Science.gov

Sample records for invasive predator rats

  1. Dietary shift of an invasive predator: rats, seabirds and sea turtles

    PubMed Central

    Caut, Stéphane; Angulo, Elena; Courchamp, Franck

    2008-01-01

    Rats have reached about 80% of the world's islands and are among the most successful invasive mammals. Rats are opportunistic predators that are notorious for their impact on a variety of animal and plant species. However, little documented evidence on the complexities of these interactions is available.In our study, we assessed the impact of black rats Rattus rattus introduced on a small uninhabited island with a relatively simple ecosystem, Surprise Island, New Caledonia. We also compared the diet of R. rattus in the presence and absence of breeding seabirds, assessing the dietary compensation for this potentially important food source. From 2002 to 2005, we used live trapping studies combined with stable isotope analysis and conventional diet analyses (direct observations, gut and faecal contents) to characterize the diet of rats.Our results suggest a heavy predatory impact on seabirds, which could constitute as much as 24% of the rat diet. Moreover, in the absence of birds, rats compensated marginally by preying more heavily on other components of their diet but mostly acquired a new resource. They shifted their diet by preying heavily upon another endangered species, the hatchlings of sea turtles Chelonia mydas, which could constitute the main resource in the diet of R. rattus in those periods. Abundance, body condition and distribution of the rats were consistent with heavy predation upon this additional resource.Synthesis and applications. In island ecosystems invasive rats prey mainly upon seabird eggs and chicks, thereby threatening their populations. Although rats are certainly capable of surviving on terrestrial foods outside the seabird nesting season, their ability to prey upon ephemeral but abundant resources, such as hatchling sea turtles, may contribute to maintaining their populations. This may explain their success on Surprise Island, an ecosystem of extreme conditions, and suggests that biologists and managers working with threatened species

  2. Discriminating the Drivers of Edge Effects on Nest Predation: Forest Edges Reduce Capture Rates of Ship Rats (Rattus rattus), a Globally Invasive Nest Predator, by Altering Vegetation Structure

    PubMed Central

    Ruffell, Jay; Didham, Raphael K.; Barrett, Paul; Gorman, Nic; Pike, Rhonda; Hickey-Elliott, Andrée; Sievwright, Karin; Armstrong, Doug P.

    2014-01-01

    Forest edges can strongly affect avian nest success by altering nest predation rates, but this relationship is inconsistent and context dependent. There is a need for researchers to improve the predictability of edge effects on nest predation rates by examining the mechanisms driving their occurrence and variability. In this study, we examined how the capture rates of ship rats, an invasive nest predator responsible for avian declines globally, varied with distance from the forest edge within forest fragments in a pastoral landscape in New Zealand. We hypothesised that forest edges would affect capture rates by altering vegetation structure within fragments, and that the strength of edge effects would depend on whether fragments were grazed by livestock. We measured vegetation structure and rat capture rates at 488 locations ranging from 0–212 m from the forest edge in 15 forest fragments, seven of which were grazed. Contrary to the vast majority of previous studies of edge effects on nest predation, ship rat capture rates increased with increasing distance from the forest edge. For grazed fragments, capture rates were estimated to be 78% lower at the forest edge than 118 m into the forest interior (the farthest distance for grazed fragments). This relationship was similar for ungrazed fragments, with capture rates estimated to be 51% lower at the forest edge than 118 m into the forest interior. A subsequent path analysis suggested that these ‘reverse’ edge effects were largely or entirely mediated by changes in vegetation structure, implying that edge effects on ship rats can be predicted from the response of vegetation structure to forest edges. We suggest the occurrence, strength, and direction of edge effects on nest predation rates may depend on edge-driven changes in local habitat when the dominant predator is primarily restricted to forest patches. PMID:25412340

  3. Discriminating the drivers of edge effects on nest predation: forest edges reduce capture rates of ship rats (Rattus rattus), a globally invasive nest predator, by altering vegetation structure.

    PubMed

    Ruffell, Jay; Didham, Raphael K; Barrett, Paul; Gorman, Nic; Pike, Rhonda; Hickey-Elliott, Andrée; Sievwright, Karin; Armstrong, Doug P

    2014-01-01

    Forest edges can strongly affect avian nest success by altering nest predation rates, but this relationship is inconsistent and context dependent. There is a need for researchers to improve the predictability of edge effects on nest predation rates by examining the mechanisms driving their occurrence and variability. In this study, we examined how the capture rates of ship rats, an invasive nest predator responsible for avian declines globally, varied with distance from the forest edge within forest fragments in a pastoral landscape in New Zealand. We hypothesised that forest edges would affect capture rates by altering vegetation structure within fragments, and that the strength of edge effects would depend on whether fragments were grazed by livestock. We measured vegetation structure and rat capture rates at 488 locations ranging from 0-212 m from the forest edge in 15 forest fragments, seven of which were grazed. Contrary to the vast majority of previous studies of edge effects on nest predation, ship rat capture rates increased with increasing distance from the forest edge. For grazed fragments, capture rates were estimated to be 78% lower at the forest edge than 118 m into the forest interior (the farthest distance for grazed fragments). This relationship was similar for ungrazed fragments, with capture rates estimated to be 51% lower at the forest edge than 118 m into the forest interior. A subsequent path analysis suggested that these 'reverse' edge effects were largely or entirely mediated by changes in vegetation structure, implying that edge effects on ship rats can be predicted from the response of vegetation structure to forest edges. We suggest the occurrence, strength, and direction of edge effects on nest predation rates may depend on edge-driven changes in local habitat when the dominant predator is primarily restricted to forest patches.

  4. Invasive predators and global biodiversity loss.

    PubMed

    Doherty, Tim S; Glen, Alistair S; Nimmo, Dale G; Ritchie, Euan G; Dickman, Chris R

    2016-10-04

    Invasive species threaten biodiversity globally, and invasive mammalian predators are particularly damaging, having contributed to considerable species decline and extinction. We provide a global metaanalysis of these impacts and reveal their full extent. Invasive predators are implicated in 87 bird, 45 mammal, and 10 reptile species extinctions-58% of these groups' contemporary extinctions worldwide. These figures are likely underestimated because 23 critically endangered species that we assessed are classed as "possibly extinct." Invasive mammalian predators endanger a further 596 species at risk of extinction, with cats, rodents, dogs, and pigs threatening the most species overall. Species most at risk from predators have high evolutionary distinctiveness and inhabit insular environments. Invasive mammalian predators are therefore important drivers of irreversible loss of phylogenetic diversity worldwide. That most impacted species are insular indicates that management of invasive predators on islands should be a global conservation priority. Understanding and mitigating the impact of invasive mammalian predators is essential for reducing the rate of global biodiversity loss.

  5. Invasive Predators Deplete Genetic Diversity of Island Lizards

    PubMed Central

    Gasc, Amandine; Duryea, M. C.; Cox, Robert M.; Kern, Andrew; Calsbeek, Ryan

    2010-01-01

    Invasive species can dramatically impact natural populations, especially those living on islands. Though numerous examples illustrate the ecological impact of invasive predators, no study has examined the genetic consequences for native populations subject to invasion. Here we capitalize on a natural experiment in which a long-term study of the brown anole lizard (Anolis sagrei) was interrupted by rat invasion. An island population that was devastated by rats recovered numerically following rat extermination. However, population genetic analyses at six microsatellite loci suggested a possible loss of genetic diversity due to invasion when compared to an uninvaded island studied over the same time frame. Our results provide partial support for the hypothesis that invasive predators can impact the genetic diversity of resident island populations. PMID:20706576

  6. Invasive predators and global biodiversity loss

    PubMed Central

    Glen, Alistair S.; Nimmo, Dale G.; Ritchie, Euan G.; Dickman, Chris R.

    2016-01-01

    Invasive species threaten biodiversity globally, and invasive mammalian predators are particularly damaging, having contributed to considerable species decline and extinction. We provide a global metaanalysis of these impacts and reveal their full extent. Invasive predators are implicated in 87 bird, 45 mammal, and 10 reptile species extinctions—58% of these groups’ contemporary extinctions worldwide. These figures are likely underestimated because 23 critically endangered species that we assessed are classed as “possibly extinct.” Invasive mammalian predators endanger a further 596 species at risk of extinction, with cats, rodents, dogs, and pigs threatening the most species overall. Species most at risk from predators have high evolutionary distinctiveness and inhabit insular environments. Invasive mammalian predators are therefore important drivers of irreversible loss of phylogenetic diversity worldwide. That most impacted species are insular indicates that management of invasive predators on islands should be a global conservation priority. Understanding and mitigating the impact of invasive mammalian predators is essential for reducing the rate of global biodiversity loss. PMID:27638204

  7. Predator control promotes invasive dominated ecological states.

    PubMed

    Wallach, Arian D; Johnson, Christopher N; Ritchie, Euan G; O'Neill, Adam J

    2010-08-01

    Invasive species are regarded as one of the top five drivers of the global extinction crisis. In response, extreme measures have been applied in an attempt to control or eradicate invasives, with little success overall. We tested the idea that state shifts to invasive dominance are symptomatic of losses in ecosystem resilience, due to the suppression of apex predators. This concept was investigated in Australia where the high rate of mammalian extinctions is largely attributed to the destructive influence of invasive species. Intensive pest control is widely applied across the continent, simultaneously eliminating Australia's apex predator, the dingo (Canis lupus dingo). We show that predator management accounts for shifts between two main ecosystem states. Lethal control fractures dingo social structure and leads to bottom-up driven increases in invasive mesopredators and herbivores. Where control is relaxed, dingoes re-establish top-down regulation of ecosystems, allowing for the recovery of biodiversity and productivity.

  8. Endemic predators, invasive prey and native diversity

    PubMed Central

    Wanger, Thomas C.; Wielgoss, Arno C.; Motzke, Iris; Clough, Yann; Brook, Barry W.; Sodhi, Navjot S.; Tscharntke, Teja

    2011-01-01

    Interactions between native diversity and invasive species can be more complex than is currently understood. Invasive ant species often substantially reduce diversity in the native ants diversity that act as natural control agents for pest insects. In Indonesia (on the island of Sulawesi), the third largest cacao producer worldwide, we show that a predatory endemic toad (Ingerophrynus celebensis) controls invasive ant (Anoplolepis gracilipes) abundance, and positively affects native ant diversity. We call this the invasive-naivety effect (an opposite of enemy release), whereby alien species may not harbour anti-predatory defences against a novel native predator. A positive effect of the toads on native ants may facilitate their predation on insect vectors of cacao diseases. Hence, toads may increase crop yield, but further research is needed on this aspect. Ironically, amphibians are globally the most threatened vertebrate class and are strongly impacted by the conversion of rainforest to cacao plantations in Sulawesi. It is, therefore, crucial to manage cacao plantations to maintain these endemic toads, as they may provide critical ecosystem services, such as invasion resistance and preservation of native insect diversity. PMID:20826488

  9. Inhibition between invasives: a newly introduced predator moderates the impacts of a previously established invasive predator.

