantail darter larvae comprised 100%, 98.9%, and 70.2% of the ichthyoplankton in the three streams. Most larval fishes (96%) drifted at night with peak catches occurring at 2400h in Orwell Brook and Trout Brook and 0400h in Little Sandy Creek. Based on stream temperatures, peak spawning and larval drift of blacknose dace probably occurred later in the season.

Larval green and white sturgeon swimming performance in relation to water-diversion flows

PubMed Central

Verhille, Christine E.; Poletto, Jamilynn B.; Cocherell, Dennis E.; DeCourten, Bethany; Baird, Sarah; Cech, Joseph J.; Fangue, Nann A.

2014-01-01

Little is known of the swimming capacities of larval sturgeons, despite global population declines in many species due in part to fragmentation of their spawning and rearing habitats by man-made water-diversion structures. Larval green (Acipenser medirostris) and white sturgeon (Acipenser transmontanus) inhabit the highly altered Sacramento–San Joaquin watershed, making them logical species to examine vulnerability to entrainment by altered water flows. The risk of larval sturgeon entrainment is influenced by the ontogeny of swimming capacity and dispersal timing and their interactions with water-diversion structure operations. Therefore, the aim of this study was to describe and compare the ontogeny and allometry of larval green and white sturgeon swimming capacities until completion of metamorphosis into juveniles. Despite the faster growth rates and eventual larger size of larval white sturgeon, green sturgeon critical swimming velocities remained consistently, though modestly, greater than those of white sturgeon throughout the larval life stage. Although behavioural interactions with water-diversion structures are also important considerations, regarding swimming capacity, Sacramento–San Joaquin sturgeons are most vulnerable to entrainment in February–May, when white sturgeon early larvae are in the middle Sacramento River, and April–May, when green sturgeon early larvae are in the upper river. Green sturgeon migrating downstream to the estuary and bays in October–November are also susceptible to entrainment due to their movements combined with seasonal declines in their swimming capacity. An additional inter-species comparison of the allometric relationship between critical swimming velocities and total length with several sturgeon species found throughout the world suggests a similar ontogeny of swimming capacity with growth. Therefore, although dispersal and behaviour differ among river systems and sturgeon species, similar recommendations are

Efficiency of two larval diets for mass-rearing of the mosquito Aedes aegypti

PubMed Central

Bond, J. G.; Ramírez-Osorio, A.; Marina, C. F.; Fernández-Salas, I.; Liedo, P.; Dor, A.

2017-01-01

Aedes aegypti is a major vector of arboviruses that may be controlled on an area-wide basis using the sterile insect technique (SIT). Larval diet is a major factor in mass-rearing for SIT programs. We compared dietary effects on immature development and adult fitness-related characteristics for an International Atomic Energy Agency (IAEA) diet, developed for rearing Ae. albopictus, and a standardized laboratory rodent diet (LRD), under a 14:10 h (light:dark) photoperiod ("light" treatment) or continuous darkness during larval rearing. Larval development was generally fastest in the IAEA diet, likely reflecting the high protein and lipid content of this diet. The proportion of larvae that survived to pupation or to adult emergence did not differ significantly between diets or light treatments. Insects from the LRD-dark treatment produced the highest proportion of male pupae (93% at 24 h after the beginning of pupation) whereas adult sex ratio from the IAEA diet tended to be more male-biased than that of the LRD diet. Adult longevity did not differ significantly with larval diet or light conditions, irrespective of sex. In other aspects the LRD diet generally performed best. Adult males from the LRD diet were significantly larger than those from the IAEA diet, irrespective of light treatment. Females from the LRD diet had ~25% higher fecundity and ~8% higher egg fertility compared to those from the IAEA diet. Adult flight ability did not differ between larval diets, and males had a similar number of copulations with wild females, irrespective of larval diet. The LRD diet had lower protein and fat content but a higher carbohydrate and energetic content than the IAEA diet. We conclude that the LRD diet is a low-cost standardized diet that is likely to be suitable for mass-rearing of Ae. aegypti for area-wide SIT-based vector control. PMID:29095933

The role of internal waves in larval fish interactions with potential predators and prey

NASA Astrophysics Data System (ADS)

Greer, Adam T.; Cowen, Robert K.; Guigand, Cedric M.; Hare, Jonathan A.; Tang, Dorothy

2014-09-01

Tidally driven internal wave packets in coastal environments have the potential to influence patchiness of larval fishes, prey, and gelatinous predators. We used the In Situ Ichthyoplankton Imaging System (ISIIS) to synoptically sample larval fishes, copepods, and planktonic predators (ctenophores, hydromedusae, chaetognaths, and polychaetes) across these predictable features in the summer near Stellwagen Bank, Massachusetts, USA. Full water column profiles and fixed depth transects (∼10 m depth) were used to quantify vertical and horizontal components of the fish and invertebrate distributions during stable and vertically mixed conditions associated with tidally generated internal waves. Larval fishes, consisting mostly of Urophycis spp., Merluccius bilinearis, and Labridae, were concentrated near the surface, with larger sizes generally occupying greater depths. During stable water column conditions, copepods formed a near surface thin layer several meters above the chlorophyll-a maximum that was absent when internal waves were propagating. In contrast, ctenophores and other predators were much more abundant at depth, but concentrations near 10 m increased immediately after the internal hydraulic jump mixed the water column. During the propagation of internal waves, the fine-scale abundance of larval fishes was more correlated with the abundance of gelatinous predators and less correlated with copepods compared to the stable conditions. Vertical oscillations caused by the internal hydraulic jump can disperse patches of zooplankton and force surface dwelling larval fishes into deeper water where probability of predator contact is increased, creating conditions potentially less favorable for larval fish growth and survival on short time scales.

Building a Beetle: How Larval Environment Leads to Adult Performance in a Horned Beetle

PubMed Central

Reaney, Leeann T.; Knell, Robert J.

2015-01-01

The link between the expression of the signals used by male animals in contests with the traits which determine success in those contests is poorly understood. This is particularly true in holometabolous insects such as horned beetles where signal expression is determined during metamorphosis and is fixed during adulthood, whereas performance is influenced by post-eclosion feeding. We used path analysis to investigate the relationships between larval and adult nutrition, horn and body size and fitness-related traits such as strength and testes mass in the horned beetle Euoniticellus intermedius. In males weight gain post-eclosion had a central role in determining both testes mass and strength. Weight gain was unaffected by adult nutrition but was strongly correlated with by horn length, itself determined by larval resource availability, indicating strong indirect effects of larval nutrition on the adult beetle’s ability to assimilate food and grow tissues. Female strength was predicted by a simple path diagram where strength was determined by eclosion weight, itself determined by larval nutrition: weight gain post-eclosion was not a predictor of strength in this sex. Based on earlier findings we discuss the insulin-like signalling pathway as a possible mechanism by which larval nutrition could affect adult weight gain and thence traits such as strength. PMID:26244874

The influence of urban heat islands and socioeconomic factors on the spatial distribution of Aedes aegypti larval habitats.

PubMed

De Azevedo, Thiago S; Bourke, Brian Patrick; Piovezan, Rafael; Sallum, Maria Anice M

2018-05-08

We addressed the potential associations among the temporal and spatial distribution of larval habitats of Aedes (Stegomyia) aegypti, the presence of urban heat islands and socioeconomic factors. Data on larval habitats were collected in Santa Bárbara d'Oeste, São Paulo, Brazil, from 2004 to 2006, and spatial and temporal variations were analysed using a wavelet-based approach. We quantified urban heat islands by calculating surface temperatures using the results of wavelet analyses and grey level transformation from Thematic Mapper images (Landsat 5). Ae. aegypti larval habitats were geo-referenced corresponding to the wavelet analyses to test the potential association between geographical distribution of habitats and surface temperature. In an inhomogeneous spatial point process, we estimated the frequency of occurrence of larval habitats in relation to temperature. The São Paulo State Social Vulnerability Index in the municipality of Santa Barbára d'Oeste was used to test the potential association between presence of larval habitats and social vulnerability. We found abundant Ae. aegypti larval habitats in areas of higher surface temperature and social vulnerability and fewer larval habitats in areas with lower surface temperature and social vulnerability.

Changes in protein expression during honey bee larval development.

PubMed

Chan, Queenie W T; Foster, Leonard J

2008-10-29

The honey bee (Apis mellifera), besides its role in pollination and honey production, serves as a model for studying the biochemistry of development, metabolism, and immunity in a social organism. Here we use mass spectrometry-based quantitative proteomics to quantify nearly 800 proteins during the 5- to 6-day larval developmental stage, tracking their expression profiles. We report that honey bee larval growth is marked by an age-correlated increase of protein transporters and receptors, as well as protein nutrient stores, while opposite trends in protein translation activity and turnover were observed. Levels of the immunity factors prophenoloxidase and apismin are positively correlated with development, while others surprisingly were not significantly age-regulated, suggesting a molecular explanation for why bees are susceptible to major age-associated bee bacterial infections such as American Foulbrood or fungal diseases such as chalkbrood. Previously unreported findings include the reduction of antioxidant and G proteins in aging larvae. These data have allowed us to integrate disparate findings in previous studies to build a model of metabolism and maturity of the immune system during larval development. This publicly accessible resource for protein expression trends will help generate new hypotheses in the increasingly important field of honey bee research.

Larval development of the subantarctic king crabs Lithodes santolla and Paralomis granulosa reared in the laboratory

NASA Astrophysics Data System (ADS)

Calcagno, J. A.; Anger, K.; Lovrich, G. A.; Thatje, S.; Kaffenberger, A.

2004-02-01

The larval development and survival in the two subantarctic lithodid crabs Lithodes santolla (Jaquinot) and Paralomis granulosa (Molina) from the Argentine Beagle Channel were studied in laboratory cultures. In L. santolla, larval development lasted about 70 days, passing through three zoeal stages and the megalopa stage, with a duration of approximately 4, 7, 11 and 48 days, respectively. The larval development in P. granulosa is more abbreviated, comprising only two zoeal stages and the megalopa stage, with 6, 11 and 43 days' duration, respectively. In both species, we tested for effects of presence versus absence of food (Artemia nauplii) on larval development duration and survival rate. In P. granulosa, we also studied effects of different rearing conditions, such as individual versus mass cultures, as well as aerated versus unaerated cultures. No differences in larval development duration and survival were observed between animals subjected to those different rearing conditions. The lack of response to the presence or absence of potential food confirms, in both species, a complete lecithotrophic mode of larval development. Since lithodid crabs are of high economic importance in the artisanal fishery in the southernmost parts of South America, the knowledge of optimal rearing conditions for lithodid larvae is essential for future attempts at repopulating the collapsing natural stocks off Tierra del Fuego.

Parallel Evolution of Larval Feeding Behavior, Morphology, and Habitat in the Snail-Kiling fly Genus Tetanocera

NASA Astrophysics Data System (ADS)

Chapman, E. G.; Foote, B. A.; Malukiewicz, J.; Hoeh, W. R.

2005-05-01

Sciomyzid larvae (Diptera: Acalyptratae) display a wide range of feeding behaviors, typically preying on a wide variety of gastropods. The genus Tetanocera is particularly interesting because its species occupy five larval feeding groups with each species' larvae living in one of two habitat types (aquatic or terrestrial). We constructed a molecular phylogeny for Tetanocera, estimated evolutionary transitions in larval feeding behaviors and habitats that occurred during Tetanocera phylogenesis, and investigated potential correlations among larval habitat and morphological characteristics. Approximately 3800 base pairs (both mitochondrial and nuclear) of sequence data were used to build the phylogeny. Larval feeding groups and habitat type were mapped onto the phylogeny and pair-wise comparisons were used to evaluate potential associations between habitat and morphology. Feeding and habitat groups within Tetanocera were usually not monophyletic and it was estimated that Tetanocera lineages made at least three independent aquatic to terrestrial transitions. These parallel habitat shifts were typically accompanied by parallel character state changes in four morphological characteristics (larval color and three posterior spiracular disc characters). These larval habitat-morphology associations were statistically significant and consistent with the action of natural selection in facilitating the morphological changes that occurred during aquatic to terrestrial habitat transitions in Tetanocera.

Gypsy moth larval defense mechanisms against pathogenic microorganisms

Treesearch

Kathleen S. Shields; Tariq M. Butt

1991-01-01

We investigated the response of gypsy moth, Lymantria dispar, larval hemocytes to L. dispar nuclear polyhedrosis virus (LdMNPV) administered per os and by injection, and to injected hyphal bodies and natural protoplasts of some entomopathogenic, entomophthoralean fungi.

Factors contributing to variability in larval ingress of Atlantic menhaden, Brevoortia tyrannus

NASA Astrophysics Data System (ADS)

Lozano, C.; Houde, E. D.

2013-02-01

Annual recruitment levels of age-0 juvenile Atlantic menhaden to Chesapeake Bay, which historically supported >65% of coastwide recruitment, have been consistently low since the 1980s. Diminished larval supply to the Bay is one hypothesized explanation. In a three-year ichthyoplankton survey at the Chesapeake Bay mouth, abundance of ingressing larvae varied nine-fold among years. Larvae were most abundant in 2007-2008 and less abundant in 2005-2006 and 2006-2007. High month-to-month variability in larval concentrations was attributable primarily to seasonality of occurrences. There was no defined spatial pattern in distribution of larvae across the 18-km-wide Bay mouth, but larvae at the south side were longer and older on average than larvae at the middle and north side. Environmental variables measured at the times of larval collections were not correlated consistently with temporal and spatial variability in abundance of larvae at ingress, highlighting complexity and suggesting that abundance may be controlled by processes occurring offshore during the pre-ingress phase. Moreover, the substantial differences in inter-annual abundances of larvae at the Bay mouth were not concordant with subsequent abundances of age-0 juveniles in the three survey years, indicating that important processes affecting recruitment of Atlantic menhaden operate after ingress, during the larval to juvenile transition stage.

Optimizing Use of Girdled Ash Trees for Management of Low-Density Emerald Ash Borer (Coleoptera: Buprestidae) Populations.

PubMed

Siegert, Nathan W; McCullough, Deborah G; Poland, Therese M; Heyd, Robert L

2017-06-01

Effective survey methods to detect and monitor recently established, low-density infestations of emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), remain a high priority because they provide land managers and property owners with time to implement tactics to slow emerald ash borer population growth and the progression of ash mortality. We evaluated options for using girdled ash (Fraxinus spp.) trees for emerald ash borer detection and management in a low-density infestation in a forested area with abundant green ash (F. pennsylvanica). Across replicated 4-ha plots, we compared detection efficiency of 4 versus 16 evenly distributed girdled ash trees and between clusters of 3 versus 12 girdled trees. We also examined within-tree larval distribution in 208 girdled and nongirdled trees and assessed adult emerald ash borer emergence from detection trees felled 11 mo after girdling and left on site. Overall, current-year larvae were present in 85-97% of girdled trees and 57-72% of nongirdled trees, and larval density was 2-5 times greater on girdled than nongirdled trees. Low-density emerald ash borer infestations were readily detected with four girdled trees per 4-ha, and 3-tree clusters were as effective as 12-tree clusters. Larval densities were greatest 0.5 ± 0.4 m below the base of the canopy in girdled trees and 1.3 ± 0.7 m above the canopy base in nongirdled trees. Relatively few adult emerald ash borer emerged from trees felled 11 mo after girdling and left on site through the following summer, suggesting removal or destruction of girdled ash trees may be unnecessary. This could potentially reduce survey costs, particularly in forested areas with poor accessibility. Published by Oxford University Press on behalf of Entomological Society of America 2017. This work is written by US Government employees and is in the public domain in the US.

Blue light-induced immunosuppression in Bactrocera dorsalis adults, as a carryover effect of larval exposure.

PubMed

Tariq, K; Noor, M; Hori, M; Ali, A; Hussain, A; Peng, W; Chang, C-J; Zhang, H

2017-12-01

Detrimental effects of ultraviolet (UV) light on living organisms are well understood, little is known about the effects of blue light irradiation. Although a recent study revealed that blue light caused more harmful effects on insects than UV light and blue light irradiation killed insect pests of various orders including Diptera, the effects of blue light on physiology of insects are still largely unknown. Here we studied the effects of blue light irradiation on cuticular melanin in larval and the immune response in adult stage of Bactrocera dorsalis. We also evaluated the effects of blue light exposure in larval stage on various age and mass at metamorphosis and the mediatory role of cuticular melanin in carryover effects of larval stressors across metamorphosis. We found that larvae exposed to blue light decreased melanin contents in their exoskeleton with smaller mass and delayed metamorphosis than insects reared without blue light exposure. Across metamorphosis, lower melanotic encapsulation response and higher susceptibility to Beauveria bassiana was detected in adults that had been exposed to blue light at their larval stage, thereby constituting the first evidence that blue light impaired adult immune function in B. dorsalis as a carryover effect of larval exposure.

High nymphal host density and mortality negatively impact parasitoid complex during an insect herbivore outbreak.

PubMed

Hall, Aidan A G; Johnson, Scott N; Cook, James M; Riegler, Markus

2017-08-26

Insect herbivore outbreaks frequently occur and this may be due to factors that restrict top-down control by parasitoids, for example, host-parasitoid asynchrony, hyperparasitization, resource limitation and climate. Few studies have examined host-parasitoid density relationships during an insect herbivore outbreak in a natural ecosystem with diverse parasitoids. We studied parasitization patterns of Cardiaspina psyllids during an outbreak in a Eucalyptus woodland. First, we established the trophic roles of the parasitoids through a species-specific multiplex PCR approach on mummies from which parasitoids emerged. Then, we assessed host-parasitoid density relationships across three spatial scales (leaf, tree and site) over one year. We detected four endoparasitoid species of the family Encyrtidae (Hymenoptera); two primary parasitoid and one heteronomous hyperparasitoid Psyllaephagus species (the latter with female development as a primary parasitoid and male development as a hyperparasitoid), and the hyperparasitoid Coccidoctonus psyllae. Parasitoid development was host-synchronized, although synchrony between sites appeared constrained during winter (due to temperature differences). Parasitization was predominantly driven by one primary parasitoid species and was mostly inversely host-density dependent across the spatial scales. Hyperparasitization by C. psyllae was psyllid-density dependent at the site scale, however, this only impacted the rarer primary parasitoid. High larval parasitoid mortality due to density-dependent nymphal psyllid mortality (a consequence of resource limitation) compounded by a summer heat wave was incorporated in the assessment and resulted in density independence of host-parasitoid relationships. As such, high larval parasitoid mortality during insect herbivore outbreaks may contribute to the absence of host density-dependent parasitization during outbreak events. © 2017 Institute of Zoology, Chinese Academy of Sciences.

Larval connectivity studies in the Western Iberian Peninsula

NASA Astrophysics Data System (ADS)

Dubert, Jesus; Nolasco, Rita; Queiroga, Henrique

2010-05-01

The study of the connectivity between populations is one of the 'hot' applications of numerical models of the ocean circulation. An IBM (Individual Based model) was developed, using Carcinus manenas larvae crab as a model. A set of particles was used as a representation of larvae, in order to study their larval life cycle, including the larval growth, larval mortality (both depending on temperature and salinity), larval dispersal by currents, diel vertical migration, and larval recruitment. The life cycle of every larvae in the ocean, was modeled from zoeae 1 stage to megalopae stage, during typical periods of 30-50 days. Larvae were initialized in 14 estuarine systems of the Atlantic Western Iberian Peninsula, from January to July. In every period, a number of 225 larvae are initialized in everyone of the 14 considered estuaries, with fortynighly periodicity. The larvae evolves during the (variable, depending mainly on temperature) period of growth in the ocean, and when a larvae reach the age for recruit, if it is located in the neighborhood of the considered estuarine systems, the larvae is accounted as a recruited larvae in that place. With this methodology, a connectivity matrix can be computed, acconting for the 225 larvae emitted in every estuary, the number of larvae that reaches the every place. The connectivity matrix depends strongly on the current regime along the Atlantic coast of Iberian Peninsula, and has been calculated for the present circulation, for the period 2001 to 2009, for runs with realistic forcing with NCEP2 and Quikscat (for winds) forcing. The connectivity matrix, have also been calculated for climatological runs. For the present climatological conditions, it is observed the prevalence of southward transport for the period January-July, because the prevalence of Northerly winds along the west coast of IP in the COADS present time climatology. Strong dispersal is observed at the Northern estuaries, during winter with strong loss of

Offshore-onshore linkages in the larval life history of sole in the Gulf of Lions (NW-Mediterranean)

NASA Astrophysics Data System (ADS)

Morat, Fabien; Letourneur, Yves; Blamart, Dominique; Pécheyran, Christophe; Darnaude, Audrey M.; Harmelin-Vivien, Mireille

2014-08-01

Understanding individual dispersion from offshore natal areas to coastal nurseries during pelagic larval life is especially important for the sustainable management of exploited marine fish species. For several years, the hatching period, the larval life duration, the average growth rate and the otolith chemical composition (δ13C, δ18O, Sr:Ca and Ba:Ca) during the larval life were studied for young of the year (YOY) of sole collected in three main nurseries of the Gulf of Lions (GoL) (Thau, Mauguio and Berre). We investigated the spatial variation in the origin of the sole larvae which colonised the nurseries around the GoL, and whether temporal differences in environmental conditions during this life stage affected growth and larval life duration. The hatching period ranges from October to March, depending on year and site. Average ages at metamorphosis varied between 43 and 50 days, with the lowest and highest values consistently found for Mauguio and Berre, respectively. Otolith growth rates ranged between 2.7 and 3.2 μm d-1, with the lowest values in Thau and Mauguio and the highest in Berre. Otolith chemical composition during the larval life also varied, suggesting contrasted larval environmental histories in YOY among nurseries. In fishes from Berre and Mauguio, larval life was more influenced by the Rhône River, showing consistently higher larval Ba:Ca ratios (10/23 μmol mol-1) and lower δ13C (-6.5/-6.1‰) and δ18O values (-1.6/0.1‰) than for Thau (with Ba:Ca ratios < 8 μmol mol-1, δ13C ˜-2.3‰ and δ18O ˜1.5‰). Differences in larval otolith composition were observed for 2004, with higher Ba:Ca and lower δ13C and δ18O values than in the two other years. These differences were explained by changes in composition and chemical signatures of water masses after an exceptional flooding event of the Rhône River in late 2003.

Variability in size-selective mortality obscures the importance of larval traits to recruitment success in a temperate marine fish.

PubMed

Murphy, Hannah M; Warren-Myers, Fletcher W; Jenkins, Gregory P; Hamer, Paul A; Swearer, Stephen E

2014-08-01

In fishes, the growth-mortality hypothesis has received broad acceptance as a driver of recruitment variability. Recruitment is likely to be lower in years when the risk of starvation and predation in the larval stage is greater, leading to higher mortality. Juvenile snapper, Pagrus auratus (Sparidae), experience high recruitment variation in Port Phillip Bay, Australia. Using a 5-year (2005, 2007, 2008, 2010, 2011) data set of larval and juvenile snapper abundances and their daily growth histories, based on otolith microstructure, we found selective mortality acted on larval size at 5 days post-hatch in 4 low and average recruitment years. The highest recruitment year (2005) was characterised by no size-selective mortality. Larval growth of the initial larval population was related to recruitment, but larval growth of the juveniles was not. Selective mortality may have obscured the relationship between larval traits of the juveniles and recruitment as fast-growing and large larvae preferentially survived in lower recruitment years and fast growth was ubiquitous in high recruitment years. An index of daily mortality within and among 3 years (2007, 2008, 2010), where zooplankton were concurrently sampled with ichthyoplankton, was related to per capita availability of preferred larval prey, providing support for the match-mismatch hypothesis. In 2010, periods of low daily mortality resulted in no selective mortality. Thus both intra- and inter-annual variability in the magnitude and occurrence of selective mortality in species with complex life cycles can obscure relationships between larval traits and population replenishment, leading to underestimation of their importance in recruitment studies.

Larval development of Brachiopod Coptothyris grayi (Davidson, 1852) (Brachiopoda, Rhynchonelliformea).

PubMed

Kuzmina, T V; Temereva, E N; Malakhov, V V

2016-11-01

The larval development of the Brachiopod Coptothyris grayi (Davidson, 1852) from the Sea of Japan is described for the first time. Ciliated blastula proved to represent the first free-swimming stage. The blastopore is initially formed as a rounded hole stretching later along the anteroposterior axis. The larva is first divided into two lobes (the apical lobe and the trunk); the mantle lobe is formed later as two lateral folds. Two pairs of seta bundles appear in the late stage larvae. The apical larval lobe in brachiopods is supposed to match the pre-oral lobe and anterior part of the trunk with tentacles in phoronids.

Polycystic echinococcosis in Colombia: the larval cestodes in infected rodents.

PubMed

Morales, G A; Guzman, V H; Wells, E A; Angel, D

1979-07-01

Described are the characteristics of the polycystic larval cestodes found in an endemic area of echinococcosis in the Easter Plains of Colombia and the tissue reaction evoked in infected rodents. Of 848 free-ranging animals examined, polycystic hydatids were found in 44/93 Cuniculus paca and 1/369 Proechimys sp. None of 20 Dasyprocta fuliginosa examined was infected, but hunters provided a heart with hydatid cysts and information about two additional animals with infected livers. Recognition of an endemic area of polycystic echinococcosis provides a means to investigate the life cycle of the parasites and to study the histogenesis of the larval cestodes in susceptible laboratory animals.

Colonization and nursery habitat use patterns of larval and juvenile flatfish species in a small temperate estuary

NASA Astrophysics Data System (ADS)

Primo, Ana Lígia; Azeiteiro, Ulisses M.; Marques, Sónia C.; Martinho, Filipe; Baptista, Joana; Pardal, Miguel A.

2013-02-01

Migrations between coastal and estuarine nursery areas are essential for successful completion of the life cycle of several marine fish. The present study evaluates the use of a small temperate estuary, the Mondego, Portugal, as a nursery habitat for several flatfishes during their early life stages. Data from seasonal and diel larval sampling at the mouth of the estuary and both larvae and juvenile monthly spatial distribution in the estuary (2005-2009) were gathered in order to investigate the life cycle of Platichthys flesus, Solea solea and Solea senegalensis. Larvae entrance in the estuary occurred mainly during summer and autumn with no evidence for diel or tidal vertical stratification. S. senegalensis larvae were present in all seasons at downstream areas presenting low successful settlement and juveniles' densities inside the estuary. Conversely, P. flesus and S. solea were mainly present as juveniles with upstream areas being preferred by flounder. Both species larvae seemed to settle in nearby coastal areas. The importance of the Mondego estuary for flatfishes differed according to the species, playing an important role mainly during the first year for all species. The present study highlights the importance of integrating larval and juvenile stages of fish to assess the very important role of estuaries as nursery areas.

Predator-induced larval cloning in the sand dollar Dendraster excentricus: might mothers matter?

PubMed

Vaughn, Dawn

2009-10-01

Predator-induced cloning in echinoid larvae, with reduced size a consequence of cloning, is a dramatic modification of development and a novel response to risks associated with prolonged planktonic development. Recent laboratory studies demonstrate that exposure to stimuli from predators (i.e., fish mucus) induces cloning in the pluteus larvae (plutei) of Dendraster excentricus. However, the timing and incidence of cloning and size reduction of unrelated conspecific plutei differed across experiments. A variable cloning response suggests the effects of such factors as cue quality, egg provisioning, maternal experience, and genetic background, indicating that the potential advantages of cloning as an adaptive response to predators are not available to all larvae. This study tested the hypothesis that cloning in D. excentricus plutei is maternally influenced. Plutei from three half-sibling larval families (different mothers, same father) were exposed to fish mucus for 9 days during early development. Cloning was inferred in a percentage of plutei from each family; however, the rate and success of cloning differed significantly among the larval half-siblings. Unexpectedly, all mucus-treated plutei were smaller and developmentally delayed when compared to all plutei reared in the absence of a mucus stimulus. Thus, while the results from this study support the hypothesis of an influence of mothers on cloning of larval offspring, reduced larval size was a uniform response to fish mucus and did not indicate an effect of mothers. Hypotheses of the developmental effects of fish mucus on larval size with or without successful cloning are discussed.

Selecting Great Lakes streams for lampricide treatment based on larval sea lamprey surveys

USGS Publications Warehouse

Christie, Gavin C.; Adams, Jean V.; Steeves, Todd B.; Slade, Jeffrey W.; Cuddy, Douglas W.; Fodale, Michael F.; Young, Robert J.; Kuc, Miroslaw; Jones, Michael L.

2003-01-01

The Empiric Stream Treatment Ranking (ESTR) system is a data-driven, model-based, decision tool for selecting Great Lakes streams for treatment with lampricide, based on estimates from larval sea lamprey (Petromyzon marinus) surveys conducted throughout the basin. The 2000 ESTR system was described and applied to larval assessment surveys conducted from 1996 to 1999. A comparative analysis of stream survey and selection data was conducted and improvements to the stream selection process were recommended. Streams were selected for treatment based on treatment cost, predicted treatment effectiveness, and the projected number of juvenile sea lampreys produced. On average, lampricide treatments were applied annually to 49 streams with 1,075 ha of larval habitat, killing 15 million larval and 514,000 juvenile sea lampreys at a total cost of $5.3 million, and marginal and mean costs of $85 and $10 per juvenile killed. The numbers of juvenile sea lampreys killed for given treatment costs showed a pattern of diminishing returns with increasing investment. Of the streams selected for treatment, those with > 14 ha of larval habitat targeted 73% of the juvenile sea lampreys for 60% of the treatment cost. Suggested improvements to the ESTR system were to improve accuracy and precision of model estimates, account for uncertainty in estimates, include all potentially productive streams in the process (not just those surveyed in the current year), consider the value of all larvae killed during treatment (not just those predicted to metamorphose the following year), use lake-specific estimates of damage, and establish formal suppression targets.

Habitat use by larval fishes in a temperate South African surf zone

NASA Astrophysics Data System (ADS)

Watt-Pringle, Peter; Strydom, Nadine A.

2003-12-01

Larval fishes were sampled in the Kwaaihoek surf zone on the south east coast of South Africa. On six occasions between February and May 2002, larval fishes were collected in two habitat types identified in the inner surf zone using a modified beach-seine net. The surf zone habitats were classified as either sheltered trough areas or adjacent exposed surf areas. Temperature, depth and current measurements were taken at all sites. Trough habitats consisted of a depression in surf topography characterised by reduced current velocities and greater average depth than adjacent surf areas. In total, 325 larval fishes were collected. Of these, 229 were collected in trough and 96 in surf habitats. At least 22 families and 37 species were represented in the catch. Dominant families were the Mugilidae, Sparidae, Atherinidae, and Engraulidae. Dominant species included Liza tricuspidens and Liza richardsonii (Mugilidae), Rhabdosargus holubi and Sarpa salpa (Sparidae), Atherina breviceps (Atherinidae) and Engraulis japonicus (Engraulide). Mean CPUE of postflexion larvae of estuary-dependent species was significantly greater in trough areas. The proportion of postflexion larval fishes in trough habitat was significantly greater than that of preflexion stages, a result that was not apparent in surf habitat sampled. CPUE of postflexion larvae of estuary-dependent fishes was negatively correlated with current magnitude and positively correlated with habitat depth. Mean body length of larval fishes was significantly greater in trough than in surf habitats. These results provide evidence that the CPUE of postflexion larvae of estuary-dependent fishes is higher in trough habitat in the surf zone and this may be indicative of active habitat selection for areas of reduced current velocity/wave action. The implications of this behaviour for estuarine recruitment processes are discussed.

Response of coccinellid larvae to conspecific and heterospecific larval tracks: a mechanism that reduces cannibalism and intraguild predation.

PubMed

Meisner, Matthew H; Harmon, Jason P; Ives, Anthony R

2011-02-01

Cannibalism, where one species feeds on individuals of its own species, and intraguild predation (IGP), where a predator feeds on other predatory species, can both pose significant threats to natural enemies and interfere with their biological control of pests. Behavioral mechanisms to avoid these threats, however, could help maintain superior pest control. Here, we ask whether larvae of Coccinella septempunctata (Coleoptera: Coccinellidae) and Harmonia axyridis (Coleoptera: Coccinellidae) respond to larval tracks deposited by the other and whether this behavioral response reduces the threat of cannibalism and IGP. In petri dish experiments, we show that both H. axyridis and C. septempunctata avoid foraging in areas with conspecific larval tracks. Using a method of preventing larvae from depositing tracks, we then demonstrate that the frequency of cannibalism is greater for both species when larvae are prevented from depositing tracks compared with when the tracks are deposited. For multi-species interactions we show in petri dish experiments that C. septempunctata avoids H. axyridis larval tracks but H. axyridis does not avoid C. septempunctata larval tracks, demonstrating an asymmetry in response to larval tracks that parallels the asymmetry in aggressiveness between these species as intraguild predators. On single plants, we show that the presence of H. axyridis larval tracks reduces the risk of IGP by H. axyridis on C. septempunctata. Our study suggests that larval tracks can be used in more ways than previously described, in this case by changing coccinellid larval behavior in a way that reduces cannibalism and IGP. © 2011 Entomological Society of America

Assessing the toxicity of sediments using the medaka embryo-larval assay and 2 other bioassays.

PubMed

Barhoumi, Badreddine; Clérandeau, Christelle; Landi, Laure; Pichon, Anaïk; Le Bihanic, Florane; Poirier, Dominique; Anschutz, Pierre; Budzinski, Hélène; Driss, Mohamed Ridha; Cachot, Jérôme

2016-09-01

Sediments are sinks for aquatic pollutants, and analyzing toxicity in such complex matrices is still challenging. To evaluate the toxicity of bioavailable pollutants accumulated in sediments from the Bizerte lagoon (Tunisia), a novel assay, the medaka embryo-larval assay by sediment contact, was applied. Japanese medaka (Oryzias latipes) embryos were incubated in direct contact with sediment samples up to hatching. Lethal and sublethal adverse effects were recorded in embryos and larvae up to 20 d postfertilization. Results from medaka embryo-larval assay were compared with cytotoxicity (Microtox®), genotoxicity (SOS chromotest), and pollutant content of sediments. The results highlight differences in the contamination profile and toxicity pattern between the different studied sediments. A significant correlation was shown between medaka embryo-larval assay by sediment contact and SOS chromotest responses and concentrations of most organic pollutants studied. No correlation was shown between pollutant levels and Microtox. According to the number of sediment samples detected as toxic, medaka embryo-larval assay by sediment contact was more sensitive than Microtox, which in turn was more sensitive than the SOS chromotest; and medaka embryo-larval assay by sediment contact allowed sediment toxicity assessment of moderately polluted sediments without pollutant extraction and using an ecologically realistic exposure scenario. Although medaka embryo-larval assay by sediment contact should be tested on a larger sample set, the results show that it is sensitive and convenient enough to monitor the toxicity of natural sediments. Environ Toxicol Chem 2016;35:2270-2280. © 2016 SETAC. © 2016 SETAC.

Phototaxis of larval and juvenile northern pike

USGS Publications Warehouse

Zigler, S.J.; Dewey, M.R.

1995-01-01

Age- Phi northern pike Esox lucius prefer vegetated habitats that are difficult to sample with standard towed gears. Light traps can be effective for sampling larval fishes in dense vegetation, given positive phototaxis of fish. We evaluated the phototactic response of young northern pike by comparing the catches of larvae and juveniles obtained with plexiglass traps deployed with a chemical light stick versus traps deployed without a light source (controls) in a laboratory raceway and in a vegetated pond. In the laboratory tests, catches of protolarvae and mesolarvae in lighted traps were 11-35 times greater than catches in control traps. The catches of juvenile northern pike in field and laboratory experiments were 3-15 times greater in lighted traps than in control traps, even though the maximum body width of the larger juveniles was similar to the width of the entrance slots of the traps (5 mm). Larval and juvenile northern pike were photopositive; thus, light traps should effectively sample age-0 northern pike for at least 6 weeks after hatching.

Tethered by Self-Generated Flow: Mucus String Augmented Feeding Current Generation in Larval Oysters

NASA Astrophysics Data System (ADS)

Jiang, H.; Wheeler, J.; Anderson, E.

2016-02-01

Marine zooplankton live in a nutritionally dilute environment. To survive, they must process an enormous volume of water relative to their own body volume for food. To achieve this, many zooplankters including copepods, invertebrate larvae, and protists create a feeding current to concentrate and transport food items to their food gathering structures. To enhance the efficiency of the feeding current, these zooplankters often rely on certain "tethering" mechanisms to retard their translational motion for producing a strong feeding current. The tethering force may include excess weight due to gravity, force from attachment to solid surfaces, and drag experienced by strategically placed morphological structures. Larval oysters are known from previous studies to release mucus strings during feeding, presumably for supplying a tethering force to enhance their feeding-current efficiency. But the underlying mechanism is unclear. In this study, we used a high-speed microscale imaging system (HSMIS) to observe the behavior of freely swimming and feeding larval oysters. We also used HSMIS to measure larval imposed feeding currents via a micro-particle image velocimetry (µPIV) technique. HSMIS allows observations along a vertically oriented focal plane in a relatively large water vessel with unprecedented spatial and temporal resolutions. Our high-speed videos show that a feeding larval oyster continuously released a long mucus string into its feeding current that flows downward; the feeding current subsequently dragged the mucus string downward. Analysis of our µPIV data combined with a hydrodynamic model further suggests that the drag force experienced by the mucus string in the feeding current contributes significantly to the tethering force required to generate the feeding current. Thus, mucus strings in larval oysters act as "anchors" in larval self-generated flow to actively tether the feeding larvae.

Embryo-larval toxicity tests with the African catfish (Clarias gariepinus): comparative sensitivity of endpoints.

PubMed

Nguyen, L T H; Janssen, C R

2002-02-01

Embryo-larval toxicity tests with the African catfish (Clarias gariepinus) were performed to assess the comparative sensitivity of different endpoints. Measured test responses included embryo and larval survival, hatching, morphological development, and larval growth. Chromium, cadmium, copper, sodium pentachlorphenol (NaPCP), and malathion were used as model toxicants. Hatching was not affected by any of the chemicals tested, and embryo survival was only affected by chromium at > or = 36 mg/L. The growth of larvae was significantly reduced at > or = 11 mg/L Cr, > or = 0.63 mg/L Cu, > or = 0.03 mg/L NaPCP, and > or = 1.25 mg/L malathion. Morphological development of C. gariepinus was affected by all of the toxicants tested. Different types of morphological aberrations were observed, i.e., reduction of pigmentation in fish exposed to cadmium and copper, yolk sac edema in fish exposed to NaPCP and malathion, and deformation of the notochord in fish exposed to chromium and malathion. The sensitivity of the endpoints measured can be summarized as follows: growth > abnormality > larval survival > embryo survival > hatching.

Gender-related family head schooling and Aedes aegypti larval breeding risk in southern Mexico.

PubMed

Danis-Lozano, Rogelio; Rodríguez, Mario H; Hernández-Avila, Mauricio

2002-01-01

To investigate if family head genre-associated education is related to the risk of domiciliary Aedes aegypti larval breeding in a dengue-endemic village of Southern Mexico. A family head was considered to have a low education level if he/she had not completed elementary school. To estimate larval breeding risk within each household, a three-category Maya index was constructed using a weighted estimation of controllable and disposable domestic water containers. A socio-economic index was constructed based on household construction characteristics. Low-level education of either family head was associated to higher larval breeding risk. Households with low-educated mothers had more larval breeding containers. These associations persisted after adjusting for household socio-economic level. These results indicate that households with female family heads with low education levels accumulate more containers that favor Ae. aegypti breeding, and that education campaigns for dengue control should be addressed to this part of the population. The English version of this paper is available too at: http://www.insp.mx/salud/index.html.