    PubMed

    Griffen, Blaine D; Guy, Travis; Buck, Julia C

    2008-01-01

    1. With continued globalization, species are being transported and introduced into novel habitats at an accelerating rate. Interactions between invasive species may provide important mechanisms that moderate their impacts on native species. 2. The European green crab Carcinus maenas is an aggressive predator that was introduced to the east coast of North America in the mid-1800 s and is capable of rapid consumption of bivalve prey. A newer invasive predator, the Asian shore crab Hemigrapsus sanguineus, was first discovered on the Atlantic coast in the 1980s, and now inhabits many of the same regions as C. maenas within the Gulf of Maine. Using a series of field and laboratory investigations, we examined the consequences of interactions between these predators. 3. Density patterns of these two species at different spatial scales are consistent with negative interactions. As a result of these interactions, C. maenas alters its diet to consume fewer mussels, its preferred prey, in the presence of H. sanguineus. Decreased mussel consumption in turn leads to lower growth rates for C. maenas, with potential detrimental effects on C. maenas populations. 4. Rather than an invasional meltdown, this study demonstrates that, within the Gulf of Maine, this new invasive predator can moderate the impacts of the older invasive predator.

  10. Invasive plants may promote predator-mediated feedback that inhibits further invasion.

    PubMed

    Smith, Lauren M; Schmitz, Oswald J

    2015-06-01

    Understanding the impacts of invasive species requires placing invasion within a full community context. Plant invaders are often considered in the context of herbivores that may drive invasion by avoiding invaders while consuming natives (enemy escape), or inhibit invasion by consuming invaders (biotic resistance). However, predators that attack those herbivores are rarely considered as major players in invasion. Invasive plants often promote predators, generally by providing improved habitat. Here, we show that predator-promoting invaders may initiate a negative feedback loop that inhibits invasion. By enabling top-down control of herbivores, predator-promoting invaders lose any advantage gained through enemy escape, indirectly favoring natives. In cases where palatable invaders encounter biotic resistance, predator promotion may allow an invader to persist, but not dominate. Overall, results indicate that placing invaders in a full community context may reveal reduced impacts of invaders compared to expectations based on simple plant-plant or plant-herbivore subsystems.

  11. Invasive plants may promote predator-mediated feedback that inhibits further invasion

    PubMed Central

    Smith, Lauren M; Schmitz, Oswald J

    2015-01-01

    Understanding the impacts of invasive species requires placing invasion within a full community context. Plant invaders are often considered in the context of herbivores that may drive invasion by avoiding invaders while consuming natives (enemy escape), or inhibit invasion by consuming invaders (biotic resistance). However, predators that attack those herbivores are rarely considered as major players in invasion. Invasive plants often promote predators, generally by providing improved habitat. Here, we show that predator-promoting invaders may initiate a negative feedback loop that inhibits invasion. By enabling top-down control of herbivores, predator-promoting invaders lose any advantage gained through enemy escape, indirectly favoring natives. In cases where palatable invaders encounter biotic resistance, predator promotion may allow an invader to persist, but not dominate. Overall, results indicate that placing invaders in a full community context may reveal reduced impacts of invaders compared to expectations based on simple plant–plant or plant–herbivore subsystems. PMID:26120430

  12. Predation by native brown shrimp on invasive Pacific oyster spat

    NASA Astrophysics Data System (ADS)

    Weerman, E. J.; Eriksson, B. K.; Olff, H.; van der Heide, T.

    2014-01-01

    In the last decades, the invasive Pacific oyster (Crassostrea gigas) increased dramatically in the Wadden Sea. One of the driving mechanisms for the success of the Pacific oyster could be a relatively low predation pressure by epibenthic predators and shore birds on oyster spat. Nevertheless, observations and experiments on predation rates on early life-stages of the Pacific oyster are rare. Therefore, we examined predation rates of brown shrimps on Pacific oyster spat in a number of laboratory experiments. Our results demonstrate that spat of Pacific oysters are most susceptible to predation by brown shrimps (Crangon crangon) in the first days after settlement, when attachment to the substrate (unglazed tiles in our study) is still absent or weak. At this stage the shell length of oyster spat is around ~ 300 μm, and around 50% of the individuals in the experiment were consumed in the two hour trials. Predation rates decreased rapidly as the spat grew larger and reached zero within 10 days after settlement of the spat (shell length > 700 μm). Additional experiments revealed that the attachment of oysters is probably limiting predation by brown shrimps rather than the size of the spat. This indicates that Pacific oyster spat may limit predation loss faster compared to native bivalves, which commonly depend on size to reduce predation rates. Overall, our results suggest that the invasive success of Pacific oysters may in part be explained by relatively low predation rates throughout their life stages.

  13. Indirect effects of invasive predators on litter decomposition and nutrient resorption on seabird-dominated islands.

    PubMed

    Wardle, David A; Bellingham, Peter J; Bonner, Karen I; Mulder, Christa P H

    2009-02-01

    Despite recent interest in the ecosystem impacts of invasive aboveground organisms, most work in this area has focused on effects of invasive plants, and the effects of invasive herbivores and predators remain poorly understood. We studied 18 forested, offshore islands in northern New Zealand. Nine of these host high densities of burrowing seabirds that serve as ecosystem drivers by transporting nutrients from the ocean to land. The other nine have been invaded over the past 50-150 years by rat species introduced from Europe which serve as predators of seabird eggs and chicks and severely reduce their densities. We collected fully expanded leaves and fresh leaf litter from invaded and uninvaded islands for each of 12 perennial plant species that represent a wide spectrum of life forms from ground dwelling to emergent canopy species. We found that, across these species, invasion by rats significantly reduced nitrogen (N) but not phosphorus (P) concentrations of foliage and litter, promoted N but not P resorption from leaves before litter fall, and reduced the release of N but not P from decomposing litter. Rat invasion also negatively affected litter decomposability but had no overall effects on litter quality variables other than N. Our results provide evidence that rat invasion causes more conservative cycling of N but not P through foliage and litter and limitation of ecological processes by N but not P. We found few instances in which the effects of rat invasion on response variables varied significantly across plant species, meaning that invasion had similar effects for species that varied greatly in growth form and foliar and litter quality. Further, correlation analyses across the 12 species showed that foliar and litter quality traits were poor predictors of how invasion effects on resorption and decomposition variables varied among species. Our results show that the effects of invasive predators on native prey can have substantial indirect effects on

  14. Invasive toads shift predator-prey densities in animal communities by removing top predators.

    PubMed

    Doody, J Sean; Soanes, Rebekah; Castellano, Christina M; Rhind, David; Green, Brian; McHenry, Colin R; Clulow, Simon

    2015-09-01

    Although invasive species can have substantial impacts on animal communities, cases of invasive species facilitating native species by removing their predators have rarely been demonstrated across vertebrate trophic linkages. The predictable spread of the invasive cane toad (Rhinella marina), however, offered a unique opportunity to quantify cascading effects. In northern Australia, three species of predatory monitor lizards suffered severe population declines due to toad-induced lethal toxic ingestion (yellow-spotted monitor (Varanus panoptes), Mertens' water monitor (V. mertensi), Mitchell's water monitor (V. mitchelli). We, thus, predicted subsequent increases in the abundance and recruitment of prey species due to the reduction of those predators. Toad-induced population-level declines in the water monitor species approached 50% over a five-year period spanning the toad invasion, apparently causing fledging success of the Crimson Finch (Neochmia.phaeton) to increase from 55% to 81%. The consensus of our original and published long-term data is that invasive cane toads are causing predators to lose a foothold on top-down regulation of their prey, triggering shifts in the relative densities of predator and prey in the Australian tropical savannah ecosystem.

  15. Differential population responses of native and alien rodents to an invasive predator, habitat alteration and plant masting.

    PubMed

    Fukasawa, Keita; Miyashita, Tadashi; Hashimoto, Takuma; Tatara, Masaya; Abe, Shintaro

    2013-12-22

    Invasive species and anthropogenic habitat alteration are major drivers of biodiversity loss. When multiple invasive species occupy different trophic levels, removing an invasive predator might cause unexpected outcomes owing to complex interactions among native and non-native prey. Moreover, external factors such as habitat alteration and resource availability can affect such dynamics. We hypothesized that native and non-native prey respond differently to an invasive predator, habitat alteration and bottom-up effects. To test the hypothesis, we used Bayesian state-space modelling to analyse 8-year data on the spatio-temporal patterns of two endemic rat species and the non-native black rat in response to the continual removal of the invasive small Indian mongoose on Amami Island, Japan. Despite low reproductive potentials, the endemic rats recovered better after mongoose removal than did the black rat. The endemic species appeared to be vulnerable to predation by mongooses, whose eradication increased the abundances of the endemic rats, but not of the black rat. Habitat alteration increased the black rat's carrying capacity, but decreased those of the endemic species. We propose that spatio-temporal monitoring data from eradication programmes will clarify the underlying ecological impacts of land-use change and invasive species, and will be useful for future habitat management.

  16. Differential population responses of native and alien rodents to an invasive predator, habitat alteration and plant masting

    PubMed Central

    Fukasawa, Keita; Miyashita, Tadashi; Hashimoto, Takuma; Tatara, Masaya; Abe, Shintaro

    2013-01-01

    Invasive species and anthropogenic habitat alteration are major drivers of biodiversity loss. When multiple invasive species occupy different trophic levels, removing an invasive predator might cause unexpected outcomes owing to complex interactions among native and non-native prey. Moreover, external factors such as habitat alteration and resource availability can affect such dynamics. We hypothesized that native and non-native prey respond differently to an invasive predator, habitat alteration and bottom-up effects. To test the hypothesis, we used Bayesian state-space modelling to analyse 8-year data on the spatio-temporal patterns of two endemic rat species and the non-native black rat in response to the continual removal of the invasive small Indian mongoose on Amami Island, Japan. Despite low reproductive potentials, the endemic rats recovered better after mongoose removal than did the black rat. The endemic species appeared to be vulnerable to predation by mongooses, whose eradication increased the abundances of the endemic rats, but not of the black rat. Habitat alteration increased the black rat's carrying capacity, but decreased those of the endemic species. We propose that spatio-temporal monitoring data from eradication programmes will clarify the underlying ecological impacts of land-use change and invasive species, and will be useful for future habitat management. PMID:24197409

  17. Disease-induced decline of an apex predator drives invasive dominated states and threatens biodiversity.

    PubMed

    Hollings, Tracey; Jones, Menna; Mooney, Nick; McCallum, Hamish

    2016-02-01

    Apex predators are important in protecting biodiversity through top-down influence on food webs. Their loss is linked with competitive release of invasive mesopredators and species extinctions. The Tasmanian devil (Sarcophilus harrisii) has experienced severe declines over a 15-yr period as a novel transmissible cancer has spread across its current geographic range. We surveyed the mammalian community, using hair traps, across the spatial extent of the devil's progressive population decline. We found increased activity of alien invasive species (feral cats, black rats), and reduced small and medium-sized native prey species in response to the timing of the decline. In areas of long-term devil decline, invasive species comprised a significantly larger proportion of the community. The results provide evidence that the devil plays a keystone role in Tasmania's ecosystem with their decline linked to a shift toward an invasive state and biodiversity loss in one of Australia's most intact faunal communities.

  18. Anomalous invasion in a 2d model of chemotactic predation

    NASA Astrophysics Data System (ADS)

    Willemsen, Jorge F.