Larval cases of caddisfly (Insecta: Trichoptera) affinity in Early Permian marine environments of Gondwana

NASA Astrophysics Data System (ADS)

Mouro, Lucas D.; Zatoń, Michał; Fernandes, Antonio C. S.; Waichel, Breno L.

2016-01-01

Caddisflies (Trichoptera) are small, cosmopolitan insects closely related to the Lepidoptera (moths and butterflies). Most caddisflies construct protective cases during their larval development. Although the earliest recognisable caddisflies date back to the early Mesozoic (Early and Middle Triassic), being particularly numerous and diverse during the Late Jurassic and Early Cretaceous, the first records of their larval case constructions are known exclusively from much younger, Early to Middle Jurassic non-marine deposits in the northern hemisphere. Here we present fossils from the Early Permian (Asselian-Sakmarian) marine deposits of Brazil which have strong morphological and compositional similarity to larval cases of caddisflies. If they are, which is very probable, these finds not only push back the fossil record of true caddisflies, but also indicate that their larvae constructed cases at the very beginning of their evolution in marine environments. Since modern caddisflies that construct larval cases in marine environments are only known from eastern Australia and New Zealand, we suggest that this marine ecology may have first evolved in western Gondwana during the Early Permian and later spread across southern Pangea.

Larval cases of caddisfly (Insecta: Trichoptera) affinity in Early Permian marine environments of Gondwana

PubMed Central

Mouro, Lucas D.; Zatoń, Michał; Fernandes, Antonio C.S.; Waichel, Breno L.

2016-01-01

Caddisflies (Trichoptera) are small, cosmopolitan insects closely related to the Lepidoptera (moths and butterflies). Most caddisflies construct protective cases during their larval development. Although the earliest recognisable caddisflies date back to the early Mesozoic (Early and Middle Triassic), being particularly numerous and diverse during the Late Jurassic and Early Cretaceous, the first records of their larval case constructions are known exclusively from much younger, Early to Middle Jurassic non-marine deposits in the northern hemisphere. Here we present fossils from the Early Permian (Asselian–Sakmarian) marine deposits of Brazil which have strong morphological and compositional similarity to larval cases of caddisflies. If they are, which is very probable, these finds not only push back the fossil record of true caddisflies, but also indicate that their larvae constructed cases at the very beginning of their evolution in marine environments. Since modern caddisflies that construct larval cases in marine environments are only known from eastern Australia and New Zealand, we suggest that this marine ecology may have first evolved in western Gondwana during the Early Permian and later spread across southern Pangea. PMID:26765261

Larval cases of caddisfly (Insecta: Trichoptera) affinity in Early Permian marine environments of Gondwana.

PubMed

Mouro, Lucas D; Zatoń, Michał; Fernandes, Antonio C S; Waichel, Breno L

2016-01-14

Caddisflies (Trichoptera) are small, cosmopolitan insects closely related to the Lepidoptera (moths and butterflies). Most caddisflies construct protective cases during their larval development. Although the earliest recognisable caddisflies date back to the early Mesozoic (Early and Middle Triassic), being particularly numerous and diverse during the Late Jurassic and Early Cretaceous, the first records of their larval case constructions are known exclusively from much younger, Early to Middle Jurassic non-marine deposits in the northern hemisphere. Here we present fossils from the Early Permian (Asselian-Sakmarian) marine deposits of Brazil which have strong morphological and compositional similarity to larval cases of caddisflies. If they are, which is very probable, these finds not only push back the fossil record of true caddisflies, but also indicate that their larvae constructed cases at the very beginning of their evolution in marine environments. Since modern caddisflies that construct larval cases in marine environments are only known from eastern Australia and New Zealand, we suggest that this marine ecology may have first evolved in western Gondwana during the Early Permian and later spread across southern Pangea.

Inhibition of coral fertilisation and larval metamorphosis by tributyltin and copper.

PubMed

Negri, A P; Heyward, A J

2001-02-01

Fertilisation and larval metamorphosis of reef-building corals are important life history events leading to recruitment of juvenile corals to reef populations. Little is known of the sensitivity of these early life phases to pollution, or their relative susceptibility to certain toxicants compared with established coral colonies. Inhibition of fertilisation and larval metamorphosis of the coral Acropora millepora (Ehrenberg, 1834) was assessed in response to solutions of the antifoulants tributyltin (TBT) and copper (Cu) using laboratory-based bioassays. Nominal concentrations that inhibited 50% fertilisation and metamorphosis (IC50) were calculated from 4 h fertilisation and 24 h metamorphosis assays and were based on introduced dose. Cu was most potent towards fertilisation with an IC50 of 17.4 micrograms/l. TBT however, proved more toxic to larval metamorphosis having an IC50 of 2.0 micrograms/l. Inert surfaces coated with either Cu- or TBT-based antifouling paint also inhibited fertilisation and metamorphosis. The degree of inhibition was correlated with surface area of the paint coating. These results indicate fertilisation and metamorphosis of coral can be sensitive to active components of antifouling paints.

Depletion of juvenile hormone esterase extends larval growth in Bombyx mori.

PubMed

Zhang, Zhongjie; Liu, Xiaojing; Shiotsuki, Takahiro; Wang, Zhisheng; Xu, Xia; Huang, Yongping; Li, Muwang; Li, Kai; Tan, Anjiang

2017-02-01

Two major hormones, juvenile hormone (JH) and 20-hydroxyecdysone (20E), regulate insect growth and development according to their precisely coordinated titres, which are controlled by both biosynthesis and degradation pathways. Juvenile hormone esterase (JHE) is the primary JH-specific degradation enzyme that plays a key role in regulating JH titers, along with JH epoxide hydrolase (JHEH) and JH diol kinase (JHDK). In the current study, a loss-of-function analysis of JHE in the silkworm, Bombyx mori, was performed by targeted gene disruption using the transgenic CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/RNA-guided Cas9 nucleases) system. Depletion of B. mori JHE (BmJHE) resulted in the extension of larval stages, especially the penultimate and ultimate larval stages, without deleterious effects to silkworm physiology. The expression of JHEH and JHDK was upregulated in mutant animals, indicating the existence of complementary routes in the JH metabolism pathway in which inactivation of one enzyme will activate other enzymes. RNA-Seq analysis of mutant animals revealed that genes involved in protein processing in the endoplasmic reticulum and in amino acid metabolism were affected by BmJHE depletion. Depletion of JHE and subsequent delayed JH metabolism activated genes in the TOR pathway, which are ultimately responsible for extending larval growth. The transgenic Cas9 system used in the current study provides a promising approach for analysing the actions of JH, especially in nondrosophilid insects. Furthermore, prolonging larval stages produced larger larvae and cocoons, which is greatly beneficial to silk production. Copyright © 2017 Elsevier Ltd. All rights reserved.

Efficiency of three diets for larval development in mass rearing Aedes albopictus (Diptera: Culicidae).

PubMed

Puggioli, Arianna; Balestrino, F; Damiens, D; Lees, R S; Soliban, S M; Madakacherry, O; Dindo, M L; Bellini, R; Gilles, J R L

2013-07-01

A fundamental step in establishing a mass production system is the development of a larval diet that promotes high adult performance at a reasonable cost. To identify a suitable larval diet for Aedes albopictus (Skuse), three diets were compared: a standard laboratory diet used at the Centro Agricoltura Ambiente, Italy (CAA) and two diets developed specifically for mosquito mass rearing at the FAO/IAEA Laboratory, Austria. The two IAEA diets, without affecting survival to the pupal stage, resulted in a shorter time to pupation and to emergence when compared with the CAA diet. At 24 h from pupation onset, 50 and 90% of the male pupae produced on the CAA and IAEA diets, respectively, had formed and could be collected. The diet received during the larval stage affected the longevity of adult males with access to water only, with best results observed when using the CAA larval diet. However, similar longevity among diet treatments was observed when males were supplied with sucrose solution. No differences were observed in the effects of larval diet on adult male size or female fecundity and fertility. Considering these results, along with the relative costs of the three diets, the IAEA 2 diet is found to be the preferred choice for mass rearing of Aedes albopictus, particularly if a sugar meal can be given to adult males before release, to ensure their teneral reserves are sufficient for survival, dispersal, and mating in the field.

Reef-fish larval dispersal patterns validate no-take marine reserve network connectivity that links human communities

NASA Astrophysics Data System (ADS)

Abesamis, Rene A.; Saenz-Agudelo, Pablo; Berumen, Michael L.; Bode, Michael; Jadloc, Claro Renato L.; Solera, Leilani A.; Villanoy, Cesar L.; Bernardo, Lawrence Patrick C.; Alcala, Angel C.; Russ, Garry R.

2017-09-01

Networks of no-take marine reserves (NTMRs) are a widely advocated strategy for managing coral reefs. However, uncertainty about the strength of population connectivity between individual reefs and NTMRs through larval dispersal remains a major obstacle to effective network design. In this study, larval dispersal among NTMRs and fishing grounds in the Philippines was inferred by conducting genetic parentage analysis on a coral-reef fish ( Chaetodon vagabundus). Adult and juvenile fish were sampled intensively in an area encompassing approximately 90 km of coastline. Thirty-seven true parent-offspring pairs were accepted after screening 1978 juveniles against 1387 adults. The data showed all types of dispersal connections that may occur in NTMR networks, with assignments suggesting connectivity among NTMRs and fishing grounds ( n = 35) far outnumbering those indicating self-recruitment ( n = 2). Critically, half (51%) of the inferred occurrences of larval dispersal linked reefs managed by separate, independent municipalities and constituent villages, emphasising the need for nested collaborative management arrangements across management units to sustain NTMR networks. Larval dispersal appeared to be influenced by wind-driven seasonal reversals in the direction of surface currents. The best-fit larval dispersal kernel estimated from the parentage data predicted that 50% of larvae originating from a population would attempt to settle within 33 km, and 95% within 83 km. Mean larval dispersal distance was estimated to be 36.5 km. These results suggest that creating a network of closely spaced (less than a few tens of km apart) NTMRs can enhance recruitment for protected and fished populations throughout the NTMR network. The findings underscore major challenges for regional coral-reef management initiatives that must be addressed with priority: (1) strengthening management of NTMR networks across political or customary boundaries; and (2) achieving adequate population

Is the Schwabe Organ a Retained Larval Eye? Anatomical and Behavioural Studies of a Novel Sense Organ in Adult Leptochiton asellus (Mollusca, Polyplacophora) Indicate Links to Larval Photoreceptors

PubMed Central

Sumner-Rooney, Lauren H.; Sigwart, Julia D.

2015-01-01

The discovery of a sensory organ, the Schwabe organ, was recently reported as a unifying feature of chitons in the order Lepidopleurida. It is a patch of pigmented tissue located on the roof of the pallial cavity, beneath the velum on either side of the mouth. The epithelium is densely innervated and contains two types of potential sensory cells. As the function of the Schwabe organ remains unknown, we have taken a cross-disciplinary approach, using anatomical, histological and behavioural techniques to understand it. In general, the pigmentation that characterises this sensory structure gradually fades after death; however, one particular concentrated pigment dot persists. This dot is positionally homologous to the larval eye in chiton trochophores, found in the same neuroanatomical location, and furthermore the metamorphic migration of the larval eye is ventral in species known to possess Schwabe organs. Here we report the presence of a discrete subsurface epithelial structure in the region of the Schwabe organ in Leptochiton asellus that histologically resembles the chiton larval eye. Behavioural experiments demonstrate that Leptochiton asellus with intact Schwabe organs actively avoid an upwelling light source, while Leptochiton asellus with surgically ablated Schwabe organs and a control species lacking the organ (members of the other extant order, Chitonida) do not (Kruskal-Wallis, H = 24.82, df = 3, p < 0.0001). We propose that the Schwabe organ represents the adult expression of the chiton larval eye, being retained and elaborated in adult lepidopleurans. PMID:26366861

Identifying the key biophysical drivers, connectivity outcomes, and metapopulation consequences of larval dispersal in the sea.

PubMed

Treml, Eric A; Ford, John R; Black, Kerry P; Swearer, Stephen E

2015-01-01

Population connectivity, which is essential for the persistence of benthic marine metapopulations, depends on how life history traits and the environment interact to influence larval production, dispersal and survival. Although we have made significant advances in our understanding of the spatial and temporal dynamics of these individual processes, developing an approach that integrates the entire population connectivity process from reproduction, through dispersal, and to the recruitment of individuals has been difficult. We present a population connectivity modelling framework and diagnostic approach for quantifying the impact of i) life histories, ii) demographics, iii) larval dispersal, and iv) the physical seascape, on the structure of connectivity and metapopulation dynamics. We illustrate this approach using the subtidal rocky reef ecosystem of Port Phillip Bay, were we provide a broadly-applicable framework of population connectivity and quantitative methodology for evaluating the relative importance of individual factors in determining local and system outcomes. The spatial characteristics of marine population connectivity are primarily influenced by larval mortality, the duration of the pelagic larval stage, and the settlement competency characteristics, with significant variability imposed by the geographic setting and the timing of larval release. The relative influence and the direction and strength of the main effects were strongly consistent among 10 connectivity-based metrics. These important intrinsic factors (mortality, length of the pelagic larval stage, and the extent of the precompetency window) and the spatial and temporal variability represent key research priorities for advancing our understanding of the connectivity process and metapopulation outcomes.

Larval feeding behavior and ant association in frosted elfin, Callophrys irus (Lycaenidae)

USGS Publications Warehouse

Albanese, G.; Nelson, M.W.; Vickery, P.D.; Sievert, P.R.

2007-01-01

Callophrys irus is a rare and declining lycaenid found in the eastern U.S., inhabiting xeric and open habitats maintained by disturbance. Populations are localized and monophagous. We document a previously undescribed larval feeding behavior in both field and lab reared larvae in which late instar larvae girdled the main stem of the host plant. Girdled stems provide a unique feeding sign that was useful in detecting the presence of larvae in the field. We also observed frequent association of field larvae with several species of ants and provide a list of ant species. We suggest two hypotheses on the potential benefits of stem-girdling to C. irus larvae: 1) Stem girdling provides phloem sap as a larval food source and increases the leaf nutrient concentration, increasing larval growth rates and providing high quality honeydew for attending ants; 2) Stem girdling reduces stem toxicity by inhibiting transport of toxins from roots to the stem.

Larval fish dispersal in a coral-reef seascape.

PubMed

Almany, Glenn R; Planes, Serge; Thorrold, Simon R; Berumen, Michael L; Bode, Michael; Saenz-Agudelo, Pablo; Bonin, Mary C; Frisch, Ashley J; Harrison, Hugo B; Messmer, Vanessa; Nanninga, Gerrit B; Priest, Mark A; Srinivasan, Maya; Sinclair-Taylor, Tane; Williamson, David H; Jones, Geoffrey P

2017-05-08

Larval dispersal is a critical yet enigmatic process in the persistence and productivity of marine metapopulations. Empirical data on larval dispersal remain scarce, hindering the use of spatial management tools in efforts to sustain ocean biodiversity and fisheries. Here we document dispersal among subpopulations of clownfish (Amphiprion percula) and butterflyfish (Chaetodon vagabundus) from eight sites across a large seascape (10,000 km 2 ) in Papua New Guinea across 2 years. Dispersal of clownfish was consistent between years, with mean observed dispersal distances of 15 km and 10 km in 2009 and 2011, respectively. A Laplacian statistical distribution (the dispersal kernel) predicted a mean dispersal distance of 13-19 km, with 90% of settlement occurring within 31-43 km. Mean dispersal distances were considerably greater (43-64 km) for butterflyfish, with kernels declining only gradually from spawning locations. We demonstrate that dispersal can be measured on spatial scales sufficient to inform the design of and test the performance of marine reserve networks.

Ocean Acidification Impacts Larval and Juvenile Growth in the Native Oyster Ostrea lurida

NASA Astrophysics Data System (ADS)

Hettinger, A.; Hoey, J. A.; Sanford, E.; Gaylord, B.; Hill, T. M.; Russell, A. D.

2008-12-01

The impacts of ocean acidification have only recently been recognized as a human-induced stressor on marine ecosystems. Ocean acidification can disrupt calcification in organisms that precipitate calcareous structures, including many ecologically and economically important species. We examined how decreased levels of carbonate saturation affected larval and juvenile growth and settlement in the native oyster Ostrea lurida. Larvae were cultured at three carbonate saturation levels that represent present day CO2 concentrations (380 ppm) and two future projected pCO2 scenarios (540 and 970 ppm). These treatments were maintained for 20 days throughout larval duration until settlement occurred. Larval and juvenile growth were determined by calculating change in shell area. Larvae exposed to 970 ppm grew 12% less than larvae held under control conditions (380 ppm). In addition, growth varied among larvae produced by different parents, suggesting that impacts of ocean acidification might vary intraspecifically. Juvenile growth (i.e., new shell added following settlement) was significantly different among CO2 treatments, and juveniles exposed to 970 ppm grew 24% less than juveniles held under control conditions (380 ppm). Carry-over effects from the larval stage influence juvenile growth, and because post-settlement mortality is often high for marine invertebrates, ocean acidification may negatively impact the size of native oyster populations.

Effectiveness of recommended euthanasia methods in larval zebrafish (Danio rerio).

PubMed

Strykowski, Jennifer L; Schech, Joseph M

2015-01-01

The popularity of zebrafish and its use as a model organism in biomedical research including genetics, development, and toxicology, has increased over the past 20 y and continues to grow. However, guidelines for euthanasia remain vague, and the responsibility of creating appropriate euthanasia protocols essentially falls on individual facilities. To reduce variation in experimental results among labs, a standard method of euthanasia for zebrafish would be useful. Although various euthanasia methods have been compared, few studies focus on the effectiveness of euthanasia methods for larval zebrafish. In this study, we exposed larval zebrafish to each of 3 euthanasia agents (MS222, eugenol, and hypothermic shock) and assessed the recovery rate. Hypothermic shock appeared to be the most effective method for euthanizing zebrafish at 14 d after fertilization; however, this method may not be considered an efficient method for large numbers of larval zebrafish. Exposure to chemicals, such as MS222 and eugenol, were ineffective methods for euthanasia at this stage of development. When these agents are used, secondary measures should be taken to ensure death. Choosing a euthanasia method that is effective, efficient, and humane can be challenging. Determining a method of euthanasia that is suitable for fish of all stages will bring the zebrafish community closer to meeting this challenge.

Effectiveness of Recommended Euthanasia Methods in Larval Zebrafish (Danio rerio)

PubMed Central

Strykowski, Jennifer L; Schech, Joseph M

2015-01-01

The popularity of zebrafish and its use as a model organism in biomedical research including genetics, development, and toxicology, has increased over the past 20 y and continues to grow. However, guidelines for euthanasia remain vague, and the responsibility of creating appropriate euthanasia protocols essentially falls on individual facilities. To reduce variation in experimental results among labs, a standard method of euthanasia for zebrafish would be useful. Although various euthanasia methods have been compared, few studies focus on the effectiveness of euthanasia methods for larval zebrafish. In this study, we exposed larval zebrafish to each of 3 euthanasia agents (MS222, eugenol, and hypothermic shock) and assessed the recovery rate. Hypothermic shock appeared to be the most effective method for euthanizing zebrafish at 14 d after fertilization; however, this method may not be considered an efficient method for large numbers of larval zebrafish. Exposure to chemicals, such as MS222 and eugenol, were ineffective methods for euthanasia at this stage of development. When these agents are used, secondary measures should be taken to ensure death. Choosing a euthanasia method that is effective, efficient, and humane can be challenging. Determining a method of euthanasia that is suitable for fish of all stages will bring the zebrafish community closer to meeting this challenge. PMID:25651096

Different key roles of mesoscale oceanographic structures and ocean bathymetry in shaping larval fish distribution pattern: A case study in Sicilian waters in summer 2009

NASA Astrophysics Data System (ADS)

Cuttitta, Angela; Quinci, Enza Maria; Patti, Bernardo; Bonomo, Sergio; Bonanno, Angelo; Musco, Marianna; Torri, Marco; Placenti, Francesco; Basilone, Gualtiero; Genovese, Simona; Armeri, Grazia Maria; Spanò, Antonina; Arculeo, Marco; Mazzola, Antonio; Mazzola, Salvatore

2016-09-01

Fish larvae data collected in year 2009 were used to examine the effects of particular environmental conditions on the structure of larval assemblages in two oligotrophic Mediterranean areas (the Southern Tyrrhenian Sea and the Strait of Sicily). For this purpose, relationships with environmental variables (temperature, salinity and fluorescence), zooplankton biomass, water circulation and bathymetry are discussed. Hydrodynamic conditions resulted very differently between two study areas. The Southern Tyrrhenian Sea was characterized by moderate shallow circulation compared to the Strait of Sicily. In this framework, distribution pattern of larval density in the Tyrrhenian Sea was mainly driven by bathymetry, due to spawning behavior of adult fish. There, results defined four assemblages: two coastal assemblages dominated by pelagic and demersal families and two oceanic assemblages dominated by mesopelagic species more abundant in western offshore and less abundant in eastern offshore. The assemblage variations in the western side was related to the presence of an anti-cyclonic gyre in the northern side of the Gulf of Palermo, while in the eastern side the effect of circulation was not very strong and the environmental conditions rather than the dispersal of species determined the larval fish communities structure. Otherwise in the Strait of Sicily the currents were the main factor governing the concentration and the assemblage structure. In fact, the distribution of larvae was largely consistent with the branch of the Atlantic Ionian Stream (AIS). Moreover, very complex oceanographic structures (two cyclonic circulations in the western part of the study area and one anti-cyclonic circulation in the eastern part) caused the formation of uncommon spatial distribution of larval fish assemblages, only partially linked to bathymetry of the study area. Typically coastal larvae (pelagic families: Engraulidae and Clupeidae) were mostly concentrated in the offshore areas

Evaluation of waste artificial larval rearing media as oviposition attractant for New World screwworm (Diptera: Calliphoridae)

USDA-ARS?s Scientific Manuscript database

The waste artificial larval rearing media of the New World Screwworm, Cochliomyia hominivorax (Coquerel) were evaluated to determine their effectiveness as oviposition attractants. Various concentrations of waste larval media resulting from rearing screwworm larvae in gel and cellulose fiber-based ...

Butterflies Do Not Alter Conspecific Avoidance in Response to Variation in Density.

PubMed

Jaumann, Sarah; Snell-Rood, Emilie C

2017-08-01

High conspecific densities are associated with increased levels of intraspecific competition and a variety of negative effects on performance. However, changes in life history strategy could compensate for some of these effects. For instance, females in crowded conditions often have fewer total offspring, but they may invest more in each one. Such investment could include the production of larger offspring, more time spent engaging in parental care, or more choosy decisions about where offspring are placed. For animals that have a relatively immobile juvenile stage, the costs of competition can be particularly high. Females may be able to avoid such costs by investing more in individual reproductive decisions, rearing young or laying eggs in locations away from other females. We tested the hypothesis that conspecific density cues during juvenile and adult life stages lead to changes in life history strategy, including both reproduction and oviposition choices. We predicted that high-density cues during the larval and adult stages of female Pieris rapae butterflies lead to lower fecundity but higher conspecific avoidance during oviposition, compared to similar low-density cues. We used a 2×2 factorial design to examine the effects of low and high conspecific density during the larval and adult stages of butterflies on avoidance behavior and fecundity. We found that past information about conspecific density did not matter; all butterflies exhibited similar levels of fecundity and a low level of conspecific avoidance during oviposition regardless of their previous experience as larvae and adults. These results suggest that P. rapae females use a fixed, rather than flexible, conspecific avoidance strategy when making oviposition decisions, and past information about conspecific density has no effect on life history and current reproductive investment. We speculate that this may be partially because past conspecific density per se is not a reliable cue for predicting

An open-source method to analyze optokinetic reflex responses in larval zebrafish.

PubMed

Scheetz, Seth D; Shao, Enhua; Zhou, Yangzhong; Cario, Clinton L; Bai, Qing; Burton, Edward A

2018-01-01

Optokinetic reflex (OKR) responses provide a convenient means to evaluate oculomotor, integrative and afferent visual function in larval zebrafish models, which are commonly used to elucidate molecular mechanisms underlying development, disease and repair of the vertebrate nervous system. We developed an open-source MATLAB-based solution for automated quantitative analysis of OKR responses in larval zebrafish. The package includes applications to: (i) generate sinusoidally-transformed animated grating patterns suitable for projection onto a cylindrical screen to elicit the OKR; (ii) determine and record the angular orientations of the eyes in each frame of a video recording showing the OKR response; and (iii) analyze angular orientation data from the tracking program to yield a set of parameters that quantify essential elements of the OKR. The method can be employed without modification using the operating manual provided. In addition, annotated source code is included, allowing users to modify or adapt the software for other applications. We validated the algorithms and measured OKR responses in normal larval zebrafish, showing good agreement with published quantitative data, where available. We provide the first open-source method to elicit and analyze the OKR in larval zebrafish. The wide range of parameters that are automatically quantified by our algorithms significantly expands the scope of quantitative analysis previously reported. Our method for quantifying OKR responses will be useful for numerous applications in neuroscience using the genetically- and chemically-tractable zebrafish model. Published by Elsevier B.V.

Properties of the Visible Light Phototaxis and UV Avoidance Behaviors in the Larval Zebrafish.

PubMed

Guggiana-Nilo, Drago A; Engert, Florian

2016-01-01

For many organisms, color is an essential source of information from visual scenes. The larval zebrafish has the potential to be a model for the study of this topic, given its tetrachromatic retina and high dependence on vision. In this study we took a step toward understanding how the larval zebrafish might use color sensing. To this end, we used a projector-based paradigm to force a choice of a color stimulus at every turn of the larva. The stimuli used spanned most of the larval spectral range, including activation of its Ultraviolet (UV) cone, which has not been described behaviorally before. We found that zebrafish larvae swim toward visible wavelengths (>400 nm) when choosing between them and darkness, as has been reported with white light. However, when presented with UV light and darkness zebrafish show an intensity dependent avoidance behavior. This UV avoidance does not interact cooperatively with phototaxis toward longer wavelengths, but can compete against it in an intensity dependent manner. Finally, we show that the avoidance behavior depends on the presence of eyes with functional UV cones. These findings open future avenues for studying the neural circuits that underlie color sensing in the larval zebrafish.

Occurrence of Terranova larval types (Nematoda: Anisakidae) in Australian marine fish with comments on their specific identities

PubMed Central

Suthar, Jaydipbhai

2016-01-01

Pseudoterranovosis is a well-known human disease caused by anisakid larvae belonging to the genus Pseudoterranova. Human infection occurs after consuming infected fish. Hence the presence of Pseudoterranova larvae in the flesh of the fish can cause serious losses and problems for the seafood, fishing and fisheries industries. The accurate identification of Pseudoterranova larvae in fish is important, but challenging because the larval stages of a number of different genera, including Pseudoterranova, Terranova and Pulchrascaris, look similar and cannot be differentiated from each other using morphological criteria, hence they are all referred to as Terranova larval type. Given that Terranova larval types in seafood are not necessarily Pseudoterranova and may not be dangerous, the aim of the present study was to investigate the occurrence of Terranova larval types in Australian marine fish and to determine their specific identity. A total of 137 fish belonging to 45 species were examined. Terranova larval types were found in 13 species, some of which were popular edible fish in Australia. The sequences of the first and second internal transcribed spacers (ITS-1 and ITS-2 respectively) of the Terranova larvae in the present study showed a high degree of similarity suggesting that they all belong to the same species. Due to the lack of a comparable sequence data of a well identified adult in the GenBank database the specific identity of Terranova larval type in the present study remains unknown. The sequence of the ITS regions of the Terranova larval type in the present study and those of Pseudoterranova spp. available in GenBank are significantly different, suggesting that larvae found in the present study do not belong to the genus Pseudoterranova, which is zoonotic. This study does not rule out the presence of Pseudoterranova larvae in Australian fish as Pseudoterranova decipiens E has been reported in adult form from seals in Antarctica and it is known that they

Temporal Patterns of Larval Fish Occurrence in a Large Subtropical River

PubMed Central

Shuai, Fangmin; Li, Xinhui; Li, Yuefei; Li, Jie; Yang, Jiping; Lek, Sovan

2016-01-01

Knowledge of temporal patterns of larval fish occurrence is limited in south China, despite its ecological importance. This research examines the annual and seasonal patterns of fish larval presence in the large subtropical Pearl River. Data is based on samples collected every two days, from 2006 to 2013. In total, 45 taxa representing 13 families and eight orders were sampled. The dominant larval family was Cyprinidae, accounting for 27 taxa. Squaliobarbus curriculus was the most abundant species, followed by Megalobrama terminalis, Xenocypris davidi, Cirrhinus molitorella, Hemiculter leuscisculus and Squalidus argentatus. Fish larvae abundances varied significantly throughout the seasons (multivariate analyses: Cluster, SIMPROF and ANOSIM). The greatest numbers occurred between May and September, peaking from June through August, which corresponds to the reproductive season. In this study, redundancy analysis was used to describe the relationship between fish larval abundance and associated environmental factors. Mean water temperature, river discharge, atmospheric pressure, maximum temperature and precipitation play important roles in larval occurrence patterns. According to seasonal variations, fish larvae occurrence is mainly affected by water temperature. It was also noted that the occurrence of Salanx reevesii and Cyprinus carpio larvae is associated with higher dissolved oxygen (DO) concentrations, higher atmospheric pressure and lower water temperatures which occur in the spring. On the other hand, M. terminalis, X. davidi, and C. molitorella are associated with high precipitation, high river discharge, low atmospheric pressure and low DO concentrations which featured during the summer months. S. curriculus also peaks in the summer and is associated with peak water temperatures and minimum NH3–N concentrations. Rhinogobius giurinus occur when higher atmospheric pressure, lower precipitation and lower river discharges occur in the autumn. Dominant fish

Therapeutic potential of larval excretory/secretory proteins of the pig whipworm Trichuris suis in allergic disease.

PubMed

Ebner, F; Hepworth, M R; Rausch, S; Janek, K; Niewienda, A; Kühl, A; Henklein, P; Lucius, R; Hamelmann, E; Hartmann, S

2014-11-01

Gastrointestinal nematodes are currently being evaluated as a novel therapeutic in the treatment of chronic human inflammatory disorders, due to their unique ability to induce immunoregulatory pathways in their hosts. In particular, administration of ova from the pig whipworm Trichuris suis (T. suis; TSO) has been proposed for the treatment of allergic, inflammatory and autoimmune disorders. Despite these advances, the biological pathways through which TSO therapy modulates the host immune system in the context of human disease remain undefined. We characterized the dominant proteins present in the excretory/secretory (E/S) products of first-stage (L1) T. suis larvae (Ts E/S) using LC-MS/MS analysis and examined the immunosuppressive properties of whole larval Ts E/S in vitro and in a murine model of allergic airway disease. Administration of larval Ts E/S proteins in vivo during the allergen sensitization phase was sufficient to suppress airway hyperreactivity, bronchiolar inflammatory infiltrate and allergen-specific IgE production. Three proteins in larval Ts E/S were unambiguously identified. The immunomodulatory function of larval Ts E/S was found to be partially dependent on the immunoregulatory cytokine IL-10. Taken together, these data demonstrate that the released proteins of larval T. suis have significant immunomodulatory capacities and efficiently dampen allergic airway hyperreactivity. Thus, the therapeutic potential of defined larval E/S proteins should be exploited for the treatment of human allergic disorders. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

[New insight into Anopheles coluzzii Coetzee & Wilkerson, 2013 larval ecology in the Wouri estuary, Littoral-Cameroon].

PubMed

Mbida Mbida, A; Etang, J; Akono Ntonga, P; Eboumbou Moukoko, C; Awono-Ambene, P; Tagne, D; Talipouo, A; Ekoko, W; Binyang, J; Tchoffo, R; Lehman, G; Mimpfoundi, R

2017-05-01

Malaria vectors control is essentially based on the use of insecticides against adult mosquitoes. However because of the development of resistance to insecticides, there is now a renewed interest in the management of larval sources. The aim of the present study was to map and characterize the breeding sites of Anopheles coluzzii in the Wouri river estuary in Cameroon. Larval surveys were carried out between December 2013 and August 2014 in rural areas on the island of Manoka and urban area in Youpwe at Douala. Culicidae breeding sites identified were georeferenced and mapped. Their larval productivity was evaluated by the method of "dipping" and their physicochemical parameters measured by spectrophotometry and oximetry. Culicidae collected larvae were reared in the insectarium to the adult stage. Adult mosquitoes were subjected to morphological identification and those belonging to the Anopheles gambiae complex have subsequently been subjected to molecular identification by the PCR-RFLP technique. A total of 240 breeding sites were geo-referenced in the two sites, including 10 types. Abandoned containers and pools were the most frequent breeding sites respectively in Manoka and in Youpwe. After morphological and molecular identification, eleven mosquito species have been identified. Anopheles coluzzii and Culex quinquefasciatus were the most frequent species respectively in Manoka and in Youpwe. Mosquito density was higher in managed gutters and canoes respectively in Manoka and in Youpwe. Culex and Aedes genus were more frequent in the hollow palm and water wells respectively in Manoka and Youpwe. The productivity of breeding sites varied according to the physicochemical parameters. Species richness varied according to the type of breeding site. Anopheles coluzzii was observed for the first time in Cameroon in water storage containers, tires, discarded containers and canoes. This study highlighted diversity in the type of breeding site of An. coluzzii in the

A developmental and energetic basis linking larval oyster shell formation to acidification sensitivity

NASA Astrophysics Data System (ADS)

Waldbusser, George G.; Brunner, Elizabeth L.; Haley, Brian A.; Hales, Burke; Langdon, Christopher J.; Prahl, Frederick G.

2013-05-01

Acidified waters are impacting commercial oyster production in the U.S. Pacific Northwest, and favorable carbonate chemistry conditions are predicted to become less frequent. Within 48 h of fertilization, unshelled Pacific oyster (Crassostrea gigas) larvae precipitate roughly 90% of their body weight as calcium carbonate. We measured stable carbon isotopes in larval shell and tissue and in algal food and seawater dissolved inorganic carbon in a longitudinal study of larval development and growth. Using these data and measured biochemical composition of larvae, we show that sensitivity of initial shell formation to ocean acidification results from diminished ability to isolate calcifying fluid from surrounding seawater, a limited energy budget and a strong kinetic demand for calcium carbonate precipitation. Our results highlight an important link between organism physiology and mineral kinetics in larval bivalves and suggest the consideration of mineral kinetics may improve understanding winners and losers in a high CO2 world.

Obligate larval inhibition of Ostertagia gruehneri in Rangifer tarandus? Causes and consequences in an Arctic system.

PubMed

Hoar, Bryanne M; Eberhardt, Alexander G; Kutz, Susan J

2012-09-01

Larval inhibition is a common strategy of Trichostrongylidae nematodes that may increase survival of larvae during unfavourable periods and concentrate egg production when conditions are favourable for development and transmission. We investigated the propensity for larval inhibition in a population of Ostertagia gruehneri, the most common gastrointestinal Trichostrongylidae nematode of Rangifer tarandus. Initial experimental infections of 4 reindeer with O. gruehneri sourced from the Bathurst caribou herd in Arctic Canada suggested that the propensity for larval inhibition was 100%. In the summer of 2009 we infected 12 additional reindeer with the F1 and F2 generations of O. gruehneri sourced from the previously infected reindeer to further investigate the propensity of larval inhibition. The reindeer were divided into 2 groups and half were infected before the summer solstice (17 June) and half were infected after the solstice (16 July). Reindeer did not shed eggs until March 2010, i.e. 8 and 9 months post-infection. These results suggest obligate larval inhibition for at least 1 population of O. gruehneri, a phenomenon that has not been conclusively shown for any other trichostrongylid species. Obligate inhibition is likely to be an adaptation to both the Arctic environment and to a migratory host and may influence the ability of O. gruehneri to adapt to climate change.

Determination of the efficiency of diets for larval development in mass rearing Aedes aegypti (Diptera: Culicidae).

PubMed

Gunathilaka, P A D H N; Uduwawala, U M H U; Udayanga, N W B A L; Ranathunge, R M T B; Amarasinghe, L D; Abeyewickreme, W

2017-11-23

Larval diet quality and rearing conditions have a direct and irreversible effect on adult traits. Therefore, the current study was carried out to optimize the larval diet for mass rearing of Aedes aegypti, for Sterile Insect Technique (SIT)-based applications in Sri Lanka. Five batches of 750 first instar larvae (L 1) of Ae. aegypti were exposed to five different concentrations (2-10%) of International Atomic Energy Agency (IAEA) recommended the larval diet. Morphological development parameters of larva, pupa, and adult were detected at 24 h intervals along with selected growth parameters. Each experiment was replicated five times. General Linear Modeling along with Pearson's correlation analysis were used for statistical treatments. Significant differences (P < 0.05) among the larvae treated with different concentrations were found using General Linear Modeling in all the stages namely: total body length and the thoracic length of larvae; cephalothoracic length and width of pupae; thoracic length, thoracic width, abdominal length and the wing length of adults; along with pupation rate and success, sex ratio, adult success, fecundity and hatching rate of Ae. aegypti. The best quality adults can be produced at larval diet concentration of 10%. However, the 8% larval diet concentration was most suitable for adult male survival.

Evidence for the Involvement of p38 MAPK Activation in Barnacle Larval Settlement

PubMed Central

He, Li-Sheng; Xu, Ying; Matsumura, Kiyotaka; Zhang, Yu; Zhang, Gen; Qi, Shu-Hua; Qian, Pei-Yuan

2012-01-01

The barnacle Balanus ( = Amphibalanus) amphitrite is a major marine fouling animal. Understanding the molecular mechanism of larval settlement in this species is critical for anti-fouling research. In this study, we cloned one isoform of p38 MAPK (Bar-p38 MAPK) from this species, which shares the significant characteristic of containing a TGY motif with other species such as yeast, Drosophila and humans. The activation of p38 MAPK was detected by an antibody that recognizes the conserved dual phosphorylation sites of TGY. The results showed that phospho-p38 MAPK (pp38 MAPK) was more highly expressed at the cyprid stage, particularly in aged cyprids, in comparison to other stages, including the nauplius and juvenile stages. Immunostaining showed that Bar-p38 MAPK and pp38 MAPK were mainly located at the cyprid antennules, and especially the third and fourth segments, which are responsible for substratum exploration during settlement. The expression and localization patterns of Bar-p38 MAPK suggest its involvement in larval settlement. This postulation was also supported by the larval settlement bioassay with the p38 MAPK inhibitor SB203580. Behavioral analysis by live imaging revealed that the larvae were still capable of exploring the surface of the substratum after SB203580 treatment. This shows that the effect of p38 MAPK on larval settlement might be by regulating the secretion of permanent proteinaceous substances. Furthermore, the level of pp38 MAPK dramatically decreased after full settlement, suggesting that Bar-p38 MAPK maybe plays a role in larval settlement rather than metamorphosis. Finally, we found that Bar-p38 MAPK was highly activated when larvae confronted extracts of adult barnacle containing settlement cues, whereas larvae pre-treated with SB203580 failed to respond to the crude adult extracts. PMID:23115639

Larval traits show temporally consistent constraints, but are decoupled from post-settlement juvenile growth, in an intertidal fish.

PubMed

Thia, Joshua A; Riginos, Cynthia; Liggins, Libby; Figueira, Will F; McGuigan, Katrina

2018-05-05

1.Complex life-cycles may evolve to dissociate distinct developmental phases in an organism's lifetime. However, genetic or environmental factors may restrict trait independence across life stages, constraining ontogenetic trajectories. Quantifying covariance across life-stages and their temporal variability is fundamental in understanding life-history phenotypes and potential distributions and consequences for selection. 2.We studied developmental constraints in an intertidal fish (Bathygobius cocosensis: Gobiidae) with a discrete pelagic larval phase and benthic juvenile phase. We tested whether traits occurring earlier in life affected those expressed later, and whether larval traits were decoupled from post-settlement juvenile traits. Sampling distinct cohorts from three annual breeding seasons afforded tests of temporally variability in trait covariance. 3.From otoliths (fish ear stones), we measured hatch size, larval duration, pelagic growth (larval traits) and early post-settlement growth (juvenile trait) in 124 juvenile B. cocoensis. We used path analyses to model trait relationships with respect to their chronological expression, comparing models among seasons. We also modelled the effect of season and hatch date on each individual trait to quantify their inherent variability. 4.Our path analyses demonstrated a decoupling of larval traits on juvenile growth. Within the larval phase, longer larval durations resulted in greater pelagic growth, and larger size-at-settlement. There was also evidence that larger hatch size might reduce larval durations, but this effect was only marginally significant. Although pelagic and post-settlement growth were decoupled, pelagic growth had post-settlement consequences: individuals with high pelagic growth were among the largest fish at settlement, and remained among the largest early post-settlement. We observed no evidence that trait relationships varied among breeding seasons, but larval duration differed among

[Canine peritoneal larval cestodosis caused by Mesocestoides spp. larval stages].

PubMed

Häußler, T C; Peppler, C; Schmitz, S; Bauer, C; Hirzmann, J; Kramer, M

2016-01-01

In a female dog with unspecific clinical symptoms, sonography detected a hyperechoic mass in the middle abdomen and blood analysis a middle grade systemic inflammatory reaction. Laparotomy revealed a peritoneal larval cestodosis (PLC). The diagnosis of an infection with tetrathyridia of Mesocestoides spp. was confirmed by parasitological examination and molecularbiological analysis. Reduction of the intra-abdominal parasitic load as well as a high dose administration of fenbendazole over 3 months led to a successful treatment which could be documented sonographically and by decreased concentrations of C-reactive protein (CRP). Seven months after discontinuation of fenbendazole administration, PLC recurred, pre-empted by an elevation of serum CRP values. According to the literature a life-long fenbendazole treatment was initiated. In cases of unclear chronic granulomatous inflammations in the abdominal cavity in dogs, PLC should be considered. CRP concentration and sonographic examinations are suitable to control for treatment success and a possibly occurring relapse.

VARIATIONS IN LARVAL GROWTH AND METABOLISM OF AN ESTUARINE SHRIMP DURING TOXICOSIS BY AN INSECT GROWTH REGULATOR

EPA Science Inventory

Exposure of the estuarine shrimp, Ptiaemonetes pugio, to a juvenile hormone analogue (> 3 ug methoprene-1) throughout larval development inhibited successful completion of metamorphosis. Methoprene exposure retarded growth in early larval stages and postlarvae enhanced growth in ...

Higher thyroid hormone receptor expression correlates with short larval periods in spadefoot toads and increases metamorphic rate

PubMed Central

Hollar, Amy R.; Choi, Jinyoung; Grimm, Adam T.; Buchholz, Daniel R.

2011-01-01

Spadefoot toad species display extreme variation in larval period duration, due in part to evolution of thyroid hormone (TH) physiology. Specifically, desert species with short larval periods have higher tail tissue content of TH and exhibit increased responsiveness to TH. To address the molecular basis of larval period differences, we examined TH receptor (TR) expression across species. Based on the dual function model for the role of TR in development, we hypothesized that desert spadefoot species with short larval periods would have 1) late onset of TR expression prior to the production of endogenous TH and 2) higher TR levels when endogenous TH becomes available. To test these hypotheses, we cloned fragments of TRα and TRβ genes from the desert spadefoot toads Scaphiopus couchii and Spea multiplicata and their non-desert relative Pelobates cultripes and measured their mRNA levels in tails using quantitative PCR in the absence (premetamorphosis) or presence (natural metamorphosis) of TH. All species express TRα and TRβ from the earliest stages measured (from just after hatching), but S. couchii, which has the shortest larval period, had more TRα throughout development compared to P. cultripes, which has the longest larval period. TRβ mRNA levels were similar across species. Exogenous T3 treatment induced faster TH-response gene expression kinetics in S. couchii compared to the other species, consistent with its increased TRα mRNA expression and indicative of a functional consequence of more TRα activity at the molecular level. To directly test whether higher TRα expression may contribute to shorter larval periods, we overexpressed TRα via plasmid injection into tail muscle cells of the model frog Xenopus laevis and found an increased rate of muscle cell death in response to TH. These results suggest that increased TRα expression evolved in S. couchii and contribute to its higher metamorphic rates. PMID:21651912

Impacts of a gape limited Brook Trout, Salvelinus fontinalis, on larval Northwestern salamander, Ambystoma gracile, growth: A field enclosure experiment

USGS Publications Warehouse

Currens, C.R.; Liss, W.J.; Hoffman, R.L.

2007-01-01

The formation of amphibian population structure is directly affected by predation. Although aquatic predators have been shown to have direct negative effects on larval salamanders in laboratory and field experiments, the potential impacts of gape-limited fish on larval salamander growth has been largely underexplored. We designed an enclosure experiment conducted in situ to quantify the effects of gape-limited Brook Trout (Salvelinus fontinalis) on larval Northwestern Salamander (Ambystoma gracile) growth. We specifically tested whether the presence of fish too small to consume larvae had a negative effect on larval growth. The results of this study indicate that the presence of a gape-limited S. fontinalis can have a negative effect on growth of larval A. gracile salamanders. Copyright 2007 Society for the Study of Amphibians and Reptiles.

Determination of antibacterial activity and minimum inhibitory concentration of larval extract of fly via resazurin-based turbidometric assay.

PubMed

Teh, Chien Huey; Nazni, Wasi Ahmad; Nurulhusna, Ab Hamid; Norazah, Ahmad; Lee, Han Lim

2017-02-16

Antimicrobial resistance is currently a major global issue. As the rate of emergence of antimicrobial resistance has superseded the rate of discovery and introduction of new effective drugs, the medical arsenal now is experiencing shortage of effective drugs to combat diseases, particularly against diseases caused by the dreadful multidrug-resistant strains, such as the methicillin-resistant Staphylococcus aureus (MRSA). The ability of fly larvae to thrive in septic habitats has prompted us to determine the antibacterial activity and minimum inhibitory concentrations (MICs) of larval extract of flies, namely Lucilia cuprina, Sarcophaga peregrina and Musca domestica against 4 pathogenic bacteria [Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa and Escherichia coli] via a simple and sensitive antibacterial assay, resazurin-based turbidometric (TB) assay as well as to demonstrate the preliminary chemical profile of larval extracts using gas chromatography-mass spectrophotometry (GC-MS). The resazurin-based TB assay demonstrated that the L. cuprina larval extract was inhibitory against all tested bacteria, whilst the larval extract of S. peregrina and M. domestica were only inhibitory against the MRSA, with a MIC of 100 mg ml -1 . Subsequent sub-culture of aliquots revealed that the larval extract of L. cuprina was bactericidal against MRSA whilst the larval extracts of S. peregrina and M. domestica were bacteriostatic against MRSA. The GC-MS analysis had quantitatively identified 20 organic compounds (fatty acids or their derivatives, aromatic acid esters, glycosides and phenol) from the larval extract of L. cuprina; and 5 fatty acid derivatives with known antimicrobial activities from S. peregrina and M. domestica. The resazurin-based turbidometric assay is a simple, reliable and feasible screening assay which evidently demonstrated the antibacterial activity of all fly larval extracts, primarily against the MRSA. The larval

Cloning of aquaporin-1 of the blue crab, Callinectes sapidus: its expression during the larval development in hyposalinity.

PubMed

Chung, J Sook; Maurer, Leah; Bratcher, Meagan; Pitula, Joseph S; Ogburn, Matthew B

2012-09-03

Ontogenetic variation in salinity adaptation has been noted for the blue crab, Callinectes sapidus, which uses the export strategy for larval development: females migrate from the estuaries to the coast to spawn, larvae develop in the ocean, and postlarvae (megalopae) colonize estuarine areas. We hypothesized that C. sapidus larvae may be stenohaline and have limited osmoregulatory capacity which compromises their ability to survive in lower salinity waters. We tested this hypothesis using hatchery-raised larvae that were traceable to specific life stages. In addition, we aimed to understand the possible involvement of AQP-1 in salinity adaptation during larval development and during exposure to hyposalinity. A full-length cDNA sequence of aquaporin (GenBank JQ970426) was isolated from the hypodermis of the blue crab, C. sapidus, using PCR with degenerate primers and 5' and 3' RACE. The open reading frame of CasAQP-1 consists of 238 amino acids containing six helical structures and two NPA motifs for the water pore. The expression pattern of CasAQP-1 was ubiquitous in cDNAs from all tissues examined, although higher in the hepatopancreas, thoracic ganglia, abdominal muscle, and hypodermis and lower in the antennal gland, heart, hemocytes, ovary, eyestalk, brain, hindgut, Y-organs, and gill. Callinectes larvae differed in their capacity to molt in hyposalinity, as those at earlier stages from Zoea (Z) 1 to Z4 had lower molting rates than those from Z5 onwards, as compared to controls kept in 30 ppt water. No difference was found in the survival of larvae held at 15 and 30 ppt. CasAQP-1 expression differed with ontogeny during larval development, with significantly higher expression at Z1-2, compared to other larval stages. The exposure to 15 ppt affected larval-stage dependent CasAQP-1 expression which was significantly higher in Z2- 6 stages than the other larval stages. We report the ontogenetic variation in CasAQP-1 expression during the larval development

Larval RNA Interference in the Red Flour Beetle, Tribolium castaneum

PubMed Central

Tomoyasu, Yoshinori

2014-01-01

The red flour beetle, Tribolium castaneum, offers a repertoire of experimental tools for genetic and developmental studies, including a fully annotated genome sequence, transposon-based transgenesis, and effective RNA interference (RNAi). Among these advantages, RNAi-based gene knockdown techniques are at the core of Tribolium research. T. castaneum show a robust systemic RNAi response, making it possible to perform RNAi at any life stage by simply injecting double-stranded RNA (dsRNA) into the beetle’s body cavity. In this report, we provide an overview of our larval RNAi technique in T. castaneum. The protocol includes (i) isolation of the proper stage of T. castaneum larvae for injection, (ii) preparation for the injection setting, and (iii) dsRNA injection. Larval RNAi is a simple, but powerful technique that provides us with quick access to loss-of-function phenotypes, including multiple gene knockdown phenotypes as well as a series of hypomorphic phenotypes. Since virtually all T. castaneum tissues are susceptible to extracellular dsRNA, the larval RNAi technique allows researchers to study a wide variety of tissues in diverse contexts, including the genetic basis of organismal responses to the outside environment. In addition, the simplicity of this technique stimulates more student involvement in research, making T. castaneum an ideal genetic system for use in a classroom setting. PMID:25350485

Embryogenesis, hatching and larval development of Artemia during orbital spaceflight

NASA Astrophysics Data System (ADS)

Spooner, B. S.; Debell, L.; Armbrust, L.; Guikema, J. A.; Metcalf, J.; Paulsen, A.

1994-08-01

Developmental biology studies, using gastrula-arrested cysts of the brine shrimp Artemia franciscana, were conducted during two flights of the space shuttle Atlantis (missions STS-37 and STS-43) in 1991. Dehydrated cysts were activated, on orbit, by addition of salt water to the cysts, and then development was terminated by the addition of fixative. Development took place in 5 ml syringes, connected by tubing to activation syringes, containing salt water, and termination syringes, containing fixative. Comparison of space results with simultaneous ground control experiments showed that equivalent percentages of naupliar larvae hatched in the syringes (40%). Thus, reactivation of development, completion of embryogenesis, emergence and hatching took place, during spaceflight, without recognizable alteration in numbers of larvae produced. Post-hatching larval development was studied in experiments where development was terminated, by intrduction of fixative, 2 days, 4 days, and 8 days after reinitiation of development. During spaceflight, successive larval instars or stages, interrupted by molts, occurred, generating brine shrimp at appropriate larval instars. Naupliar larvae possessed the single naupliar eye, and development of the lateral pair of adult eyes also took place in space. Transmission electron microscopy revealed extensive differentiation, including skeletal muscle and gut endoderm, as well as the eye tissues. These studies demonstrate the potential value of Artemia for developmental biology studies during spaceflight, and show that extensive degress of development can take place in this microgravity environment.

Acquisition of Borrelia burgdorferi infection by larval Ixodes scapularis (Acari: Ixodidae) associated with engorgement measures

USGS Publications Warehouse

Couret, Janelle; Dyer, M.C.; Mather, T.N.; Han, S.; Tsao, J.I.; LeBrun, R.A.; Ginsberg, Howard

2017-01-01

Measuring rates of acquisition of the Lyme disease pathogen, Borrelia burgdorferi sensu lato Johnson, Schmid, Hyde, Steigerwalt & Brenner, by the larval stage of Ixodes scapularis Say is a useful tool for xenodiagnoses of B. burgdorferi in vertebrate hosts. In the nymphal and adult stages of I. scapularis, the duration of attachment to hosts has been shown to predict both body engorgement during blood feeding and the timing of infection with B. burgdorferi. However, these relationships have not been established for the larval stage of I. scapularis. We sought to establish the relationship between body size during engorgement of larval I. scapularis placed on B. burgdorferi-infected, white-footed mice (Peromyscus leucopus Rafinesque) and the presence or absence of infection in larvae sampled from hosts over time. Body size, time, and their interaction were the best predictors of larval infection with B. burgdorferi. We found that infected larvae showed significantly greater engorgement than uninfected larvae as early as 24 h after placement on a host. These findings may suggest that infection with B. burgdorferi affects the larval feeding process. Alternatively, larvae that engorge more rapidly on hosts may acquire infections faster. Knowledge of these relationships can be applied to improve effective xenodiagnosis of B. burgdorferi in white-footed mice. Further, these findings shed light on vector–pathogen–host interactions during an understudied part of the Lyme disease transmission cycle.

[Carbohydrate restriction in the larval diet causes oxidative stress in adult insects of Drosophila melanogaster].

PubMed

Rovenko, B M; Lushchak, V I; Lushchak, O V

2013-01-01

The influence of 20 and 1% glucose and fructose, which were components of larval diet, on the level of oxidized proteins and lipids, low molecular mass antioxidant content as well as activities of antioxidant and associated enzymes in adult fruit fly Drosophila melanogaster were investigated. The restriction of carbohydrates in larval diet leads to oxidative stress in adult insects. It is supported by 40-50% increased content of protein carbonyl groups and by 60-70% decreased level of protein thiol groups as well as by a 4-fold increase of lipid peroxide content in 2-day-old flies of both sexes, developed on the diet with 1% carbohydrates. Oxidative stress, induced by carbohydrate restriction of the larval diet, caused the activation of antioxidant defence, differently exhibited in male and female fruit flies. Caloric restriction increased activity of superoxide dismutase and thioredoxin reductase associating only in males with 2-fold higher activity of NADPH-producing enzymes--glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase. Carbohydrate restriction in the larval diet caused the increase of uric acid content, but the decrease in catalase activity in males. In females the values of these parameters were changed in opposite direction compared with males. The obtained results let us conclude the different involvement of low molecular mass antioxidants, glutathione and uric acid, and antioxidant enzyme catalase in the protection of male and female fruit fly macromolecules against oxidative damages, caused by calorie restriction of larval diet.

Rapid whole brain imaging of neural activity in freely behaving larval zebrafish (Danio rerio)

PubMed Central

Shang, Chunfeng; Yang, Wenbin; Bai, Lu; Du, Jiulin

2017-01-01

The internal brain dynamics that link sensation and action are arguably better studied during natural animal behaviors. Here, we report on a novel volume imaging and 3D tracking technique that monitors whole brain neural activity in freely swimming larval zebrafish (Danio rerio). We demonstrated the capability of our system through functional imaging of neural activity during visually evoked and prey capture behaviors in larval zebrafish. PMID:28930070

Sublethal Dosage of Imidacloprid Reduces the Microglomerular Density of Honey Bee Mushroom Bodies

PubMed Central

Peng, Yi-Chan; Yang, En-Cheng

2016-01-01

The dramatic loss of honey bees is a major concern worldwide. Previous studies have indicated that neonicotinoid insecticides cause behavioural abnormalities and have proven that exposure to sublethal doses of imidacloprid during the larval stage decreases the olfactory learning ability of adults. The present study shows the effect of sublethal doses of imidacloprid on the neural development of the honey bee brain by immunolabelling synaptic units in the calyces of mushroom bodies. We found that the density of the synaptic units in the region of the calyces, which are responsible for olfactory and visual functions, decreased after being exposed to a sublethal dose of imidacloprid. This not only links a decrease in olfactory learning ability to abnormal neural connectivity but also provides evidence that imidacloprid damages the development of the nervous system in regions responsible for both olfaction and vision during the larval stage of the honey bee. PMID:26757950

Induction of Larval Settlement in the Reef Coral Porites astreoides by a Cultivated Marine Roseobacter Strain.

PubMed

Sharp, K H; Sneed, J M; Ritchie, K B; Mcdaniel, L; Paul, V J

2015-04-01

Successful larval settlement and recruitment by corals is critical for the survival of coral reef ecosystems. Several closely related strains of γ-proteobacteria have been identified as cues for coral larval settlement, but the inductive properties of other bacterial taxa naturally occurring in reef ecosystems have not yet been explored. In this study, we assayed bacterial strains representing taxonomic groups consistently detected in corals for their ability to influence larval settlement in the coral Porites astreoides. We identified one α-proteobacterial strain, Roseivivax sp. 46E8, which significantly increased larval settlement in P. astreoides. Logarithmic growth phase (log phase) cell cultures of Roseivivax sp. 46E8 and filtrates (0.22μm) from log phase Roseivivax sp. 46E8 cultures significantly increased settlement, suggesting that an extracellular settlement factor is produced during active growth phase. Filtrates from log phase cultures of two other bacterial isolates, Marinobacter sp. 46E3, and Cytophaga sp. 46B6, also significantly increased settlement, but the cell cultures themselves did not. Monospecific biofilms of the three strains did not result in significant increases in larval settlement. Organic and aqueous/methanol extracts of Roseivivax sp. 46E8 cultures did not affect larval settlement. Examination of filtrates from cell cultures showed that Roseivivax sp. 46E8 spontaneously generated virus-like particles in log and stationary phase growth. Though the mechanism of settlement enhancement by Roseivivax sp. 46E8 is not yet elucidated, our findings point to a new aspect of coral-Roseobacter interactions that should be further investigated, especially in naturally occurring, complex microbial biofilms on reef surfaces. © 2015 Marine Biological Laboratory.

Binary Cell Fate Decisions and Fate Transformation in the Drosophila Larval Eye

PubMed Central

Rister, Jens; Ng, June; Celik, Arzu; Sprecher, Simon G.

2013-01-01

The functionality of sensory neurons is defined by the expression of specific sensory receptor genes. During the development of the Drosophila larval eye, photoreceptor neurons (PRs) make a binary choice to express either the blue-sensitive Rhodopsin 5 (Rh5) or the green-sensitive Rhodopsin 6 (Rh6). Later during metamorphosis, ecdysone signaling induces a cell fate and sensory receptor switch: Rh5-PRs are re-programmed to express Rh6 and become the eyelet, a small group of extraretinal PRs involved in circadian entrainment. However, the genetic and molecular mechanisms of how the binary cell fate decisions are made and switched remain poorly understood. We show that interplay of two transcription factors Senseless (Sens) and Hazy control cell fate decisions, terminal differentiation of the larval eye and its transformation into eyelet. During initial differentiation, a pulse of Sens expression in primary precursors regulates their differentiation into Rh5-PRs and repression of an alternative Rh6-cell fate. Later, during the transformation of the larval eye into the adult eyelet, Sens serves as an anti-apoptotic factor in Rh5-PRs, which helps in promoting survival of Rh5-PRs during metamorphosis and is subsequently required for Rh6 expression. Comparably, during PR differentiation Hazy functions in initiation and maintenance of rhodopsin expression. Hazy represses Sens specifically in the Rh6-PRs, allowing them to die during metamorphosis. Our findings show that the same transcription factors regulate diverse aspects of larval and adult PR development at different stages and in a context-dependent manner. PMID:24385925

Binary cell fate decisions and fate transformation in the Drosophila larval eye.

PubMed

Mishra, Abhishek Kumar; Tsachaki, Maria; Rister, Jens; Ng, June; Celik, Arzu; Sprecher, Simon G

2013-01-01

The functionality of sensory neurons is defined by the expression of specific sensory receptor genes. During the development of the Drosophila larval eye, photoreceptor neurons (PRs) make a binary choice to express either the blue-sensitive Rhodopsin 5 (Rh5) or the green-sensitive Rhodopsin 6 (Rh6). Later during metamorphosis, ecdysone signaling induces a cell fate and sensory receptor switch: Rh5-PRs are re-programmed to express Rh6 and become the eyelet, a small group of extraretinal PRs involved in circadian entrainment. However, the genetic and molecular mechanisms of how the binary cell fate decisions are made and switched remain poorly understood. We show that interplay of two transcription factors Senseless (Sens) and Hazy control cell fate decisions, terminal differentiation of the larval eye and its transformation into eyelet. During initial differentiation, a pulse of Sens expression in primary precursors regulates their differentiation into Rh5-PRs and repression of an alternative Rh6-cell fate. Later, during the transformation of the larval eye into the adult eyelet, Sens serves as an anti-apoptotic factor in Rh5-PRs, which helps in promoting survival of Rh5-PRs during metamorphosis and is subsequently required for Rh6 expression. Comparably, during PR differentiation Hazy functions in initiation and maintenance of rhodopsin expression. Hazy represses Sens specifically in the Rh6-PRs, allowing them to die during metamorphosis. Our findings show that the same transcription factors regulate diverse aspects of larval and adult PR development at different stages and in a context-dependent manner.

Development of the Acoustically Evoked Behavioral Response in Larval Plainfin Midshipman Fish, Porichthys notatus

PubMed Central

Alderks, Peter W.; Sisneros, Joseph A.

2013-01-01

The ontogeny of hearing in fishes has become a major interest among bioacoustics researchers studying fish behavior and sensory ecology. Most fish begin to detect acoustic stimuli during the larval stage which can be important for navigation, predator avoidance and settlement, however relatively little is known about the hearing capabilities of larval fishes. We characterized the acoustically evoked behavioral response (AEBR) in the plainfin midshipman fish, Porichthys notatus, and used this innate startle-like response to characterize this species' auditory capability during larval development. Age and size of larval midshipman were highly correlated (r2 = 0.92). The AEBR was first observed in larvae at 1.4 cm TL. At a size ≥1.8 cm TL, all larvae responded to a broadband stimulus of 154 dB re1 µPa or −15.2 dB re 1 g (z-axis). Lowest AEBR thresholds were 140–150 dB re 1 µPa or −33 to −23 dB re 1 g for frequencies below 225 Hz. Larval fish with size ranges of 1.9–2.4 cm TL had significantly lower best evoked frequencies than the other tested size groups. We also investigated the development of the lateral line organ and its function in mediating the AEBR. The lateral line organ is likely involved in mediating the AEBR but not necessary to evoke the startle-like response. The midshipman auditory and lateral line systems are functional during early development when the larvae are in the nest and the auditory system appears to have similar tuning characteristics throughout all life history stages. PMID:24340003

Development of the acoustically evoked behavioral response in larval plainfin midshipman fish, Porichthys notatus.

PubMed

Alderks, Peter W; Sisneros, Joseph A

2013-01-01

The ontogeny of hearing in fishes has become a major interest among bioacoustics researchers studying fish behavior and sensory ecology. Most fish begin to detect acoustic stimuli during the larval stage which can be important for navigation, predator avoidance and settlement, however relatively little is known about the hearing capabilities of larval fishes. We characterized the acoustically evoked behavioral response (AEBR) in the plainfin midshipman fish, Porichthys notatus, and used this innate startle-like response to characterize this species' auditory capability during larval development. Age and size of larval midshipman were highly correlated (r(2) = 0.92). The AEBR was first observed in larvae at 1.4 cm TL. At a size ≥ 1.8 cm TL, all larvae responded to a broadband stimulus of 154 dB re1 µPa or -15.2 dB re 1 g (z-axis). Lowest AEBR thresholds were 140-150 dB re 1 µPa or -33 to -23 dB re 1 g for frequencies below 225 Hz. Larval fish with size ranges of 1.9-2.4 cm TL had significantly lower best evoked frequencies than the other tested size groups. We also investigated the development of the lateral line organ and its function in mediating the AEBR. The lateral line organ is likely involved in mediating the AEBR but not necessary to evoke the startle-like response. The midshipman auditory and lateral line systems are functional during early development when the larvae are in the nest and the auditory system appears to have similar tuning characteristics throughout all life history stages.

Impacts of Larval Connectivity on Coral Heat Tolerance

NASA Astrophysics Data System (ADS)

Pinsky, M. L.; Kleypas, J. A.; Thompson, D. M.; Castruccio, F. S.; Curchitser, E. N.; Watson, J. R.

2016-02-01

The sensitivity of corals to elevated temperature depends on their acclimation and adaptation to the local maximum temperature regime. Through larval dispersal, however, coral populations can receive larvae from regions that are significantly warmer or colder. If these exogenous larvae carry genetic-based tolerances to colder or warmer temperatures, then the thermal sensitivity of the receiving population may be lower or higher, respectively. Using a high-resolution Regional Ocean Modeling System (ROMS) configuration for the Coral Triangle region, we quantify the potential role of connectivity in determining the thermal stress threshold (TST) of a typical broadcast spawner. The model results suggest that even with a pelagic larval dispersal period of only 10 days, many reefs receive larvae from reefs that are warmer or cooler than the local temperature, and that accounting for this connectivity improves bleaching predictions. This has important implications for conservation planning, because connectivity may allow some reefs to have an inherited heat tolerance that is higher or lower than would be predicted based on local conditions alone.

Factors affecting infection of corals and larval oysters by Vibrio coralliilyticus.

PubMed

Ushijima, Blake; Richards, Gary P; Watson, Michael A; Schubiger, Carla B; Häse, Claudia C

2018-01-01

The bacterium Vibrio coralliilyticus can threaten vital reef ecosystems by causing disease in a variety of coral genera, and, for some strains, increases in virulence at elevated water temperatures. In addition, strains of V. coralliilyticus (formally identified as V. tubiashii) have been implicated in mass mortalities of shellfish larvae causing significant economic losses to the shellfish industry. Recently, strain BAA-450, a coral pathogen, was demonstrated to be virulent towards larval Pacific oysters (Crassostrea gigas). However, it is unclear whether other coral-associated V. coralliilyticus strains can cause shellfish mortalities and if infections are influenced by temperature. This study compared dose dependence, temperature impact, and gross pathology of four V. coralliilyticus strains (BAA-450, OCN008, OCN014 and RE98) on larval C. gigas raised at 23°C and 27°C, and evaluated whether select virulence factors are required for shellfish infections as they are for corals. All strains were infectious to larval oysters in a dose-dependent manner with OCN014 being the most pathogenic and BAA-450 being the least. At 27°C, higher larval mortalities (p < 0.05) were observed for all V. coralliilyticus strains, ranging from 38.8-93.7%. Gross pathological changes to the velum and cilia occurred in diseased larvae, but there were no distinguishable differences between oysters exposed to different V. coralliilyticus strains or temperatures. Additionally, in OCN008, the predicted transcriptional regulator ToxR and the outer membrane protein OmpU were important for coral and oyster disease, while mannose sensitive hemagglutinin type IV pili were required only for coral infection. This study demonstrated that multiple coral pathogens can infect oyster larvae in a temperature-dependent manner and identified virulence factors required for infection of both hosts.

Properties of the Visible Light Phototaxis and UV Avoidance Behaviors in the Larval Zebrafish

PubMed Central

Guggiana-Nilo, Drago A.; Engert, Florian

2016-01-01

For many organisms, color is an essential source of information from visual scenes. The larval zebrafish has the potential to be a model for the study of this topic, given its tetrachromatic retina and high dependence on vision. In this study we took a step toward understanding how the larval zebrafish might use color sensing. To this end, we used a projector-based paradigm to force a choice of a color stimulus at every turn of the larva. The stimuli used spanned most of the larval spectral range, including activation of its Ultraviolet (UV) cone, which has not been described behaviorally before. We found that zebrafish larvae swim toward visible wavelengths (>400 nm) when choosing between them and darkness, as has been reported with white light. However, when presented with UV light and darkness zebrafish show an intensity dependent avoidance behavior. This UV avoidance does not interact cooperatively with phototaxis toward longer wavelengths, but can compete against it in an intensity dependent manner. Finally, we show that the avoidance behavior depends on the presence of eyes with functional UV cones. These findings open future avenues for studying the neural circuits that underlie color sensing in the larval zebrafish. PMID:27594828

Pelagic larval duration and settlement size of a reef fish are spatially consistent, but post-settlement growth varies at the reef scale

NASA Astrophysics Data System (ADS)

Leahy, Susannah M.; Russ, Garry R.; Abesamis, Rene A.

2015-12-01

Recent research has demonstrated that, despite a pelagic larval stage, many coral reef fishes disperse over relatively small distances, leading to well-connected populations on scales of 0-30 km. Although variation in key biological characteristics has been explored on the scale of 100-1000 s of km, it has rarely been explored at the scale relevant to actual larval dispersal and population connectivity on ecological timescales. In this study, we surveyed the habitat and collected specimens ( n = 447) of juvenile butterflyfish, Chaetodon vagabundus, at nine sites along an 80-km stretch of coastline in the central Philippines to identify variation in key life history parameters at a spatial scale relevant to population connectivity. Mean pelagic larval duration (PLD) was 24.03 d (SE = 0.16 d), and settlement size was estimated to be 20.54 mm total length (TL; SE = 0.61 mm). Both traits were spatially consistent, although this PLD is considerably shorter than that reported elsewhere. In contrast, post-settlement daily growth rates, calculated from otolith increment widths from 1 to 50 d post-settlement, varied strongly across the study region. Elevated growth rates were associated with rocky habitats that this species is known to recruit to, but were strongly negatively correlated with macroalgal cover and exhibited negative density dependence with conspecific juveniles. Larger animals had lower early (first 50 d post-settlement) growth rates than smaller animals, even after accounting for seasonal variation in growth rates. Both VBGF and Gompertz models provided good fits to post-settlement size-at-age data ( n = 447 fish), but the VBGF's estimate of asymptotic length ( L ∞ = 168 mm) was more consistent with field observations of maximum fish length. Our findings indicate that larval characteristics are consistent at the spatial scale at which populations are likely well connected, but that site-level biological differences develop post-settlement, most likely as a

Surveillance and Control of Aedes albopictus in the Swiss-Italian Border Region: Differences in Egg Densities between Intervention and Non-intervention Areas

PubMed Central

Suter, Tobias T.; Flacio, Eleonora; Feijoó Fariña, Begoña; Engeler, Lukas; Tonolla, Mauro; Regis, Lêda N.; de Melo Santos, Maria A. V.; Müller, Pie

2016-01-01

Background Aedes albopictus, the Asian tiger mosquito, originates from the tropical and subtropical regions of Southeast Asia. Over the recent decades it has been passively spread across the globe, primarily through the used tyre trade and passive transportation along major traffic routes. A. albopictus is a proven vector for many arboviruses, most notably chikungunya and dengue, with recent outbreaks also in continental Europe. In southern Switzerland, in the Canton of Ticino A. albopictus was spotted for the first time in 2003. Since then the local authorities have implemented a control programme based on larval source reduction. Despite these efforts, mosquito densities have increased over the last decade, casting doubts on the effectiveness of such larval control programmes. Methodology/Principal Findings The Italian communities just across the Swiss-Italian border lack a control programme. This motivated us to compare the intervention and the non-intervention areas side by side in an attempt to find evidence for, or against, the effectiveness of larval A. albopictus control. Using ovitraps and a randomised sampling scheme, we examined the seasonal and spatial abundance of A. albopictus in sylvatic and urban environments across the Swiss-Italian border in 2012 and 2013. In the urban environments of the non-intervention area, egg densities were 2.26 times higher as compared to the intervention area. In the sylvatic environments, as compared to the urban environments, egg densities were 36% in the intervention area and 18% in the non-intervention area. Conclusions/Significance Though alternative explanations are also valid, the results support the hypothesis that the Ticino intervention programme does have an impact. At the same time the data also suggest that current larval interventions fall short in gaining full control over the mosquito, calling for the evaluation of additional, or alternative, approaches. Ideally, these should also consider inclusion of the

Learning the specific quality of taste reinforcement in larval Drosophila.

PubMed

Schleyer, Michael; Miura, Daisuke; Tanimura, Teiichi; Gerber, Bertram

2015-01-27

The only property of reinforcement insects are commonly thought to learn about is its value. We show that larval Drosophila not only remember the value of reinforcement (How much?), but also its quality (What?). This is demonstrated both within the appetitive domain by using sugar vs amino acid as different reward qualities, and within the aversive domain by using bitter vs high-concentration salt as different qualities of punishment. From the available literature, such nuanced memories for the quality of reinforcement are unexpected and pose a challenge to present models of how insect memory is organized. Given that animals as simple as larval Drosophila, endowed with but 10,000 neurons, operate with both reinforcement value and quality, we suggest that both are fundamental aspects of mnemonic processing-in any brain.

LARVAL FISH HABITAT QUALITY : THE EFFECTS OF FRESHWATER FLOW

EPA Science Inventory

We sampled larval fish in Suisun Marsh, in the San Francisco Bay estuary from February to June 1994-1999. We used principal components analysis (PCA) and canonical correspondence analysis (CCA) on 13 taxonomic groups making up 99.7% of the catch and several environmental variable...

Gene expression patterns during the larval development of European sea bass (dicentrarchus labrax) by microarray analysis.

PubMed

Darias, M J; Zambonino-Infante, J L; Hugot, K; Cahu, C L; Mazurais, D

2008-01-01

During the larval period, marine teleosts undergo very fast growth and dramatic changes in morphology, metabolism, and behavior to accomplish their metamorphosis into juvenile fish. Regulation of gene expression is widely thought to be a key mechanism underlying the management of the biological processes required for harmonious development over this phase of life. To provide an overall analysis of gene expression in the whole body during sea bass larval development, we monitored the expression of 6,626 distinct genes at 10 different points in time between 7 and 43 days post-hatching (dph) by using heterologous hybridization of a rainbow trout cDNA microarray. The differentially expressed genes (n = 485) could be grouped into two categories: genes that were generally up-expressed early, between 7 and 23 dph, and genes up-expressed between 25 and 43 dph. Interestingly, among the genes regulated during the larval period, those related to organogenesis, energy pathways, biosynthesis, and digestion were over-represented compared with total set of analyzed genes. We discuss the quantitative regulation of whole-body contents of these specific transcripts with regard to the ontogenesis and maturation of essential functions that take place over larval development. Our study is the first utilization of a transcriptomic approach in sea bass and reveals dynamic changes in gene expression patterns in relation to marine finfish larval development.

Hematopoiesis in larval Pseudoplusia includens and Spodoptera frugiperda.

PubMed

Gardiner, E M; Strand, M R

2000-04-01

Maintenance of circulating hemocytes in larval Lepidoptera has been attributed to both mitosis of hemocytes already in circulation and the release of hemocytes from hematopoietic organs. In this study, we compared hematopoiesis in the noctuids Pseudoplusia includens and Spodoptera frugiperda. For both species, hemocyte densities per microl of blood increased with instar. Differential hemocyte counts indicated that plasmatocytes were the most abundant hemocyte type during early instars but granular cells were the most abundant hemocyte type in the last instar. Hematopoietic organs were located in the meso- and metathorax of S. Frugiperda and P. Includens. These organs contained large numbers of hemocytes in S. Frugiperda, but contained few hemocytes in P. Includens. The majority of the hemocytes recovered from hematopoietic organs were identified as plasmatocytes. Using hemocyte type-specific markers and bromodeoxyuridine (BrdU) incorporation experiments, we determined that all hemocyte types with the exception of oenocytoids synthesize DNA. BrdU labeling indices for both species also fluctuated with the molting cycle. Ligation experiments suggested that hematopoietic organs are an important source of circulating plasmatocytes in S. Frugiperda but not in P. Includens. Injection of heat killed bacteria into larvae induced higher levels of BrdU labeling than injection of sterile saline, suggesting that infection and wounding induce different levels of hemocyte proliferation. Arch. Copyright 2000 Wiley-Liss, Inc.

Physico-chemical and biological characterization of anopheline mosquito larval habitats (Diptera: Culicidae): implications for malaria control.

PubMed

Mereta, Seid Tiku; Yewhalaw, Delenasaw; Boets, Pieter; Ahmed, Abdulhakim; Duchateau, Luc; Speybroeck, Niko; Vanwambeke, Sophie O; Legesse, Worku; De Meester, Luc; Goethals, Peter L M

2013-11-04

A fundamental understanding of the spatial distribution and ecology of mosquito larvae is essential for effective vector control intervention strategies. In this study, data-driven decision tree models, generalized linear models and ordination analysis were used to identify the most important biotic and abiotic factors that affect the occurrence and abundance of mosquito larvae in Southwest Ethiopia. In total, 220 samples were taken at 180 sampling locations during the years 2010 and 2012. Sampling sites were characterized based on physical, chemical and biological attributes. The predictive performance of decision tree models was evaluated based on correctly classified instances (CCI), Cohen's kappa statistic (κ) and the determination coefficient (R2). A conditional analysis was performed on the regression tree models to test the relation between key environmental and biological parameters and the abundance of mosquito larvae. The decision tree model developed for anopheline larvae showed a good model performance (CCI = 84 ± 2%, and κ = 0.66 ± 0.04), indicating that the genus has clear habitat requirements. Anopheline mosquito larvae showed a widespread distribution and especially occurred in small human-made aquatic habitats. Water temperature, canopy cover, emergent vegetation cover, and presence of predators and competitors were found to be the main variables determining the abundance and distribution of anopheline larvae. In contrast, anopheline mosquito larvae were found to be less prominently present in permanent larval habitats. This could be attributed to the high abundance and diversity of natural predators and competitors suppressing the mosquito population densities. The findings of this study suggest that targeting smaller human-made aquatic habitats could result in effective larval control of anopheline mosquitoes in the study area. Controlling the occurrence of mosquito larvae via drainage of permanent wetlands may not be a good management

Physico-chemical and biological characterization of anopheline mosquito larval habitats (Diptera: Culicidae): implications for malaria control

PubMed Central

2013-01-01

Background A fundamental understanding of the spatial distribution and ecology of mosquito larvae is essential for effective vector control intervention strategies. In this study, data-driven decision tree models, generalized linear models and ordination analysis were used to identify the most important biotic and abiotic factors that affect the occurrence and abundance of mosquito larvae in Southwest Ethiopia. Methods In total, 220 samples were taken at 180 sampling locations during the years 2010 and 2012. Sampling sites were characterized based on physical, chemical and biological attributes. The predictive performance of decision tree models was evaluated based on correctly classified instances (CCI), Cohen’s kappa statistic (κ) and the determination coefficient (R2). A conditional analysis was performed on the regression tree models to test the relation between key environmental and biological parameters and the abundance of mosquito larvae. Results The decision tree model developed for anopheline larvae showed a good model performance (CCI = 84 ± 2%, and κ = 0.66 ± 0.04), indicating that the genus has clear habitat requirements. Anopheline mosquito larvae showed a widespread distribution and especially occurred in small human-made aquatic habitats. Water temperature, canopy cover, emergent vegetation cover, and presence of predators and competitors were found to be the main variables determining the abundance and distribution of anopheline larvae. In contrast, anopheline mosquito larvae were found to be less prominently present in permanent larval habitats. This could be attributed to the high abundance and diversity of natural predators and competitors suppressing the mosquito population densities. Conclusions The findings of this study suggest that targeting smaller human-made aquatic habitats could result in effective larval control of anopheline mosquitoes in the study area. Controlling the occurrence of mosquito larvae via drainage

Larval food quantity affects development time, survival and adult biological traits that influence the vectorial capacity of Anopheles darlingi under laboratory conditions.