    2010-09-01

    It has been hypothesized that plankton predators sense the presence of their prey through detection of chemical signals exuded by the prey. This process is formulated using elements of existing models, tailored to correspond to the specific process under investigation. The motivation for the resulting model is discussed in detail. Numerical results are then presented. It is found that the front representing the advance of the predator into the prey is irregular in a novel way, and the reasons for this anomalous invasion are discussed. It is recognized that reaction-diffusion models, starting perhaps with Turing, can lead to what might have been thought of as anomalous patterns - yet the “flicker” front advance discovered here is indeed novel.

  19. Unexpected consequences of control: competitive vs. predator release in a four-species assemblage of invasive mammals.

    PubMed

    Ruscoe, Wendy A; Ramsey, David S L; Pech, Roger P; Sweetapple, Peter J; Yockney, Ivor; Barron, Mandy C; Perry, Mike; Nugent, Graham; Carran, Roger; Warne, Rodney; Brausch, Chris; Duncan, Richard P

    2011-10-01

    Invasive species are frequently the target of eradication or control programmes to mitigate their impacts. However, manipulating single species in isolation can lead to unexpected consequences for other species, with outcomes such as mesopredator release demonstrated both theoretically and empirically in vertebrate assemblages with at least two trophic levels. Less is known about the consequences of species removal in more complex assemblages where a greater number of interacting invaders increases the potential for selective species removal to result in unexpected changes in community structure. Using a replicated Before-After Control-Impact field experiment with a four-species assemblage of invasive mammals we show that species interactions in the community are dominated by competition rather than predation. There was no measurable response of two mesopredators (rats and mice) following control of the top predator (stoats), but there was competitive release of rats following removal of a herbivore (possums), and competitive release of mice following removal of rats.

  20. Fortune favours the bold: a higher predator reduces the impact of a native but not an invasive intermediate predator.

    PubMed

    Barrios-O'Neill, Daniel; Dick, Jaimie T A; Emmerson, Mark C; Ricciardi, Anthony; MacIsaac, Hugh J; Alexander, Mhairi E; Bovy, Helene C

    2014-05-01

    Emergent multiple predator effects (MPEs) might radically alter predictions of predatory impact that are based solely on the impact of individuals. In the context of biological invasions, determining if and how the individual-level impacts of invasive predators relates to their impacts in multiple-individual situations will inform understanding of how such impacts might propagate through recipient communities. Here, we use functional responses (the relationship between prey consumption rate and prey density) to compare the impacts of the invasive freshwater mysid crustacean Hemimysis anomala with a native counterpart Mysis salemaai when feeding on basal cladoceran prey (i) as individuals, (ii) in conspecific groups and (iii) in conspecific groups in the presence of a higher fish predator, Gasterosteus aculeatus. In the absence of the higher predator, the invader consumed significantly more basal prey than the native, and consumption was additive for both mysid species - that is, group consumption was predictable from individual-level consumption. Invaders and natives were themselves equally susceptible to predation when feeding with the higher fish predator, but an MPE occurred only between the natives and higher predator, where consumption of basal prey was significantly reduced. In contrast, consumption by the invaders and higher predator remained additive. The presence of a higher predator serves to exacerbate the existing difference in individual-level consumption between invasive and native mysids. We attribute the mechanism responsible for the MPE associated with the native to a trait-mediated indirect interaction, and further suggest that the relative indifference to predator threat on the part of the invader contributes to its success and impacts within invaded communities.

  1. Finely tuned response of native prey to an invasive predator in a freshwater system.

    PubMed

    Bourdeau, Paul E; Pangle, Kevin L; Reed, Emily M; Peacor, Scott D

    2013-07-01

    Lack of shared evolutionary history reduces the expectation that native prey will detect and respond to invasive predators. Four mechanisms may explain the adaptive response that is nevertheless seen in various systems: prey may perceive the invasive predator through cue similarity with preexisting predators, cues of conspecifics eaten by the invasive predator, a learned response based on experience with the invasive predator (e.g., cue association), and cues from the invasive predator that are specific to it. We performed laboratory experiments in which zooplankton (Daphnia mendotae) responded adaptively to the zooplanktivore Bythotrephes longimanus (migrating downward), showed no response to taxonomically similar predatory cladocerans, and responded adaptively to more taxonomically distant native fish (migrating downward) and native shrimp (migrating upward). Conspecific cues associated with Bythotrephes predation actually reduced the response of D. mendotae to Bythotrephes. Combined with previous experiments that rule out learning, our experiments rule out the first three mechanisms above, demonstrating that D. mendotae respond to cues specific to and produced directly by Bythotrephes. This finely tuned response may be retained from an ancestral species that coevolved with Bythotrephes in its native range, or may have rapidly evolved due to strong selection by the invasive predator.

  2. Does differential predation permit invasive and native mosquito larvae to coexist in Florida?

    PubMed

    Griswold, Marcus W; Lounibos, L Philip

    2005-05-01

    1. The hypothesis that selective predation on larvae of the invasive Aedes albopictus (Skuse) could account for its stable coexistence with the native mosquito species and inferior competitor Ochlerotatus triseriatus (Say) in Florida treeholes and container systems was tested experimentally.2. Functional responses of the two dipteran predators Toxorhynchites rutilus (Coquillett) and Corethrella appendiculata (Grabham) were evaluated separately for A. albopictus and O. triseriatus prey. Both predators exhibited type II functional responses and consistently consumed more of the invasive species. Handling time of T. rutilus feeding upon O. triseriatus was significantly longer than when preying upon the invasive species.3. When either predator species was offered varying ratios of the two prey species, A. albopictus was consumed preferentially. The absence of a prey ratio effect on preference indicated that switching probably does not occur.4. The higher maximum feeding rate upon, and preference for, A. albopictus suggests that differential predation may foster coexistence of the invasive and native mosquito prey species in Florida.

  3. Intraguild predation and successful invasion by introduced ladybird beetles.

    PubMed

    Snyder, William E; Clevenger, Garrett M; Eigenbrode, Sanford D

    2004-08-01

    Introductions of two ladybird beetle (Coleoptera: Coccinellidae) species, Coccinella septempunctata and Harmonia axyridis, into North America for aphid biocontrol have been followed by declines in native species. We examined intraguild predation (IGP) between larvae of these two exotic species and larvae of the two most abundant native coccinellids in eastern Washington State, C. transversoguttata and Hippodamia convergens. In pairings between the two native species in laboratory microcosms containing pea ( Pisum sativum) plants, neither native had a clear advantage over the other in IGP. When the natives were paired with either Harmonia axyridis or C. septempunctata, the natives were more frequently the victims than perpetrators of IGP. In contrast, in pairings between the exotic species, neither had an IGP advantage, although overall rates of IGP between these two species were very high. Adding alternative prey (aphids) to microcosms did not alter the frequency and patterns of relative IGP among the coccinellid species. In observations of encounters between larvae, the introduced H. axyridis frequently survived multiple encounters with the native C. transversoguttata, whereas the native rarely survived a single encounter with H. axyridis. Our results suggest that larvae of the native species face increased IGP following invasion by C. septempunctata and H. axyridis, which may be contributing to the speed with which these exotic ladybird beetles displace the natives following invasion.

  4. Ecology of the spined soldier bug, Podisus maculiventris: an important generalist predator of invasive insect pests

    USDA-ARS?s Scientific Manuscript database

    The spined soldier bug, Podisus maculiventris (Heteroptera: Pentatomidae) is a generalist predator known to feed on over 75 insect species, several of which are important invasive insect pests. A substantial body of knowledge from our research studies on the ecology of this predator will be presente...

  5. New parasitoid-predator associations: female parasitoids do not avoid competition with generalist predators when sharing invasive prey

    NASA Astrophysics Data System (ADS)

    Chailleux, Anaïs; Wajnberg, Eric; Zhou, Yuxiang; Amiens-Desneux, Edwige; Desneux, Nicolas

    2014-12-01

    Optimal habitat selection is essential for species survival in ecosystems, and interspecific competition is a key ecological mechanism for many observed species association patterns. Specialized animal species are commonly affected by resource and interference competition with generalist and/or omnivorous competitors, so avoidance behavior could be expected. We hypothesize that specialist species may exploit broad range cues from such potential resource competitors (i.e., cues possibly common to various generalist and/or omnivorous predators) to avoid costly competition regarding food or reproduction, even in new species associations. We tested this hypothesis by studying short-term interactions between a native larval parasitoid and a native generalist omnivorous predator recently sharing the same invasive host/prey, the leaf miner Tuta absoluta. We observed a strong negative effect of kleptoparasitism (food resource stealing) instead of classical intraguild predation on immature parasitoids. There was no evidence that parasitoid females avoided the omnivorous predator when searching for oviposition sites, although we studied both long- and short-range known detection mechanisms. Therefore, we conclude that broad range cue avoidance may not exist in our biological system, probably because it would lead to too much oviposition site avoidance which would not be an efficient and, thus, beneficial strategy. If confirmed in other parasitoids or specialist predators, our findings may have implications for population dynamics, especially in the current context of increasing invasive species and the resulting creation of many new species associations.

  6. Summer time predation on the obligatory off-host stage of an invasive ectoparasite.

    PubMed

    Kaunisto, Sirpa; Raunismaa, Ilkka; Kortet, Raine; Ylönen, Hannu

    2016-12-01

    Predation can regulate populations and strongly affect invasion success of novel prey. The deer ked (Lipoptena cervi; Linnaeus 1758) is an invasive ectoparasite of cervids that spends a long period of its life cycle outside the host. Prior to this study, virtually nothing was known about natural summer time predation on the deer ked. We aimed to evaluate the magnitude of summer time predation on L. cervi pupae in different habitats and to identify potential predators. We conducted a set of field experiments, where we exposed L. cervi pupae to various ground-dwelling vertebrate and invertebrate predators. The loss of pupae was monitored for different predator guilds. Three habitats of the moose, the main host species, were studied: (1) moist heath forest; (2) dry, logged heath forest; and (3) moist meadow. The results indicate notable summer time predation on L. cervi pupae, and the pupal predation varied within and between habitats, being lowest in the meadow habitat. We found a positive correlation between pupal loss and abundance of the common lizard (Zootoca vivipara), harvestmen (Opiliones), ground spiders (Gnaphosidae) and Formicinae-ants. We conclude that summer time predation during the pupal phase can have a notable local importance for the L. cervi abundance.

  7. Resistance of a food chain to invasion by a top predator.

    PubMed

    Kooi, B W; Boer, M P; Kooijman, S A

    1999-03-15

    We study the invasion of a top predator into a food chain in a chemostat. For each trophic level, a bioenergetic model is used in which maintenance and energy reserves are taken into account. Bifurcation analysis is performed on the set of nonlinear ordinary differential equations which describe the dynamic behaviour of the food chain. In this paper, we analyse how the ability of a top predator to invade the food chain depends on the values of two control parameters: the dilution rate and the concentration of the substrate in the input. We investigate invasion by studying the long-term behaviour after introduction of a small amount of top predator. To that end we look at the stability of the boundary attractors; equilibria, limit cycles as well as chaotic attractors using bifurcation analysis. It will be shown that the invasibility criterion is the positiveness of the Lyapunov exponent associated with the change of the biomass of the top predator. It appears that the region in the control parameter space where a predator can invade increases with its growth rate. The resulting system becomes more resistant to further invasion when the top predator grows faster. This implies that short food chains with moderate growth rate of the top predator are liable to be invaded by fast growing invaders which consume the top predator. There may be, however, biological constraints on the top predator's growth rate. Predators are generally larger than prey while larger organisms commonly grow slower. As a result, the growth rate generally decreases with the trophic level. This may enable short food chains to be resistant to invaders. We will relate these results to ecological community assembly and the debate on the length of food chains in nature.

  8. Predator odor exposure increases food-carrying behavior in rats.

    PubMed

    Wernecke, Kerstin E A; Brüggemann, Judith; Fendt, Markus

    2016-02-01

    To cover their energy demands, prey animals are forced to search for food. However, during foraging they also expose themselves to the risk of becoming the prey of predators. Consequently, in order to increase their fitness foraging animals have to trade-off efficiency of foraging against the avoidance of predation risk. For example, the decision on whether a found food piece should be eaten at the food source or whether it should be carried to a protective site such as the nest (food-carrying behavior), is strongly dependent on different incentive factors (e.g., hunger level, food size, distance to the nest). It has been shown that food-carrying behavior increases the more risky the foraging situation becomes. Since predator odors are clearly fear-inducing in rats, we ask here whether the detection of predator odors in close proximity to the food source modulates food-carrying behavior. In the present study, the food-carrying behavior of rats for six different food pellet sizes was measured in a "low risk" and a "high risk" testing condition by presenting water or a fox urine sample, respectively, next to the food source. For both testing conditions, food-carrying behavior of rats increased with increasing food pellet weight. Importantly, the proportion of food-carrying rats was significantly higher during exposure to fox urine ("high risk") than when rats were tested with the water control ("low risk"). Taken together, these results demonstrate that food-carrying behavior of rats is increased by the detection of a predator odor. Our data also support the idea that such food-carrying behavior can be considered as a pre-encounter defensive response. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Ocean acidification increases the vulnerability of native oysters to predation by invasive snails.

    PubMed

    Sanford, Eric; Gaylord, Brian; Hettinger, Annaliese; Lenz, Elizabeth A; Meyer, Kirstin; Hill, Tessa M

    2014-03-07

    There is growing concern that global environmental change might exacerbate the ecological impacts of invasive species by increasing their per capita effects on native species. However, the mechanisms underlying such shifts in interaction strength are poorly understood. Here, we test whether ocean acidification, driven by elevated seawater pCO₂, increases the susceptibility of native Olympia oysters to predation by invasive snails. Oysters raised under elevated pCO₂ experienced a 20% increase in drilling predation. When presented alongside control oysters in a choice experiment, 48% more high-CO₂ oysters were consumed. The invasive snails were tolerant of elevated CO₂ with no change in feeding behaviour. Oysters raised under acidified conditions did not have thinner shells, but were 29-40% smaller than control oysters, and these smaller individuals were consumed at disproportionately greater rates. Reduction in prey size is a common response to environmental stress that may drive increasing per capita effects of stress-tolerant invasive predators.

  10. Stronger biotic resistance in tropics relative to temperate zone: effects of predation on marine invasion dynamics.

    PubMed

    Freestone, Amy L; Rutz, Gregory M; Torchin, Mark E

    2013-06-01

    Latitudinal patterns of nonnative species richness suggest fewer successful invasions in the tropics, relative to temperate regions. One main hypothesis for this pattern is that biotic resistance to invasion is stronger in the tropics than at higher latitudes. Biotic resistance can limit the distribution and abundance of nonnative species and, in extreme cases, can prevent establishment. We provide the first experimental test of this hypothesis, comparing the strength of biotic resistance in a tropical and a temperate marine ecosystem. Predation is one mechanism of biotic resistance, and since predation can be stronger at lower latitudes, we predicted that predation will serve to increase biotic resistance more in the tropics than at higher latitude. We conducted predator-exclusion experiments on marine epifaunal communities, a heavily invaded system, focusing on nonnative tunicates as a model fauna. The effect of predation on species richness of nonnative tunicates was more than three times greater at sites in tropical Panama than in temperate Connecticut, consistent with the prediction of stronger biotic resistance in the tropics. In Connecticut, predation reduced the abundance of one nonnative tunicate but did not affect the abundances of any other nonnative tunicate species, and no species were excluded from communities. In contrast, predation resulted in striking reductions in abundance and often exclusion of nonnative tunicates from experimental communities in Panama. If proved to be general, latitudinal differences in the biotic resistance of communities to nonnative species establishment may help explain emerging patterns of global invasions.

  11. Reproduction in Risky Environments: The Role of Invasive Egg Predators in Ladybird Laying Strategies

    PubMed Central

    Paul, Sarah C.; Pell, Judith K.; Blount, Jonathan D.

    2015-01-01

    Reproductive environments are variable and the resources available for reproduction are finite. If reliable cues about the environment exist, mothers can alter offspring phenotype in a way that increases both offspring and maternal fitness (‘anticipatory maternal effects’—AMEs). Strategic use of AMEs is likely to be important in chemically defended species, where the risk of offspring predation may be modulated by maternal investment in offspring toxin level, albeit at some cost to mothers. Whether mothers adjust offspring toxin levels in response to variation in predation risk is, however, unknown, but is likely to be important when assessing the response of chemically defended species to the recent and pervasive changes in the global predator landscape, driven by the spread of invasive species. Using the chemically defended two-spot ladybird, Adalia bipunctata, we investigated reproductive investment, including egg toxin level, under conditions that varied in the degree of simulated offspring predation risk from larval harlequin ladybirds, Harmonia axyridis. H. axyridis is a highly voracious alien invasive species in the UK and a significant intraguild predator of A. bipunctata. Females laid fewer, larger egg clusters, under conditions of simulated predation risk (P+) than when predator cues were absent (P-), but there was no difference in toxin level between the two treatments. Among P- females, when mean cluster size increased there were concomitant increases in both the mass and toxin concentration of eggs, however when P+ females increased cluster size there was no corresponding increase in egg toxin level. We conclude that, in the face of offspring predation risk, females either withheld toxins or were physiologically constrained, leading to a trade-off between cluster size and egg toxin level. Our results provide the first demonstration that the risk of offspring predation by a novel invasive predator can influence maternal investment in toxins within

  12. Preference and Prey Switching in a Generalist Predator Attacking Local and Invasive Alien Pests

    PubMed Central

    Jaworski, Coline C.; Bompard, Anaïs; Genies, Laure; Amiens-Desneux, Edwige; Desneux, Nicolas

    2013-01-01

    Invasive pest species may strongly affect biotic interactions in agro-ecosystems. The ability of generalist predators to prey on new invasive pests may result in drastic changes in the population dynamics of local pest species owing to predator-mediated indirect interactions among prey. On a short time scale, the nature and strength of such indirect interactions depend largely on preferences between prey and on predator behavior patterns. Under laboratory conditions we evaluated the prey preference of the generalist predator Macrolophus pygmaeus Rambur (Heteroptera: Miridae) when it encounters simultaneously the local tomato pest Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) and the invasive alien pest Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). We tested various ratios of local vs. alien prey numbers, measuring switching by the predator from one prey to the other, and assessing what conditions (e.g. prey species abundance and prey development stage) may favor such prey switching. The total predation activity of M. pygmaeus was affected by the presence of T. absoluta in the prey complex with an opposite effect when comparing adult and juvenile predators. The predator showed similar preference toward T. absoluta eggs and B. tabaci nymphs, but T. absoluta larvae were clearly less attacked. However, prey preference strongly depended on prey relative abundance with a disproportionately high predation on the most abundant prey and disproportionately low predation on the rarest prey. Together with the findings of a recent companion study (Bompard et al. 2013, Population Ecology), the insight obtained on M. pygmaeus prey switching may be useful for Integrated Pest Management in tomato crops, notably for optimal simultaneous management of B. tabaci and T. absoluta, which very frequently co-occur on tomato. PMID:24312646

  13. Preference and prey switching in a generalist predator attacking local and invasive alien pests.

    PubMed

    Jaworski, Coline C; Bompard, Anaïs; Genies, Laure; Amiens-Desneux, Edwige; Desneux, Nicolas

    2013-01-01

    Invasive pest species may strongly affect biotic interactions in agro-ecosystems. The ability of generalist predators to prey on new invasive pests may result in drastic changes in the population dynamics of local pest species owing to predator-mediated indirect interactions among prey. On a short time scale, the nature and strength of such indirect interactions depend largely on preferences between prey and on predator behavior patterns. Under laboratory conditions we evaluated the prey preference of the generalist predator Macrolophus pygmaeus Rambur (Heteroptera: Miridae) when it encounters simultaneously the local tomato pest Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) and the invasive alien pest Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). We tested various ratios of local vs. alien prey numbers, measuring switching by the predator from one prey to the other, and assessing what conditions (e.g. prey species abundance and prey development stage) may favor such prey switching. The total predation activity of M. pygmaeus was affected by the presence of T. absoluta in the prey complex with an opposite effect when comparing adult and juvenile predators. The predator showed similar preference toward T. absoluta eggs and B. tabaci nymphs, but T. absoluta larvae were clearly less attacked. However, prey preference strongly depended on prey relative abundance with a disproportionately high predation on the most abundant prey and disproportionately low predation on the rarest prey. Together with the findings of a recent companion study (Bompard et al. 2013, Population Ecology), the insight obtained on M. pygmaeus prey switching may be useful for Integrated Pest Management in tomato crops, notably for optimal simultaneous management of B. tabaci and T. absoluta, which very frequently co-occur on tomato.

  14. Reproduction in Risky Environments: The Role of Invasive Egg Predators in Ladybird Laying Strategies.

    PubMed

    Paul, Sarah C; Pell, Judith K; Blount, Jonathan D

    2015-01-01

    Reproductive environments are variable and the resources available for reproduction are finite. If reliable cues about the environment exist, mothers can alter offspring phenotype in a way that increases both offspring and maternal fitness ('anticipatory maternal effects'-AMEs). Strategic use of AMEs is likely to be important in chemically defended species, where the risk of offspring predation may be modulated by maternal investment in offspring toxin level, albeit at some cost to mothers. Whether mothers adjust offspring toxin levels in response to variation in predation risk is, however, unknown, but is likely to be important when assessing the response of chemically defended species to the recent and pervasive changes in the global predator landscape, driven by the spread of invasive species. Using the chemically defended two-spot ladybird, Adalia bipunctata, we investigated reproductive investment, including egg toxin level, under conditions that varied in the degree of simulated offspring predation risk from larval harlequin ladybirds, Harmonia axyridis. H. axyridis is a highly voracious alien invasive species in the UK and a significant intraguild predator of A. bipunctata. Females laid fewer, larger egg clusters, under conditions of simulated predation risk (P+) than when predator cues were absent (P-), but there was no difference in toxin level between the two treatments. Among P- females, when mean cluster size increased there were concomitant increases in both the mass and toxin concentration of eggs, however when P+ females increased cluster size there was no corresponding increase in egg toxin level. We conclude that, in the face of offspring predation risk, females either withheld toxins or were physiologically constrained, leading to a trade-off between cluster size and egg toxin level. Our results provide the first demonstration that the risk of offspring predation by a novel invasive predator can influence maternal investment in toxins within their

  15. Your worst enemy could be your best friend: predator contributions to invasion resistance and persistence of natives.