PubMed

Araújo, Maisa da-Silva; Gil, Luiz Herman S; e-Silva, Alexandre de-Almeida

2012-08-02

The incidence of malaria in the Amazon is seasonal and mosquito vectorial capacity parameters, including abundance and longevity, depend on quantitative and qualitative aspects of the larval diet. Anopheles darlingi is a major malaria vector in the Amazon, representing >95% of total Anopheles population present in the Porto Velho region. Despite its importance in the transmission of the Plasmodium parasite, knowledge of the larval biology and ecology is limited. Studies regarding aspects of adult population ecology are more common than studies on larval ecology. However, in order develop effective control strategies and laboratory breeding conditions for this species, more data on the factors affecting vector biology is needed. The aim of the present study is to assess the effects of larval food quantity on the vectorial capacity of An. darling under laboratory conditions. Anopheles darlingi was maintained at 28°C, 80% humidity and exposed to a daily photoperiod of 12 h. Larvae were divided into three experimental groups that were fed either a low, medium, or high food supply (based on the food amounts consumed by other species of culicids). Each experiment was replicated for six times. A cohort of adults were also exposed to each type of diet and assessed for several biological characteristics (e.g. longevity, bite frequency and survivorship), which were used to estimate the vectorial capacity of each experimental group. The group supplied with higher food amounts observed a reduction in development time while larval survival increased. In addition to enhanced longevity, increasing larval food quantity was positively correlated with increasing frequency of bites, longer blood meal duration and wing length, resulting in greater vectorial capacity. However, females had greater longevity than males despite having smaller wings. Overall, several larval and adult biological traits were significantly affected by larval food availability. Greater larval food supply

Larval competition between An. coluzzii and An. gambiae in insectary and semi-field conditions in Burkina Faso.

PubMed

Gimonneau, Geoffrey; Brossette, Lou; Mamaï, Wadaka; Dabiré, Roch K; Simard, Frédéric

2014-02-01

Competition in mosquito larvae is common and different ecological context could change competitive advantage between species. Here, larval competition between the widely sympatric African malaria mosquitoes, Anopheles coluzzii and Anopheles gambiae were investigated in controlled insectary conditions using individuals from laboratory colonies and under ambient conditions using wild mosquitoes in a semi-field enclosure in western Burkina Faso. Larvae of both species were reared in trays at the same larval density and under the same feeding regimen in either single-species or mixed-species populations at varying species ratios reflecting 0%, 25%, 50% and 75% of competitor species. In the insectaries, where environmental variations are controlled, larvae of the An. coluzzii colony developed faster and with lower mortality than larvae of the An. gambiae colony (8.8±0.1 days and 21±3% mortality vs. 9.5±0.1 days and 32±3% mortality, respectively). Although there was no significant effect of competition on these phenotypic traits in any species, there was a significant trend for higher fitness of the An. coluzzii colony when competing with An. gambiae under laboratory conditions (i.e. lower development time and increased wing length at emergence, Cuzik's tests, P<0.05). In semi-field experiments, competition affected the life history traits of both species in a different way. Larvae of An. gambiae tended to reduce development time when in competition with An. coluzzii (Cuzick's test, P=0.002) with no impact either on mortality or size at emergence. On the other hand, An. coluzzii showed a significant trend for reduced larval mortality with increasing competition pressure (Cuzick's test, P=0.037) and production of smaller females when grown together with An. gambiae (Cuzick's test, P=0.002). Our results hence revealed that competitive interactions between larvae of the two species are context dependent. They further call for caution when exploring ecological processes

Integrating larval connectivity with local demography reveals regional dynamics of a marine metapopulation.

PubMed

Johnson, Darren W; Christie, Mark R; Pusack, Timothy J; Stallings, Christopher D; Hixon, Mark A

2018-06-01

Many ocean species exist within what are called marine metapopulations: networks of otherwise isolated local populations connected by the exchange of larval offspring. In order to manage these species as effectively as possible (e.g., by designing and implementing effective networks of marine protected areas), we must know how many offspring are produced within each local population (i.e., local demography), and where those offspring disperse (i.e., larval connectivity). Although there is much interest in estimating connectivity in the relatively simple sense of identifying the locations of spawning parents and their settling offspring, true measures of demographic connectivity that account for among-site variation in offspring production have been lacking. We combined detailed studies of local reproductive output and larval dispersal of a coral reef fish to quantify demographic connectivity within a regional metapopulation that included four widely spaced islands in the Bahamas. We present a new method for estimating demographic connectivity when the levels of dispersal among populations are inferred by the collection of genetically "tagged" offspring. We estimated that 13.3% of recruits returned to natal islands, on average (95% CI = 1.1-50.3%), that local retention was high on one of the islands (41%, 95% CI = 6.0-97.0%), and that larval connectivity was appreciable, even between islands 129 km apart (mean = 1.6%, 95% CI = 0.20-8.8%). Our results emphasize the importance of properly integrating measurements of production with measurements of connectivity. Had we not accounted for among-site variation in offspring production, our estimates of connectivity would have been inaccurate by a factor as much as 6.5. At a generational timescale, lifetime offspring production varied substantially (a fivefold difference among islands) and the importance of each island to long-term metapopulation growth was dictated by both larval production and connectivity. At the scale

The geometric framework for nutrition reveals interactions between protein and carbohydrate during larval growth in honey bees

USDA-ARS?s Scientific Manuscript database

In holometabolous insects, larval nutrition affects adult body size, a life history trait with a profound influence on performance and fitness. Individual nutritional components of larval diet are often complex and may interact with one another, necessitating the use of a geometric framework for und...

Balb/Cj male mice do not feminize after infection with larval Taenia crassiceps.

PubMed

Aldridge, Jerry R; Jennette, Mary A; Kuhn, R E

2007-02-01

Balb/cJ mice fail to mount an immune response capable of clearing infection with larval Taenia crassiceps. Additionally, male Balb/cJ mice display a lag in larval growth of approximately 3 wk as compared to growth in female mice. It has been reported that male Balb/ cAnN mice generate a protective immune response early in infection, and become permissive to larval growth after they feminize (200-fold increase in serum estradiol and 90% decrease in serum testosterone). To determine if a different strain of Balb/c mice (Balb/cJ) also feminize, serum was collected from infected male mice for 16 wk and levels of 17-beta-estradiol and testosterone were measured via ELISA. In addition, the mounting responses of 12- and 16-wk infected male mice, as well as uninfected control mice, were determined after isolation with a female mouse. The results of these experiments show that male Balb/cJ mice do not feminize during infection with larval T. crassiceps. There was no significant change in serum levels of either 17-beta-estradiol or testosterone during the course of infection (> 16 wk). Moreover, there was no significant decrease in the number of times infected male mice mounted the female mouse as compared to uninfected controls. These results suggest that there may be variances between the substrains of Balb/c mice that lead to the phenotypic differences reported for male Balb/cJ and Balb/cAnN mice.

Hiding opaque eyes in transparent organisms: a potential role for larval eyeshine in stomatopod crustaceans.

PubMed

Feller, K D; Cronin, T W

2014-09-15

Opaque screening pigments are a fundamental requisite for preserving resolution in image-forming eyes. Possession of any type of image-forming eye in a transparent, pelagic animal will thus undermine the ability of that animal to be invisible in the water column. Transparent, pelagic animals must therefore deal with the trade-off between the ability to see and the ability of other animals to see them. Stomatopod larvae, like many transparent crustaceans, possess specialized optics in their compound eyes that minimize the volume of the opaque retina. Though the volumes of these retinas are reduced, their opacity remains conspicuous to an observer. The light reflected from structures overlying the retinas of stomatopod crustacean larval eyes, referred to here as eyeshine, is hypothesized to further reduce the visibility of opaque retinas. Blue or green wavelengths of light are most strongly reflected in stomatopod larval eyeshine, suggesting a putative spectral matching to the light environment against which the larval eyes are viewed. We tested the efficacy of stomatopod crustacean larval eyeshine as an ocular camouflaging mechanism by photographing larvae in their natural light environment and analysing the contrast of eyes with the background light. To test for spectral matching between stomatopod larval eyeshine and the background light environment, we characterized the spectrum of eyeshine and calculated its performance using radiometric measurements collected at the time of each photographic series. These results are the first to demonstrate an operative mirror camouflage matched in both spectrum and radiance to the pelagic background light environment. © 2014. Published by The Company of Biologists Ltd.

Role of specific activators of intestinal amino acid transport in Bombyx mori larval growth and nutrition.

PubMed

Leonardi, M G; Casartelli, M; Fiandra, L; Parenti, P; Giordana, B

2001-12-01

Nutrient absorption and its modulation are critical for animal growth. In this paper, we demonstrate that leucine methyl ester (Leu-OMe) can greatly increase the activity of the transport system responsible for the absorption of most essential amino acids in the larval midgut of the silkworm Bombyx mori. We investigated leucine uptake activation by Leu-OMe in brush border membrane vesicles and in the apical membrane of epithelial cells in the midgut incubated in vitro. Moreover, the addition of this strong activator of amino acid absorption to diet significantly affected larval growth. Silkworms fed on artificial diet supplemented with Leu-OMe reached maximum body weight 12-18 h before control larvae, and produced cocoon shells up to 20% heavier than those of controls. The activation of amino acid absorption plays an essential role in larval development so that larval growth and cocoon production similar to controls reared on an artificial diet with 25% of dry mulberry leaf powder were observed in silkworms fed on an artificial diet with only 5% of mulberry powder. Arch. Copyright 2001 Wiley-Liss, Inc.

Fish larval recruitment to reefs is a thyroid hormone-mediated metamorphosis sensitive to the pesticide chlorpyrifos

PubMed Central

Lambert, Anne; François, Loïc; Barth, Paul; Gillet, Benjamin; Hughes, Sandrine; Piganeau, Gwenaël; Leulier, Francois; Viriot, Laurent

2017-01-01

Larval recruitment, the transition of pelagic larvae into reef-associated juveniles, is a critical step for the resilience of marine fish populations but its molecular control is unknown. Here, we investigate whether thyroid-hormones (TH) and their receptors (TR) coordinate the larval recruitment of the coral-reef-fish Acanthurus triostegus. We demonstrate an increase of TH-levels and TR-expressions in pelagic-larvae, followed by a decrease in recruiting juveniles. We generalize these observations in four other coral reef-fish species. Treatments with TH or TR-antagonist, as well as relocation to the open-ocean, disturb A. triostegus larvae transformation and grazing activity. Likewise, chlorpyrifos, a pesticide often encountered in coral-reefs, impairs A. triostegus TH-levels, transformation, and grazing activity, hence diminishing this herbivore’s ability to control the spread of reef-algae. Larval recruitment therefore corresponds to a TH-controlled metamorphosis, sensitive to endocrine disruption. This provides a framework to understand how larval recruitment, critical to reef-ecosystems maintenance, is altered by anthropogenic stressors. PMID:29083300

Toxicity of the mosquito control pesticide Scourge to adult and larval grass shrimp (Palaemonetes pugio).

PubMed

Key, Peter; DeLorenzo, Marie; Gross, Kristen; Chung, Katy; Clum, Allan

2005-01-01

This study investigated the toxicity of various concentrations of technical resmethrin and Scourge on adult and larval Palaemonetes pugio, a common grass shrimp species. Two types of tests were conducted for each of the resmethrin formulations using adult and larval grass shrimp life stages, a 96-h static renewal aqueous test without sediment, and a 24-h static nonrenewal aqueous test with sediment. For resmethrin, the 96-h aqueous LC50 value for adult shrimp was 0.53 microg/L (95% confidence interval (CI): 0.46-0.60 microg/L), and for larval shrimp was 0.35 microg/L (95% CI: 0.28-0.42 microg/L). In the presence of sediment, technical resmethrin produced a 24-h LC50 value for adult shrimp of 5.44 microg/L (95% CI: 4.52-6.55 microg/L), and for larval shrimp of 2.15 microg/L (95% CI: 1.35-3.43 microg/L). For Scourge, the 96-h aqueous LC50 for adult shrimp was 2.08 microg/L (95% CI: 1.70-2.54 microg/L), and for larval shrimp was 0.36 microg/L (95% CI: 0.24-0.55 microg/L). The 24-h sediment test yielded an LC50 value of 16.12 microg/L (95% CI: 14.79-17.57 microg/L) for adult shrimp, and 14.16 microg/L (95% CI: 12.21-16.43 microg/L) for larvae. Adjusted LC50 values to reflect the 18% resmethrin concentration in Scourge are 0.37 microg/L (adult), 0.07 microg/L (larvae) for the 96-h aqueous test, and 2.90 microg/L (adult), 2.6 microg/L (larvae) for the 24-h sediment test. Larval grass shrimp were more sensitive to technical resmethrin and Scourge than the adult life stage. The results also demonstrate that synergized resmethrin is more toxic to P. pugio than the nonsynergized form, and that the presence of sediment decreases the toxicity of both resmethrin and Scourge.

Long-Term Changes in the Distributions of Larval and Adult Fish in the Northeast U.S. Shelf Ecosystem.

PubMed

Walsh, Harvey J; Richardson, David E; Marancik, Katrin E; Hare, Jonathan A

2015-01-01

Many studies have documented long-term changes in adult marine fish distributions and linked these changes to climate change and multi-decadal climate variability. Most marine fish, however, have complex life histories with morphologically distinct stages, which use different habitats. Shifts in distribution of one stage may affect the connectivity between life stages and thereby impact population processes including spawning and recruitment. Specifically, many marine fish species have a planktonic larval stage, which lasts from weeks to months. We compared the spatial distribution and seasonal occurrence of larval fish in the Northeast U.S. Shelf Ecosystem to test whether spatial and temporal distributions changed between two decades. Two large-scale ichthyoplankton programs sampled using similar methods and spatial domain each decade. Adult distributions from a long-term bottom trawl survey over the same time period and spatial area were also analyzed using the same analytical framework to compare changes in larval and adult distributions between the two decades. Changes in spatial distribution of larvae occurred for 43% of taxa, with shifts predominately northward (i.e., along-shelf). Timing of larval occurrence shifted for 49% of the larval taxa, with shifts evenly split between occurring earlier and later in the season. Where both larvae and adults of the same species were analyzed, 48% exhibited different shifts between larval and adult stages. Overall, these results demonstrate that larval fish distributions are changing in the ecosystem. The spatial changes are largely consistent with expectations from a changing climate. The temporal changes are more complex, indicating we need a better understanding of reproductive timing of fishes in the ecosystem. These changes may impact population productivity through changes in life history connectivity and recruitment, and add to the accumulating evidence for changes in the Northeast U.S. Shelf Ecosystem with

Long-Term Changes in the Distributions of Larval and Adult Fish in the Northeast U.S. Shelf Ecosystem

PubMed Central

2015-01-01

Many studies have documented long-term changes in adult marine fish distributions and linked these changes to climate change and multi-decadal climate variability. Most marine fish, however, have complex life histories with morphologically distinct stages, which use different habitats. Shifts in distribution of one stage may affect the connectivity between life stages and thereby impact population processes including spawning and recruitment. Specifically, many marine fish species have a planktonic larval stage, which lasts from weeks to months. We compared the spatial distribution and seasonal occurrence of larval fish in the Northeast U.S. Shelf Ecosystem to test whether spatial and temporal distributions changed between two decades. Two large-scale ichthyoplankton programs sampled using similar methods and spatial domain each decade. Adult distributions from a long-term bottom trawl survey over the same time period and spatial area were also analyzed using the same analytical framework to compare changes in larval and adult distributions between the two decades. Changes in spatial distribution of larvae occurred for 43% of taxa, with shifts predominately northward (i.e., along-shelf). Timing of larval occurrence shifted for 49% of the larval taxa, with shifts evenly split between occurring earlier and later in the season. Where both larvae and adults of the same species were analyzed, 48% exhibited different shifts between larval and adult stages. Overall, these results demonstrate that larval fish distributions are changing in the ecosystem. The spatial changes are largely consistent with expectations from a changing climate. The temporal changes are more complex, indicating we need a better understanding of reproductive timing of fishes in the ecosystem. These changes may impact population productivity through changes in life history connectivity and recruitment, and add to the accumulating evidence for changes in the Northeast U.S. Shelf Ecosystem with

Model-Derived Dispersal Pathways from Multiple Source Populations Explain Variability of Invertebrate Larval Supply

PubMed Central

Domingues, Carla P.; Nolasco, Rita; Dubert, Jesus; Queiroga, Henrique

2012-01-01

Background Predicting the spatial and temporal patterns of marine larval dispersal and supply is a challenging task due to the small size of the larvae and the variability of oceanographic processes. Addressing this problem requires the use of novel approaches capable of capturing the inherent variability in the mechanisms involved. Methodology/Principal Findings In this study we test whether dispersal and connectivity patterns generated from a bio-physical model of larval dispersal of the crab Carcinus maenas, along the west coast of the Iberian Peninsula, can predict the highly variable daily pattern of wind-driven larval supply to an estuary observed during the peak reproductive season (March–June) in 2006 and 2007. Cross-correlations between observed and predicted supply were significant (p<0.05) and strong, ranging from 0.34 to 0.81 at time lags of −6 to +5 d. Importantly, the model correctly predicted observed cross-shelf distributions (Pearson r = 0.82, p<0.001, and r = 0.79, p<0.01, in 2006 and 2007) and indicated that all supply events were comprised of larvae that had been retained within the inner shelf; larvae transported to the outer shelf and beyond never recruited. Estimated average dispersal distances ranged from 57 to 198 km and were only marginally affected by mortality. Conclusions/Significance The high degree of predicted demographic connectivity over relatively large geographic scales is consistent with the lack of genetic structuring in C. maenas along the Iberian Peninsula. These findings indicate that the dynamic nature of larval dispersal can be captured by mechanistic biophysical models, which can be used to provide meaningful predictions of the patterns and causes of fine-scale variability in larval supply to marine populations. PMID:22558225

Embryogenesis, hatching and larval development of Artemia during orbital spaceflight

NASA Technical Reports Server (NTRS)

Spooner, B. S.; Debell, L.; Armbrust, L.; Guikema, J. A.; Metcalf, J.; Paulsen, A.

1994-01-01

Developmental biology studies, using gastrula-arrested cysts of the brine shrimp Artemia franciscana, were conducted during two flights of the space shuttle Atlantis (missions STS-37 and STS-43) in 1991. Dehydrated cysts were activated, on orbit, by addition of salt water to the cysts, and then development was terminated by the addition of fixative. Development took place in 5 ml syringes, connected by tubing to activation syringes, containing salt water, and termination syringes, containing fixative. Comparison of space results with simultaneous ground control experiments showed that equivalent percentages of naupliar larvae hatched in the syringes (40%). Thus, reactivation of development, completion of embryogenesis, emergence and hatching took place, during spaceflight, without recognizable alteration in numbers of larvae produced. Post-hatching larval development was studied in experiments where development was terminated, by introduction of fixative, 2 days, 4 days, and 8 days after reinitiation of development. During spaceflight, successive larval instars or stages, interrupted by molts, occurred, generating brine shrimp at appropriate larval instars. Naupliar larvae possessed the single naupliar eye, and development of the lateral pair of adult eyes also took place in space. Transmission electron microscopy revealed extensive differentiation, including skeletal muscle and gut endoderm, as well as the eye tissues. These studies demonstrate the potential value of Artemia for developmental biology studies during spa ceflight, and show that extensive degrees of development can take place in this microgravity environment.

Mosquito larval source management for controlling malaria

PubMed Central

Tusting, Lucy S; Thwing, Julie; Sinclair, David; Fillinger, Ulrike; Gimnig, John; Bonner, Kimberly E; Bottomley, Christian; Lindsay, Steven W

2015-01-01

Background Malaria is an important cause of illness and death in people living in many parts of the world, especially sub-Saharan Africa. Long-lasting insecticide treated bed nets (LLINs) and indoor residual spraying (IRS) reduce malaria transmission by targeting the adult mosquito vector and are key components of malaria control programmes. However, mosquito numbers may also be reduced by larval source management (LSM), which targets mosquito larvae as they mature in aquatic habitats. This is conducted by permanently or temporarily reducing the availability of larval habitats (habitat modification and habitat manipulation), or by adding substances to standing water that either kill or inhibit the development of larvae (larviciding). Objectives To evaluate the effectiveness of mosquito LSM for preventing malaria. Search methods We searched the Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; EMBASE; CABS Abstracts; and LILACS up to 24 October 2012. We handsearched the Tropical Diseases Bulletin from 1900 to 2010, the archives of the World Health Organization (up to 11 February 2011), and the literature database of the Armed Forces Pest Management Board (up to 2 March 2011). We also contacted colleagues in the field for relevant articles. Selection criteria We included cluster randomized controlled trials (cluster-RCTs), controlled before-and-after trials with at least one year of baseline data, and randomized cross-over trials that compared LSM with no LSM for malaria control. We excluded trials that evaluated biological control of anopheline mosquitoes with larvivorous fish. Data collection and analysis At least two authors assessed each trial for eligibility. We extracted data and at least two authors independently determined the risk of bias in the included studies. We resolved all disagreements through discussion with a third author. We analyzed the data using Review Manager 5 software

Uranium in larval shells as a barometer of molluscan ocean acidification exposure.

PubMed

Frieder, Christina A; Gonzalez, Jennifer P; Levin, Lisa A

2014-06-03

As the ocean undergoes acidification, marine organisms will become increasingly exposed to reduced pH, yet variability in many coastal settings complicates our ability to accurately estimate pH exposure for those organisms that are difficult to track. Here we present shell-based geochemical proxies that reflect pH exposure from laboratory and field settings in larvae of the mussels Mytilus californianus and M. galloprovincialis. Laboratory-based proxies were generated from shells precipitated at pH 7.51 to 8.04. U/Ca, Sr/Ca, and multielemental signatures represented as principal components varied with pH for both species. Of these, U/Ca was the best predictor of pH and did not vary with larval size, with semidiurnal pH fluctuations, or with oxygen concentration. Field applications of U/Ca were tested with mussel larvae reared in situ at both known and unknown pH conditions. Larval shells precipitated in a region of greater upwelling had higher U/Ca, and these U/Ca values corresponded well with the laboratory-derived U/Ca-pH proxy. Retention of the larval shell after settlement in molluscs allows use of this geochemical proxy to assess ocean acidification effects on marine populations.

Seasonal variations in larval biomass and biochemical composition of brown shrimp, Crangon crangon (Decapoda, Caridea), at hatching

NASA Astrophysics Data System (ADS)

Urzúa, Ángel; Anger, Klaus

2013-06-01

The "brown shrimp", Crangon crangon (Linnaeus 1758), is a benthic key species in the North Sea ecosystem, supporting an intense commercial fishery. Its reproductive pattern is characterized by a continuous spawning season from mid-winter to early autumn. During this extended period, C. crangon shows significant seasonal variations in egg size and embryonic biomass, which may influence larval quality at hatching. In the present study, we quantified seasonal changes in dry weight (W) and chemical composition (CHN, protein and lipid) of newly hatched larvae of C. crangon. Our data revealed significant variations, with maximum biomass values at the beginning of the hatching season (February-March), a decrease throughout spring (April-May) and a minimum in summer (June-September). While all absolute values of biomass and biochemical constituents per larva showed highly significant differences between months ( P < 0.001), CHN, protein and lipid concentrations (expressed as percentage values of dry weight) showed only marginally significant differences ( P < 0.05). According to generalized additive models (GAM), key variables of embryonic development exerted significant effects on larval condition at hatching: The larval carbon content (C) was positively correlated with embryonic carbon content shortly after egg-laying ( r 2 = 0.60; P < 0.001) and negatively with the average incubation temperature during the period of embryonic development ( r 2 = 0.35; P < 0.001). Additionally, water temperature ( r 2 = 0.57; P < 0.001) and food availability (phytoplankton C; r 2 = 0.39; P < 0.001) at the time of hatching were negatively correlated with larval C content at hatching. In conclusion, "winter larvae" hatching from larger "winter eggs" showed higher initial values of biomass compared to "summer larvae" originating from smaller "summer eggs". This indicates carry-over effects persisting from the embryonic to the larval phase. Since "winter larvae" are more likely exposed to

Learning the specific quality of taste reinforcement in larval Drosophila

PubMed Central

Schleyer, Michael; Miura, Daisuke; Tanimura, Teiichi; Gerber, Bertram

2015-01-01

The only property of reinforcement insects are commonly thought to learn about is its value. We show that larval Drosophila not only remember the value of reinforcement (How much?), but also its quality (What?). This is demonstrated both within the appetitive domain by using sugar vs amino acid as different reward qualities, and within the aversive domain by using bitter vs high-concentration salt as different qualities of punishment. From the available literature, such nuanced memories for the quality of reinforcement are unexpected and pose a challenge to present models of how insect memory is organized. Given that animals as simple as larval Drosophila, endowed with but 10,000 neurons, operate with both reinforcement value and quality, we suggest that both are fundamental aspects of mnemonic processing—in any brain. DOI: http://dx.doi.org/10.7554/eLife.04711.001 PMID:25622533

Burrowing activities of the larval lamprey

USGS Publications Warehouse

Sawyer, Philip J.

1959-01-01

Since the appearance in 1950 of Applegate's work on the sea lamprey in Michigan (U. S. Fish and Wildl. Serv., Spec. Sci. Rept.; Fish, No. 55) and the subsequent development of means to control lampreys in the Great Lakes, biologists have accumulated much additional information on adult lampreys. Larval lampreys, however, are difficult animals to observe in the field, and many facets of their behavior are still unknown. While working with the U. S. Fish and Wildlife Service, I kept ammocetes in captivity, and was able to observe their burrowing activities.

Distribution and condition of larval and juvenile Lost River and shortnose suckers in the Williamson River Delta restoration project and Upper Klamath Lake, Oregon

USGS Publications Warehouse

Burdick, Summer M.; Brown, Daniel T.

2010-01-01

larger than those captured in the adjacent lake habitat in 2008, but the opposite was true for larval shortnose suckers in 2009. Mean sample density was greater for both species in the Williamson River Delta than adjacent lake habitats in both years. Larval suckers captured in the restoration area, however, had less food in their guts compared to those captured in Upper Klamath or Agency Lakes. Differential distribution among sucker species within the Williamson River Delta and between the delta and adjacent lakes indicated that shortnose suckers likely benefited more from the restored Williamson River Delta than Lost River or Klamath largescale suckers (Catostomus snyderi). Catch rates in shallow-water habitats with vegetation within the delta were higher for shortnose and Klamath largescale suckers than for larval Lost River suckers in 2008 and 2009.However, catch rates at the mouth of the Williamson River in 2008 and in Upper Klamath Lake in 2009 were higher for larval Lost River suckers than for larvae identified as either shortnose or Klamath largescale suckers. Shortnose suckers also comprised the greatest portion of age-0 suckers captured in the Williamson River Delta in 2008 and 2009. The relative abundance of age-1 shortnose suckers was high in our catches compared to age-1 Lost River suckers in 2009 in the delta and adjacent lakes, which may or may not indicate shortnose suckers experienced better survival than Lost River suckers in 2008. Age-0 and age-1 suckers were similarly distributed throughout the Williamson River Delta in 2008 and 2009. Age-0 suckers used shallow vegetated and unvegetated habitats primarily in mid- to late July in both years. A comparison of catch rates between our study and a concurrent study in Upper Klamath Lake indicated that Goose Bay was the most used habitat in 2009 and the Tulana Unit was the one of the least used habitats in 2008 and 2009 by age-0 suckers. Catch rates for age-1 suckers, however, indicated that bo

Expanding Larval Fish DNA Metabarcoding to All the Great Lakes

EPA Science Inventory

Fish larvae represent a largely untapped community for detecting and monitoring breeding non-native species, mainly due to the difficulty of identifying larvae to species through morphological methods. Molecular genetic methods offer means to identify larval specimens to species ...

Swimming Speed of Larval Snail Does Not Correlate with Size and Ciliary Beat Frequency

PubMed Central

Chan, Kit Yu Karen; Jiang, Houshuo; Padilla, Dianna K.

2013-01-01

Many marine invertebrates have planktonic larvae with cilia used for both propulsion and capturing of food particles. Hence, changes in ciliary activity have implications for larval nutrition and ability to navigate the water column, which in turn affect survival and dispersal. Using high-speed high-resolution microvideography, we examined the relationship between swimming speed, velar arrangements, and ciliary beat frequency of freely swimming veliger larvae of the gastropod Crepidula fornicata over the course of larval development. Average swimming speed was greatest 6 days post hatching, suggesting a reduction in swimming speed towards settlement. At a given age, veliger larvae have highly variable speeds (0.8–4 body lengths s−1) that are independent of shell size. Contrary to the hypothesis that an increase in ciliary beat frequency increases work done, and therefore speed, there was no significant correlation between swimming speed and ciliary beat frequency. Instead, there are significant correlations between swimming speed and visible area of the velar lobe, and distance between centroids of velum and larval shell. These observations suggest an alternative hypothesis that, instead of modifying ciliary beat frequency, larval C. fornicata modify swimming through adjustment of velum extension or orientation. The ability to adjust velum position could influence particle capture efficiency and fluid disturbance and help promote survival in the plankton. PMID:24367554

A global comparative analysis of the feeding dynamics and environmental conditions of larval tunas, mackerels, and billfishes

NASA Astrophysics Data System (ADS)

Llopiz, Joel K.; Hobday, Alistair J.

2015-03-01

Scombroid fishes, including tunas, mackerels, and billfishes, constitute some of the most important fisheries in lower latitudes around the world. Though the early life stages of these taxa are relatively well-studied, worldwide patterns in larval feeding dynamics and how such patterns relate to environmental conditions are poorly resolved. We present a synthesis of feeding success (i.e. feeding incidences) and diets of larval scombroids from around the world, and relate these results to water column and sea surface properties for the several regions in which larval feeding studies have been conducted. Feeding success of larval tunas was shown to be distinctly different among regions. In some locations (the Straits of Florida and the Mediterranean Sea), nearly no larvae had empty guts, whereas in other locations (the Gulf of California and off NW Australia) 40-60% of larvae were empty. Diets were consistently narrow in each region (dominated by cyclopoid copepods, appendicularians, nauplii, and other fish larvae), and were usually, but not always, similar for a given scombroid taxon among regions (though diets differed among taxa). Larval habitat conditions were often similar among the 9 regions examined, but some clear differences included low levels of eddy kinetic energy and cooler waters (at the surface and at depth) in the Mediterranean, and lower chlorophyll concentrations around the Nansei Islands, Japan and off NW Australia where feeding success was low. When observed zooplankton abundances are also taken into account, the compiled results on feeding and environmental conditions indicate a bottom-up influence on feeding success. Moreover, the variability among regions highlights the potential for region-specific mechanisms regulating larval survival and, ultimately, levels of adult recruitment.

Molecular phylogeny and larval morphological diversity of the lanternfish genus Hygophum (Teleostei: Myctophidae).

PubMed

Yamaguchi, M; Miya, M; Okiyama, M; Nishida, M

2000-04-01

Larvae of the deep-sea lanternfish genus Hygophum (Myctophidae) exhibit a remarkable morphological diversity that is quite unexpected, considering their homogeneous adult morphology. In an attempt to elucidate the evolutionary patterns of such larval morphological diversity, nucleotide sequences of a portion of the mitochondrially encoded 16S ribosomal RNA gene were determined for seven Hygophum species and three outgroup taxa. Secondary structure-based alignment resulted in a character matrix consisting of 1172 bp of unambiguously aligned sequences, which were subjected to phylogenetic analyses using maximum-parsimony, maximum-likelihood, and neighbor-joining methods. The resultant tree topologies from the three methods were congruent, with most nodes, including that of the genus Hygophum, being strongly supported by various tree statistics. The most parsimonious reconstruction of the three previously recognized, distinct larval morphs onto the molecular phylogeny revealed that one of the morphs had originated as the common ancestor of the genus, the other two having diversified separately in two subsequent major clades. The patterns of such diversification are discussed in terms of the unusual larval eye morphology and geographic distribution. Copyright 2000 Academic Press.

Correlation of hemocyte counts with different developmental parameters during the last larval instar of the tobacco hornworm, Manduca sexta.

PubMed

Beetz, Susann; Holthusen, Traute K; Koolman, Jan; Trenczek, Tina

2008-02-01

We determined the changes in hemocyte titer and in the abundance of hemocyte types of the tobacco hornworm Manduca sexta during the fourth and fifth larval stadium and the beginning of the pupal stadium. As we analyzed the samples of individual insects at daily intervals, we were able to correlate phenotypical features, body weight, as well as total protein content and lysozyme activity in the hemolymph with the observations on hemocytes. In the course of the fifth larval stadium, the hemocyte titer decreased slightly and declined further after pupation. Using calculated values for total hemocyte numbers, females had about five times and males three times more hemocytes in the circulating population at the beginning of the wandering stage (in the middle of the fifth larval stadium) than immediately after the last larval--larval molt (from the fourth to the fifth larval stadium). This sexual difference was mainly due to an increase in the number of plasmatocytes, which was more prominent in females than in males. Granular cells were dominant in early fifth larval stadium while plasmatocytes were the most abundant cells in pupae. Oenocytoids and spherule cells disappeared during the wandering stage. Lysozyme activity in the hemolymph rose to a maximum during the wandering stage, with females having lysozyme values twice as high as those for males. These changes in lysozyme activity, however, did not correlate with the increase of total hemolymph protein titer which occurred already at the beginning of the wandering stage. We postulate that changes in hemocyte titers are under direct hormonal control, which has to be proven in future experiments. (c) 2007 Wiley-Liss, Inc.

PHOTO-INDUCED POLYCYCLIC AROMATIC HYDROCARBON TOXIC POTENTIALS OF NEAR SHORE LARVAL FISH HABITAT IN THE GREAT LAKES, USA

EPA Science Inventory

Photo-induced toxicity (PIT) of polycyclic aromatic hydrocarbons (PAH) has been documented in laboratory studies for both invertebrate and vertebrate aquatic organisms. PIT has not been verified in field studies for larval fish to date. Filtered water samples and larval fish were...

Larval control of Anopheles (Nyssorhinchus) darlingi using granular formulation of Bacillus sphaericus in abandoned gold-miners excavation pools in the Brazilian Amazon rainforest.

PubMed

Galardo, Allan Kardec Ribeiro; Zimmerman, Robert; Galardo, Clícia Denis

2013-01-01

Use of a Bacillus sphaericus based mosquito larvicide was evaluated as an intervention for malaria vector control at a mining site in Amapá, Brazil. Impacts on larval and adult densities of the primary vector Anopheles darlingi were measured over the course of a 52 week study period. In Calçoene, State of Amapá, gold mining activity occurs in 19 mining sites in gold-miners of Lourenço. Large pools are formed in mining sites and naturally colonized by Anopheles darlingi. During one year, the impact of applications of VectoLex® CG to these larval sources was evaluated. Applications of 20kg/ha were made as needed, based on 10 immature (3rd, 4th instars and pupae) surveillance of health and established thresholds. One hundred percent initial control was observed 48h after each treatment. The pools received from 2-10 (5.3±1.6) treatments during the year. The average re-treatment interval in productive pools was 9.4±4.3 weeks. During weeks 3-52 of the study, mean density of late stage larvae was 78% and pupae were 93% lower in the treated pools than in untreated pools (p< 0.0001, n=51) while reduction of adult mosquitoes was 53% in comparison to the untreated area during the last five months of the study, which were the rainy season (p<0.001). VectoLex® CG reduced immature Anopheles darlingi infestation levels during the entire study period, and reduced adult mosquito populations during the rainy season.

The relationship between pelagic larval duration and range size in tropical reef fishes: a synthetic analysis

PubMed Central

Lester, Sarah E; Ruttenberg, Benjamin I

2005-01-01

We address the conflict in earlier results regarding the relationship between dispersal potential and range size. We examine all published pelagic larval duration data for tropical reef fishes. Larval duration is a convenient surrogate for dispersal potential in marine species that are sedentary as adults and that therefore only experience significant dispersal during their larval phase. Such extensive quantitative dispersal data are only available for fishes and thus we use a unique dataset to examine the relationship between dispersal potential and range size. We find that dispersal potential and range size are positively correlated only in the largest ocean basin, the Indo-Pacific, and that this pattern is driven primarily by the spatial distribution of habitat and dispersal barriers. Furthermore, the relationship strengthens at higher taxonomic levels, suggesting an evolutionary mechanism. We document a negative correlation between species richness and larval duration at the family level in the Indo-Pacific, implying that speciation rate may be negatively related to dispersal potential. If increased speciation rate within a taxonomic group results in smaller range sizes within that group, speciation rate could regulate the association between range size and dispersal potential. PMID:16007745

New records of larval stages of the eel cod genus Muraenolepis Günther 1880 (Gadiformes: Muraenolepididae) from the western Antarctic Peninsula.

PubMed

Konstantinidis, P; Hilton, E J; Matarese, A C

2016-08-01

Three newly discovered larval specimens of the genus Muraenolepis collected from the waters of the western Antarctic Peninsula are described. Knowledge of their natural history is sparse and information about their early life history is based on only a few larval stages. Here, the available literature on larval eel cods is reviewed, and the specimens placed in context. © 2016 The Fisheries Society of the British Isles.

The density and spatial arrangement of the invasive oyster Crassostrea gigas determines its impact on settlement of native oyster larvae

PubMed Central

Wilkie, Emma M; Bishop, Melanie J; O'Connor, Wayne A

2013-01-01

Understanding how the density and spatial arrangement of invaders is critical to developing management strategies of pest species. The Pacific oyster, Crassostrea gigas, has been translocated around the world for aquaculture and in many instances has established wild populations. Relative to other species of bivalve, it displays rapid suspension feeding, which may cause mortality of pelagic invertebrate larvae. We compared the effect on settlement of Sydney rock oyster, Saccostrea glomerata, larvae of manipulating the spatial arrangement and density of native S. glomerata, and non-native C. gigas. We hypothesized that while manipulations of dead oysters would reveal the same positive relationship between attachment surface area and S. glomerata settlement between the two species, manipulations of live oysters would reveal differing density-dependent effects between the native and non-native oyster. In the field, whether oysters were live or dead, more larvae settled on C. gigas than S. glomerata when substrate was arranged in monospecific clumps. When, however, the two species were interspersed, there were no differences in larval settlement between them. By contrast, in aquaria simulating a higher effective oyster density, more larvae settled on live S. glomerata than C. gigas. When C. gigas was prevented from suspension feeding, settlement of larvae on C. gigas was enhanced. By contrast, settlement was similar between the two species when dead. While the presently low densities of the invasive oyster C. gigas may enhance S. glomerata larval settlement in east Australian estuaries, future increases in densities could produce negative impacts on native oyster settlement. Synthesis and applications: Our study has shown that both the spatial arrangement and density of invaders can influence their impact. Hence, management strategies aimed at preventing invasive populations reaching damaging sizes should not only consider the threshold density at which impacts exceed

Exploring the larval fish community of the central Red Sea with an integrated morphological and molecular approach.

PubMed

Isari, Stamatina; Pearman, John K; Casas, Laura; Michell, Craig T; Curdia, Joao; Berumen, Michael L; Irigoien, Xabier

2017-01-01

An important aspect of population dynamics for coral reef fishes is the input of new individuals from the pelagic larval pool. However, the high biodiversity and the difficulty of identifying larvae of closely related species represent obstacles to more fully understanding these populations. In this study, we combined morphology and genetic barcoding (Cytochrome Oxidase I gene) to characterize the seasonal patterns of the larval fish community at two sites in close proximity to coral reefs in the central-north Red Sea: one shallower inshore location (50 m depth) and a nearby site located in deeper and more offshore waters (~ 500 m depth). Fish larvae were collected using oblique tows of a 60 cm-bongo net (500 μm mesh size) every month for one year (2013). During the warmer period of the year (June-November), the larval fish stock was comparable between sampling sites. However, during the colder months, abundances were higher in the inshore than in the offshore waters. Taxonomic composition and temporal variation of community structure differed notably between sites, potentially reflecting habitat differences, reproductive patterns of adults, and/or advective processes in the area. Eleven out of a total of 62 recorded families comprised 69-94% of the fish larval community, depending on sampling site and month. Richness of taxa was notably higher in the inshore station compared to the offshore, particularly during the colder period of the year and especially for the gobiids and apogonids. Two mesopelagic taxa (Vinciguerria sp. and Benthosema spp.) comprised an important component of the larval community at the deeper site with only a small and sporadic occurrence in the shallower inshore waters. Our data provide an important baseline reference for the larval fish communities of the central Red Sea, representing the first such study from Saudi Arabian waters.

Exploring the larval fish community of the central Red Sea with an integrated morphological and molecular approach

PubMed Central

Pearman, John K.; Casas, Laura; Michell, Craig T.; Curdia, Joao; Berumen, Michael L.; Irigoien, Xabier

2017-01-01

An important aspect of population dynamics for coral reef fishes is the input of new individuals from the pelagic larval pool. However, the high biodiversity and the difficulty of identifying larvae of closely related species represent obstacles to more fully understanding these populations. In this study, we combined morphology and genetic barcoding (Cytochrome Oxidase I gene) to characterize the seasonal patterns of the larval fish community at two sites in close proximity to coral reefs in the central-north Red Sea: one shallower inshore location (50 m depth) and a nearby site located in deeper and more offshore waters (~ 500 m depth). Fish larvae were collected using oblique tows of a 60 cm-bongo net (500 μm mesh size) every month for one year (2013). During the warmer period of the year (June-November), the larval fish stock was comparable between sampling sites. However, during the colder months, abundances were higher in the inshore than in the offshore waters. Taxonomic composition and temporal variation of community structure differed notably between sites, potentially reflecting habitat differences, reproductive patterns of adults, and/or advective processes in the area. Eleven out of a total of 62 recorded families comprised 69–94% of the fish larval community, depending on sampling site and month. Richness of taxa was notably higher in the inshore station compared to the offshore, particularly during the colder period of the year and especially for the gobiids and apogonids. Two mesopelagic taxa (Vinciguerria sp. and Benthosema spp.) comprised an important component of the larval community at the deeper site with only a small and sporadic occurrence in the shallower inshore waters. Our data provide an important baseline reference for the larval fish communities of the central Red Sea, representing the first such study from Saudi Arabian waters. PMID:28771590

Ocean acidification alters temperature and salinity preferences in larval fish.

PubMed

Pistevos, Jennifer C A; Nagelkerken, Ivan; Rossi, Tullio; Connell, Sean D

2017-02-01

Ocean acidification alters the way in which animals perceive and respond to their world by affecting a variety of senses such as audition, olfaction, vision and pH sensing. Marine species rely on other senses as well, but we know little of how these might be affected by ocean acidification. We tested whether ocean acidification can alter the preference for physicochemical cues used for dispersal between ocean and estuarine environments. We experimentally assessed the behavioural response of a larval fish (Lates calcarifer) to elevated temperature and reduced salinity, including estuarine water of multiple cues for detecting settlement habitat. Larval fish raised under elevated CO 2 concentrations were attracted by warmer water, but temperature had no effect on fish raised in contemporary CO 2 concentrations. In contrast, contemporary larvae were deterred by lower salinity water, where CO 2 -treated fish showed no such response. Natural estuarine water-of higher temperature, lower salinity, and containing estuarine olfactory cues-was only preferred by fish treated under forecasted high CO 2 conditions. We show for the first time that attraction by larval fish towards physicochemical cues can be altered by ocean acidification. Such alterations to perception and evaluation of environmental cues during the critical process of dispersal can potentially have implications for ensuing recruitment and population replenishment. Our study not only shows that freshwater species that spend part of their life cycle in the ocean might also be affected by ocean acidification, but that behavioural responses towards key physicochemical cues can also be negated through elevated CO 2 from human emissions.

Global mismatch between fishing dependency and larval supply from marine reserves

NASA Astrophysics Data System (ADS)

Andrello, Marco; Guilhaumon, François; Albouy, Camille; Parravicini, Valeriano; Scholtens, Joeri; Verley, Philippe; Barange, Manuel; Sumaila, U. Rashid; Manel, Stéphanie; Mouillot, David

2017-07-01

Marine reserves are viewed as flagship tools to protect exploited species and to contribute to the effective management of coastal fisheries. Yet, the extent to which marine reserves are globally interconnected and able to effectively seed areas, where fisheries are most critical for food and livelihood security is largely unknown. Using a hydrodynamic model of larval dispersal, we predict that most marine reserves are not interconnected by currents and that their potential benefits to fishing areas are presently limited, since countries with high dependency on coastal fisheries receive very little larval supply from marine reserves. This global mismatch could be reversed, however, by placing new marine reserves in areas sufficiently remote to minimize social and economic costs but sufficiently connected through sea currents to seed the most exploited fisheries and endangered ecosystems.

Global mismatch between fishing dependency and larval supply from marine reserves

PubMed Central

Andrello, Marco; Guilhaumon, François; Albouy, Camille; Parravicini, Valeriano; Scholtens, Joeri; Verley, Philippe; Barange, Manuel; Sumaila, U. Rashid; Manel, Stéphanie; Mouillot, David

2017-01-01

Marine reserves are viewed as flagship tools to protect exploited species and to contribute to the effective management of coastal fisheries. Yet, the extent to which marine reserves are globally interconnected and able to effectively seed areas, where fisheries are most critical for food and livelihood security is largely unknown. Using a hydrodynamic model of larval dispersal, we predict that most marine reserves are not interconnected by currents and that their potential benefits to fishing areas are presently limited, since countries with high dependency on coastal fisheries receive very little larval supply from marine reserves. This global mismatch could be reversed, however, by placing new marine reserves in areas sufficiently remote to minimize social and economic costs but sufficiently connected through sea currents to seed the most exploited fisheries and endangered ecosystems. PMID:28691710

Patterning the dorsal longitudinal flight muscles (DLM) of Drosophila: insights from the ablation of larval scaffolds

NASA Technical Reports Server (NTRS)

Fernandes, J. J.; Keshishian, H.

1996-01-01

The six Dorsal Longitudinal flight Muscles (DLMs) of Drosophila develop from three larval muscles that persist into metamorphosis and serve as scaffolds for the formation of the adult fibers. We have examined the effect of muscle scaffold ablation on the development of DLMs during metamorphosis. Using markers that are specific to muscle and myoblasts we show that in response to the ablation, myoblasts which would normally fuse with the larval muscle, fuse with each other instead, to generate the adult fibers in the appropriate regions of the thorax. The development of these de novo DLMs is delayed and is reflected in the delayed expression of erect wing, a transcription factor thought to control differentiation events associated with myoblast fusion. The newly arising muscles express the appropriate adult-specific Actin isoform (88F), indicating that they have the correct muscle identity. However, there are frequent errors in the number of muscle fibers generated. Ablation of the larval scaffolds for the DLMs has revealed an underlying potential of the DLM myoblasts to initiate de novo myogenesis in a manner that resembles the mode of formation of the Dorso-Ventral Muscles, DVMs, which are the other group of indirect flight muscles. Therefore, it appears that the use of larval scaffolds is a superimposition on a commonly used mechanism of myogenesis in Drosophila. Our results show that the role of the persistent larval muscles in muscle patterning involves the partitioning of DLM myoblasts, and in doing so, they regulate formation of the correct number of DLM fibers.

Functional genomics identifies regulators of the phototransduction machinery in the Drosophila larval eye and adult ocelli.

PubMed

Mishra, Abhishek Kumar; Bargmann, Bastiaan O R; Tsachaki, Maria; Fritsch, Cornelia; Sprecher, Simon G

2016-02-15

Sensory perception of light is mediated by specialized Photoreceptor neurons (PRs) in the eye. During development all PRs are genetically determined to express a specific Rhodopsin (Rh) gene and genes mediating a functional phototransduction pathway. While the genetic and molecular mechanisms of PR development is well described in the adult compound eye, it remains unclear how the expression of Rhodopsins and the phototransduction cascade is regulated in other visual organs in Drosophila, such as the larval eye and adult ocelli. Using transcriptome analysis of larval PR-subtypes and ocellar PRs we identify and study new regulators required during PR differentiation or necessary for the expression of specific signaling molecules of the functional phototransduction pathway. We found that the transcription factor Krüppel (Kr) is enriched in the larval eye and controls PR differentiation by promoting Rh5 and Rh6 expression. We also identified Camta, Lola, Dve and Hazy as key genes acting during ocellar PR differentiation. Further we show that these transcriptional regulators control gene expression of the phototransduction cascade in both larval eye and adult ocelli. Our results show that PR cell type-specific transcriptome profiling is a powerful tool to identify key transcriptional regulators involved during several aspects of PR development and differentiation. Our findings greatly contribute to the understanding of how combinatorial action of key transcriptional regulators control PR development and the regulation of a functional phototransduction pathway in both larval eye and adult ocelli. Copyright © 2015 Elsevier Inc. All rights reserved.

Isolation and characterization of the stage-specific cytochrome b small subunit (CybS) of Ascaris suum complex II from the aerobic respiratory chain of larval mitochondria.

PubMed

Amino, Hisako; Osanai, Arihiro; Miyadera, Hiroko; Shinjyo, Noriko; Tomitsuka, Eriko; Taka, Hikari; Mineki, Reiko; Murayama, Kimie; Takamiya, Shinzaburo; Aoki, Takashi; Miyoshi, Hideto; Sakamoto, Kimitoshi; Kojima, Somei; Kita, Kiyoshi

2003-05-01

We recently reported that Ascaris suum mitochondria express stage-specific isoforms of complex II: the flavoprotein subunit and the small subunit of cytochrome b (CybS) of the larval complex II differ from those of adult enzyme, while two complex IIs share a common iron-sulfur cluster subunit (Ip). In the present study, A. suum larval complex II was highly purified to characterize the larval cytochrome b subunits in more detail. Peptide mass fingerprinting and N-terminal amino acid sequencing showed that the larval and adult cytochrome b (CybL) proteins are identical. In contrast, cDNA sequences revealed that the small subunit of larval cytochrome b (CybS(L)) is distinct from the adult CybS (CybS(A)). Furthermore, Northern analysis and immunoblotting showed stage-specific expression of CybS(L) and CybS(A) in larval and adult mitochondria, respectively. Enzymatic assays revealed that the ratio of rhodoquinol-fumarate reductase (RQFR) to succinate-ubiquinone reductase (SQR) activities and the K(m) values for quinones are almost identical for the adult and larval complex IIs, but that the fumarate reductase (FRD) activity is higher for the adult form than for the larval form. These results indicate that the adult and larval A. suum complex IIs have different properties than the complex II of the mammalian host and that the larval complex II is able to function as a RQFR. Such RQFR activity of the larval complex II would be essential for rapid adaptation to the dramatic change of oxygen availability during infection of the host.

Do human activities influence survival and orientation abilities of larval fishes in the ocean?

PubMed

Siebeck, Ulrike E; O'Connor, Jack; Braun, Christoph; Leis, Jeffrey M

2015-01-01

The larval stages of most marine fishes spend days to weeks in the pelagic environment, where they must find food and avoid predators in order to survive. Some fish only spend part of their life history in the pelagic environment before returning to their adult habitat, for example, a coral reef. The sensory systems of larval fish develop rapidly during the first few days of their lives, and here we concentrate on the various sensory cues the fish have available to them for survival in the pelagic environment. We focus on the larvae of reef fishes because most is known about them. We also review the major threats caused by human activities that have been identified to have worldwide impact and evaluate how these threats may impact larval-fish survival and orientation abilities. Many human activities negatively affect larval-fish sensory systems or the cues the fish need to detect. Ultimately, this could lead to decreased numbers of larvae surviving to settlement, and, therefore, to decreased abundance of adult fishes. Although we focus on species wherein the larvae and adults occupy different habitats (pelagic and demersal, respectively), it is important to acknowledge that the potential anthropogenic effects we identify may also apply to larvae of species like tuna and herring, where both larvae and adults are pelagic. © 2014 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and Wiley Publishing Asia Pty Ltd.

Circulating Biomphalaria glabrata hemocyte subpopulations possess shared schistosome glycans and receptors capable of binding larval glycoconjugates

PubMed Central

Yoshino, Timothy P.; Wu, Xiao-Jun; Gonzalez, Laura A.; Hokke, Cornelis H.

2013-01-01

Host lectin-like recognition molecules may play an important role in innate resistance in Biomphalaria glabrata snails to larval schistosome infection, thus implicating parasite-expressed glycans as putative ligands for these lectin receptors. While host lectins may utilize specific glycan structures for parasite recognition, it also has been hypothesized that the parasite may use this system to evade immune detection by mimicking naturally-expressed host glycans, resulting in reduced immunorecognition capacity. By employing immunocytochemical (ICC) and Western blot assays using schistosome glycan-specific monoclonal antibodies (mABs) we sought to identify specific glycan epitopes (glycotopes) shared in common between larval S. mansoni and B. glabrata hemocytes, the primary immune effector cells in snails. Results confirmed the presence of selected larval glycotopes on subpopulations of hemocytes by ICC and association with numerous hemocyte proteins by Western blot analyses, including a trimannosyl core N-glycan (TriMan), and two fucosylated lacdiNAc (LDN) variants, F-LDN and F-LDN-F. Snail strain differences were seen in the prevalence of constitutively expressed F-LDN on hemocytes, and in the patterns of protein immunoreactivity with these mABs. In contrast, there was little to no hemocyte reactivity with mABs for Lewis X (LeX), LDN, LDN-F or LDN-DF. When intact hemocytes were exposed to larval transformation products (LTPs), distinct cell subpopulations displayed weak (LeX, LDN-DF) to moderate (LDN, LDN-F) glycotope reactivity by ICC, including snail strain differences in the prevalence of LDN-reactive cellular subsets. Far-Western blot analyses of the hemocytes following exposure to larval transformation proteins (LTPs) also revealed multiple mAB-reactive hemocyte protein bands for LeX, LDN, LDN-F, and LDN-DF. These results demonstrate the existence of complex patterns of shared larval glycan constitutively expressed on hemocytes and their proteins, as well as

Patterns in larval fish assemblages under the influence of the Brazil current

NASA Astrophysics Data System (ADS)

Katsuragawa, M.; Dias, J. F.; Harari, J.; Namiki, C.; Zani-Teixeira, M. L.

2014-10-01

The present work investigates the composition of larval fish assemblages in the area under the influence of the Brazil Current (BC) off the Southeastern Brazilian Bight. Ichthyoplankton was sampled during two oceanographic cruises (November-December/1997 - spring; May/2001 - autumn) with bongo nets oblique tows. Seasonal variation and a coastal-ocean pattern in the distribution of larval fish was observed and was influenced by the dynamics of the water masses, Coastal Water (CW), Tropical Water (TW) and South Atlantic Central Water (SACW), the last two of which were transported by the BC. During spring, the shelf assemblage was dominated by larvae of small pelagic fishes, such as Sardinella brasiliensis, Engraulis anchoita and Trachurus lathami, and was associated with the enrichment of shallow water by the SACW upwelling. In autumn, the abundance of coastal species larvae was reduced, and the shelf assemblage was dominated by Bregmaceros cantori. A transitional assemblage occurred during the spring, and comprised mesopelagic and coastal species. In both seasons, the oceanic assemblage was dominated by the mesopelagic families, Myctophidae, Sternopthychidae and Phosichthyidae. The oceanographic conditions also demonstrated clear differences between the northern and southern subareas, particularly in the shelf zone. This was especially the case during autumn when a latitudinal gradient in larval fish assemblages became more pronounced.

The post-larval and juvenile fish assemblage in the Sukhothai floodplain, Thailand

NASA Astrophysics Data System (ADS)

Siriwan, Suksri; Boonsatien, Boonsoong

2017-06-01

This study investigated abundance, species composition and spatial and temporal distributions of fish larvae and their relationship with some environmental variables in the Sukhothai floodplain in northern Thailand. Fish larvae were collected from 33 sampling stations on 8 occasions between August 2010 and October 2013. The study collected and identified 149 296 individuals, representing 32 families and 165 taxa. The species composition of larval fish was dominated by the Cyprinidae (47.27%), Cobitidae (7.88%), Siluridae (6.67%), Bagridae (6.06%) and Mastacembelidae (3.33%) families. The most-abundant larval species were the Striped flying barb Esomus metallicus (16.90%), the Siamese mud carp Henicorhynchus siamensis (8.48%) and the Sumatran river sprat Clupeichthys goniognathus (8.31%). The greatest abundance and species diversity of larvae were found when the river flow runs onto the floodplain. PCA and nMDS analysis revealed that the samples plot is associated with temporal distribution among years. The discharge was a major factor determining fish larvae assemblage and environmental variables in the Sukhothai floodplain. Four fish larval species were positively correlated with the samples for 2013. The result of the CCA ordination plot showed that only the discharge variable was strongly correlated with fish larvae abundance, especially two cyprinid Rasbora species.

Survival and growth of larval coastal giant salamanders (Dicamptodon tenebrosus) in streams in the Oregon Coast Range.

Treesearch

J.P. Sagar; D.H. Olson; R.A. Schmitz

2007-01-01

The purpose of this study was to estimate the variation in growth and survival that occur during the larval stage of Dicamptodon tenebrosus. We used mark-recapture to assess the rates of apparent survival and growth for two larval age classes (first-years and second/third-years), in winter and summer seasons and in the presence of culverts. By...

Host-plant effects on larval survival of a salicin-using leaf beetle Chrysomela aeneicollis Schaeffer (Coleoptera: Chrysomelidae).

PubMed

Rank, Nathan Egan

1994-04-01

Several species of willow leaf beetles use hostplant salicin to produce a defensive secretion that consists of salicylaldehyde. Generalist arthropod predators such as ants, ladybird beetles, and spiders are repelled by this secretion. The beetle larvae produce very little secretion when they feed on willows that lack salicylates, and salicin-using beetles prefer salicylate-rich willows over salicylate-poor ones. This preference may exist because the larvae are better defended against natural enemies on salicylate-rich willows. If this is true, the larvae should survive longer on those willows in nature. However, this prediction has not been tested. I determined the larval growth and survival of Chrysomela aeneicollis (Coleoptera: Chrysomelidae) on five willow species (Salix boothi, S. drummondiana, S. geyeriana, S. lutea, and S. orestera). These species differed in their salicylate chemistries and in leaf toughness but not in water content. The water content varied among the individual plants. Larval growth of C. aeneicollis did not differ among the five species in the laboratory, but it varied among the individual plants and it was related to the water content. In the field, C. aeneicollis larvae developed equally rapidly on the salicylate-poor S. lutea and on the salicylate-rich S. orestera. Larval survival was greater on S. orestera than on S. lutea in one year (1986), but there was no difference between them during three succeeding years. In another survivorship experiment, larval survival was low on the medium-salicylate S. geyeriana, but high on the salicylate-poor S. boothi and on S. orestera. Larval survival in the field was related to the larval growth and water content that had been previously measured in the laboratory. These results showed that the predicted relationship between the host plant chemistry and larval survival did not usually exist for C. aeneicollis. One possible reason for this was that the most important natural enemies were specialist

Predicting developmental neurotoxicity in rodents from larval zebrafish - - and vice versa

EPA Science Inventory

The complexity of standard mammalian developmental neurotoxicity tests limits evaluation of large numbers of chemicals. Less complex, more rapid assays using larval zebrafish are gaining popularity for evaluating the developmental neurotoxicity of chemicals; there remains, howeve...

Detection of in situ protein-protein complexes at the Drosophila larval neuromuscular junction using proximity ligation assay.

PubMed

Wang, Simon; Yoo, SooHyun; Kim, Hae-Yoon; Wang, Mannan; Zheng, Clare; Parkhouse, Wade; Krieger, Charles; Harden, Nicholas

2015-01-20

Discs large (Dlg) is a conserved member of the membrane-associated guanylate kinase family, and serves as a major scaffolding protein at the larval neuromuscular junction (NMJ) in Drosophila. Previous studies have shown that the postsynaptic distribution of Dlg at the larval NMJ overlaps with that of Hu-li tai shao (Hts), a homologue to the mammalian adducins. In addition, Dlg and Hts are observed to form a complex with each other based on co-immunoprecipitation experiments involving whole adult fly lysates. Due to the nature of these experiments, however, it was unknown whether this complex exists specifically at the NMJ during larval development. Proximity Ligation Assay (PLA) is a recently developed technique used mostly in cell and tissue culture that can detect protein-protein interactions in situ. In this assay, samples are incubated with primary antibodies against the two proteins of interest using standard immunohistochemical procedures. The primary antibodies are then detected with a specially designed pair of oligonucleotide-conjugated secondary antibodies, termed PLA probes, which can be used to generate a signal only when the two probes have bound in close proximity to each other. Thus, proteins that are in a complex can be visualized. Here, it is demonstrated how PLA can be used to detect in situ protein-protein interactions at the Drosophila larval NMJ. The technique is performed on larval body wall muscle preparations to show that a complex between Dlg and Hts does indeed exist at the postsynaptic region of NMJs.

Adaptations to host infection and larval parasitism in Unionoida

Treesearch

Christopher M. Barnhart; Wendell R. Haag; William N. Roston

2008-01-01

Freshwater mussel larval parasitism of fish is unique among bivalves. The relationship is primarily phoretic rather than nutritive; only the smallest glochidia and the haustorial larva grow substantially while on the host. Growth of the smallest larvae suggests a lower functional size limit of -150 )um for the juvenile stage. Most Ambleminae, the most diverse North...

The Implications of Temperature-Mediated Plasticity in Larval Instar Number for Development within a Marine Invertebrate, the Shrimp Palaemonetes varians

PubMed Central

Oliphant, Andrew; Hauton, Chris; Thatje, Sven

2013-01-01

Variations in larval instar number are common among arthropods. Here, we assess the implications of temperature-mediated variations in larval instar number for larval development time, larval growth rates, and juvenile dry weight within the palaemonid shrimp, Palaemonetes varians. In contrast with previous literature, which focuses on terrestrial arthropods, particularly model and pest species often of laboratory lines, we use wild shrimp, which differ in their life history from previous models. Newly-hatched P. varians larvae were first reared at 5, 10, 17, 25, and 30°C to assess their thermal scope for development. Larvae developed at 17, 25, and 30°C. At higher temperatures, larvae developed through fewer larval instars. Two dominant developmental pathways were observed; a short pathway of four instars and a long pathway of five instars. Longer developmental pathways of six to seven instars were rarely observed (mostly at lower temperatures) and consisted of additional instars as ‘repeat’ instars; i.e. little developmental advance over the preceding instar. To assess the implications of temperature-mediated variation in larval instar number, newly-hatched larvae were then reared at 15, 20, and 25°C. Again, the proportion of larvae developing through four instars increased with temperature. At all temperatures, larval development time and juvenile dry weight were greater for larvae developing through five instars. Importantly, because of the increasing proportion of larvae developing through four instars with increasing temperature, larval traits associated with this pathway (reduced development time and juvenile dry weight) became more dominant. As a consequence of increasing growth rate with temperature, and the shift in the proportion of larvae developing through four instars, juvenile dry weight was greatest at intermediate temperatures (20°C). We conclude that at settlement P. varians juveniles do not follow the temperature-size rule; this is of

The implications of temperature-mediated plasticity in larval instar number for development within a marine invertebrate, the shrimp Palaemonetes varians.

PubMed

Oliphant, Andrew; Hauton, Chris; Thatje, Sven

2013-01-01

Variations in larval instar number are common among arthropods. Here, we assess the implications of temperature-mediated variations in larval instar number for larval development time, larval growth rates, and juvenile dry weight within the palaemonid shrimp, Palaemonetes varians. In contrast with previous literature, which focuses on terrestrial arthropods, particularly model and pest species often of laboratory lines, we use wild shrimp, which differ in their life history from previous models. Newly-hatched P. varians larvae were first reared at 5, 10, 17, 25, and 30 °C to assess their thermal scope for development. Larvae developed at 17, 25, and 30 °C. At higher temperatures, larvae developed through fewer larval instars. Two dominant developmental pathways were observed; a short pathway of four instars and a long pathway of five instars. Longer developmental pathways of six to seven instars were rarely observed (mostly at lower temperatures) and consisted of additional instars as 'repeat' instars; i.e. little developmental advance over the preceding instar. To assess the implications of temperature-mediated variation in larval instar number, newly-hatched larvae were then reared at 15, 20, and 25 °C. Again, the proportion of larvae developing through four instars increased with temperature. At all temperatures, larval development time and juvenile dry weight were greater for larvae developing through five instars. Importantly, because of the increasing proportion of larvae developing through four instars with increasing temperature, larval traits associated with this pathway (reduced development time and juvenile dry weight) became more dominant. As a consequence of increasing growth rate with temperature, and the shift in the proportion of larvae developing through four instars, juvenile dry weight was greatest at intermediate temperatures (20 °C). We conclude that at settlement P. varians juveniles do not follow the temperature-size rule; this is of

Toxicant induced behavioural aberrations in larval zebrafish are dependent on minor methodological alterations.

PubMed

Fraser, Thomas W K; Khezri, Abdolrahman; Jusdado, Juan G H; Lewandowska-Sabat, Anna M; Henry, Theodore; Ropstad, Erik

2017-07-05

Alterations in zebrafish motility are used to identify neurotoxic compounds, but few have reported how methodology may affect results. To investigate this, we exposed embryos to bisphenol A (BPA) or tetrabromobisphenol A (TBBPA) before assessing larval motility. Embryos were maintained on a day/night cycle (DN) or in constant darkness, were reared in 96 or 24 well plates (BPA only), and behavioural tests were carried out at 96, 100, or 118 (BPA only) hours post fertilisation (hpf). We found that the prior photo-regime, larval age, and/or arena size influence behavioural outcomes in response to toxicant exposure. For example, methodology determined whether 10μM BPA induced hyperactivity, hypoactivity, or had no behavioural effect. Furthermore, the minimum effect concentration was not consistent between different methodologies. Finally, we observed a mechanism previously used to explain hyperactivity following BPA exposure does not appear to explain the hypoactivity observed following minor alterations in methodology. Therefore, we demonstrate how methodology can have notable implications on dose responses and behavioural outcomes in larval zebrafish motility following identical chemical exposures. As such, our results have significant consequences for human and environmental risk assessment. Copyright © 2017 Elsevier B.V. All rights reserved.

Toxicity of organophosphorus pesticide sumithion on larval stages of stinging catfish Heteropneustes fossilis

NASA Astrophysics Data System (ADS)

Shahjahan, Md.; Kabir, Md. Farajul; Sumon, Kizar Ahmed; Bhowmik, Lipi Rani; Rashid, Harunur

2017-01-01

Sumithion is widely used to control brittle in paddy fields and tiger bug in fish larval rearing ponds. The objective of this study was to elucidate the toxic effects of sumithion on larval stages of stinging catfish Heteropneustes fossilis. Larvae were exposed to two concentrations (150 and 250 μg/L) of sumithion with one control in three replicates of each. Larvae samples were collected at 20- and 24-h intervals followed by observation under a digital microscope. Exposures of stinging catfish larvae to sumithion produced deformities including irregular head shape, lordosis, yolk sac edema, body arcuation, tissue ulceration, etc. The mortality rates of larvae were significantly increased in response to increase in sumithion concentrations. Furthermore, around 30% of the total adult stinging catfish reared in sumithiontreated aquaculture ponds were found to be deformed permanently. These findings highlight that exposure of stinging catfish to sumithion at the critical and sensitive stages in their life cycle may significantly reduce the number of returning adults. Therefore, the use of sumithion for crop protection needs to be considered carefully and alternatives to sumithion should to be developed for controlling aquatic insects in aqua-ponds during larval rearing.

Plant microRNAs in larval food regulate honeybee caste development

PubMed Central

Zhou, Zhen; Kong, Yan; Liang, Hongwei; Lin, Zheguang; Luo, Jun; Zheng, Huoqing; Wan, Ping; Zhang, Junfeng; Zen, Ke; Chen, Jiong; Hu, Fuliang; Zhang, Chen-Yu; Ren, Jie

2017-01-01

The major environmental determinants of honeybee caste development come from larval nutrients: royal jelly stimulates the differentiation of larvae into queens, whereas beebread leads to worker bee fate. However, these determinants are not fully characterized. Here we report that plant RNAs, particularly miRNAs, which are more enriched in beebread than in royal jelly, delay development and decrease body and ovary size in honeybees, thereby preventing larval differentiation into queens and inducing development into worker bees. Mechanistic studies reveal that amTOR, a stimulatory gene in caste differentiation, is the direct target of miR162a. Interestingly, the same effect also exists in non-social Drosophila. When such plant RNAs and miRNAs are fed to Drosophila larvae, they cause extended developmental times and reductions in body weight and length, ovary size and fecundity. This study identifies an uncharacterized function of plant miRNAs that fine-tunes honeybee caste development, offering hints for understanding cross-kingdom interaction and co-evolution. PMID:28859085

Plant microRNAs in larval food regulate honeybee caste development.

PubMed

Zhu, Kegan; Liu, Minghui; Fu, Zheng; Zhou, Zhen; Kong, Yan; Liang, Hongwei; Lin, Zheguang; Luo, Jun; Zheng, Huoqing; Wan, Ping; Zhang, Junfeng; Zen, Ke; Chen, Jiong; Hu, Fuliang; Zhang, Chen-Yu; Ren, Jie; Chen, Xi

2017-08-01

The major environmental determinants of honeybee caste development come from larval nutrients: royal jelly stimulates the differentiation of larvae into queens, whereas beebread leads to worker bee fate. However, these determinants are not fully characterized. Here we report that plant RNAs, particularly miRNAs, which are more enriched in beebread than in royal jelly, delay development and decrease body and ovary size in honeybees, thereby preventing larval differentiation into queens and inducing development into worker bees. Mechanistic studies reveal that amTOR, a stimulatory gene in caste differentiation, is the direct target of miR162a. Interestingly, the same effect also exists in non-social Drosophila. When such plant RNAs and miRNAs are fed to Drosophila larvae, they cause extended developmental times and reductions in body weight and length, ovary size and fecundity. This study identifies an uncharacterized function of plant miRNAs that fine-tunes honeybee caste development, offering hints for understanding cross-kingdom interaction and co-evolution.

Larval development sites of the main Culicoides species (Diptera: Ceratopogonidae) in northern Europe and distribution of coprophilic species larvae in Belgian pastures.

PubMed

Zimmer, Jean-Yves; Brostaux, Yves; Haubruge, Eric; Francis, Frédéric

2014-10-15

Some Culicoides species of biting midges (Diptera: Ceratopogonidae) are biological virus vectors worldwide and have indeed been associated with outbreaks of important epizoonoses in recent years, such as bluetongue and Schmallenberg disease in northern Europe. These diseases, which affect domestic and wild ruminants, have caused considerable economic losses. Knowledge of substrates suitable for Culicoides larval development is important, particularly for the main vector temperate species. This study, realized during two years, aimed to highlight the larval development sites of these biting midge species in the immediate surroundings of ten Belgian cattle farms. Moreover, spatial distribution of the coprophilic Culicoides larvae (C. chiopterus and C. dewulfi) within pastures was studied with increasing distance from farms along linear transects (farm-pasture-woodland). A total of 4347 adult specimens belonging to 13 Culicoides species were obtained by incubation of 2131 soil samples belonging to 102 different substrates; 18 of these substrates were suitable for larval development. The Obsoletus complex (formed by two species) was observed in a wide range of substrates, including silage residues, components of a chicken coop, dung adhering to walls inside stables, leftover feed along the feed bunk, a compost pile of sugar beet residues, soil of a livestock trampling area, and decaying wood, while the following served as substrates for the other specimens: C. chiopterus, mainly cow dung; C. dewulfi, cow dung and molehill soil; C. circumscriptus, algae; C. festivipennis, algae and soil in stagnant water; C. nubeculosus, algae and silt specifically from the edge of a pond; C. punctatus, mainly wet soil between silage reserves; C. salinarius, algae; and C. stigma, algae and wet soil between silage reserves. We also recorded significantly higher densities of coprophilic larvae within pastures in cow dung located near forests, which is likely due to the localization of

Modelling larval dispersal and settlement of the reef-building polychaete Sabellaria alveolata: Role of hydroclimatic processes on the sustainability of biogenic reefs

NASA Astrophysics Data System (ADS)

Ayata, Sakina-Dorothée; Ellien, Céline; Dumas, Franck; Dubois, Stanislas; Thiébaut, Éric

2009-06-01

The honeycomb worm Sabellaria alveolata forms biogenic reefs which constitute diversity hotspots on tidal flats. The largest known reefs in Europe, located in the Bay of Mont-Saint-Michel (English Channel), are suffering increasing anthropogenic disturbances which raise the question of their sustainability. As the ability to recover depends partly on the recolonization of damaged reefs by larval supply, evaluating larval dispersal and the connectivity between distant reefs is a major challenge for their conservation. In the present study, we used a 3D biophysical model to simulate larval dispersal under realistic hydroclimatic conditions and estimate larval retention and exchanges among the two reefs of different sizes within the bay. The model takes into account fine-scale hydrodynamic circulation (800×800 m 2), advection-diffusion larval transport, and gregarious settlement behaviour. According to the field data, larval dispersal was simulated for a minimal planktonic larval duration ranging from 4 to 8 weeks and the larval mortality was set to 0.09 d -1. The results highlighted the role played by a coastal eddy on larval retention within the bay, as suggested by previous in situ observations. Very different dispersal patterns were revealed depending on the spawning reef location, although the two reefs were located only 15 km apart. The settlement success of the larvae released from the smallest reef was mainly related to tidal conditions at spawning, with the highest settlement success for releases at neap tide. The settlement success of the larvae from the biggest reef was more dependent on meteorological conditions: favourable W and SW winds may promote a ten-fold increase in settlement success. Strong year-to-year variability was observed in settlers' numbers, with favourable environmental windows not always coinciding with the main reproductive periods of Sabellaria. Settlement kinetics indicated that the ability to delay metamorphosis could significantly

Comparative evaluation of sea-urchin larval stage sensitivity to ocean acidification.

PubMed

Passarelli, M C; Cesar, A; Riba, I; DelValls, T A

2017-10-01

Changes in the marine carbonate system may affect various calcifying organisms. This study is aimed to compare the sensitivity of embryo-larval development of two species of sea urchins (Paracentrutos lividus and Lytechinus variegatus) collected and exposed to samples from different coastal zone (Spain and Brazil) to ocean acidification. The results showed that the larval stages are very sensitive to small changes in the seawater's pH. The larvae from P. lividus species showed to be more sensitive to acidified elutriate sediments than larvae from L. variegatus sea urchin. Furthermore, this study has demonstrated that the CO 2 enrichment in aquatic ecosystems cause changes on the mobility of the metals: Zn, Cu, Fe, Al and As, which was presented different behavior among them. Although an increase on the mobility of metals was found, the results using the principal component analysis showed that the pH reduction show the highest correlations with the toxicity and is the main cause of embryo-larval development inhibition. In this comparative study it is demonstrated that both species are able to assess potential effects of the ocean acidification related to CO 2 enrichment by both near future scenarios and the risk associated with CO 2 leakages in the Carbon Capture and Storage (CCS) process, and the importance of comparative studies in different zones to improve the understanding of the impacts caused by ocean acidification. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of water availability on emerald ash borer larval performance and phloem phenolics of Manchurian and black ash.

PubMed

Chakraborty, Sourav; Whitehill, Justin G A; Hill, Amy L; Opiyo, Stephen O; Cipollini, Don; Herms, Daniel A; Bonello, Pierluigi

2014-04-01

The invasive emerald ash borer (EAB) beetle is a significant threat to the survival of North American ash. In previous work, we identified putative biochemical and molecular markers of constitutive EAB resistance in Manchurian ash, an Asian species co-evolved with EAB. Here, we employed high-throughput high-performance liquid chromatography with photodiode array detection and mass spectrometry (HPLC-PDA-MS) to characterize the induced response of soluble phloem phenolics to EAB attack in resistant Manchurian and susceptible black ash under conditions of either normal or low water availability, and the effects of water availability on larval performance. Total larval mass per tree was lower in Manchurian than in black ash. Low water increased larval numbers and mean larval mass overall, but more so in Manchurian ash. Low water did not affect levels of phenolics in either host species, but six phenolics decreased in response to EAB. In both ashes, pinoresinol A was induced by EAB, especially in Manchurian ash. Pinoresinol A and pinoresinol B were negatively correlated with each other in both species. The higher accumulation of pinoresinol A in Manchurian ash after attack may help explain the resistance of this species to EAB, but none of the responses measured here could explain increased larval performance in trees subjected to low water availability. © 2013 John Wiley & Sons Ltd.

Larval habitat for the avian malaria vector culex quinquefasciatus (Diptera: Culicidae) in altered mid-elevation mesic-dry forests in Hawai'i

USGS Publications Warehouse

Reiter, M.E.; Lapointe, D.A.