    PubMed

    Juliano, Steven A; Lounibos, L Philip; Nishimura, Naoya; Greene, Krystle

    2010-03-01

    Native predators are postulated to have an important role in biotic resistance of communities to invasion and community resilience. Effects of predators can be complex, and mechanisms by which predators affect invasion success and impact are understood for only a few well-studied communities. We tested experimentally whether a native predator limits an invasive species' success and impact on a native competitor for a community of aquatic insect larvae in water-filled containers. The native mosquito Aedes triseriatus alone had no significant effect on abundance of the invasive mosquito Aedes albopictus. The native predatory midge Corethrella appendiculata, at low or high density, significantly reduced A. albopictus abundance. This effect was not caused by trait-mediated oviposition avoidance of containers with predators, but instead was a density-mediated effect caused by predator-induced mortality. The presence of this predator significantly reduced survivorship of the native species, but high predator density also significantly increased development rate of the native species when the invader was present, consistent with predator-mediated release from interspecific competition with the invader. Thus, a native predator can indirectly benefit its native prey when a superior competitor invades. This shows the importance of native predators as a component of biodiversity for both biotic resistance to invasion and resilience of a community perturbed by successful invasion.

  16. Your worst enemy could be your best friend: predator contributions to invasion resistance and persistence of natives

    PubMed Central

    Lounibos, L. Philip; Nishimura, Naoya; Greene, Krystle

    2010-01-01

    Native predators are postulated to have an important role in biotic resistance of communities to invasion and community resilience. Effects of predators can be complex, and mechanisms by which predators affect invasion success and impact are understood for only a few well-studied communities. We tested experimentally whether a native predator limits an invasive species' success and impact on a native competitor for a community of aquatic insect larvae in water-filled containers. The native mosquito Aedes triseriatus alone had no significant effect on abundance of the invasive mosquito Aedes albopictus. The native predatory midge Corethrella appendiculata, at low or high density, significantly reduced A. albopictus abundance. This effect was not caused by trait-mediated oviposition avoidance of containers with predators, but instead was a density-mediated effect caused by predator-induced mortality. The presence of this predator significantly reduced survivorship of the native species, but high predator density also significantly increased development rate of the native species when the invader was present, consistent with predator-mediated release from interspecific competition with the invader. Thus, a native predator can indirectly benefit its native prey when a superior competitor invades. This shows the importance of native predators as a component of biodiversity for both biotic resistance to invasion and resilience of a community perturbed by successful invasion. PMID:19841945

  17. Native predators living in invaded areas: responses of terrestrial amphibian species to an Argentine ant invasion.

    PubMed

    Alvarez-Blanco, Paloma; Caut, Stephane; Cerdá, Xim; Angulo, Elena

    2017-08-22

    Predator-prey interactions play a key role in the success and impacts of invasive species. However, the effects of invasive preys on native predators have been poorly studied. Here, we first reviewed hypotheses describing potential relationships between native predators and invasive preys. Second, we examined how an invasive prey, the Argentine ant (Linepithema humile), affected a native terrestrial amphibian community. In the field, we looked at the structure of the amphibian community in invaded versus uninvaded areas and characterized amphibian trophic ecology. The amphibian community sampled seemed to show a species-dependent response in abundance to invasion: adults of the natterjack toad (Bufo calamita), the species demonstrating the highest degree of ant specialization, were less abundant in invaded areas. Although available ant biomass was significantly greater in invaded than in uninvaded areas (only Argentine ants occurred in the former), amphibians consumed relatively fewer ants in invaded areas. In the lab, we quantified amphibian consumption of Argentine ants versus native ants and assessed whether consumption patterns could have been influenced by prior exposure to the invader. The lab experiments corroborated the field results: amphibians preferred native ants over Argentine ants, and prior exposure did not influence consumption. Differences in preference explained why amphibians consumed fewer Argentine ants in spite of their greater relative availability; they might also explain why the most ant-specialized amphibians seemed to avoid invaded areas. Our results suggest the importance to account for predator feeding capacities and dietary ranges to understand the effects of invasive species at higher trophic levels.

  18. Inducible defenses in Olympia oysters in response to an invasive predator.

    PubMed

    Bible, Jillian M; Griffith, Kaylee R; Sanford, Eric

    2017-03-01

    The prey naiveté hypothesis suggests that native prey may be vulnerable to introduced predators because they have not evolved appropriate defenses. However, recent evidence suggests that native prey sometimes exhibit induced defenses to introduced predators, as a result of rapid evolution or other processes. We examined whether Olympia oysters (Ostrea lurida) display inducible defenses in the presence of an invasive predator, the Atlantic oyster drill (Urosalpinx cinerea), and whether these responses vary among oyster populations from estuaries with and without this predator. We spawned oysters from six populations distributed among three estuaries in northern California, USA, and raised their offspring through two generations under common conditions to minimize effects of environmental history. We exposed second-generation oysters to cue treatments: drills eating oysters, drills eating barnacles, or control seawater. Oysters from all populations grew smaller shells when exposed to drill cues, and grew thicker and harder shells when those drills were eating oysters. Oysters exposed to drills eating other oysters were subsequently preyed upon at a slower rate. Although all oyster populations exhibited inducible defenses, oysters from the estuary with the greatest exposure to drills grew the smallest shells suggesting that oyster populations have evolved adaptive differences in the strength of their responses to predators. Our findings add to a growing body of literature that suggests that marine prey may be less likely to exhibit naiveté in the face of invasive predators than prey in communities that are more isolated from native predators, such as many freshwater and terrestrial island ecosystems.

  19. Does differential predation permit invasive and native mosquito larvae to coexist in Florida?

    PubMed Central

    GRISWOLD, MARCUS W.; LOUNIBOS, L. PHILIP

    2012-01-01

    1. The hypothesis that selective predation on larvae of the invasive Aedes albopictus (Skuse) could account for its stable coexistence with the native mosquito species and inferior competitor Ochlerotatus triseriatus (Say) in Florida treeholes and container systems was tested experimentally. 2. Functional responses of the two dipteran predators Toxorhynchites rutilus (Coquillett) and Corethrella appendiculata (Grabham) were evaluated separately for A. albopictus and O. triseriatus prey. Both predators exhibited type II functional responses and consistently consumed more of the invasive species. Handling time of T. rutilus feeding upon O. triseriatus was significantly longer than when preying upon the invasive species. 3. When either predator species was offered varying ratios of the two prey species, A. albopictus was consumed preferentially. The absence of a prey ratio effect on preference indicated that switching probably does not occur. 4. The higher maximum feeding rate upon, and preference for, A. albopictus suggests that differential predation may foster coexistence of the invasive and native mosquito prey species in Florida. PMID:22532705

  20. Eating chemically defended prey: alkaloid metabolism in an invasive ladybird predator of other ladybirds (Coleoptera: Coccinellidae).

    PubMed

    Sloggett, J J; Davis, A J

    2010-01-15

    By comparison with studies of herbivore physiological adaptation to plant allelochemicals, work on predator physiological adaptation to potentially toxic prey has been very limited. Such studies are important in understanding how evolution could shape predator diets. An interesting question is the specificity of predator adaptation to prey allelochemicals, given that many predators consume diverse prey with different chemical defences. The ladybird Harmonia axyridis, an invasive species in America, Europe and Africa, is considered a significant predatory threat to native invertebrates, particularly other aphid-eating ladybirds of which it is a strong intraguild predator. Although ladybirds possess species-specific alkaloid defences, H. axyridis exhibits high tolerance for allospecific ladybird prey alkaloids. Nonetheless, it performs poorly on species with novel alkaloids not commonly occurring within its natural range. We examined alkaloid fate in H. axyridis larvae after consumption of two other ladybird species, one containing an alkaloid historically occurring within the predator's native range (isopropyleine) and one containing a novel alkaloid that does not (adaline). Our results indicate that H. axyridis rapidly chemically modifies the alkaloid to which it has been historically exposed to render it less harmful: this probably occurs outside of the gut. The novel, more toxic alkaloid persists in the body unchanged for longer. Our results suggest metabolic alkaloid specialisation, in spite of the diversity of chemically defended prey that the predator consumes. Physiological adaptations appear to have made H. axyridis a successful predator of other ladybirds; however, limitations are imposed by its physiology when it eats prey with novel alkaloids.

  1. Kangaroo rats change temperature when investigating rattlesnake predators.

    PubMed

    Schraft, Hannes A; Clark, Rulon W

    2017-05-01

    Predator presence causes acute stress in mammals. A prey animal's stress response increases its chance of survival during life-threatening situations through adaptive changes in behavior and physiology. Some components of the physiological stress response can lead to changes in body surface temperatures. Body temperature changes in prey could provide information about prey state to predators that sense heat, such as pit vipers. We determined whether wild rodents undergo a stress-induced change in body surface temperature upon detecting and investigating rattlesnake predators. We staged encounters between free-ranging Merriam's kangaroo rats (Dipodomys merriami) and tethered Mojave rattlesnakes (Crotalus scutulatus) at baited feeding stations, and recorded interactions with a thermal-imaging camera. Kangaroo rats showed a significant change in maximum head temperature, snout temperature, and hind leg temperature during interactions with rattlesnakes. This supports the hypothesis that presence of a predator induces body temperature changes in prey animals. If changes in prey heat signature are detectable by heat-sensitive rattlesnakes, rattlesnakes could use this information to evaluate prey vigilance or arousal before striking; however, more detailed information on the sensory ecology of the pit organ under field conditions is needed to evaluate this possibility. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. Native Predators Do Not Influence Invasion Success of Pacific Lionfish on Caribbean Reefs

    PubMed Central

    Hackerott, Serena; Valdivia, Abel; Green, Stephanie J.; Côté, Isabelle M.; Cox, Courtney E.; Akins, Lad; Layman, Craig A.; Precht, William F.; Bruno, John F.