2009-01-01

Effective management of avian malaria (Plasmodium relictum) in Hawai'i's endemic honeycreepers (Drepanidinae) requires the identification and subsequent reduction or treatment of larval habitat for the mosquito vector, Culex quinquefasciatus (Diptera: Culicidae). We conducted ground surveys, treehole surveys, and helicopter aerial surveys from 20012003 to identify all potential larval mosquito habitat within two 100+ ha mesic-dry forest study sites in Hawai'i Volcanoes National Park, Hawai'i; 'Ainahou Ranch and Mauna Loa Strip Road. At 'Ainahou Ranch, anthropogenic sites (43%) were more likely to contain mosquitoes than naturally occurring (8%) sites. Larvae of Cx. quinquefasciatus were predominately found in anthropogenic sites while Aedes albopictus larvae occurred less frequently in both anthropogenic sites and naturally-occurring sites. Additionally, moderate-size (???20-22,000 liters) anthropogenic potential larval habitat had >50% probability of mosquito presence compared to larger- and smaller-volume habitat (<50%). Less than 20% of trees surveyed at ' Ainahou Ranch had treeholes and few mosquito larvae were detected. Aerial surveys at 'Ainahou Ranch detected 56% (95% CI: 42-68%) of the potential larval habitat identified in ground surveys. At Mauna Loa Strip Road, Cx. quinquefasciatus larvae were only found in the rock holes of small intermittent stream drainages that made up 20% (5 of 25) of the total potential larval habitat. The volume of the potential larval habitat did not influence the probability of mosquito occurrence at Mauna Loa Strip Road. Our results suggest that Cx. quinquefasciatus abundance, and subsequently avian malaria, may be controlled by larval habitat reduction in the mesic-dry landscapes of Hawai'i where anthropogenic sources predominate.

Effects of neem oil (Azadirachta indica A. Juss) on midgut cells of predatory larvae Ceraeochrysa claveri (Navás, 1911) (Neuroptera: Chrysopidae).

PubMed

Scudeler, Elton Luiz; dos Santos, Daniela Carvalho

2013-01-01

The effects of ingested neem oil, a botanical insecticide obtained from the seeds of the neem tree, Azadirachta indica, on the midgut cells of predatory larvae Ceraeochrysa claveri were analyzed. C. claveri were fed on eggs of Diatraea saccharalis treated with neem oil at a concentration of 0.5%, 1% and 2% during throughout the larval period. Light and electron microscopy showed severe damages in columnar cells, which had many cytoplasmic protrusions, clustering and ruptured of the microvilli, swollen cells, ruptured cells, dilatation and vesiculation of rough endoplasmic reticulum, development of smooth endoplasmic reticulum, enlargement of extracellular spaces of the basal labyrinth, intercellular spaces and necrosis. The indirect ingestion of neem oil with prey can result in severe alterations showing direct cytotoxic effects of neem oil on midgut cells of C. claveri larvae. Therefore, the safety of neem oil to non-target species as larvae of C. claveri was refuted, thus the notion that plants derived are safer to non-target species must be questioned in future ecotoxicological studies. Copyright © 2012 Elsevier Ltd. All rights reserved.

Coupling suitable prey field to in situ fish larval condition and abundance in a subtropical estuary

NASA Astrophysics Data System (ADS)

Machado, Irene; Calliari, Danilo; Denicola, Ana; Rodríguez-Graña, Laura

2017-03-01

Survival of fish larvae is influenced by the suitability of the prey field and its variability in time and space. Relationships among food quality, quantity and recruitment have been explored in temperate ecosystems where spawning and secondary production are strongly seasonal, but for subtropical estuaries the mechanisms responsible for larval survival remain poorly identified. This study evaluated the nutritional condition (feeding incidence and AARS activity) and abundance of a multi-specific assemblage of fish larvae from a subtropical estuary in South America (Solís Grande, Uruguay) during the fish reproductive season; and related both variables to prey abundance, composition, size and fatty acids content. The larval assemblage was composed of 13 species belonging to different functional groups and composition varied seasonally. Contrary to expectations larval condition did not match an increase in prey quality. Food availability was high throughout the study period, although significant changes existed in the size and taxonomic structure of the prey assemblage. The temporal succession of complementary factors - temperature, prey composition, abundance and quality - promoted a wide window of opportunity for larvae, where quality seemed to have compensated quantity. Such combination of factors could allow an extended larval survival along the spawning season. These findings underline the importance of a better understanding of subtropical estuaries as nursery areas.

In vitro manipulation of gene expression in larval Schistosoma: a model for postgenomic approaches in Trematoda

PubMed Central

YOSHINO, TIMOTHY P.; DINGUIRARD, NATHALIE; DE MORAES MOURÃO, MARINA

2013-01-01

SUMMARY With rapid developments in DNA and protein sequencing technologies, combined with powerful bioinformatics tools, a continued acceleration of gene identification in parasitic helminths is predicted, potentially leading to discovery of new drug and vaccine targets, enhanced diagnostics and insights into the complex biology underlying host-parasite interactions. For the schistosome blood flukes, with the recent completion of genome sequencing and comprehensive transcriptomic datasets, there has accumulated massive amounts of gene sequence data, for which, in the vast majority of cases, little is known about actual functions within the intact organism. In this review we attempt to bring together traditional in vitro cultivation approaches and recent emergent technologies of molecular genomics, transcriptomics and genetic manipulation to illustrate the considerable progress made in our understanding of trematode gene expression and function during development of the intramolluscan larval stages. Using several prominent trematode families (Schistosomatidae, Fasciolidae, Echinostomatidae), we have focused on the current status of in vitro larval isolation/cultivation as a source of valuable raw material supporting gene discovery efforts in model digeneans that include whole genome sequencing, transcript and protein expression profiling during larval development, and progress made in the in vitro manipulation of genes and their expression in larval trematodes using transgenic and RNA interference (RNAi) approaches. PMID:19961646

Phenology of larval fish in the St. Louis River estuary

EPA Science Inventory

Little work has been done on the phenology of fish larvae in Great Lakes coastal wetlands. As part of an aquatic invasive species early detection study, we conducted larval fish surveys in the St. Louis River estuary (SLRE) in 2012 and 2013. Using multiple gears in a spatially ba...

Body shape, burst speed and escape behavior of larval anurans

Treesearch

Gage H. Dayton; Daniel Saenz; Kristen A. Baum; R. Brian Langerhans; Thomas J. DeWitt

2005-01-01

Variation in behavior, morphology and life history traits of larval anurans across predator gradients, and consequences of that variation, have been abundantly studied. Yet the functional link between morphology and burst-swimming speed is largely unknown. We conducted experiments with two divergent species of anurans, Scaphiopus holbrookii and

Effects of Vegetation Microclimate on Larval Cattle Fever Tick Survival

USDA-ARS?s Scientific Manuscript database

Cattle Fever Ticks (CFT), Rhipicephalus annulatus and R. microplus, have been a threat to the livestock industry for many years. These ticks are vectors of cattle fever, a disease produced by the hemoparasite Babesia bovis and B. bigemina. Laboratory research on CFT larval survival has shown that co...

Recruitment phenology and pelagic larval duration in Caribbean amphidromous fishes

USGS Publications Warehouse

Engman, Augustin C.; Kwak, Thomas J.; Fischer, Jesse R.

2017-01-01

Amphidromous fishes are major components of oceanic tropical island stream ecosystems, such as those of the Caribbean island, Puerto Rico. Fishes with this life history face threats related to the requirement for connectivity between freshwater and marine environments during early life stages. Pelagic larval duration and recruitment phenology are 2 early life-history processes that are crucial for the biology, ecology, conservation, and management of amphidromous fishes. However, these processes are understudied in the Caribbean in general and have never been quantified in Puerto Rico. We quantified recruit abundance, recruitment phenology, and pelagic larval duration of several Caribbean amphidromous fish species in multiple rivers in Puerto Rico and explored the effects of environmental variables on recruit abundances. Two fish taxa—sirajo goby (Sicydium spp.) and River Goby (Awaous banana)—were exceptionally abundant as postlarvae and recruited to Caribbean rivers in pulsed migration episodes that were periodic at annual and lunar scales. Sirajo goby and River Goby recruit abundances varied among rivers, were greater at sunrise than at sunset, and were positively related to river discharge. The pelagic larval duration of 4 fish taxa ranged from a minimum of 28 d to a maximum of 103 d with means between 43 ± 7 d (SD) and 65 ± 11 d. We identified the last-quarter moon phase during the months of June through January as periods of maximum amphidromous fish recruitment to freshwater streams. The results and conclusions of our study can be applied to identify critical times to maintain river–ocean connectivity and stream flow for the benefit of the amphidromous fish population dynamics, stream ecology, and natural resources of the Caribbean.

Larval dispersal underlies demographically important inter-system connectivity in a Great Lakes yellow perch (Perca flavescens) population

USGS Publications Warehouse

Brodnik, Reed M.; Fraker, Michael E.; Anderson, Eric J.; Carreon-Martinez, Lucia; DeVanna, Kristen M.; Heath, Dan D.; Reichert, Julie M.; Roseman, Edward F.; Ludsin, Stuart A.

2016-01-01

Ability to quantify connectivity among spawning subpopulations and their relative contribution of recruits to the broader population is a critical fisheries management need. By combining microsatellite and age information from larval yellow perch (Perca flavescens) collected in the Lake St. Clair – Detroit River system (SC-DRS) and western Lake Erie with a hydrodynamic backtracking approach, we quantified subpopulation structure, connectivity, and contributions of recruits to the juvenile stage in western Lake Erie during 2006-2007. After finding weak (yet stable) genetic structure between the SC-DRS and two western Lake Erie subpopulations, microsatellites also revealed measurable recruitment of SC-DRS larvae to the juvenile stage in western Lake Erie (17-21% during 2006-2007). Consideration of pre-collection larval dispersal trajectories, using hydrodynamic backtracking, increased estimated contributions to 65% in 2006 and 57% in 2007. Our findings highlight the value of complementing subpopulation discrimination methods with hydrodynamic predictions of larval dispersal by revealing the SC-DRS as a source of recruits to western Lake Erie and also showing that connectivity through larval dispersal can affect the structure and dynamics of large-lake fish populations.

The effects of larval habitat quality on Aedes albopictus skip oviposition

USDA-ARS?s Scientific Manuscript database

Aedes albopictus, an invasive mosquito species that transmits disease-causing pathogens, oviposits in containers in resource-limited habitats. To mitigate larval competition, Ae. albopictus females may choose to distribute eggs from a single gonotrophic cycle among multiple containers through skip o...

Plastic larval development in a butterfly has complex environmental and genetic causes and consequences for population dynamics.

PubMed

Saastamoinen, Marjo; Ikonen, Suvi; Wong, Swee C; Lehtonen, Rainer; Hanski, Ilkka

2013-05-01

1. In insects, the length of larval development time typically influences adult body size and individual fitness, and hence development time can be expected to respond in an adaptive manner to variation in environmental conditions. In the wild, larval growth may be influenced by individual condition, which can be affected by population-level parameters such as population density and abundance and quality of resources. 2. We sampled larvae of the Glanville fritillary butterfly (Melitaea cinxia) from 514 local populations across a large metapopulation before the winter diapause and reared the larvae in common garden conditions after diapause. Here, we report that small post-diapause larvae prolonged their development via an extra larval instar, apparently to compensate for their 'bad start' after diapause. The number of instars was additionally a plastic response to environmental conditions, as the frequency of the extra instar increased under cooler thermal conditions. 3. The benefit of the extra instar is clear, as it allows individuals to develop into larger adults, but the cost is delayed adult eclosion, which is likely to select against the extra instar especially in males, in which early eclosion is critical for mating success. In support of this, the frequency of the extra instar was significantly lower in males (7%) than in females (42%). 4. Polymorphisms in three genes, serpin-1, vitellin-degrading protease precursor and phosphoglucose isomerase, which are known to influence development in insects, were associated with the occurrence of the extra instar. 5. At the level of local populations, the frequency of the extra instar was higher in newly established populations than that in old local ones, possibly reflecting maternal effects, as new populations are often established by females with heavy investment in dispersal. The frequency of the extra instar in turn correlated with the change in population size over 1 year and the risk of local extinction in the

Navigational strategies underlying phototaxis in larval zebrafish

PubMed Central

Chen, Xiuye; Engert, Florian

2014-01-01

Understanding how the brain transforms sensory input into complex behavior is a fundamental question in systems neuroscience. Using larval zebrafish, we study the temporal component of phototaxis, which is defined as orientation decisions based on comparisons of light intensity at successive moments in time. We developed a novel “Virtual Circle” assay where whole-field illumination is abruptly turned off when the fish swims out of a virtually defined circular border, and turned on again when it returns into the circle. The animal receives no direct spatial cues and experiences only whole-field temporal light changes. Remarkably, the fish spends most of its time within the invisible virtual border. Behavioral analyses of swim bouts in relation to light transitions were used to develop four discrete temporal algorithms that transform the binary visual input (uniform light/uniform darkness) into the observed spatial behavior. In these algorithms, the turning angle is dependent on the behavioral history immediately preceding individual turning events. Computer simulations show that the algorithms recapture most of the swim statistics of real fish. We discovered that turning properties in larval zebrafish are distinctly modulated by temporal step functions in light intensity in combination with the specific motor history preceding these turns. Several aspects of the behavior suggest memory usage of up to 10 swim bouts (~10 sec). Thus, we show that a complex behavior like spatial navigation can emerge from a small number of relatively simple behavioral algorithms. PMID:24723859

Navigational strategies underlying phototaxis in larval zebrafish.

PubMed

Chen, Xiuye; Engert, Florian

2014-01-01

Understanding how the brain transforms sensory input into complex behavior is a fundamental question in systems neuroscience. Using larval zebrafish, we study the temporal component of phototaxis, which is defined as orientation decisions based on comparisons of light intensity at successive moments in time. We developed a novel "Virtual Circle" assay where whole-field illumination is abruptly turned off when the fish swims out of a virtually defined circular border, and turned on again when it returns into the circle. The animal receives no direct spatial cues and experiences only whole-field temporal light changes. Remarkably, the fish spends most of its time within the invisible virtual border. Behavioral analyses of swim bouts in relation to light transitions were used to develop four discrete temporal algorithms that transform the binary visual input (uniform light/uniform darkness) into the observed spatial behavior. In these algorithms, the turning angle is dependent on the behavioral history immediately preceding individual turning events. Computer simulations show that the algorithms recapture most of the swim statistics of real fish. We discovered that turning properties in larval zebrafish are distinctly modulated by temporal step functions in light intensity in combination with the specific motor history preceding these turns. Several aspects of the behavior suggest memory usage of up to 10 swim bouts (~10 sec). Thus, we show that a complex behavior like spatial navigation can emerge from a small number of relatively simple behavioral algorithms.

Large-scale use of mosquito larval source management for malaria control in Africa: a cost analysis.

PubMed

Worrall, Eve; Fillinger, Ulrike

2011-11-08

At present, large-scale use of two malaria vector control methods, long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) is being scaled up in Africa with substantial funding from donors. A third vector control method, larval source management (LSM), has been historically very successful and is today widely used for mosquito control globally, except in Africa. With increasing risk of insecticide resistance and a shift to more exophilic vectors, LSM is now under re-evaluation for use against afro-tropical vector species. Here the costs of this intervention were evaluated. The 'ingredients approach' was used to estimate the economic and financial costs per person protected per year (pppy) for large-scale LSM using microbial larvicides in three ecologically diverse settings: (1) the coastal metropolitan area of Dar es Salaam in Tanzania, (2) a highly populated Kenyan highland area (Vihiga District), and (3) a lakeside setting in rural western Kenya (Mbita Division). Two scenarios were examined to investigate the cost implications of using alternative product formulations. Sensitivity analyses on product prices were carried out. The results show that for programmes using the same granular formulation larviciding costs the least pppy in Dar es Salaam (US$0.94), approximately 60% more in Vihiga District (US$1.50) and the most in Mbita Division (US$2.50). However, these costs are reduced substantially if an alternative water-dispensable formulation is used; in Vihiga, this would reduce costs to US$0.79 and, in Mbita Division, to US$1.94. Larvicide and staff salary costs each accounted for approximately a third of the total economic costs per year. The cost pppy depends mainly on: (1) the type of formulation required for treating different aquatic habitats, (2) the human population density relative to the density of aquatic habitats and (3) the potential to target the intervention in space and/or time. Costs for LSM compare favourably with costs for IRS

Large-scale use of mosquito larval source management for malaria control in Africa: a cost analysis

PubMed Central

2011-01-01

Background At present, large-scale use of two malaria vector control methods, long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) is being scaled up in Africa with substantial funding from donors. A third vector control method, larval source management (LSM), has been historically very successful and is today widely used for mosquito control globally, except in Africa. With increasing risk of insecticide resistance and a shift to more exophilic vectors, LSM is now under re-evaluation for use against afro-tropical vector species. Here the costs of this intervention were evaluated. Methods The 'ingredients approach' was used to estimate the economic and financial costs per person protected per year (pppy) for large-scale LSM using microbial larvicides in three ecologically diverse settings: (1) the coastal metropolitan area of Dar es Salaam in Tanzania, (2) a highly populated Kenyan highland area (Vihiga District), and (3) a lakeside setting in rural western Kenya (Mbita Division). Two scenarios were examined to investigate the cost implications of using alternative product formulations. Sensitivity analyses on product prices were carried out. Results The results show that for programmes using the same granular formulation larviciding costs the least pppy in Dar es Salaam (US$0.94), approximately 60% more in Vihiga District (US$1.50) and the most in Mbita Division (US$2.50). However, these costs are reduced substantially if an alternative water-dispensable formulation is used; in Vihiga, this would reduce costs to US$0.79 and, in Mbita Division, to US$1.94. Larvicide and staff salary costs each accounted for approximately a third of the total economic costs per year. The cost pppy depends mainly on: (1) the type of formulation required for treating different aquatic habitats, (2) the human population density relative to the density of aquatic habitats and (3) the potential to target the intervention in space and/or time. Conclusion Costs for LSM

Larval dispersal in three coral reef decapod species: Influence of larval duration on the metapopulation structure.

PubMed

Sanvicente-Añorve, Laura; Zavala-Hidalgo, Jorge; Allende-Arandía, Eugenia; Hermoso-Salazar, Margarita

2018-01-01

Most coral-associated decapod species have non-migratory adult populations and depend on their planktonic larvae for dispersal. This study examined the metapopulation structure of three decapod species with different pelagic larval duration (PLD) from twelve coral reef complexes of the Gulf of Mexico. The dispersion of larvae was analyzed through the use of a realistic numerical simulation of the Gulf of Mexico with the Hybrid Coordinate Ocean Model. To study the transport and dispersion of particles in near-surface waters, a particle-tracking subroutine was run using as input the currents from the model. The simulation consisted of the launch of 100 passive particles (virtual larvae) every 24 hours from each reef throughout five years, and tracked for as long as 210 days. Results indicated that species with a short PLD, Mithraculus sculptus (PLD 8‒13 days), had a weak connection among the reefs, but higher self-recruitment, especially on the narrow western shelf. The species with a longer PLD, Dromia erythropus (28‒30 days), had a stronger connection among neighboring reefs (< 300 km). Finally, the species with an even longer PLD, Stenopus hispidus (123‒210 days), had a wider potential distribution than the other species. Circulation on synoptic, seasonal and interannual scales had differential effects on the larval dispersal of each species. The metapopulation structure of M. sculptus and D. erythropus seemed to combine features of the non-equilibrium and the patchy models, whereas that of S. hispidus presumably fit to a patchy model. These findings support previous observations that indicate that species with longer PLD tend to occupy larger areas than species with short PLD, although recruitment of juveniles to the adult populations will also depend on other factors, such as the availability of suitable habitats and the ability to colonize them.

Larval dispersal in three coral reef decapod species: Influence of larval duration on the metapopulation structure

PubMed Central

Zavala-Hidalgo, Jorge; Allende-Arandía, Eugenia; Hermoso-Salazar, Margarita

2018-01-01

Most coral-associated decapod species have non-migratory adult populations and depend on their planktonic larvae for dispersal. This study examined the metapopulation structure of three decapod species with different pelagic larval duration (PLD) from twelve coral reef complexes of the Gulf of Mexico. The dispersion of larvae was analyzed through the use of a realistic numerical simulation of the Gulf of Mexico with the Hybrid Coordinate Ocean Model. To study the transport and dispersion of particles in near-surface waters, a particle-tracking subroutine was run using as input the currents from the model. The simulation consisted of the launch of 100 passive particles (virtual larvae) every 24 hours from each reef throughout five years, and tracked for as long as 210 days. Results indicated that species with a short PLD, Mithraculus sculptus (PLD 8‒13 days), had a weak connection among the reefs, but higher self-recruitment, especially on the narrow western shelf. The species with a longer PLD, Dromia erythropus (28‒30 days), had a stronger connection among neighboring reefs (< 300 km). Finally, the species with an even longer PLD, Stenopus hispidus (123‒210 days), had a wider potential distribution than the other species. Circulation on synoptic, seasonal and interannual scales had differential effects on the larval dispersal of each species. The metapopulation structure of M. sculptus and D. erythropus seemed to combine features of the non-equilibrium and the patchy models, whereas that of S. hispidus presumably fit to a patchy model. These findings support previous observations that indicate that species with longer PLD tend to occupy larger areas than species with short PLD, although recruitment of juveniles to the adult populations will also depend on other factors, such as the availability of suitable habitats and the ability to colonize them. PMID:29558478

Variation in larval properties of the Atlantic brooding coral Porites astreoides between different reef sites in Bermuda

NASA Astrophysics Data System (ADS)

de Putron, Samantha J.; Lawson, Julia M.; White, Kascia Q. L.; Costa, Matthew T.; Geronimus, Miriam V. B.; MacCarthy, Anne

2017-06-01

Recent research has documented phenotypic differences among larvae released from corals with a brooding reproductive mode, both among species and within broods from a single species. We studied larvae released from the common Atlantic coral Porites astreoides in Bermuda to further evaluate phenotypic variability. Inter-site differences were investigated in larvae from conspecifics at a rim and patch reef site. Larvae were collected daily for one lunar cycle from several colonies per site each year over 5 yr. Larval volume varied with reef site of origin, with colonies from the rim reef site producing larger larvae than colonies from the patch reef site. This inter-site variation in larval size could not be explained by corallite size and may be a response to different environmental conditions at the sites. Larvae from both reef sites also varied in size depending on lunar day of release over 4 yr of study. Regardless of site of origin, smaller larvae were released earlier in the lunar cycle. Over 1 yr of study, lipid and zooxanthellae content and settlement success after 48 h covaried with larval size. However, there may be a trade-off between larger larvae and reduced fecundity. Overall, larvae released from colonies from the rim reef site were larger and had greater settlement success than those from colonies from the patch reef site. This study documents larval phenotypic variability and a distinct inter-site difference in larval ecology among conspecifics within the same geographic area, which may have implications for recruitment success, population dynamics, and resilience.

Wing Shape as an Indicator of Larval Rearing Conditions for Aedes albopictus and Ae. aegypti (Diptera: Culicidae)

PubMed Central

Stephens, C. R.; Juliano, S. A.

2012-01-01

Estimating a mosquito’s vector competence, or likelihood of transmitting disease, if it takes an infectious blood meal, is an important aspect of predicting when and where outbreaks of infectious diseases will occur. Vector competence can be affected by rearing temperature and inter- and intraspecific competition experienced by the individual mosquito during its larval development. This research investigates whether a new morphological indicator of larval rearing conditions, wing shape, can be used to distinguish reliably temperature and competitive conditions experienced during larval stages. Aedes albopictus and Aedes aegypti larvae were reared in low intra-specific, high intra-specific, or high inter-specific competition treatments at either 22°C or 32°C. The right wing of each dried female was removed and photographed. Nineteen landmarks and twenty semilandmarks were digitized on each wing. Shape variables were calculated using geometric morphometric software. Canonical variate analysis, randomization multivariate analysis of variance, and visualization of landmark movement using deformation grids provided evidence that although semilandmark position was significantly affected by larval competition and temperature for both species, the differences in position did not translate into differences in wing shape, as shown in deformation grids. Two classification procedures yielded success rates of 26–49%. Accounting for wing size produced no increase in classification success. There appeared to be a significant relationship between shape and size. These results, particularly the low success rate of classification based on wing shape, show that shape is unlikely to be a reliable indicator of larval rearing competition and temperature conditions for Aedes albopictus and Aedes aegypti. PMID:22897054

Can metamorphosis survival during larval development in spiny lobster Sagmariasus verreauxi be improved through quantitative genetic inheritance?

PubMed

Nguyen, Nguyen H; Fitzgibbon, Quinn P; Quinn, Jane; Smith, Greg; Battaglene, Stephen; Knibb, Wayne

2018-05-04

One of the major impediments to spiny lobster aquaculture is the high cost of hatchery production due to the long and complex larval cycle and poor survival during the many moult stages, especially at metamorphosis. We examined if the key trait of larval survival can be improved through selection by determining if genetic variance exists for this trait. Specifically, we report, for the first time, genetic parameters (heritability and correlations) for early survival rates recorded at five larval phases; early-phyllosoma stages (instars 1-6; S1), mid-phyllosoma stages (instars; 7-12; S2), late-phyllosoma stages (instars 13-17; S3), metamorphosis (S4) and puerulus stage (S5) in hatchery-reared spiny lobster Sagmariasus verreauxi. The data were collected from a total of 235,060 larvae produced from 18 sires and 30 dams over nine years (2006 to 2014). Parentage of the offspring and full-sib families was verified using ten microsatellite markers. Analysis of variance components showed that the estimates of heritability for all the five phases of larval survival obtained from linear mixed model were generally similar to those obtained from threshold logistic generalised models (0.03-0.47 vs. 0.01-0.50). The heritability estimates for survival traits recorded in the early larval phases (S1 and S2) were higher than those estimated in later phases (S3, S4 and S5). The existence of the additive genetic component in larval survival traits indicate that they could be improved through selection. Both phenotypic and genetic correlations among the five survival measures studied were moderate to high and positive. The genetic associations between successive rearing periods were stronger than those that are further apart. Our estimates of heritability and genetic correlations reported here in a spiny lobster species indicate that improvement in the early survival especially during metamorphosis can be achieved through genetic selection in this highly economic value species.

Modelling developmental changes in the carbon and nitrogen budgets of larval brachyuran crabs

NASA Astrophysics Data System (ADS)

Anger, K.

1990-03-01

The uptake and partitioning of nutritional carbon (C) and nitrogen (N) were studied during the complete larval development of a brachyuran crab, Hyas araneus, reared under constant conditions in the laboratory. Biochemical and physiological data were published in a foregoing paper, and complete budgets of C and N were now constructed from these data. Regression equations describing rates of feeding ( F), growth ( G), respiration ( R), and ammonia excretion ( U) as functions of time during individual larval moult cycles were inserted in a simulation model, in order to analyse time-dependent (i.e. developmental) patterns of variation in these parameters as well as in bioenergetic efficiencies. Absolute daily feeding rates ( F; per individual) as well as carbon and nitrogen-specific rates ( F/C, F/N) are in general maximum in early, and minimum in late stages of individual larval moult cycles (postmoult and premoult, respectively). Early crab zoeae may ingest equivalents of up to ca 40% body C and 30% body N per day, respectively, whereas megalopa larvae usually eat less than 10%. Also growth rates ( G; G/C, G/N) reveal decreasing tendencies both during individual moult cycles and, on the average, in subsequent instars. Conversion of C and N data to lipid and protein, respectively, suggests that in all larval instars there is initially an increase in the lipid: protein ratio. Protein, however, remains clearly the predominant biochemical constituent in larval biomass. The absolute and specific values of respiration ( R; R/C) and excretion ( U; U/N) vary only little during the course of individual moult cycles. Thus, their significance in relation to G increases within the C and N budgets, and net growth efficiency ( K 2) decreases concurrently. Also gross growth and assimilation efficiency ( K 2; A/F) are, in general, maximum in early stages of the moult cycle (postmoult). Biochemical data suggest that lipid utilization efficiency is particularly high in early moult

Larval ecology of mosquitoes in sylvatic arbovirus foci in southeastern Senegal

PubMed Central

2012-01-01

Background Although adult mosquito vectors of sylvatic arbovirus [yellow fever (YFV), dengue-2 (DENV-2) and chikungunya (CHIKV)] have been studied for the past 40 years in southeastern Senegal, data are still lacking on the ecology of larval mosquitoes in this area. In this study, we investigated the larval habitats of mosquitoes and characterized their seasonal and spatial dynamics in arbovirus foci. Methods We searched for wet microhabitats, classified in 9 categories, in five land cover classes (agriculture, forest, savannah, barren and village) from June, 2010 to January, 2011. Mosquito immatures were sampled monthly in up to 30 microhabitats of each category per land cover and bred until adult stage for determination. Results No wet microhabitats were found in the agricultural sites; in the remaining land covers immature stages of 35 mosquito species in 7 genera were sampled from 9 microhabitats (tree holes, fresh fruit husks, decaying fruit husks, puddles, bamboo holes, discarded containers, tires, rock holes and storage containers). The most abundant species was Aedes aegypti formosus, representing 30.2% of the collections, followed by 12 species, representing each more than 1% of the total, among them the arbovirus vectors Ae. vittatus (7.9%), Ae. luteocephalus (5.7%), Ae. taylori (5.0%), and Ae. furcifer (1.3%). Aedes aegypti, Cx. nebulosus, Cx. perfuscus, Cx. tritaeniorhynchus, Er. chrysogster and Ae. vittatus were the only common species collected from all land covers. Aedes furcifer and Ae. taylori were collected in fresh fruit husks and tree holes. Species richness and dominance varied significantly in land covers and microhabitats. Positive associations were found mainly between Ae. furcifer, Ae. taylori and Ae. luteocephalus. A high proportion of potential enzootic vectors that are not anthropophilic were found in the larval mosquito fauna. Conclusions In southeastern Senegal, Ae. furcifer and Ae. taylori larvae showed a more limited distribution

Variability in oceanographic barriers to coral larval dispersal: Do currents shape biodiversity?

NASA Astrophysics Data System (ADS)

Thompson, D. M.; Kleypas, J.; Castruccio, F.; Curchitser, E. N.; Pinsky, M. L.; Jönsson, B.; Watson, J. R.

2018-07-01

The global center of marine biodiversity is located in the western tropical Pacific in a region known as the "Coral Triangle" (CT). This region is also considered the most threatened of all coral reef regions, because multiple impacts, including rising temperatures and coral bleaching, have already caused high mortality of reef corals over large portions of the CT. Larval dispersal and recruitment play a critical role in reef recovery after such disturbances, but our understanding of reproductive connectivity between reefs is limited by a paucity of observations. Oceanographic modeling can provide an economical and efficient way to augment our understanding of reef connectivity, particularly over an area as large as the CT, where marine ecosystem management has become a priority. This work combines daily averaged surface current velocity and direction from a Regional Ocean Modeling System developed for the CT region (CT-ROMS) with a Lagrangian particle tracking tool (TRACMASS) to investigate the probability of larval transport between reefs for a typical broadcasting coral. A 47-year historical simulation (1960-2006) was used to analyze the potential connectivity, the physical drivers of larval transport, and its variability following bi-annual spawning events in April and September. Potential connectivity between reefs was highly variable from year to year, emphasizing the need for long simulations. The results suggest that although reefs in this region are highly self-seeded, comparatively rare long-distance dispersal events may play a vital role in shaping regional patterns of reef biodiversity and recovery following disturbance. The spatial pattern of coral "subpopulations," which are based on the potential connectivity between reefs, agrees with observed regional-scale patterns of biodiversity, suggesting that the physical barriers to larval dispersal are a first-order driver of coral biodiversity in the CT region. These physical barriers persist through the

A Biophysical Model for Hawaiian Coral Reefs: Coupling Local Ecology, Larval Transport and Climate Change

NASA Astrophysics Data System (ADS)

Kapur, M. R.

2016-02-01

Simulative models of reef ecosystems have been used to evaluate ecological responses to a myriad of disturbance events, including fishing pressure, coral bleaching, invasion by alien species, and nutrient loading. The Coral Reef Scenario Evaluation Tool (CORSET), has been developed and instantiated for both the Meso-American Reef (MAR) and South China Sea (SCS) regions. This model is novel in that it accounts for the many scales at which reef ecosystem processes take place; is comprised of a "bottom-up" structure wherein complex behaviors are not pre-programmed, but emergent and highly portable to new systems. Local-scale dynamics are coupled across regions through larval connectivity matrices, derived sophisticated particle transport simulations that include key elements of larval behavior. By this approach, we are able to directly evaluate some of the potential consequences of larval connectivity patterns across a range of spatial scales and under multiple climate scenarios. This work develops and applies the CORSET (Coral Reef Scenario Evaluation Tool) to the Main Hawaiian Islands under a suite of climate and ecological scenarios. We introduce an adaptation constant into reef-building coral dynamics to simulate observed resiliencies to bleaching events. This presentation will share results from the model's instantiation under two Resource Concentration Pathway climate scenarios, with emphasis upon larval connectivity dynamics, emergent coral tolerance to increasing thermal anomalies, and patterns of spatial fishing closures. Results suggest that under a business-as-usual scenario, thermal tolerance and herbivore removal will have synergistic effects on reef resilience.

Response of larval sea lampreys (Petromyzon marinus) to pulsed DC electrical stimuli in laboratory experiments

USGS Publications Warehouse

Bowen, Anjanette K.; Weisser, John W.; Bergstedt, Roger A.; Famoye, Felix

2003-01-01

Four electrical factors that are used in pulsed DC electrofishing for larval sea lampreys (Petromyzon marinus) were evaluated in two laboratory studies to determine the optimal values to induce larval emergence over a range of water temperatures and conductivities. Burrowed larvae were exposed to combinations of pulsed DC electrical factors including five pulse frequencies, three pulse patterns, and two levels of duty cycle over a range of seven voltage gradients in two separate studies conducted at water temperatures of 10, 15, and 20°C and water conductivities of 25, 200, and 900 μS/cm. A four-way analysis of variance was used to determine significant (α = 0.05) influences of each electrical factor on larval emergence. Multiple comparison tests with Bonferroni adjustments were used to determine which values of each factor resulted in significantly higher emergence at each temperature and conductivity. Voltage gradient and pulse frequency significantly affected emergence according to the ANOVA model at each temperature and conductivity tested. Duty cycle and pulse pattern generally did not significantly influence the model. Findings suggest that a setting of 2.0 V/cm, 3 pulses/sec, 10% duty, and 2:2 pulse pattern seems the most promising in waters of medium conductivity and across a variety of temperatures. This information provides a basis for understanding larval response to pulsed DC electrofishing gear factors and identifies electrofisher settings that show promise to increase the efficiency of the gear during assessments for burrowed sea lamprey larvae.

Seasonal Differences in Density But Similar Competitive Impact of Aedes albopictus (Skuse) on Aedes aegypti (L.) in Rio de Janeiro, Brazil

PubMed Central

Camara, Daniel Cardoso Portela; Codeço, Claudia Torres; Juliano, Steven A.; Lounibos, L. Philip; Riback, Thais Irene Souza; Pereira, Glaucio Rocha; Honorio, Nildimar Alves

2016-01-01

Previous studies have shown that the negative effects of density of Ae. albopictus on Ae. aegypti exceed those of Ae. aegypti on Ae. albopictus for population growth, adult size, survivorship, and developmental rate. This competitive superiority has been invoked to explain the displacement of Ae. aegypti by Ae. albopictus in the southeastern USA. In Brazil, these species coexist in many vegetated suburban and rural areas. We investigated a related, but less-well-studied question: do effects of Ae. albopictus on Ae. aegypti larval development and survival occur under field conditions at realistic densities across multiple seasons in Brazil? We conducted additive competition experiments in a vegetated area of Rio de Janeiro where these species coexist. We tested the hypothesis that Ae. aegypti (the focal species, at a fixed density) suffers negative effects on development and survivorship across a gradient of increasing densities of Ae. albopictus (the associate species) in three seasons. The results showed statistically significant effects of both season and larval density on Ae. aegypti survivorship, and significant effects of season on development rate, with no significant season-density interactions. Densities of Aedes larvae in these habitats differed among seasons by a factor of up to 7x. Overall, Spring was the most favorable season for Ae. aegypti survivorship and development. Results showed that under natural conditions the negative competitive effects of Ae. albopictus on Ae. aegypti were expressed primarily as lower survivorship. Coexistence between Ae. aegypti and Ae. albopictus in vegetated areas is likely affected by seasonal environmental differences, such as detrital resource levels or egg desiccation, which can influence competition between these species. Interactions between these Aedes are important in Brazil, where both species are well established and widely distributed and vector dengue, Zika and chikungunya viruses. PMID:27322537

Small nonnative fishes as predators of larval razorback suckers

USGS Publications Warehouse

Carpenter, J.; Mueller, G.A.

2008-01-01

The razorback sucker (Xyrauchen texanus), an endangered big-river fish of the Colorado River basin, has demonstrated no sustainable recruitment in 4 decades, despite presence of spawning adults and larvae. Lack of adequate recruitment has been attributed to several factors, including predation by nonnative fishes. Substantial funding and effort has been expended on mechanically removing nonnative game fishes, typically targeting large predators. As a result, abundance of larger predators has declined, but the abundance of small nonnative fishes has increased in some areas. We conducted laboratory experiments to determine if small nonnative fishes would consume larval razorback suckers. We tested adults of three small species (threadfin shad, Dorosoma petenense; red shiner, Cyprinella lutrensis; fathead minnow, Pimephales promelas) and juveniles of six larger species (common carp, Cyprinus carpio; yellow bullhead, Ameiurus natalis; channel catfish, Ictalurus punctatus; rainbow trout, Oncorhynchus mykiss; green sunfish, Lepomis cyanellus; bluegill, L. macrochirus). These nonnative fishes span a broad ecological range and are abundant within the historical range of the razorback sucker. All nine species fed on larval razorback suckers (total length, 9-16 mm). Our results suggest that predation by small nonnative fishes could be responsible for limiting recovery of this endangered species.

Mutation of a cuticular protein, BmorCPR2, alters larval body shape and adaptability in silkworm, Bombyx mori.

PubMed

Qiao, Liang; Xiong, Gao; Wang, Ri-xin; He, Song-zhen; Chen, Jie; Tong, Xiao-ling; Hu, Hai; Li, Chun-lin; Gai, Ting-ting; Xin, Ya-qun; Liu, Xiao-fan; Chen, Bin; Xiang, Zhong-huai; Lu, Cheng; Dai, Fang-yin

2014-04-01

Cuticular proteins (CPs) are crucial components of the insect cuticle. Although numerous genes encoding cuticular proteins have been identified in known insect genomes to date, their functions in maintaining insect body shape and adaptability remain largely unknown. In the current study, positional cloning led to the identification of a gene encoding an RR1-type cuticular protein, BmorCPR2, highly expressed in larval chitin-rich tissues and at the mulberry leaf-eating stages, which is responsible for the silkworm stony mutant. In the Dazao-stony strain, the BmorCPR2 allele is a deletion mutation with significantly lower expression, compared to the wild-type Dazao strain. Dysfunctional BmorCPR2 in the stony mutant lost chitin binding ability, leading to reduced chitin content in larval cuticle, limitation of cuticle extension, abatement of cuticle tensile properties, and aberrant ratio between internodes and intersegmental folds. These variations induce a significant decrease in cuticle capacity to hold the growing internal organs in the larval development process, resulting in whole-body stiffness, tightness, and hardness, bulging intersegmental folds, and serious defects in larval adaptability. To our knowledge, this is the first study to report the corresponding phenotype of stony in insects caused by mutation of RR1-type cuticular protein. Our findings collectively shed light on the specific role of cuticular proteins in maintaining normal larval body shape and will aid in the development of pest control strategies for the management of Lepidoptera.

Large wood and in-stream habitat for juvenile coho salmon and larval lampreys in a Pacific Northwest stream

USGS Publications Warehouse

Gonzalez, Rosalinda; Dunham, Jason B.; Lightcap, Scott W.; McEnroe, Jeffery R.

2017-01-01

The influences of large wood on Pacific salmon are well-studied, but studies of nonsalmonid species such as lampreys are uncommon. To address this need, we evaluated the potential effects of large wood on larval lampreys (Pacific Lamprey, Entosphenus tridentatus; and potentially Western Brook Lamprey Lampetra richardsoni), as well as juvenile Coho Salmon Oncorhynchus kisutch, in a small coastal Oregon stream. Our objectives were to 1) identify in-stream habitat characteristics associated with the presence of larval lampreys and abundance of juvenile Coho Salmon; and 2) evaluate how these characteristics were associated with in-stream wood. To address habitat use, we quantified presence of larval lampreys in 92 pools and abundance of juvenile Coho Salmon in 44 pools during summer low flows. We focused on a study reach where large wood was introduced into the stream between 2008 and 2009. Results indicated that presence of larval lampreys was significantly associated with availability of fine sediment and deeper substrate. The abundance of juvenile Coho Salmon (fish/pool) was strongly associated with pool surface area and to a weaker extent with the proportion of cobble and boulder substrates in pools. Pools with wood, regardless of whether they were formed by wood, had significantly greater coverage of fine sediment, deeper substrate, and greater pool surface area. Taken together, these results suggest that in-stream wood can provide habitat associated with presence of larval lampreys and greater abundance of juvenile Coho Salmon.

Convergent adaptive radiations in Madagascan and Asian ranid frogs reveal covariation between larval and adult traits

PubMed Central

Bossuyt, Franky; Milinkovitch, Michel C.

2000-01-01

Recent studies have reported that independent adaptive radiations can lead to identical ecomorphs. Our phylogenetic analyses of nuclear and mitochondrial DNA sequences here indicate that a major radiation of ranid frogs on Madagascar produced morphological, physiological, and developmental characters that are remarkably similar to those that independently evolved on the Indian subcontinent. We demonstrate further that, in several cases, adult and larval stages each evolved sets of characters which are not only convergent between independent lineages, but also allowed both developmental stages to invade the same adaptive zone. It is likely that such covariations are produced by similar selective pressures on independent larval and adult characters rather than by genetic or functional linkage. We briefly discuss why larval/adult covariations might constitute an important evolutionary phenomenon in species for which more than one developmental stage potentially has access to multiple environmental conditions. PMID:10841558

Mosquito Larval Habitats, Land Use, and Potential Malaria Risk in Northern Belize from Satellite Image Analyses

NASA Technical Reports Server (NTRS)

Pope, Kevin; Masuoka, Penny; Rejmankova, Eliska; Grieco, John; Johnson, Sarah; Roberts, Donald

2004-01-01

The distribution of Anopheles mosquito habitats and land use in northern Belize is examined with satellite data. -A land cover classification based on multispectral SPOT and multitemporal Radarsat images identified eleven land cover classes, including agricultural, forest, and marsh types. Two of the land cover types, Typha domingensis marsh and flooded forest, are Anopheles vestitipennis larval habitats. Eleocharis spp. marsh is the larval habitat for Anopheles albimanus. Geographic Information Systems (GIS) analyses of land cover demonstrate that the amount of T-ha domingensis in a marsh is positively correlated with the amount of agricultural land in the adjacent upland, and negatively correlated with the amount of adjacent forest. This finding is consistent with the hypothesis that nutrient (phosphorus) runoff from agricultural lands is causing an expansion of Typha domingensis in northern Belize. This expansion of Anopheles vestitipennis larval habitat may in turn cause an increase in malaria risk in the region.

Ontogenetic changes in larval swimming and orientation of pre-competent sea urchin Arbacia punctulata in turbulence

PubMed Central

Wheeler, Jeanette D.; Chan, Kit Yu Karen; Anderson, Erik J.; Mullineaux, Lauren S.

2016-01-01

ABSTRACT Many marine organisms have complex life histories, having sessile adults and relying on the planktonic larvae for dispersal. Larvae swim and disperse in a complex fluid environment and the effect of ambient flow on larval behavior could in turn impact their survival and transport. However, to date, most studies on larvae–flow interactions have focused on competent larvae near settlement. We examined the importance of flow on early larval stages by studying how local flow and ontogeny influence swimming behavior in pre-competent larval sea urchins, Arbacia punctulata. We exposed larval urchins to grid-stirred turbulence and recorded their behavior at two stages (4- and 6-armed plutei) in three turbulence regimes. Using particle image velocimetry to quantify and subtract local flow, we tested the hypothesis that larvae respond to turbulence by increasing swimming speed, and that the increase varies with ontogeny. Swimming speed increased with turbulence for both 4- and 6-armed larvae, but their responses differed in terms of vertical swimming velocity. 4-Armed larvae swam most strongly upward in the unforced flow regime, while 6-armed larvae swam most strongly upward in weakly forced flow. Increased turbulence intensity also decreased the relative time that larvae spent in their typical upright orientation. 6-Armed larvae were tilted more frequently in turbulence compared with 4-armed larvae. This observation suggests that as larvae increase in size and add pairs of arms, they are more likely to be passively re-oriented by moving water, rather than being stabilized (by mechanisms associated with increased mass), potentially leading to differential transport. The positive relationship between swimming speed and larval orientation angle suggests that there was also an active response to tilting in turbulence. Our results highlight the importance of turbulence to planktonic larvae, not just during settlement but also in earlier stages through morphology�

Not my "type": larval dispersal dimorphisms and bet-hedging in opisthobranch life histories.

PubMed

Krug, Patrick J

2009-06-01

When conditions fluctuate unpredictably, selection may favor bet-hedging strategies that vary offspring characteristics to avoid reproductive wipe-outs in bad seasons. For many marine gastropods, the dispersal potential of offspring reflects both maternal effects (egg size, egg mass properties) and larval traits (development rate, habitat choice). I present data for eight sea slugs in the genus Elysia (Opisthobranchia: Sacoglossa), highlighting potentially adaptive variation in traits like offspring size, timing of metamorphosis, hatching behavior, and settlement response. Elysia zuleicae produced both planktotrophic and lecithotrophic larvae, a true case of poecilogony. Both intracapsular and post-hatching metamorphosis occurred among clutches of "Boselia" marcusi, E. cornigera, and E. crispata, a dispersal dimorphism often misinterpreted as poecilogony. Egg masses of E. tuca hatched for up to 16 days but larvae settled only on the adult host alga Halimeda, whereas most larvae of E. papillosa spontaneously metamorphosed 5-7 days after hatching. Investment in extra-capsular yolk may allow mothers to increase larval size relative to egg size and vary offspring size within and among clutches. Flexible strategies of larval dispersal and offspring provisioning in Elysia spp. may represent adaptations to the patchy habitat of these specialized herbivores, highlighting the evolutionary importance of variation in a range of life-history traits.

[Effects of temperature on the embryonic development and larval growth of Sepia lycidas].

PubMed

Jiang, Xia-Min; Peng, Rui-Bing; Luo, Jiang; Tang, Feng

2013-05-01

A single-factor experiment was conducted to study the effects of different temperature (15, 18, 21, 24, 27, 30, and 33 degrees C) on the embryonic development and larval growth of Sepia lycidas, aimed to search for the optimum temperature for the development and growth of S. lycidas. The results showed that temperature had significant effects on the embryonic development and larval growth of S. lycidas (P < 0.05). The suitable temperature for hatching ranged from 21 degrees C to 30 degrees C, and the optimum temperature was 24 degrees C. At the optimum temperature, the hatching rate was (93.3 +/- 2.9)%, incubation period was (24.33 +/- 0.58) d, hatching period was (6.00 +/- 1.00) d, completely absorked rate of yolk sac was (96.4 +/- 3.1)%, and newly hatched larvae mass was (0.258 +/- 0.007) g. The effective accumulated temperature model was N = 284.42/(T-12.57). The suitable temperature for the larval survival and growth ranged from 21 degrees C to 30 degrees C, and the optimum temperature was from 24 degrees C to 27 degrees C. At the optimum temperature, the survival rate ranged from 70.0% to 73.3%, and the specific growth rate was from 2.4% to 3.8%.

Spontaneous heterosis in larval life-history traits of hemiclonal frog hybrids

PubMed Central

Hotz, Hansjürg; Semlitsch, Raymond D.; Gutmann, Eva; Guex, Gaston-Denis; Beerli, Peter

1999-01-01

European water frog hybrids Rana esculenta (Rana ridibunda × Rana lessonae) reproduce hemiclonally, transmitting only their ridibunda genome to gametes. We compared fitness-related larval life-history traits of natural R. esculenta from Poland with those of the two sympatric parental species and of newly generated F1 hybrids. Compared with either parental species, F1 hybrid offspring had higher survival, higher early growth rates, a more advanced developmental stage by day 49, and earlier metamorphosis, but similar mass at metamorphosis. R. esculenta from natural lineages had trait values intermediate between those of F1 offspring and of the two parental species. The data support earlier observations on natural R. esculenta that had faster larval growth, earlier metamorphosis, and higher resistance to hypoxic conditions compared with either parental species. Observing larval heterosis in F1 hybrids in survival, growth rate, and time to metamorphosis, however, at an even higher degree than in hybrids from natural lineages, demonstrates that heterosis is spontaneous and results from hybridity per se rather than from subsequent interclonal selection; in natural lineages the effects of hybridity and of clonal history are confounded. This is compelling evidence for spontaneous heterosis in hybrid clonals. Results on hemiclonal fish hybrids (Poeciliopsis) showed no spontaneous heterosis; thus, our frog data are not applicable to all hybrid clonals. Our data do show, however, that heterosis is an important potential source for the extensively observed ecological success of hybrid clonals. We suggest that heterosis and interclonal selection together shape fitness of natural R. esculenta lineages. PMID:10051613

The Role of Climatic and Density Dependent Factors in Shaping Mosquito Population Dynamics: The Case of Culex pipiens in Northwestern Italy

PubMed Central

Giacobini, Mario; Pugliese, Andrea; Merler, Stefano; Rosà, Roberto

2016-01-01

Culex pipiens mosquito is a species widely spread across Europe and represents a competent vector for many arboviruses such as West Nile virus (WNV), which has been recently circulating in many European countries, causing hundreds of human cases. In order to identify the main determinants of the high heterogeneity in Cx. pipiens abundance observed in Piedmont region (Northwestern Italy) among different seasons, we developed a density-dependent stochastic model that takes explicitly into account the role played by temperature, which affects both developmental and mortality rates of different life stages. The model was calibrated with a Markov chain Monte Carlo approach exploring the likelihood of recorded capture data gathered in the study area from 2000 to 2011; in this way, we disentangled the role played by different seasonal eco-climatic factors in shaping the vector abundance. Illustrative simulations have been performed to forecast likely changes if temperature or density–dependent inputs would change. Our analysis suggests that inter-seasonal differences in the mosquito dynamics are largely driven by different temporal patterns of temperature and seasonal-specific larval carrying capacities. Specifically, high temperatures during early spring hasten the onset of the breeding season and increase population abundance in that period, while, high temperatures during the summer can decrease population size by increasing adult mortality. Higher densities of adult mosquitoes are associated with higher larval carrying capacities, which are positively correlated with spring precipitations. Finally, an increase in larval carrying capacity is expected to proportionally increase adult mosquito abundance. PMID:27105065

Climate change and larval transport in the ocean: fractional effects from physical and physiological factors.

PubMed

Kendall, Matthew S; Poti, Matt; Karnauskas, Kristopher B

2016-04-01

Changes in larval import, export, and self-seeding will affect the resilience of coral reef ecosystems. Climate change will alter the ocean currents that transport larvae and also increase sea surface temperatures (SST), hastening development, and shortening larval durations. Here, we use transport simulations to estimate future larval connectivity due to: (1) physical transport of larvae from altered circulation alone, and (2) the combined effects of altered currents plus physiological response to warming. Virtual larvae from islands throughout Micronesia were moved according to present-day and future ocean circulation models. The Hybrid Coordinate Ocean Model (HYCOM) spanning 2004-2012 represented present-day currents. For future currents, we altered HYCOM using analysis from the National Center for Atmospheric Research Community Earth System Model, version 1-Biogeochemistry, Representative Concentration Pathway 8.5 experiment. Based on the NCAR model, regional SST is estimated to rise 2.74 °C which corresponds to a ~17% decline in larval duration for some taxa. This reduction was the basis for a separate set of simulations. Results predict an increase in self-seeding in 100 years such that 62-76% of islands experienced increased self-seeding, there was an average domainwide increase of ~1-3% points in self-seeding, and increases of up to 25% points for several individual islands. When changed currents alone were considered, approximately half (i.e., random) of all island pairs experienced decreased connectivity but when reduced PLD was added as an effect, ~65% of connections were weakened. Orientation of archipelagos relative to currents determined the directional bias in connectivity changes. There was no universal relationship between climate change and connectivity applicable to all taxa and settings. Islands that presently export large numbers of larvae but that also maintain or enhance this role into the future should be the focus of conservation

Bioecology of Stenoma catenifer (Lepidoptera: Elachistidae) and associated larval parasitoids reared from Hass avocados in Guatemala.

PubMed

Hoddle, Mark S; Hoddle, Christina D

2008-06-01

A 10-wk study of the avocado seed-feeding moth Stenoma catenifer Walsingham (Lepidoptera: Elachistidae), was conducted in a commercial 'Hass' avocado (Persea americana Miller [Lauraceae]) orchard in Guatemala. Up to 45% of fruit in the orchard were damaged by larval S. catenifer. Larval-to-adult survivorship for 1,881 S. catenifer larvae in Hass fruit was 37%, and adult sex ratio was 51% female. Four species of larval parasitoid were reared from field-collected S. catenifer larvae. The most common parasitoid reared was a gregarious Apanteles sp., which parasitized 53% of larvae and produced on average eight to nine cocoons per host. Apanteles sp. sex ratio was 47% female and 87% of parasitoids emerged successfully from cocoons. Apanteles sp. longevity was approximately equal to 1.5 d in the absence of food, and when provisioned with honey, parasitoids survived for 5-7 d. The mean number of cocoons produced by Apanteles sp. per host, and larval parasitism rates were not significantly affected by the number of S. catenifer larvae inhabiting seeds. Oviposition studies conducted with S. catenifer in the laboratory indicated that this moth lays significantly more eggs on the branch to which the fruit pedicel is attached than on avocado fruit. When given a choice between Hass and non-Hass avocados, S. catenifer lays up to 2.69 times more eggs on Hass.

Calcified aquatic insect larval constructions in the Pleistocene tufa of Jebel El Mida, Gafsa, southern Tunisia: Recognition and paleoenvironmental significance

NASA Astrophysics Data System (ADS)

Ben Ahmed, Walid; Henchiri, Mohsen; Mastouri, Amna; Slim S'himi, Najet

2018-04-01

Calcified aquatic larval cases were recognized and identified in the Pleistocene tufa masses of Jebel El Mida, Gafsa, southern Tunisia. These larval constructions belong to three main insect families: caddisflies (Trichoptera, Hydropsychidae), midges (Diptera, Chironomidae) and aquatic moths (Lepidoptera, Pyralidae) that inhabited tubes in the tufa and spun nets. Each insect community has its distinctive characteristics of larval constructions that allow their recognition. The larval constructions recognized comprise fixed and portable (for caddisflies) dwelling cases and silken retreats and feeding capture nets. These last-mentioned are almost completely eroded and only remnants are preserved. The spatial distribution of these larval cases within the tufa is not random but, rather imposed by some specific paleohydraulic conditions. It's the reason why aquatic insect larval constructions are considered as prominent tool for the reconstruction of tufa and travertine depositional environments. Chironomid fixed dwelling cases (diameters range from 0.6 mm for clustered tubes to 3 mm) indicate the deposition of tufa under lotic (flowing) or lentic (standing) water conditions. The later hydraulic condition is shared with hydropsychids with fixed retreats (0.2-4 mm in diameter). Portable case-building caddisflies (case length ranging from 5 to 20 mm, and diameter from 3 to 5 mm at the cephalic end) prefer lentic conditions and are almost completely missing in high-energy flowing water locations that are preferred by pyralids (tubes are between 5 and 10 mm long and 3 mm in diameter). These insect families benefit from inhabiting the tufa by the availability of construction materials of their cases and the necessary space for their development.

Morphological analysis of Drosophila larval peripheral sensory neuron dendrites and axons using genetic mosaics.

PubMed

Karim, M Rezaul; Moore, Adrian W

2011-11-07

Nervous system development requires the correct specification of neuron position and identity, followed by accurate neuron class-specific dendritic development and axonal wiring. Recently the dendritic arborization (DA) sensory neurons of the Drosophila larval peripheral nervous system (PNS) have become powerful genetic models in which to elucidate both general and class-specific mechanisms of neuron differentiation. There are four main DA neuron classes (I-IV)(1). They are named in order of increasing dendrite arbor complexity, and have class-specific differences in the genetic control of their differentiation(2-10). The DA sensory system is a practical model to investigate the molecular mechanisms behind the control of dendritic morphology(11-13) because: 1) it can take advantage of the powerful genetic tools available in the fruit fly, 2) the DA neuron dendrite arbor spreads out in only 2 dimensions beneath an optically clear larval cuticle making it easy to visualize with high resolution in vivo, 3) the class-specific diversity in dendritic morphology facilitates a comparative analysis to find key elements controlling the formation of simple vs. highly branched dendritic trees, and 4) dendritic arbor stereotypical shapes of different DA neurons facilitate morphometric statistical analyses. DA neuron activity modifies the output of a larval locomotion central pattern generator(14-16). The different DA neuron classes have distinct sensory modalities, and their activation elicits different behavioral responses(14,16-20). Furthermore different classes send axonal projections stereotypically into the Drosophila larval central nervous system in the ventral nerve cord (VNC)(21). These projections terminate with topographic representations of both DA neuron sensory modality and the position in the body wall of the dendritic field(7,22,23). Hence examination of DA axonal projections can be used to elucidate mechanisms underlying topographic mapping(7,22,23), as well as

Effects of density on growth, metamorphosis, and survivorship in tadpoles of Scaphiopus holbrooki

DOE Office of Scientific and Technical Information (OSTI.GOV)

Semlitsch, R.D.; Caldwell, J.P.

1982-08-01

Density-dependent aspects of growth, metamorphosis, and survivorship of Scaphiopus holbrooki tadpoles were examined in the laboratory under two experimental regimes. In the first density experiment, the growth index (W) of tadpoles decreased exponentially with density. Mean growth rate varied from 0.023 mL/d at the lowest density to 0.006 mL/d at the highest density. The mean number of days to metamorphic climax was positively associated with the initial density treatment: 27 d at the lowest density to 86 d at the highest density. The body size of tadpoles at metamorphosis showed a concave curvilinear relationship to initial density, indicating tadpoles atmore » the highest densities are apparently capable to growth recovery once released from density stress. The survival of tadpoles decreased exponentially with initial density, from 90% at the lowest density to 20% at the highest initial density. In the second experiment a cross-classified design was used to examine the effects of density and duration of treatment (time) on growth and metamorphosis. Density and time had significant effects on body size at metamorphosis and days to metamorphosis. There was no significant interaction between density and time. These results indicate that the inhibitory effect of density stress varies with the duration of the stress. Scaphiopus holbrooki tadpoles exhibit developmental traits (rapid growth, short larval period, small body size at metamorphosis) that should be favored by natural selection in high density habitats. Dispersability may be a mechanism whereby S. holbrooki can minimize the detrimental effects of density stress.« less

Relations between conspecific density and effects of ultraviolet-b radiation on tadpole size in the striped marsh frog.

PubMed

Mitchell, Toby; Alton, Lesley A; White, Craig R; Franklin, Craig E

2012-12-01

Global increases in ultraviolet-B radiation (UVBR) associated with stratospheric ozone depletion are potentially contributing to the decline of numerous amphibian species around the world. Exposure to UVBR alone reduces survival and induces a range of sublethal effects in embryonic and larval amphibians. When additional environmental stressors are present, UVBR can have compounding negative effects. Thus, examination of the effects of UVBR in the absence of other stressors may substantially underestimate its potential to affect amphibians in natural habitats. We examined the independent and interactive effects of increased UVBR and high conspecific density would have embryonic and larval striped marsh frogs (Limnodynastes peronii). We exposed individuals to a factorial combination of low and high UVBR levels and low, medium, and high densities of striped marsh frog tadpoles. The response variables were time to hatching, hatching success, posthatch survival, burst-swimming performance of tadpoles (maximum instantaneous swim speed following an escape response), and size and morphology of tadpoles. Consistent with results of previous studies, we found that exposure to UVBR alone increased the time to hatching of embryos and reduced the burst-swimming performance and size of tadpoles. Similarly, increasing conspecific density increased the time to hatching of embryos and reduced the size of tadpoles, but had no effect on burst-swimming performance. The negative effect of UVBR on tadpole size was not apparent at high densities of tadpoles. This result suggests that tadpoles living at higher densities may invest relatively less energy in growth and thus have more energy to repair UVBR-induced damage. Lower densities of conspecifics increased the negative effects of UVBR on developing amphibians. Thus, low-density populations, which may include declining populations, may be particularly susceptible to the detrimental effects of increased UVBR and thus may be driven toward

Mechanisms to Explain the Elemental Composition of the Initial Aragonite Shell of Larval Oysters

NASA Astrophysics Data System (ADS)

Haley, Brian A.; Hales, Burke; Brunner, Elizabeth L.; Kovalchik, Kevin; Waldbusser, George G.

2018-04-01

Calcifying organisms face increasing stress from the changing carbonate chemistry of an acidifying ocean, particularly bivalve larvae that live in upwelling regions of the world, such as the coastal and estuarine waters of Oregon (USA). Arguably the first and most significant developmental hurdle faced by larval oysters is formation of their initial prodissoconch I (PDI) shell, upon which further ontological development depends. We measured the minor metal compositions (Sr/Ca, Mg/Ca) of this aragonitic PDI shell and of post-PDI larval Crassostrea gigas shell, as well as the water they were reared in, over ˜20 days for a May and an August cohort in 2011, during which time there was no period of carbonate under-saturation. After testing various methods, we successfully isolated the shell from organic tissue using a 5% active chlorine bleach solution. Elemental compositions (Sr, Mg, C, N) of the shells post-treatment showed that shell Sr/Ca ranged from 1.55 to 1.82 mmol/mol; Mg/Ca from 0.60 to 1.11 mmol/mol, similar to the few comparable published data for larval oyster aragonite compositions. We compare these data in light of possible biomineralization mechanisms: an amorphous calcium carbonate (ACC) path, an intercellular path, and a direct-from-seawater path to shell formation via biologically induced inorganic precipitation of aragonite. The last option provides a mechanistic explanation for: (1) the accelerated precipitation rates of biogenic calcification in the absence of a calcifying fluid; (2) consistently elevated precipitation rates at varying ambient-water saturation states; and (3) the high Ca-selectivity of the early larval calcification despite rapid precipitation rates.

Sampling little fish in big rivers: Larval fish detection probabilities in two Lake Erie tributaries and implications for sampling effort and abundance indices

USGS Publications Warehouse

Pritt, Jeremy J.; DuFour, Mark R.; Mayer, Christine M.; Roseman, Edward F.; DeBruyne, Robin L.

2014-01-01

Larval fish are frequently sampled in coastal tributaries to determine factors affecting recruitment, evaluate spawning success, and estimate production from spawning habitats. Imperfect detection of larvae is common, because larval fish are small and unevenly distributed in space and time, and coastal tributaries are often large and heterogeneous. We estimated detection probabilities of larval fish from several taxa in the Maumee and Detroit rivers, the two largest tributaries of Lake Erie. We then demonstrated how accounting for imperfect detection influenced (1) the probability of observing taxa as present relative to sampling effort and (2) abundance indices for larval fish of two Detroit River species. We found that detection probabilities ranged from 0.09 to 0.91 but were always less than 1.0, indicating that imperfect detection is common among taxa and between systems. In general, taxa with high fecundities, small larval length at hatching, and no nesting behaviors had the highest detection probabilities. Also, detection probabilities were higher in the Maumee River than in the Detroit River. Accounting for imperfect detection produced up to fourfold increases in abundance indices for Lake Whitefish Coregonus clupeaformis and Gizzard Shad Dorosoma cepedianum. The effect of accounting for imperfect detection in abundance indices was greatest during periods of low abundance for both species. Detection information can be used to determine the appropriate level of sampling effort for larval fishes and may improve management and conservation decisions based on larval fish data.

Spinal motor neurons are regenerated after mechanical lesion and genetic ablation in larval zebrafish.

PubMed

Ohnmacht, Jochen; Yang, Yujie; Maurer, Gianna W; Barreiro-Iglesias, Antón; Tsarouchas, Themistoklis M; Wehner, Daniel; Sieger, Dirk; Becker, Catherina G; Becker, Thomas

2016-05-01

In adult zebrafish, relatively quiescent progenitor cells show lesion-induced generation of motor neurons. Developmental motor neuron generation from the spinal motor neuron progenitor domain (pMN) sharply declines at 48 hours post-fertilisation (hpf). After that, mostly oligodendrocytes are generated from the same domain. We demonstrate here that within 48 h of a spinal lesion or specific genetic ablation of motor neurons at 72 hpf, the pMN domain reverts to motor neuron generation at the expense of oligodendrogenesis. By contrast, generation of dorsal Pax2-positive interneurons was not altered. Larval motor neuron regeneration can be boosted by dopaminergic drugs, similar to adult regeneration. We use larval lesions to show that pharmacological suppression of the cellular response of the innate immune system inhibits motor neuron regeneration. Hence, we have established a rapid larval regeneration paradigm. Either mechanical lesions or motor neuron ablation is sufficient to reveal a high degree of developmental flexibility of pMN progenitor cells. In addition, we show an important influence of the immune system on motor neuron regeneration from these progenitor cells. © 2016. Published by The Company of Biologists Ltd.

Natural variability in Drosophila larval and pupal NaCl tolerance.

PubMed

Riedl, Craig A L; Oster, Sara; Busto, Macarena; Mackay, Trudy F C; Sokolowski, Marla B

2016-05-01

The regulation of NaCl is essential for the maintenance of cellular tonicity and functionality, and excessive salt exposure has many adverse effects. The fruit fly, Drosophila melanogaster, is a good osmoregulator and some strains can survive on media with very low or high NaCl content. Previous analyses of mutant alleles have implicated various stress signaling cascades in NaCl sensitivity or tolerance; however, the genes influencing natural variability of NaCl tolerance remain for the most part unknown. Here, we use two approaches to investigate natural variation in D. melanogaster NaCl tolerance. We describe four D. melanogaster lines that were selected for different degrees of NaCl tolerance, and present data on their survival, development, and pupation position when raised on varying NaCl concentrations. After finding evidence for natural variation in salt tolerance, we present the results of Quantitative Trait Loci (QTL) mapping of natural variation in larval and pupal NaCl tolerance, and identify different genomic regions associated with NaCl tolerance during larval and pupal development. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of biological and physicochemical characteristics of larval habitats on the body size of Anopheles gambiae mosquitoes (Diptera: Culicidae) along the Kenyan coast.

PubMed

Mwangangi, Joseph M; Mbogo, Charles M; Muturi, Ephantus J; Nzovua, Joseph G; Kabiru, Ephantus W; Githure, John I; Novak, Robert J; Beier, John C

2007-06-01

The number and productivity of larval habitats ultimately determine the density of adult mosquitoes. The biological and physicochemical conditions at the larval habitat affect larval development hence affecting the adult body size. The influence of biological and physicochemical characteristics on the body size of Anopheles gambiae was assessed in Jaribuni village, Kilifi district along the Kenyan Coast. Ten cages measuring 1 x 1 x 1 m (1 m3) with a netting material were placed in 10 different aquatic habitats, which were positive for anopheline mosquito larvae. Emergent mosquitoes were collected daily by aspiration and the wing lengths were determined by microscopy. In the habitats, physicochemical parameters were assessed: pH, surface debris, algae and emergent plants, turbidity, substrate, nitrate, ammonia, phosphate and chlorophyll a content. A total of 685 anopheline and culicine mosquitoes were collected from the emergent cages. Only female mosquitoes were considered in this study. Among the Anopheles spp, 202 were An. gambiae s.s., eight An. arabiensis, two An. funestus, whereas the Culex spp was composed of 214 Cx. quinquefasciatus, 10 Cx. tigripes, eight Cx. annulioris and one Cx. cumminsii. The mean wing length of the female An. gambiae s.s. mosquitoes was 3.02 mm (n=157), while that of An. arabiensis was 3.09 mm (n=9). There were no associations between the wing lengths and the environmental and chemical parameters, except for a positive correlation between wing length of An. gambiae and chlorophyll a content (r = 0.622). The day on which the mosquitoes emerged was not significant for the anopheline (p = 0.324) or culicine mosquitoes (p = 0.374), because the mosquito emerged from the cages on a daily basis. In conclusion, there was variability in production of emergent mosquitoes from different habitats, which means that there should be targeted control on these habitats based on productivity.

The geometric framework for nutrition reveals interactions between protein and carbohydrate during larval growth in honey bees

PubMed Central

Slater, Garett P.; Rajamohan, Arun; Yocum, George D.; Greenlee, Kendra J.; Bowsher, Julia H.

2017-01-01

ABSTRACT In holometabolous insects, larval nutrition affects adult body size, a life history trait with a profound influence on performance and fitness. Individual nutritional components of larval diets are often complex and may interact with one another, necessitating the use of a geometric framework for elucidating nutritional effects. In the honey bee, Apis mellifera, nurse bees provision food to developing larvae, directly moderating growth rates and caste development. However, the eusocial nature of honey bees makes nutritional studies challenging, because diet components cannot be systematically manipulated in the hive. Using in vitro rearing, we investigated the roles and interactions between carbohydrate and protein content on larval survival, growth, and development in A. mellifera. We applied a geometric framework to determine how these two nutritional components interact across nine artificial diets. Honey bees successfully completed larval development under a wide range of protein and carbohydrate contents, with the medium protein (∼5%) diet having the highest survival. Protein and carbohydrate both had significant and non-linear effects on growth rate, with the highest growth rates observed on a medium-protein, low-carbohydrate diet. Diet composition did not have a statistically significant effect on development time. These results confirm previous findings that protein and carbohydrate content affect the growth of A. mellifera larvae. However, this study identified an interaction between carbohydrate and protein content that indicates a low-protein, high-carb diet has a negative effect on larval growth and survival. These results imply that worker recruitment in the hive would decline under low protein conditions, even when nectar abundance or honey stores are sufficient. PMID:28396492

Hydrodynamic regime determines the feeding success of larval fish through the modulation of strike kinematics

PubMed Central

China, Victor; Levy, Liraz; Elmaliach, Tal

2017-01-01

Larval fishes experience extreme mortality rates, with 99% of a cohort perishing within days after starting to actively feed. While recent evidence suggests that hydrodynamic factors contribute to constraining larval feeding during early ontogeny, feeding is a complex process that involves numerous interacting behavioural and biomechanical components. How these components change throughout ontogeny and how they contribute to feeding remain unclear. Using 339 observations of larval feeding attempts, we quantified the effects of morphological and behavioural traits on feeding success of Sparus aurata larvae during early ontogeny. Feeding success was determined using high-speed videography, under both natural and increased water viscosity treatments. Successful strikes were characterized by Reynolds numbers that were an order of magnitude higher than those of failed strikes. The pattern of increasing strike success with increasing age was driven by the ontogeny of traits that facilitate the transition to higher Reynolds numbers. Hence, the physical growth of a larva plays an important role in its transition to a hydrodynamic regime of higher Reynolds numbers, in which suction feeding is more effective. PMID:28446697

Hydrodynamic regime determines the feeding success of larval fish through the modulation of strike kinematics.

PubMed

China, Victor; Levy, Liraz; Liberzon, Alex; Elmaliach, Tal; Holzman, Roi

2017-04-26

Larval fishes experience extreme mortality rates, with 99% of a cohort perishing within days after starting to actively feed. While recent evidence suggests that hydrodynamic factors contribute to constraining larval feeding during early ontogeny, feeding is a complex process that involves numerous interacting behavioural and biomechanical components. How these components change throughout ontogeny and how they contribute to feeding remain unclear. Using 339 observations of larval feeding attempts, we quantified the effects of morphological and behavioural traits on feeding success of Sparus aurata larvae during early ontogeny. Feeding success was determined using high-speed videography, under both natural and increased water viscosity treatments. Successful strikes were characterized by Reynolds numbers that were an order of magnitude higher than those of failed strikes. The pattern of increasing strike success with increasing age was driven by the ontogeny of traits that facilitate the transition to higher Reynolds numbers. Hence, the physical growth of a larva plays an important role in its transition to a hydrodynamic regime of higher Reynolds numbers, in which suction feeding is more effective. © 2017 The Author(s).

CCDC-55 is required for larval development and distal tip cell migration in Caenorhabditis elegans.

PubMed

Kovacevic, Ismar; Ho, Richard; Cram, Erin J

2012-01-01

The Caenorhabditis elegans distal tip cells (DTCs) are an in vivo model for the study of developmentally regulated cell migration. In this study, we characterize a novel role for CCDC-55, a conserved coiled-coil domain containing protein, in DTC migration and larval development in C. elegans. Although animals homozygous for a probable null allele, ccdc-55(ok2851), display an early larval arrest, RNAi depletion experiments allow the analysis of later phenotypes and suggest that CCDC-55 is needed within the DTC for migration to cease at the end of larval morphogenesis. The ccdc-55 gene is found in an operon with rnf-121 and rnf-5, E3 ubiquitin ligases that target cell migration genes such as the β-integrin PAT-3. Genetic interaction studies using RNAi depletion and the deletion alleles rnf-121(ok848) and rnf-5(tm794) indicate that CCDC-55 and the RNF genes act at least partially in parallel to promote termination of cell migration in the adult DTC. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

CCDC-55 is required for larval development and distal tip cell migration in C. elegans

PubMed Central

Kovacevic, Ismar; Ho, Richard; Cram, Erin J.

2012-01-01

The C. elegans distal tip cells (DTCs) are an in vivo model for the study of developmentally regulated cell migration. In this study we characterize a novel role for CCDC-55, a conserved coiled-coil domain containing protein, in DTC migration and larval development in C. elegans. Although animals homozygous for a probable null allele, ccdc-55(ok2851), display an early larval arrest, RNAi depletion experiments allow the analysis of later phenotypes and suggest that CCDC-55 is needed within the DTC for migration to cease at the end of larval morphogenesis. The ccdc-55 gene is found in an operon with rnf-121 and rnf-5, E3 ubiquitin ligases that target cell migration genes such as the β-integrin PAT-3. Genetic interaction studies using RNAi depletion and the deletion alleles rnf-121(ok848) and rnf-5(tm794) indicate that CCDC-55 and the RNF genes act at least partially in parallel to promote termination of cell migration in the adult DTC. PMID:22285439

Techniques and methods for estimating abundance of larval and metamorphosed sea lampreys in Great Lakes tributaries, 1995 to 2001

USGS Publications Warehouse

Slade, Jeffrey W.; Adams, Jean V.; Christie, Gavin C.; Cuddy, Douglas W.; Fodale, Michael F.; Heinrich, John W.; Quinlan, Henry R.; Weise, Jerry G.; Weisser, John W.; Young, Robert J.

2003-01-01

Before 1995, Great Lakes streams were selected for lampricide treatment based primarily on qualitative measures of the relative abundance of larval sea lampreys, Petromyzon marinus. New integrated pest management approaches required standardized quantitative measures of sea lamprey. This paper evaluates historical larval assessment techniques and data and describes how new standardized methods for estimating abundance of larval and metamorphosed sea lampreys were developed and implemented. These new methods have been used to estimate larval and metamorphosed sea lamprey abundance in about 100 Great Lakes streams annually and to rank them for lampricide treatment since 1995. Implementation of these methods has provided a quantitative means of selecting streams for treatment based on treatment cost and estimated production of metamorphosed sea lampreys, provided managers with a tool to estimate potential recruitment of sea lampreys to the Great Lakes and the ability to measure the potential consequences of not treating streams, resulting in a more justifiable allocation of resources. The empirical data produced can also be used to simulate the impacts of various control scenarios.

Habitat association of larval fish assemblages in the northern Persian Gulf.

PubMed

Rabbaniha, Mahnaz; Molinero, Juan Carlos; López-López, Lucia; Javidpour, Jamileh; Primo, Ana Ligia; Owfi, Feryadoon; Sommer, Ulrich

2015-08-15

We examined the habitat use of fish larvae in the northern Persian Gulf from July 2006 to June 2007. Correspondence Analysis showed significant differences between hydrological seasons in habitat use and structure of larval fish assemblages, while no differences were found regarding abundance among coralline and non-coralline habitats. The observed configuration resulted in part from seasonal reproductive patterns of dominant fish influencing the ratio pelagic:demersal spawned larvae. The ratio increased along with temperature and chlorophyll-a concentration, which likely fostered the reproduction of pelagic spawner fish. The close covariation with temperature throughout hydrographic seasons suggests a leading role of temperature in the seasonal structure of larvae assemblages. Our results provide new insights on fish larval ecology in a traditionally sub-sampled and highly exposed zone to anthropogenic pollution, the northern Persian Gulf, and highlight the potential role of Khark and Kharko Islands in conservation and fishery management in the area. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evaluation of nine genotypes of oilseed rape (Brassica napus L.) for larval infestation and performance of rape stem weevil (Ceutorhynchus napi Gyll.)