    2013-01-01

    Biotic resistance, the process by which new colonists are excluded from a community by predation from and/or competition with resident species, can prevent or limit species invasions. We examined whether biotic resistance by native predators on Caribbean coral reefs has influenced the invasion success of red lionfishes (Pterois volitans and Pterois miles), piscivores from the Indo-Pacific. Specifically, we surveyed the abundance (density and biomass) of lionfish and native predatory fishes that could interact with lionfish (either through predation or competition) on 71 reefs in three biogeographic regions of the Caribbean. We recorded protection status of the reefs, and abiotic variables including depth, habitat type, and wind/wave exposure at each site. We found no relationship between the density or biomass of lionfish and that of native predators. However, lionfish densities were significantly lower on windward sites, potentially because of habitat preferences, and in marine protected areas, most likely because of ongoing removal efforts by reserve managers. Our results suggest that interactions with native predators do not influence the colonization or post-establishment population density of invasive lionfish on Caribbean reefs. PMID:23874565

  3. Native predators do not influence invasion success of pacific lionfish on Caribbean reefs.

    PubMed

    Hackerott, Serena; Valdivia, Abel; Green, Stephanie J; Côté, Isabelle M; Cox, Courtney E; Akins, Lad; Layman, Craig A; Precht, William F; Bruno, John F

    2013-01-01

    Biotic resistance, the process by which new colonists are excluded from a community by predation from and/or competition with resident species, can prevent or limit species invasions. We examined whether biotic resistance by native predators on Caribbean coral reefs has influenced the invasion success of red lionfishes (Pterois volitans and Pterois miles), piscivores from the Indo-Pacific. Specifically, we surveyed the abundance (density and biomass) of lionfish and native predatory fishes that could interact with lionfish (either through predation or competition) on 71 reefs in three biogeographic regions of the Caribbean. We recorded protection status of the reefs, and abiotic variables including depth, habitat type, and wind/wave exposure at each site. We found no relationship between the density or biomass of lionfish and that of native predators. However, lionfish densities were significantly lower on windward sites, potentially because of habitat preferences, and in marine protected areas, most likely because of ongoing removal efforts by reserve managers. Our results suggest that interactions with native predators do not influence the colonization or post-establishment population density of invasive lionfish on Caribbean reefs.

  4. Gape-limited predators as agents of selection on the defensive morphology of an invasive invertebrate.

    PubMed

    Miehls, Andrea L J; Peacor, Scott D; McAdam, Andrew G

    2014-09-01

    Invasive species have widespread and pronounced effects on ecosystems and adaptive evolution of invaders is often considered responsible for their success. Despite the potential importance of adaptation to invasion, we still have limited knowledge of the agents of natural selection on invasive species. Bythotrephes longimanus, a cladoceran zooplankton, invaded multiple Canadian Shield lakes over the past several decades. Bythotrephes have a conspicuous caudal process (tail spine) that provides a morphological defense against fish predation. We measured viability selection on the longest component of the Bythotrephes spine, the distal spine segment, through a comparison of the lengths of first and second instar Bythotrephes collected from lakes differing in the dominance of gape-limited predation (GLP) and nongape-limited predation (NGLP) by fish. We found that natural selection varied by predator gape-limitation, with strong selection (selection intensity: 0.20-0.79) for increased distal spine length in lakes dominated by GLP, and no significant selection in lakes dominated by NGLP. Further, distal spine length was 17% longer in lakes dominated by GLP, suggesting the possibility of local adaptation. As all study lakes were invaded less than 20 years prior to our collections, our results suggest rapid divergence in defensive morphology in response to selection from fish predators.

  5. Central-place foraging and ecological effects of an invasive predator across multiple habitats.

    PubMed

    Benkwitt, Cassandra E

    2016-10-01

    Cross-habitat foraging movements of predators can have widespread implications for predator and prey populations, community structure, nutrient transfer, and ecosystem function. Although central-place foraging models and other aspects of optimal foraging theory focus on individual predator behavior, they also provide useful frameworks for understanding the effects of predators on prey populations across multiple habitats. However, few studies have examined both the foraging behavior and ecological effects of nonnative predators across multiple habitats, and none has tested whether nonnative predators deplete prey in a manner predicted by these foraging models. I conducted behavioral observations of invasive lionfish (Pterois volitans) to determine whether they exhibit foraging movements similar to other central-place consumers. Then, I used a manipulative field experiment to test whether their effects on prey populations are consistent with three qualitative predictions from optimal foraging models. Specifically, I predicted that the effects of invasive lionfish on native prey will (1) occur at central sites first and then in surrounding habitats, (2) decrease with increasing distance away from their shelter site, and (3) extend to greater distances when prey patches are spaced closer together. Approximately 40% of lionfish exhibited short-term crepuscular foraging movements into surrounding habitats from the coral patch reefs where they shelter during daylight hours. Over the course of 7 weeks, lionfish depleted native fish populations on the coral patch reefs where they reside, and subsequently on small structures in the surrounding habitat. However, their effects did not decrease with increasing distance from the central shelter site and the influence of patch spacing was opposite the prediction. Instead, lionfish always had the greatest effects in areas with the highest prey densities. The differences between the predicted and observed effects of lionfish

  6. Intraguild predation behaviour of ladybirds in semi-field experiments explains invasion success of Harmonia axyridis.

    PubMed

    Raak-van den Berg, C Lidwien; De Lange, Hendrika J; Van Lenteren, Joop C

    2012-01-01

    Harmonia axyridis has been introduced as a biological control agent in Europe and the USA. Since its introduction, it has established and spread, and it is now regarded as an invasive alien species. It has been suggested that intraguild predation is especially important for the invasion success of H. axyridis. The aim of this study was to compare the intraguild predation behaviour of three ladybird species (Coccinella septempunctata, Adalia bipunctata, and H. axyridis). Predation behaviour was investigated in semi-field experiments on small lime trees (Tilia platyphyllos). Two fourth-instar larvae placed on a tree rarely made contact during 3-hour observations. When placed together on a single leaf in 23%-43% of the observations at least one contact was made. Of those contacts 0%-27% resulted in an attack. Harmonia axyridis attacked mostly heterospecifics, while A. bipunctata and C. septempunctata attacked heterospecifics as often as conspecifics. In comparison with A. bipunctata and C. septempunctata, H. axyridis was the most successful intraguild predator as it won 86% and 44% of heterospecific battles against A. bipunctata and C. septempunctata respectively, whilst A. bipunctata won none of the heterospecific battles and C. septempunctata won only the heterospecific battles against A. bipunctata. Coccinella septempunctata dropped from a leaf earlier and more often than the other two species but was in some cases able to return to the tree, especially under cloudy conditions. The frequency with which a species dropped did not depend on the species the larva was paired with. The results of these semi-field experiments confirm that H. axyridis is a strong intraguild predator as a consequence of its aggressiveness and good defence against predation from heterospecific species. The fact that H. axyridis is such a strong intraguild predator helps to explain its successful establishment as invasive alien species in Europe and the USA.

  7. Intraguild Predation Behaviour of Ladybirds in Semi-Field Experiments Explains Invasion Success of Harmonia axyridis

    PubMed Central

    Van Lenteren, Joop C.

    2012-01-01

    Harmonia axyridis has been introduced as a biological control agent in Europe and the USA. Since its introduction, it has established and spread, and it is now regarded as an invasive alien species. It has been suggested that intraguild predation is especially important for the invasion success of H. axyridis. The aim of this study was to compare the intraguild predation behaviour of three ladybird species (Coccinella septempunctata, Adalia bipunctata, and H. axyridis). Predation behaviour was investigated in semi-field experiments on small lime trees (Tilia platyphyllos). Two fourth-instar larvae placed on a tree rarely made contact during 3-hour observations. When placed together on a single leaf in 23%–43% of the observations at least one contact was made. Of those contacts 0%–27% resulted in an attack. Harmonia axyridis attacked mostly heterospecifics, while A. bipunctata and C. septempunctata attacked heterospecifics as often as conspecifics. In comparison with A. bipunctata and C. septempunctata, H. axyridis was the most successful intraguild predator as it won 86% and 44% of heterospecific battles against A. bipunctata and C. septempunctata respectively, whilst A. bipunctata won none of the heterospecific battles and C. septempunctata won only the heterospecific battles against A. bipunctata. Coccinella septempunctata dropped from a leaf earlier and more often than the other two species but was in some cases able to return to the tree, especially under cloudy conditions. The frequency with which a species dropped did not depend on the species the larva was paired with. The results of these semi-field experiments confirm that H. axyridis is a strong intraguild predator as a consequence of its aggressiveness and good defence against predation from heterospecific species. The fact that H. axyridis is such a strong intraguild predator helps to explain its successful establishment as invasive alien species in Europe and the USA. PMID:22815790

  8. Temporal dynamics of woodpecker predation on the invasive emerald ash borer (Agrilus planipennis) in North America

    USDA-ARS?s Scientific Manuscript database

    Woodpeckers (Picidae) are among the most prevalent natural enemies attacking the invasive emerald ash borer (EAB), Agrilus planipennis Fairmaire, in North America, but there can be considerable variation in the levels of EAB predation on ash trees (Oleaceae: Fraxinus) within and between sites as wel...

  9. Invasive plant architecture alters trophic interactions by changing predator abundance and behavior

    Treesearch

    Dean E. Pearson

    2009-01-01

    As primary producers, plants are known to influence higher trophic interactions by initiating food chains. However, as architects, plants may bypass consumers to directly affect predators with important but underappreciated trophic ramifications. Invasion of western North American grasslands by the perennial forb, spotted knapweed (Centaurea maculosa...

  10. Predators

    USGS Publications Warehouse

    Young, Donald D.; McCabe, Thomas R.; Ambrose, Robert E.; Garner, Gerald W.; Weiler, Greg J.; Reynolds, Harry V.; Udevitz, Mark S.; Reed, Dan J.; Griffith, Brad; Douglas, David C.; Reynolds, Patricia E.; Rhode, E.B.

    2002-01-01

    Calving caribou (Rangifer tarandus) of the Central Arctic herd, Alaska, have avoided the infrastructure associated with the complex of petroleum development areas from Prudhoe Bay to Kuparuk (Cameron et al. 1992, Nellemann and Cameron 1998, and Section 4 of this document). Calving females of the Porcupine caribou herd may similarly avoid any oil field roads and pipelines developed in areas traditionally used during the calving and post-calving periods. This may displace the caribou females and calves to areas east and south of the 1002 Area of the Arctic National Wildlife Refuge.Increased calf mortality could occur if calving caribou are displaced into areas that have a higher density of predators, higher rates of predation, or where a higher proportion of the predators regularly use caribou as a food source (Whitten et al. 1992).Our study assessed predation risks to caribou calving in the 1002 Area versus calving in potential displacement areas. Due to funding constraints, our research focused on grizzly bears (Ursus arctos), with wolves (Camus lupus) and golden eagles (Aquila chrysaetos) receiving only cursory attention. Our research objectives were 1) to compare relative abundance of predators within the 1002 Area with that in adjacent peripheral areas, 2) to determine factors affecting predator abundance on the calving grounds, and 3) to quantify the use of caribou as a food source for predators and the importance of caribou to the productivity of predator populations using the coastal plain of the Arctic National Wildlife Refuge.

  11. Large nonlethal effects of an invasive invertebrate predator on zooplankton population growth rate.

    PubMed

    Pangle, Kevin L; Peacor, Scott D; Johannsson, Ora E

    2007-02-01

    We conducted a study to determine the contribution of lethal and nonlethal effects to a predator's net effect on a prey's population growth rate in a natural setting. We focused on the effects of an invasive invertebrate predator, Bythotrephes longimanus, on zooplankton prey populations in Lakes Michigan and Erie. Field data taken at multiple dates and locations in both systems indicated that the prey species Daphnia mendotae, Daphnia retrocurva, and Bosmina longirostris inhabited deeper portions of the water column as Bythotrephes biomass increased, possibly as an avoidance response to predation. This induced migration reduces predation risk but also can reduce birth rate due to exposure to cooler temperatures. We estimated the nonlethal (i.e., resulting from reduced birth rate) and lethal (i.e., consumptive) effects of Bythotrephes on D. mendotae and Bosmina longirostris. These estimates used diel field survey data of the vertical gradient of zooplankton prey density, Bythotrephes density, light intensity, and temperature with growth and predation rate models derived from laboratory studies. Results indicate that nonlethal effects played a substantial role in the net effect of Bythotrephes on several prey population growth rates in the field, with nonlethal effects on the same order of magnitude as or greater (up to 10-fold) than lethal effects. Our results further indicate that invasive species can have strong nonlethal, behaviorally based effects, despite short evolutionary coexistence with prey species.

  12. Do anuran larvae respond behaviourally to chemical cues from an invasive crayfish predator? A community-wide study.

    PubMed

    Nunes, Ana L; Richter-Boix, Alex; Laurila, Anssi; Rebelo, Rui

    2013-01-01

    Antipredator behaviour is an important fitness component in most animals. A co-evolutionary history between predator and prey is important for prey to respond adaptively to predation threats. When non-native predator species invade new areas, native prey may not recognise them or may lack effective antipredator defences. However, responses to novel predators can be facilitated by chemical cues from the predators' diet. The red swamp crayfish Procambarus clarkii is a widespread invasive predator in the Southwest of the Iberian Peninsula, where it preys upon native anuran tadpoles. In a laboratory experiment we studied behavioural antipredator defences (alterations in activity level and spatial avoidance of predator) of nine anurans in response to P. clarkii chemical cues, and compared them with the defences towards a native predator, the larval dragonfly Aeshna sp. To investigate how chemical cues from consumed conspecifics shape the responses, we raised tadpoles with either a tadpole-fed or starved crayfish, or dragonfly larva, or in the absence of a predator. Five species significantly altered their behaviour in the presence of crayfish, and this was largely mediated by chemical cues from consumed conspecifics. In the presence of dragonflies, most species exhibited behavioural defences and often these did not require the presence of cues from predation events. Responding to cues from consumed conspecifics seems to be a critical factor in facilitating certain behavioural responses to novel exotic predators. This finding can be useful for predicting antipredator responses to invasive predators and help directing conservation efforts to the species at highest risk.

  13. Roles of spatial partitioning, competition, and predation in the North American invasion of an exotic mosquito.

    PubMed

    Freed, T Z; Leisnham, P T

    2014-06-01

    Invasion success and species coexistence are often mediated by species interactions across patchily distributed habitats and resources. The invasive mosquito Aedes japonicus japonicus has established in the North American range of the competitively superior resident congener, Aedes albopictus, and the predatory native mosquito Toxorhynchites rutilus. We tested predictions for two hypotheses of invasion success and species coexistence: keystone predation and spatial partitioning. We tested competition between A. japonicus japonicus and A. albopictus with or without T. rutilus in laboratory microcosms, and measured abundances of A. japonicus japonicus, A. albopictus, other resident competing mosquito species, and the presence of T. rutilus among tree holes and tires in metropolitan Washington, DC. In laboratory microcosms, A. albopictus was competitively dominant over A. japonicus japonicus, which is consistent with the few prior studies of competition between these two Aedes species. T. rutilus predation severely lowered performances of both Aedes species but more severely lowered A. japonicus japonicus performance than A. albopictus performance when all three species co-occurred, thus yielding no evidence for keystone predation. Consistent with the spatial partitioning hypothesis, A. japonicus japonicus was negatively correlated and independently aggregated with A. albopictus and all combined resident mosquito competitors and was not associated with T. rutilus among field containers. These results suggest that predation from T. rutilus and competition from A. albopictus are barriers to the spread of A. japonicus japonicus, but that A. japonicus japonicus may escape these interspecific effects by utilizing spatially partitioned container habitats.

  14. Ocean acidification increases the vulnerability of native oysters to predation by invasive snails

    PubMed Central

    Sanford, Eric; Gaylord, Brian; Hettinger, Annaliese; Lenz, Elizabeth A.; Meyer, Kirstin; Hill, Tessa M.

    2014-01-01

    There is growing concern that global environmental change might exacerbate the ecological impacts of invasive species by increasing their per capita effects on native species. However, the mechanisms underlying such shifts in interaction strength are poorly understood. Here, we test whether ocean acidification, driven by elevated seawater pCO2, increases the susceptibility of native Olympia oysters to predation by invasive snails. Oysters raised under elevated pCO2 experienced a 20% increase in drilling predation. When presented alongside control oysters in a choice experiment, 48% more high-CO2 oysters were consumed. The invasive snails were tolerant of elevated CO2 with no change in feeding behaviour. Oysters raised under acidified conditions did not have thinner shells, but were 29–40% smaller than control oysters, and these smaller individuals were consumed at disproportionately greater rates. Reduction in prey size is a common response to environmental stress that may drive increasing per capita effects of stress-tolerant invasive predators. PMID:24430847

  15. Stealth predation and the predatory success of the invasive ctenophore Mnemiopsis leidyi

    PubMed Central

    Colin, Sean P.; Costello, John H.; Hansson, Lars J.; Titelman, Josefin; Dabiri, John O.

    2010-01-01

    In contrast to higher metazoans such as copepods and fish, ctenophores are a basal metazoan lineage possessing a relatively narrow set of sensory-motor capabilities. Yet lobate ctenophores can capture prey at rates comparable to sophisticated predatory copepods and fish, and they are capable of altering the composition of coastal planktonic communities. Here, we demonstrate that the predatory success of the lobate ctenophore Mnemiopsis leidyi lies in its use of cilia to generate a feeding current that continuously entrains large volumes of fluid, yet is virtually undetectable to its prey. This form of stealth predation enables M. leidyi to feed as a generalist predator capturing prey, including microplankton (approximately 50 μm), copepods (approximately 1 mm), and fish larvae (>3 mm). The efficacy and versatility of this stealth feeding mechanism has enabled M. leidyi to be notoriously destructive as a predator and successful as an invasive species. PMID:20855619

  16. Stealth predation and the predatory success of the invasive ctenophore Mnemiopsis leidyi.

    PubMed

    Colin, Sean P; Costello, John H; Hansson, Lars J; Titelman, Josefin; Dabiri, John O

    2010-10-05

    In contrast to higher metazoans such as copepods and fish, ctenophores are a basal metazoan lineage possessing a relatively narrow set of sensory-motor capabilities. Yet lobate ctenophores can capture prey at rates comparable to sophisticated predatory copepods and fish, and they are capable of altering the composition of coastal planktonic communities. Here, we demonstrate that the predatory success of the lobate ctenophore Mnemiopsis leidyi lies in its use of cilia to generate a feeding current that continuously entrains large volumes of fluid, yet is virtually undetectable to its prey. This form of stealth predation enables M. leidyi to feed as a generalist predator capturing prey, including microplankton (approximately 50 μm), copepods (approximately 1 mm), and fish larvae (>3 mm). The efficacy and versatility of this stealth feeding mechanism has enabled M. leidyi to be notoriously destructive as a predator and successful as an invasive species.

  17. Effects of Competition and Predation by Native Mosquitoes on the North American Invasion of Aedes japonicus japonicus (Diptera: Culicidae).

    PubMed

    Freed, T Z; Kesavaraju, B; Leisnham, P T

    2014-11-01

    The success and effects of a biological invasion can be dependent on species interactions with resident competitors and predators. Indirect interactions between competition and predation, such as keystone predation, can influence both invasion success and the impact of an invasive species on resident competitors. The invasive mosquito Aedes japonicus japonicus (Theobald) has been established within the North American range of the indigenous competitor Aedes triseriatus (Say) and indigenous mosquito predator Toxorhynchites rutilus (Coquillett). The effects of Tx. rutilus predation on competition between Ae. j. japonicus and Ae. triseriatus were tested in laboratory microcosms. Consistent with a prior study, there was minimal evidence of competitive asymmetry between Ae. j. japonicus and Ae. triseriatus, with similar effects of intraspecific versus interspecific interactions on both species. Tx. rutilus predation caused high mortality of both Ae. j. japonicus and Ae. triseriatus, and minimized the effects of density-dependent competition. Ae. japonicus females that survived predation had larger adult body sizes than those in treatments without predators. Ae. triseriatus females that survived Tx. rutilus predation were larger and developed quicker than individuals in treatments without predators. Intraspecific competition and predation negatively affected the finite rate of population increase for Ae. j. japonicus, but only affected individual fitness correlates for Ae. triseriatus, indicating that the overall population performance of the invader is more sensitive to these interactions than the native species. Based on these results, we predict that predation is likely to be an important barrier to the establishment and spread of Ae. j. japonicus in tree holes in North America. © 2014 Entomological Society of America.

  18. Molecular analysis of predation by carabid beetles (Carabidae) on the invasive Iberian slug Arion lusitanicus.

    PubMed

    Hatteland, B A; Symondson, W O C; King, R A; Skage, M; Schander, C; Solhøy, T

    2011-12-01

    The invasive Iberian slug, Arion lusitanicus, is spreading through Europe and poses a major threat to horticulture and agriculture. Natural enemies, capable of killing A. lusitanicus, may be important to our understanding of its population dynamics in recently invaded regions. We used polymerase chain reaction (PCR) to study predation on A. lusitanicus by carabid beetles in the field. A first multiplex PCR was developed, incorporating species-specific primers, and optimised in order to amplify parts of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene of large Arion slugs, including A. lusitanicus from the gut contents of the predators. A second multiplex PCR, targeting 12S rRNA mtDNA, detected predation on smaller Arion species and the field slug Deroceras reticulatum. Feeding trials were conducted to measure the effects of digestion time on amplicon detectability. The median detection times (the time at which 50% of samples tested positive) for A. lusitanicus and D. reticulatum DNA in the foreguts of Carabus nemoralis were 22 h and 20 h, respectively. Beetle activity-densities were monitored using pitfall traps, and slug densities were estimated using quadrats. Predation rates on slugs in the field by C. nemoralis in spring ranged from 16-39% (beetles positive for slug DNA) and were density dependent, with numbers of beetles testing positive being positively correlated with densities of the respective slug species. Carabus nemoralis was shown to be a potentially important predator of the alien A. lusitanicus in spring and may contribute to conservation biological control.