PubMed Central

Becker, Heiko C.; Vidal, Stefan

2017-01-01

The rape stem weevil, Ceutorhynchus napi Gyll., is a serious pest of winter oilseed rape (Brassica napus L.) crops in Europe causing severe yield loss. In currently used oilseed rape cultivars no resistance to C. napi has been identified. Resynthesized lines of B. napus have potential to broaden the genetic variability and may improve resistance to insect pests. In this study, the susceptibility to C. napi of three cultivars, one breeding line and five resynthesized lines of oilseed rape was compared in a semi-field plot experiment under multi-choice conditions. Plant acceptance for oviposition was estimated by counting the number of C. napi larvae in stems. The larval instar index and the dry body mass were assessed as indicators of larval performance. The extent of larval feeding within stems was determined by the stem injury coefficient. Morphological stem traits and stem contents of glucosinolates were assessed as potential mediators of resistance. The resynthesized line S30 had significantly fewer larvae than the cultivars Express617 and Visby and the resynthesized lines L122 and L16. The low level of larval infestation in S30 was associated with a low larval instar and stem injury index. Low numbers of larvae were not correlated with the length or diameter of stems, and the level of stem glucosinolates. As indicated by the low larval infestation and slow larval development the resistance of S30 to C. napi is based on both antixenotic and antibiotic properties of the genotypes. The resynthesized line S30 should therefore be introduced into B. napus breeding programs to enhance resistance against C. napi. PMID:28686731

Species composition, larval habitats, seasonal occurrence and distribution of potential malaria vectors and associated species of Anopheles (Diptera: Culicidae) from the Republic of Korea

PubMed Central

2010-01-01

Background Larval mosquito habitats of potential malaria vectors and related species of Anopheles from three provinces (Gyeonggi, Gyeongsangbuk, Chungcheongbuk Provinces) of the Republic of Korea were surveyed in 2007. This study aimed to determine the species composition, seasonal occurrence and distributions of Anopheles mosquitoes. Satellite derived normalized difference vegetation index data (NDVI) was also used to study the seasonal abundance patterns of Anopheles mosquitoes. Methods Mosquito larvae from various habitats were collected using a standard larval dipper or a white plastic larval tray, placed in plastic bags, and were preserved in 100% ethyl alcohol for species identification by PCR and DNA sequencing. The habitats in the monthly larval surveys included artificial containers, ground depressions, irrigation ditches, drainage ditches, ground pools, ponds, rice paddies, stream margins, inlets and pools, swamps, and uncultivated fields. All field-collected specimens were identified to species, and relationships among habitats and locations based on species composition were determined using cluster statistical analysis. Results In about 10,000 specimens collected, eight species of Anopheles belonging to three groups were identified: Hyrcanus Group - Anopheles sinensis, Anopheles kleini, Anopheles belenrae, Anopheles pullus, Anopheles lesteri, Anopheles sineroides; Barbirostris Group - Anopheles koreicus; and Lindesayi Group - Anopheles lindesayi japonicus. Only An. sinensis was collected from all habitats groups, while An. kleini, An. pullus and An. sineroides were sampled from all, except artificial containers. The highest number of Anopheles larvae was found in the rice paddies (34.8%), followed by irrigation ditches (23.4%), ponds (17.0%), and stream margins, inlets and pools (12.0%). Anopheles sinensis was the dominant species, followed by An. kleini, An. pullus and An. sineroides. The monthly abundance data of the Anopheles species from three

The ecology and larval habitats characteristics of anopheline mosquitoes (Diptera: Culicidae) in Aligudarz County (Luristan province, western Iran)

PubMed Central

Amani, Hamid; Yaghoobi-Ershadi, Mohammad Reza; Kassiri, Hamid

2014-01-01

Objective To determine ecology and characteristics of the larval habitats of the genus Anopheles (Dipetra: Culicidae) in Aligudarz County, western Iran. Methods This descriptive cross-sectional research was carried out to study the anopheline larvae ecology in seven rural districts, Aligudarz County, from late April to late November 1997. Larvae were captured using the dipping method. Larval breeding places characteristics were noted according to water situation (turbid or clean, stagnant or running), substrate type, site type (man-made or natural), sunlight situation, site situation (transient or permanent, with or without vegetation). Results A total of 9 620 3rd and 4th instar larvae of Anopheles from 115 breeding places in 22 villages were captured, which belonged to the following species: Anopheles stephensi, Anopheles d'thali, Anopheles apoci, Anopheles superpictus (forms A and B), Anopheles marterii sogdianus, Anopheles turkhodi, Anopheles maculipennis S.L and Anopheles claviger. Anopheles stephensi, Anopheles maculipennis S.L and Anopheles apoci were collected for the first time in this county. Anopheles superpictus (93.18%) was the most prevailed one and dispersed over the entire region. Larval habitats consisted of nine natural and three artificial larval habitats. The most important larval habitats were river edges (54.8%), rice fields (12.2%), and grassland (8.7%) with permanent or transient, stagnant or running and clean water, with or without vegetation, sand or mud substrate in full sunlight area. Conclusions Regarding this research, river edges and rice fields are the most important breeding places of malaria vectors in Aligudarz County. It is worthy of note in larvicidal programs. PMID:25183088

Larval spicules, cilia, and symmetry as remnants of indirect development in the direct developing sea urchin Heliocidaris erythrogramma.

PubMed

Emlet, R B

1995-02-01

Nonfeeding larvae of the echinoid Heliocidaris erythrogramma were raised in culture and examined for expression of a larval skeleton and for the arrangement of the ciliated band. Opaque larvae were fixed, cleared, and examined under polarized light for evidence of calcification. By 35 hr after fertilization (at 22 degrees C), a pair of triradiate spicules was present at the posterior end of the larvae. Each member of this pair formed a fenestrated spicule as it grew laterally. This pair and another pair which formed subsequently, were arranged across a plane of bilateral symmetry orthagonal to the juvenile oral aboral axis. These paired larval spicules can be identified as reduced expressions of postoral and posterodorsal rods found in plutei, and their expression indicates that the juvenile rudiment of H. erythrogramma forms on the left side and that larval body axes are conserved in this modified larva. By 44 hr the ciliated band formed as an incomplete transverse loop of three segments at the posterior end and on the dorsal surface of the ovoid larva. Cilia in these segments grew to lengths of 45-50 microns, longer than other swimming and feeding cilia reported for echinoderm larvae. Band segments are interpreted as expressions of epaulettes (specialized swimming bands) rather than the feeding ciliated band of the pluteus. The ciliated band segments and the larval spicules are both bilaterally symmetrical with respect to the same plane and indicate conserved larval bilateral symmetry despite the major asymmetry of the fates of cells on either side of this plane in their contribution to juvenile development.

Safety of methionine, a novel biopesticide, to adult and larval honey bees (Apis mellifera L.).

PubMed

Weeks, Emma N I; Schmehl, Daniel R; Baniszewski, Julie; Tomé, Hudson V V; Cuda, James P; Ellis, James D; Stevens, Bruce R

2018-03-01

Methionine is an essential/indispensible amino acid nutrient required by adult and larval honey bees (Apis mellifera L. [Hymenoptera: Apidae]). Bees are unable to rear broods on pollen deficient in methionine, and reportedly behaviorally avoid collecting pollen or nectar from florets deficient in methioinine. In contrast, it has been demonstrated that methionine is toxic to certain pest insects; thus it has been proposed as an effective biopesticide. As an ecofriendly integrated pest management agent, methionine boasts a novel mode of action differentiating it from conventional pesticides, while providing non-target safety. Pesticides that minimize collateral effects on bees are desirable, given the economic and ecological concerns about honey bee health. The aim of the present study was to assess the potential impact of the biopesticide methionine on non-target adult and larval honey bees. Acute contact adult toxicology bioassays, oral adult assessments and chronic larval toxicity assessments were performed as per U.S. Environmental Protection Agency (EPA) requirements. Our results demonstrated that methionine fits the U.S. EPA category of practically nontoxic (i.e. lethal dose to 50% mortality or LD 50 > 11µg/bee) to adult honey bees. The contact LD 50 was > 25µg/bee and the oral LD 50 was > 100µg/bee. Mortality was observed in larval bees that ingested DL-methionine (effective concentration to 50% mortality or EC 50 560µg/bee). Therefore, we conclude that methionine poses little threat to the health of the honey bee, due to unlikely exposure at concentrations shown to elicit toxic effects. Copyright © 2017 Elsevier Inc. All rights reserved.

Host plant choice in the comma butterfly-larval choosiness may ameliorate effects of indiscriminate oviposition.

PubMed

Gamberale-Stille, Gabriella; Söderlind, Lina; Janz, Niklas; Nylin, Sören

2014-08-01

In most phytophagous insects, the larval diet strongly affects future fitness and in species that do not feed on plant parts as adults, larval diet is the main source of nitrogen. In many of these insect-host plant systems, the immature larvae are considered to be fully dependent on the choice of the mothers, who, in turn, possess a highly developed host recognition system. This circumstance allows for a potential mother-offspring conflict, resulting in the female maximizing her fecundity at the expense of larval performance on suboptimal hosts. In two experiments, we aimed to investigate this relationship in the polyphagous comma butterfly, Polygonia c-album, by comparing the relative acceptance of low- and medium-ranked hosts between females and neonate larvae both within individuals between life stages, and between mothers and their offspring. The study shows a variation between females in oviposition acceptance of low-ranked hosts, and that the degree of acceptance in the mothers correlates with the probability of acceptance of the same host in the larvae. We also found a negative relationship between stages within individuals as there was a higher acceptance of lower ranked hosts in females who had abandoned said host as a larva. Notably, however, neonate larvae of the comma butterfly did not unconditionally accept to feed from the least favorable host species even when it was the only food source. Our results suggest the possibility that the disadvantages associated with a generalist oviposition strategy can be decreased by larval participation in host plant choice. © 2013 Institute of Zoology, Chinese Academy of Sciences.

Effect of Moringa oleifera flower extract on larval trypsin and acetylcholinesterase activities in Aedes aegypti.

PubMed

Pontual, Emmanuel Viana; Napoleão, Thiago Henrique; Dias de Assis, Caio Rodrigo; de Souza Bezerra, Ranilson; Xavier, Haroudo Satiro; Navarro, Daniela Maria do Amaral Ferraz; Coelho, Luana Cassandra Breitenbach Barroso; Paiva, Patrícia Maria Guedes

2012-03-01

Aedes aegypti control is crucial to reducing dengue fever. Aedes aegypti larvae have developed resistance to organophosporous insecticides and the use of natural larvicides may help manage larval resistance by increasing elements in insecticide rotation programs. Here, we report on larvicidal activity of Moringa oleifera flower extract against A. aegypti L(1), L(2), L(3), and L(4) as well as the effect of flower extract on gut trypsin and whole-larval acetylcholinesterase from L(4.) In addition, the heated flower extract was investigated for larvicidal activity against L(4) and effect on larval gut trypsin. Moringa oleifera flower extract contains a proteinaceous trypsin inhibitor (M. oleifera flower trypsin inhibitor, MoFTI), triterpene (β-amyrin), sterol (β-sitosterol) as well as flavonoids (kaempferol and quercetin). Larvicidal activity was detected against L(2), L(3), and L(4) (LC(50) of 1.72%, 1.67%, and 0.92%, respectively). Flower extract inhibited L(4) gut trypsin (MoFTI K(i) = 0.6 nM) and did not affect acetylcholinesterase activity. In vivo assay showed that gut trypsin activity from L(4) treated with M. oleifera flower extract decreased over time (0-1,440 min) and was strongly inhibited (98.6%) after 310 min incubation; acetylcholinesterase activity was not affected. Thermal treatment resulted in a loss of trypsin inhibitor and larvicidal activities, supporting the hypothesis that flower extract contains a proteinaceous trypsin inhibitor that may be responsible for the deleterious effects on larval mortality. © 2012 Wiley Periodicals, Inc.

A comparison of spring larval fish assemblages in the Strait of Georgia (British Columbia, Canada) between the early 1980s and late 2000s

NASA Astrophysics Data System (ADS)

Guan, Lu; Dower, John F.; McKinnell, Skip M.; Pepin, Pierre; Pakhomov, Evgeny A.; Hunt, Brian P. V.

2015-11-01

The concentration and composition of the larval fish assemblage in the Strait of Georgia (British Columbia, Canada) has changed between the early 1980s (1980 and 1981) and the late 2000s (2007, 2009 and 2010). During both periods, the spring larval fish assemblages were dominated by pelagic species: Clupea pallasi (Pacific herring), Merluccius productus (Pacific hake), Leuroglossus schmidti (northern smoothtongue) and Theragra chalcogramma (walleye Pollock). The average concentration of Merluccius productus, Theragra chalcogramma, Leuroglossus schmidti, and Sebastes spp. declined between the early 1980s and the late 2000s; in contrast, the absolute concentration and proportion of Pleuronectidae and several demersal fish taxa increased in the spring larval assemblage. Examination of the associations between larval fish assemblages and environmental fluctuations suggests that large-scale climate processes are potential contributors to variations in overall larval concentrations of the dominant taxa and assemblage composition in the Strait of Georgia.

Snail shells as larval habitat of Limatus durhamii (Diptera: Culicidae) in the Yungas of Argentina.

PubMed

Mangudo, Carolina; Campos, Raúl E; Rossi, Gustavo C; Gleiser, Raquel M

2017-03-01

The shells of dead snails collect water from rainfalls producing aquatic microenvironments called gastrotelmata. These habitats are small and hold simple detritus based on animal communities, being rotifers and culicids the most studied. Although a high diversity of aquatic microhabitats has been reported as larval habitats of mosquitoes in Argentina, the shell of snails has not been investigated yet. We report the shells of three species of native Megalobulimus genus as larval habitats of a neotropical mosquito and suspected vector of bunyaviruses, Limatus durhamii, and describe these microhabitats in the Yungas forest of Argentina. Copyright © 2016 Elsevier B.V. All rights reserved.

A SoxC gene related to larval shell development and co-expression analysis of different shell formation genes in early larvae of oyster.

PubMed

Liu, Gang; Huan, Pin; Liu, Baozhong

2017-06-01

Among the potential larval shell formation genes in mollusks, most are expressed in cells surrounding the shell field during the early phase of shell formation. The only exception (cgi-tyr1) is expressed in the whole larval mantle and thus represents a novel type of expression pattern. This study reports another gene with such an expression pattern. The gene encoded a SoxC homolog of the Pacific oyster Crassostrea gigas and was named cgi-soxc. Whole-mount in situ hybridization revealed that the gene was highly expressed in the whole larval mantle of early larvae. Based on its spatiotemporal expression, cgi-soxc is hypothesized to be involved in periostracum biogenesis, biomineralization, and regulation of cell proliferation. Furthermore, we investigated the interrelationship between cgi-soxc expression and two additional potential shell formation genes, cgi-tyr1 and cgi-gata2/3. The results confirmed co-expression of the three genes in the larval mantle of early D-veliger. Nevertheless, cgi-gata2/3 was only expressed in the mantle edge, and the other two genes were expressed in all mantle cells. Based on the spatial expression patterns of the three genes, two cell groups were identified from the larval mantle (tyr1 + /soxc + /gata2/3 + cells and tyr1 + /soxc + /gata2/3 - cells) and are important to study the differentiation and function of this tissue. The results of this study enrich our knowledge on the structure and function of larval mantle and provide important information to understand the molecular mechanisms of larval shell formation.

Cottonwood Leaf Beetle (Coleoptera: Chrysomelidae) Larval Performance on Eight Populus Clones

Treesearch

David R. Coyle; Joel D. McMillin; Richard B. Hall; Elwood R. Hart

2001-01-01

Abstract: The cottonwood leaf beetle, Chrysomela scripta F., is the most serious defoliator of young plantation-grown Populus in the eastern United States, yet there is a paucity of data on larval feeding performance across Populus clones used in tree breeding. Field experiments were conducted in 1998 and 1999...

Survey of larval fish in the Michigan waters of Lake Erie, 1975 and 1976. Final report, 1975-1978

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waybrant, R.C.; Shauver, J.M.

1979-08-01

Surveys in 1975 and 1976 in the Michigan waters of Lake Erie assessed the relative abundance and distribution of larval fish. Seasonal fluctuations, patterns of distribution, and depth preferences were noted for the 24 larval fish taxa identified. Special emphasis was placed on four target species, walleye (Stizostedion vitreum), yellow perch (Perca flavescens), white bass (Morone chrysops) and channel catfish (Ictalurus punctatus). Of these 4 species only yellow perch and white bass were found more than occasionally. Of the remaining 20 species collected during the study only 5 were regularly captured. The northern and southern extremes of the study areamore » held many more fish than the central portion. The 0- to 12-ft depth zone had the largest concentrations of larval fish and concentrations gradually decreased as the depth increased.« less

Staggered larval time-to-hatch and insecticide resistance in the major malaria vector Anopheles gambiae S form.

PubMed

Kaiser, Maria L; Koekemoer, Lizette L; Coetzee, Maureen; Hunt, Richard H; Brooke, Basil D

2010-12-14

Anopheles gambiae is a major vector of malaria in the West African region. Resistance to multiple insecticides has been recorded in An. gambiae S form in the Ahafo region of Ghana. A laboratory population (GAH) established using wild material from this locality has enabled a mechanistic characterization of each resistance phenotype as well as an analysis of another adaptive characteristic - staggered larval time-to-hatch. Individual egg batches obtained from wild caught females collected from Ghana and the Republic of the Congo were monitored for staggered larval time-to-hatch. In addition, early and late larval time-to-hatch sub-colonies were selected from GAH. These selected sub-colonies were cross-mated and their hybrid progeny were subsequently intercrossed and back-crossed to the parental strains. The insecticide susceptibilities of the GAH base colony and the time-to-hatch selected sub-colonies were quantified for four insecticide classes using insecticide bioassays. Resistance phenotypes were mechanistically characterized using insecticide-synergist bioassays and diagnostic molecular assays for known reduced target-site sensitivity mutations. Anopheles gambiae GAH showed varying levels of resistance to all insecticide classes. Metabolic detoxification and reduced target-site sensitivity mechanisms were implicated. Most wild-caught families showed staggered larval time-to-hatch. However, some families were either exclusively early hatching or late hatching. Most GAH larvae hatched early but many egg batches contained a proportion of late hatching larvae. Crosses between the time-to-hatch selected sub-colonies yielded ambiguous results that did not fit any hypothetical models based on single-locus Mendelian inheritance. There was significant variation in the expression of insecticide resistance between the time-to-hatch phenotypes. An adaptive response to the presence of multiple insecticide classes necessarily involves the development of multiple resistance

Influence of summer conditions on the larval fish assemblage in the eastern coast of Tunisia (Ionian Sea, Southern Mediterranean)

NASA Astrophysics Data System (ADS)

Zarrad, Rafik; Alemany, Francisco; Rodriguez, José-María; Jarboui, Othman; Lopez-Jurado, José-Luis; Balbin, Rosa

2013-02-01

The structure of the summer larval fish assemblage off the eastern coast of Tunisia and its relation to environmental conditions was studied, from ichthyoplankton samples taken during a survey conducted between 23rd June and 9th July 2008. A total of 68 larval fish taxa were identified, 52 to species level. The taxonomic composition and abundance of the larval fish assemblage showed high spatial heterogeneity. Mesoscale hydrographic features, such as eddies, seem to play an important role in the spatial distribution of fish larvae in the area, enhancing concentration and retention. The larval fish assemblage was dominated by the small pelagic species Sardinella aurita (26.6% of the total larval fish abundance), followed by Engraulis encrasicolus (22.6%), Spicara spp. (8.6%) and Mullus barbatus (6.8%). Shannon-Weaver index (H') ranged between 0 and 2.62. The highest values were found offshore, at 95 miles east of Sousse, over depths around 250 m. The diversity was higher in this region as a result of transport by currents and retention by eddies. It has also been shown that the eastern coast of Tunisia is a spawning ground for the tuna species Auxis rochei, Thunnus thynnus and Thunnus alalunga. Larvae of mesopelagic fishes represented 5.46% of the total abundance, with Cyclothone braueri, Ceratoscopelus maderensis and Lampanyctus crocodilus being the most important species. Canonical correspondence analysis (CCA) indicated that depth was the most important environmental factor in explaining species distribution.

Integrated control of peridomestic larval habitats of Aedes and Culex mosquitoes (Diptera: Culicidae) in atoll villages of French Polynesia.

PubMed

Lardeux, Frederic; Sechan, Yves; Loncke, Stepiiane; Deparis, Xavier; Cheffort, Jules; Faaruia, Marc

2002-05-01

An integrated larval mosquito control program was carried out in Tiputa village on Rangiroa atoll of French Polynesia. Mosquito abundance before and after treatment was compared with the abundance in an untreated village. Mosquito larval habitats consisted of large concrete or polyurethane cisterns, wells, and 200-liter drums. Depending on the target species, larval habitat category, its configuration, and purpose (drinking consumption or not), abatement methods consisted of sealing the larval habitats with mosquito gauze, treating them with 1% Temephos, covering the water with a 10-cm thick layer of polystyrene beads or introducing fish (Poecillia reticulata Rosen & Bailey). All premises of the chosen village were treated and a health education program explained basic mosquito ecology and the methods of control. A community health agent was trained to continue the control program at the end of the experiment. Entomological indices from human bait collections and larval surveys indicated that mosquito populations were reduced significantly, compared with concurrent samples from the untreated control village, and that mosquito control remained effective for 6 mo after treatment. Effects of the treatment were noticed by the inhabitants in terms of a reduction in the number of mosquito bites. In the Polynesian context, such control programs may succeed in the long-term only if strong political decisions are taken at the village level, if a community member is designated as being responsible for maintaining the program, and if the inhabitants are motivated sufficiently by the mosquito nuisance to intervene.

Behavioral and physiological responses to prey match-mismatch in larval herring

NASA Astrophysics Data System (ADS)

Illing, Björn; Moyano, Marta; Berg, Julia; Hufnagl, Marc; Peck, Myron A.

2018-02-01

The year-class success of Atlantic herring (Clupea harengus) spawning in the autumn/winter in the North Sea (NSAS stock) and in the spring in the western Baltic Sea (WBSS) appears driven by prey match-mismatch dynamics affecting the survival of larvae during the first weeks of life. To better understand and model the consequences of prey match-mismatch from an individual-based perspective, we measured aspects of the physiology and behavior of NSAS and WBSS herring larvae foraging in markedly different prey concentrations. When matched with prey (ad libitum concentrations of the copepod Acartia tonsa) larval growth, swimming activity, nutritional condition and metabolic rates were relatively high. When prey was absent (mismatch), swimming and feeding behavior rapidly declined within 2 and 4 days, for WBSS and NSAS larvae, respectively, concomitant with reductions in nutritional (RNA-DNA ratio) and somatic (weight-at-length) condition. After several days without prey, respiration measurements made on WBSS larvae suggested metabolic down-regulation (8-34%). An individual-based model depicting the time course of these Behavioral and physiological responses suggested that 25-mm larvae experiencing a mismatch would survive 25-33% (10, 7 °C) longer than 12-mm larvae. Warmer temperatures exacerbate starvation-induced decrements in performance. Without Behavioral and metabolic adjustments, survival of 25-mm larvae would be reduced from 8 to 6 days at 7 °C. Our findings highlight how adaptive Behavioral and physiological responses are tightly linked to prey match-mismatch dynamics in larval herring and how these responses can be included in models to better explore how bottom-up processes regulate larval fish growth and survival.

Ecological Support of Larval Fish During Multigenerational Studies on Space Station

NASA Technical Reports Server (NTRS)

Taub, Frieda B.

1998-01-01

Live, microscopic food is required by larval Zebrafish, Danio rerio, which are candidates for the Aquatic Habitat of the Space Station Biological Research Project (SSBRP). Zebrafish have proven to be convenient research animals, and their embryology and genetics are extensively documented. Their ability to mature at 3 months of age, and the transparent eggs which hatches in 2 days, are attractive attributes for space research. Among the goals of the SSBRP Aquatic Habitat is the ability to study three generations, with the objective of maintaining adults, their offspring, and the maintaining of these offspring through maturity and spawning. For Zebrafish, it is anticipated that sexually mature fish (PI) would be delivered to Space Station and spawned in space. The challenge would be it to provide appropriate microscopic foods for the offspring (FI), and 3 months later for the next generation (F2); if these were raised to maturity and bred, live foods would be required at approximately 6 months. In laboratories where Zebrafish are traditionally reared, the larval foods are the protozoan Parameciwn micromultinucleatwn and later brine shrimp Artemia nauplii. Under normal laboratory conditions, the rearing of these foods are relatively easy, although time consuming because of the food organisms must be separated from their rearing medium which is discarded. A freshwater food chain that would ensur-e healthy on- orbit research animals is needed. ne food chain should (a) be reared in conditions that are compatible with the larval fish (water chemistry, pH, temperature and light), (b) assist in maintaining water quality (by removing ammonia, nitrate, phosphate, carbon dioxide, and bacteria) and (c) be convenient for the space crew (minimize handling and waste production).

3D Finite Element Electrical Model of Larval Zebrafish ECG Signals

PubMed Central

Crowcombe, James; Dhillon, Sundeep Singh; Hurst, Rhiannon Mary; Egginton, Stuart; Müller, Ferenc; Sík, Attila; Tarte, Edward

2016-01-01

Assessment of heart function in zebrafish larvae using electrocardiography (ECG) is a potentially useful tool in developing cardiac treatments and the assessment of drug therapies. In order to better understand how a measured ECG waveform is related to the structure of the heart, its position within the larva and the position of the electrodes, a 3D model of a 3 days post fertilisation (dpf) larval zebrafish was developed to simulate cardiac electrical activity and investigate the voltage distribution throughout the body. The geometry consisted of two main components; the zebrafish body was modelled as a homogeneous volume, while the heart was split into five distinct regions (sinoatrial region, atrial wall, atrioventricular band, ventricular wall and heart chambers). Similarly, the electrical model consisted of two parts with the body described by Laplace’s equation and the heart using a bidomain ionic model based upon the Fitzhugh-Nagumo equations. Each region of the heart was differentiated by action potential (AP) parameters and activation wave conduction velocities, which were fitted and scaled based on previously published experimental results. ECG measurements in vivo at different electrode recording positions were then compared to the model results. The model was able to simulate action potentials, wave propagation and all the major features (P wave, R wave, T wave) of the ECG, as well as polarity of the peaks observed at each position. This model was based upon our current understanding of the structure of the normal zebrafish larval heart. Further development would enable us to incorporate features associated with the diseased heart and hence assist in the interpretation of larval zebrafish ECGs in these conditions. PMID:27824910

Larval development to the first eighth zoeal stages in the deep-sea caridean shrimp Plesionika grandis Doflein, 1902 (Crustacea, Decapoda, Pandalidae).

PubMed

Jiang, Guo-Chen; Chan, Tin-Yam; Shih, Tung-Wei

2017-01-01

The larvae of the deep-sea pandalid shrimp Plesionika grandis Doflein, 1902 were successfully reared in the laboratory for the first time. The larvae reached the eighth zoeal stage in 36 days, both of which are longest records for the genus. Early larval stages of P. grandis bear the general characters of pandalid shrimps and differ from the other two species of Plesionika with larval morphology known in the number of spines on the anteroventral margin of carapace, number of tubercles on antennule, endopod segmentation in antenna, and third maxilliped setation. Although members in Plesionika are often separated into species groups, members of the same species group do not necessarily have similar early larval morphology. Since the zoea VIII of P. grandis still lacks pleopods and fifth pereiopod, this shrimp likely has at least 12 zoeal stages and a larval development of 120 days.

Functional Assays and Alternative Species: Using Larval Zebrafish in Developmental Neurotoxicity Screening

EPA Science Inventory

The U.S. Environmental Protection Agency is developing and evaluating methods to screen and prioritize large numbers of chemicals for developmental toxicity. Towards this goal, we are exploring methods to detect developmental neurotoxicants in very young larval zebrafish. We have...

Pheromone modulates two phenotypically plastic traits - adult reproduction and larval diapause - in the nematode Caenorhabditis elegans.

PubMed

Wharam, Barney; Weldon, Laura; Viney, Mark

2017-08-22

Animals use information from their environment to make decisions, ultimately to maximize their fitness. The nematode C. elegans has a pheromone signalling system, which hitherto has principally been thought to be used by worms in deciding whether or not to arrest their development as larvae. Recent studies have suggested that this pheromone can have other roles in the C. elegans life cycle. Here we demonstrate a new role for the C. elegans pheromone, showing that it accelerates hermaphrodites' reproductive rate, a phenomenon which we call pheromone-dependent reproductive plasticity (PDRP). We also find that pheromone accelerates larval growth rates, but this depends on a live bacterial food source, while PDRP does not. Different C. elegans strains all show PDRP, though the magnitude of these effects differ among the strains, which is analogous to the diversity of arrested larval phenotypes that this pheromone also induces. Using a selection experiment we also show that selection for PDRP or for larval arrest affects both the target and the non-target trait, suggesting that there is cross-talk between these two pheromone-dependent traits. Together, these results show that C. elegans' pheromone is a signal that acts at two key life cycle points, controlling alternative larval fates and affecting adult hermaphrodites' reproduction. More broadly, these results suggest that to properly understand and interpret the biology of pheromone signalling in C. elegans and other nematodes, the life-history biology of these organisms in their natural environment needs to be considered.

Purification and analyses of the specificity of two putative diagnostic antigens for larval cyathostomin infection in horses.

PubMed

Dowdall, S M J; Proudman, C J; Love, S; Klei, T R; Matthews, J B

2003-12-01

Cyathostomins are important equine gastrointestinal parasites. Mass emergence of mucosal stage larvae causes a potentially fatal colitis. Mucosal stages are undetectable non-invasively. An assay that would estimate mucosal larval stage infection would greatly assist in treatment, control and prognosis. Previously, we identified two putative diagnostic antigens (20 and 25 kDa) in somatic larval preparations. Here, we describe their purification and antigen-specific IgG(T) responses to them. Western blots confirmed the purity of the antigens and showed that epitopes in the 20 kDa complex were specific to larval cyathostomins. No cross-reactive antigens appeared to be present in Parascaris equorum or Strongyloides westeri species. Low levels of cross-reactivity were observed in Strongylus edentatus and Strongylus vulgaris species. Use of purified antigens greatly reduced background binding in equine sera. These results indicate that both antigen complexes may be of use in a diagnostic assay.

Isolation of bacterial metabolites as natural inducers for larval settlement in the marine polychaete Hydroides elegans (Haswell).

PubMed

Harder, Tilmann; Lau, Stanley Chun Kwan; Dahms, Hans-Uwe; Qian, Pei-Yuan

2002-10-01

The bacterial component of marine biofilms plays an important role in the induction of larval settlement in the polychaete Hydroides elegans. In this study, we provide experimental evidence that bacterial metabolites comprise the chemical signal for larval settlement. Bacteria were isolated from biofilms, purified and cultured according to standard procedures. Bacterial metabolites were isolated from spent culture broth by chloroform extraction as well as by closed-loop stripping and adsorption of volatile components on surface-modified silica gel. A pronounced biological activity was exclusively observed when concentrated metabolites were adsorbed on activated charcoal. Larvae did not respond to waterbome metabolites when prevented from contacting the bacterial film surface. These results indicate that an association of the chemical signal with a sorbent-like substratum may be an essential cofactor for the expression of biological activity. The functional role of bacterial exopolymers as an adsorptive matrix for larval settlement signals is discussed.

Impact of stress, fear and anxiety on the nociceptive responses of larval zebrafish.

PubMed

Lopez-Luna, Javier; Al-Jubouri, Qussay; Al-Nuaimy, Waleed; Sneddon, Lynne U

2017-01-01

Both adult and larval zebrafish have been demonstrated to show behavioural responses to noxious stimulation but also to potentially stress- and fear or anxiety- eliciting situations. The pain or nociceptive response can be altered and modulated by these situations in adult fish through a mechanism called stress-induced analgesia. However, this phenomenon has not been described in larval fish yet. Therefore, this study explores the behavioural changes in larval zebrafish after noxious stimulation and exposure to challenges that can trigger a stress, fear or anxiety reaction. Five-day post fertilization zebrafish were exposed to either a stressor (air emersion), a predatory fear cue (alarm substance) or an anxiogenic (caffeine) alone or prior to immersion in acetic acid 0.1%. Pre- and post-stimulation behaviour (swimming velocity and time spent active) was recorded using a novel tracking software in 25 fish at once. Results show that larvae reduced both velocity and activity after exposure to the air emersion and alarm substance challenges and that these changes were attenuated using etomidate and diazepam, respectively. Exposure to acetic acid decreased velocity and activity as well, whereas air emersion and alarm substance inhibited these responses, showing no differences between pre- and post-stimulation. Therefore, we hypothesize that an antinociceptive mechanism, activated by stress and/or fear, occur in 5dpf zebrafish, which could have prevented the larvae to display the characteristic responses to pain.

Morphology of First Zoeal Stage of Four Genera of Alvinocaridid Shrimps from Hydrothermal Vents and Cold Seeps: Implications for Ecology, Larval Biology and Phylogeny

PubMed Central

Hernández-Ávila, Iván; Cambon-Bonavita, Marie-Anne; Pradillon, Florence

2015-01-01

Alvinocaridid shrimps are endemic species inhabiting hydrothermal vents and/or cold seeps. Although indirect evidences (genetic and lipid markers) suggest that their larval stages disperse widely and support large scale connectivity, larval life and mechanisms underlying dispersal are unknown in alvinocaridids. Here we provide for the first time detailed descriptions of the first larval stage (zoea I) of four alvinocaridid species: Rimicaris exoculata and Mirocaris fortunata from the Mid-Atlantic Ridge, Alvinocaris muricola from the Congo Basin and Nautilocaris saintlaurentae from the Western Pacific. The larvae were obtained from onboard hatching of brooding females (either at atmospheric pressure or at habitat pressure in hyperbaric chambers) and from the water column near adult habitats, sampled with plankton pumps or sediment traps. Major characteristics of the alvinocaridid larvae include undeveloped mandible and almost complete absence of setation in the inner margin of the mouth parts and maxillipeds. Although the larvae are very similar between the four species studied, some morphological features could be used for species identification. In addition, undeveloped mouthparts and the large amount of lipid reserves strongly support the occurrence of primary lecithotrophy in the early stage of alvinocaridids. Although lecithotrophy in decapod crustaceans is usually associated with abbreviated larval development, as a mechanism of larval retention, morphological and physiological evidences suggest the occurrence of an extended and lecithotrophic larval stage in the Alvinocarididae. These traits permit the colonization of widely dispersed and fragmented environments of hydrothermal vents and cold seeps. Distribution of larval traits along the phylogenetic reconstruction of the Alvinocarididae and related families suggest that lecithotrophy/planktotrophy and extended/abbreviated development have evolved independently along related families in all potential

Dietary supplementation with vitamin k affects transcriptome and proteome of Senegalese sole, improving larval performance and quality.

PubMed

Richard, Nadège; Fernández, Ignacio; Wulff, Tune; Hamre, Kristin; Cancela, Leonor; Conceição, Luis E C; Gavaia, Paulo J

2014-10-01

Nutritional factors strongly influence fish larval development and skeletogenesis, and may induce skeletal deformities. Vitamin K (VK) has been largely disregarded in aquaculture nutrition, despite its important roles in bone metabolism, in γ-carboxylation of Gla proteins, and in regulating gene expression through the pregnane X receptor (Pxr). Since the mechanisms mediating VK effects over skeletal development are poorly known, we investigated the effects of VK-supplementation on skeletal development in Senegalese sole larvae, aiming to identify molecular pathways involved. Larvae were fed live preys enriched with graded levels of phylloquinone (PK) (0, 50, and 250 mg kg(-1)) and survival rate, growth, VK contents, calcium content and incidence of skeletal deformities were determined, revealing an improvement of larval performance and decreasing the incidence of deformities in VK-supplemented groups. Comparative proteome analysis revealed a number of differentially expressed proteins between Control and Diet 250 associated with key biological processes including skin, muscle, and bone development. Expression analysis showed that genes encoding proteins related to the VK cycle (ggcx, vkor), VK nuclear receptor (pxr), and VK-dependent proteins (VKDPs; oc1 and grp), were differentially expressed. This study highlights the potential benefits of increasing dietary VK levels in larval diets, and brings new insights on the mechanisms mediating the positive effects observed on larval performance and skeletal development.

On the morphology of the central nervous system in larval stages of Carcinus maenas L. (Decapoda, Brachyura)

NASA Astrophysics Data System (ADS)

Harzsch, S.; Dawirs, R. R.

1993-02-01

We investigated the morphology of the central nervous system throughout the larval development of Carcinus maenas. For that purpose single larvae were reared in the laboratory from hatching through metamorphosis. Complete series of whole mout semithin sections were obtained from individuals of all successive larval stages and analysed with a light microscope. Morphological feature and spatial arrangement of discernable neural cell clusters, fibre tracts and neuropile are described and compared with the adult pattern. We found that most of the morphological features characterizing the adult nervous system are already present in the zoea-1. Nevertheless, there are marked differences with respect to the arrangement of nerve cell bodies, organization of cerebral neuropile, and disposition of ganglia in the ventral nerve cord. It appears that complexity of the central nervous neuropile is selectively altered during postmetamorphotic development, probably reflecting adaptive changes of sensory-motor integration in response to behavioural maturation. In contrast, during larval development there was little change in the overall structural organization of the central nervous system despite some considerable growth. However, the transition from zoea-4 to megalopa brings about multiple fundamental changes in larval morphology and behavioural pattern. Since central nervous integration should properly adapt to the altered behavioural repertoire of the megalopa, it seems necessary to ask in which respect synaptic rearrangement might characterize development of the central nervous system.

Butterfly Larval Host Plant use in a Tropical Urban Context: Life History Associations, Herbivory, and Landscape Factors

PubMed Central

Tiple, Ashish D.; Khurad, Arun M.; Dennis, Roger L. H.

2011-01-01

This study examines butterfly larval host plants, herbivory and related life history attributes within Nagpur City, India. The larval host plants of 120 butterfly species are identified and their host specificity, life form, biotope, abundance and perennation recorded; of the 126 larval host plants, most are trees (49), with fewer herbs (43), shrubs (22), climbers (7) and stem parasites (2). They include 89 wild, 23 cultivated, 11 wild/cultivated and 3 exotic plant species; 78 are perennials, 43 annuals and 5 biannuals. Plants belonging to Poaceae and Fabaceae are most widely used by butterfly larvae. In addition to distinctions in host plant family affiliation, a number of significant differences between butterfly families have been identified in host use patterns: for life forms, biotopes, landforms, perennation, host specificity, egg batch size and ant associations. These differences arising from the development of a butterfly resource database have important implications for conserving butterfly species within the city area. Differences in overall butterfly population sizes within the city relate mainly to the number of host plants used, but other influences, including egg batch size and host specificity are identified. Much of the variation in population size is unaccounted for and points to the need to investigate larval host plant life history and strategies as population size is not simply dependent on host plant abundance. PMID:21864159

Comparative Transcriptomic Analysis Reveals Candidate Genes and Pathways Involved in Larval Settlement of the Barnacle Megabalanus volcano.

PubMed

Yan, Guoyong; Zhang, Gen; Huang, Jiaomei; Lan, Yi; Sun, Jin; Zeng, Cong; Wang, Yong; Qian, Pei-Yuan; He, Lisheng

2017-10-27

Megabalanus barnacle is one of the model organisms for marine biofouling research. However, further elucidation of molecular mechanisms underlying larval settlement has been hindered due to the lack of genomic information thus far. In the present study, cDNA libraries were constructed for cyprids, the key stage for larval settlement, and adults of Megabalanus volcano . After high-throughput sequencing and de novo assembly, 42,620 unigenes were obtained with a N50 value of 1532 bp. These unigenes were annotated by blasting against the NCBI non-redundant (nr), Swiss-Prot, Cluster of Orthologous Groups (COG), and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Finally, 19,522, 15,691, 14,459, and 10,914 unigenes were identified correspondingly. There were 22,158 differentially expressed genes (DEGs) identified between two stages. Compared with the cyprid stage, 8241 unigenes were down-regulated and 13,917 unigenes were up-regulated at the adult stage. The neuroactive ligand-receptor interaction pathway (ko04080) was significantly enriched by KEGG enrichment analysis of the DEGs, suggesting that it possibly involved in larval settlement. Potential functions of three conserved allatostatin neuropeptide-receptor pairs and two light-sensitive opsin proteins were further characterized, indicating that they might regulate attachment and metamorphosis at cyprid stage. These results provided a deeper insight into the molecular mechanisms underlying larval settlement of barnacles.