  19. Sea Urchins Predation Facilitates Coral Invasion in a Marine Reserve

    PubMed Central

    Coma, Rafel; Serrano, Eduard; Linares, Cristina; Ribes, Marta; Díaz, David; Ballesteros, Enric

    2011-01-01

    Macroalgae is the dominant trophic group on Mediterranean infralittoral rocky bottoms, whereas zooxanthellate corals are extremely rare. However, in recent years, the invasive coral Oculina patagonica appears to be increasing its abundance through unknown means. Here we examine the pattern of variation of this species at a marine reserve between 2002 and 2010 and contribute to the understanding of the mechanisms that allow its current increase. Because indirect interactions between species can play a relevant role in the establishment of species, a parallel assessment of the sea urchin Paracentrotus lividus, the main herbivorous invertebrate in this habitat and thus a key species, was conducted. O. patagonica has shown a 3-fold increase in abundance over the last 8 years and has become the most abundant invertebrate in the shallow waters of the marine reserve, matching some dominant erect macroalgae in abundance. High recruitment played an important role in this increasing coral abundance. The results from this study provide compelling evidence that the increase in sea urchin abundance may be one of the main drivers of the observed increase in coral abundance. Sea urchins overgraze macroalgae and create barren patches in the space-limited macroalgal community that subsequently facilitate coral recruitment. This study indicates that trophic interactions contributed to the success of an invasive coral in the Mediterranean because sea urchins grazing activity indirectly facilitated expansion of the coral. Current coral abundance at the marine reserve has ended the monopolization of algae in rocky infralittoral assemblages, an event that could greatly modify both the underwater seascape and the sources of primary production in the ecosystem. PMID:21789204

  20. Invasive plant architecture alters trophic interactions by changing predator abundance and behavior.

    PubMed

    Pearson, Dean E

    2009-03-01

    As primary producers, plants are known to influence higher trophic interactions by initiating food chains. However, as architects, plants may bypass consumers to directly affect predators with important but underappreciated trophic ramifications. Invasion of western North American grasslands by the perennial forb, spotted knapweed (Centaurea maculosa), has fundamentally altered the architecture of native grassland vegetation. Here, I use long-term monitoring, observational studies, and field experiments to document how changes in vegetation architecture have affected native web spider populations and predation rates. Native spiders that use vegetation as web substrates were collectively 38 times more abundant in C. maculosa-invaded grasslands than in uninvaded grasslands. This increase in spider abundance was accompanied by a large shift in web spider community structure, driven primarily by the strong response of Dictyna spiders to C. maculosa invasion. Dictyna densities were 46-74 times higher in C. maculosa-invaded than native grasslands, a pattern that persisted over 6 years of monitoring. C. maculosa also altered Dictyna web building behavior and foraging success. Dictyna webs on C. maculosa were 2.9-4.0 times larger and generated 2.0-2.3 times higher total prey captures than webs on Achillea millefolium, their primary native substrate. Dictyna webs on C. maculosa also captured 4.2 times more large prey items, which are crucial for reproduction. As a result, Dictyna were nearly twice as likely to reproduce on C. maculosa substrates compared to native substrates. The overall outcome of C. maculosa invasion and its transformative effects on vegetation architecture on Dictyna density and web building behavior were to increase Dictyna predation on invertebrate prey >/=89 fold. These results indicate that invasive plants that change the architecture of native vegetation can substantially impact native food webs via nontraditional plant --> predator --> consumer

  1. Experimental Test of Preferences for an Invasive Prey by an Endangered Predator: Implications for Conservation

    PubMed Central

    Wilcox, Rebecca C.

    2016-01-01

    Identifying impacts of exotic species on native populations is central to ecology and conservation. Although the effects of exotic predators on native prey have received much attention, the role of exotic prey on native predators is poorly understood. Determining if native predators actively prefer invasive prey over native prey has implications for interpreting invasion impacts, identifying the presence of evolutionary traps, and predator persistence. One of the world’s most invasive species, Pomacea maculata, has recently established in portions of the endangered Everglade snail kite’s (Rostrhamus sociabilis plumbeus) geographic range. Although these exotic snails could provide additional prey resources, they are typically much larger than the native snail, which can lead to lower foraging success and the potential for diminished energetic benefits in comparison to native snails. Nonetheless, snail kites frequently forage on exotic snails. We used choice experiments to evaluate snail kite foraging preference in relation to exotic species and snail size. We found that snail kites do not show a preference for native or exotic snails. Rather, snail kites generally showed a preference for medium-sized snails, the sizes reflective of large native snails. These results suggest that while snail kites frequently forage on exotic snails in the wild, this behavior is likely driven simply by the abundance of exotic snails rather than snail kites preferring exotics. This lack of preference offers insights to hypotheses regarding effects of exotic species, guidance regarding habitat and invasive species management, and illustrates how native-exotic relationships can be misleading in the absence of experimental tests of such interactions. PMID:27829031

  2. Keystone predators (eastern newts, Notophthalmus viridescens) reduce the impacts of an aquatic invasive species

    USGS Publications Warehouse

    Smith, Kimberly G.

    2006-01-01

    Predation, competition, and their interaction are known to be important factors that influence the structure of ecological communities. In particular, in those cases where a competitive hierarchy exists among prey species, the presence of certain keystone predators can result in enhanced diversity in the prey community. However, little is known regarding the influence of keystone predator presence on invaded prey communities. Given the widespread occurrence of invasive species and substantial concern regarding their ecological impacts, studies on this topic are needed. In this study I used naturalistic replications of an experimental tadpole assemblage to assess the influence of predatory eastern newts, Notophthalmus viridescens, on the outcome of interspecific competition among native and nonindigenous tadpoles. When newts were absent, the presence of the tadpoles of one invasive species, the Cuban treefrog, Osteopilus septentrionalis, resulted in decreased survival and growth rate of the dominant native species, Bufo terrestris, and dominance of the tadpole assemblage by O. septentrionalis. However, the presence of one adult newt generally reduced or eliminated the negative impacts of O. septentrionalis tadpoles, resulting in comparable survival and performance of native species in invaded and noninvaded treatments. Differential mortality among the tadpole species suggests that newts preyed selectively on O. septentrionalis tadpoles, supporting the hypothesis that newts acted as keystone predators in the invaded assemblage. The presence of nonindigenous larval cane toads, Bufo marinus, did not significantly affect native species, and this species was not negatively affected by the presence of newts. Collectively, these results suggest that eastern newts significantly modified the competitive hierarchy of the invaded tadpole assemblage and reduced the impacts of a competitively superior invasive species. If general, these results suggest that the presence of

  3. Experimental Test of Preferences for an Invasive Prey by an Endangered Predator: Implications for Conservation.

    PubMed

    Wilcox, Rebecca C; Fletcher, Robert J

    2016-01-01

    Identifying impacts of exotic species on native populations is central to ecology and conservation. Although the effects of exotic predators on native prey have received much attention, the role of exotic prey on native predators is poorly understood. Determining if native predators actively prefer invasive prey over native prey has implications for interpreting invasion impacts, identifying the presence of evolutionary traps, and predator persistence. One of the world's most invasive species, Pomacea maculata, has recently established in portions of the endangered Everglade snail kite's (Rostrhamus sociabilis plumbeus) geographic range. Although these exotic snails could provide additional prey resources, they are typically much larger than the native snail, which can lead to lower foraging success and the potential for diminished energetic benefits in comparison to native snails. Nonetheless, snail kites frequently forage on exotic snails. We used choice experiments to evaluate snail kite foraging preference in relation to exotic species and snail size. We found that snail kites do not show a preference for native or exotic snails. Rather, snail kites generally showed a preference for medium-sized snails, the sizes reflective of large native snails. These results suggest that while snail kites frequently forage on exotic snails in the wild, this behavior is likely driven simply by the abundance of exotic snails rather than snail kites preferring exotics. This lack of preference offers insights to hypotheses regarding effects of exotic species, guidance regarding habitat and invasive species management, and illustrates how native-exotic relationships can be misleading in the absence of experimental tests of such interactions.

  4. Ankyrin-mediated self-protection during cell invasion by the bacterial predator Bdellovibrio bacteriovorus

    PubMed Central

    Lambert, Carey; Cadby, Ian T.; Till, Rob; Bui, Nhat Khai; Lerner, Thomas R.; Hughes, William S.; Lee, David J.; Alderwick, Luke J.; Vollmer, Waldemar; Sockett, Elizabeth R.; Lovering, Andrew L.

    2015-01-01

    Predatory Bdellovibrio bacteriovorus are natural antimicrobial organisms, killing other bacteria by whole-cell invasion. Self-protection against prey-metabolizing enzymes is important for the evolution of predation. Initial prey entry involves the predator's peptidoglycan DD-endopeptidases, which decrosslink cell walls and prevent wasteful entry by a second predator. Here we identify and characterize a self-protection protein from B. bacteriovorus, Bd3460, which displays an ankyrin-based fold common to intracellular pathogens of eukaryotes. Co-crystal structures reveal Bd3460 complexation of dual targets, binding a conserved epitope of each of the Bd3459 and Bd0816 endopeptidases. Complexation inhibits endopeptidase activity and cell wall decrosslinking in vitro. Self-protection is vital — ΔBd3460 Bdellovibrio deleteriously decrosslink self-peptidoglycan upon invasion, adopt a round morphology, and lose predatory capacity and cellular integrity. Our analysis provides the first mechanistic examination of self-protection in Bdellovibrio, documents protection-multiplicity for products of two different genomic loci, and reveals an important evolutionary adaptation to an invasive predatory bacterial lifestyle. PMID:26626559

  5. Ankyrin-mediated self-protection during cell invasion by the bacterial predator Bdellovibrio bacteriovorus.

    PubMed

    Lambert, Carey; Cadby, Ian T; Till, Rob; Bui, Nhat Khai; Lerner, Thomas R; Hughes, William S; Lee, David J; Alderwick, Luke J; Vollmer, Waldemar; Sockett, R Elizabeth; Sockett, Elizabeth R; Lovering, Andrew L

    2015-12-02

    Predatory Bdellovibrio bacteriovorus are natural antimicrobial organisms, killing other bacteria by whole-cell invasion. Self-protection against prey-metabolizing enzymes is important for the evolution of predation. Initial prey entry involves the predator's peptidoglycan DD-endopeptidases, which decrosslink cell walls and prevent wasteful entry by a second predator. Here we identify and characterize a self-protection protein from B. bacteriovorus, Bd3460, which displays an ankyrin-based fold common to intracellular pathogens of eukaryotes. Co-crystal structures reveal Bd3460 complexation of dual targets, binding a conserved epitope of each of the Bd3459 and Bd0816 endopeptidases. Complexation inhibits endopeptidase activity and cell wall decrosslinking in vitro. Self-protection is vital - ΔBd3460 Bdellovibrio deleteriously decrosslink self-peptidoglycan upon invasion, adopt a round morphology, and lose predatory capacity and cellular integrity. Our analysis provides the first mechanistic examination of self-protection in Bdellovibrio, documents protection-multiplicity for products of two different genomic loci, and reveals an important evolutionary adaptation to an invasive predatory bacterial lifestyle.

  6. Predation.

    ERIC Educational Resources Information Center

    Spain, James D.; Soldan, Theodore

    1983-01-01

    Describes two computer simulations of the predator-prey interaction in which students explore theories and mathematical equations involved in this biological process. The programs (for Apple II), designed for college level ecology, may be used in lecture/demonstrations or as a basis for laboratory assignments. A list of student objectives is…

  7. Predation.

    ERIC Educational Resources Information Center

    Spain, James D.; Soldan, Theodore

    1983-01-01

    Describes two computer simulations of the predator-prey interaction in which students explore theories and mathematical equations involved in this biological process. The programs (for Apple II), designed for college level ecology, may be used in lecture/demonstrations or as a basis for laboratory assignments. A list of student objectives is…

  8. Morphological and life-history responses of anurans to predation by an invasive crayfish: an integrative approach.

    PubMed

    Nunes, Ana L; Orizaola, Germán; Laurila, Anssi; Rebelo, Rui

    2014-04-01

    Predator-induced phenotypic plasticity has been widely documented in response to native predators, but studies examining the extent to which prey can respond to exotic invasive predators are scarce. As native prey often do not share a long evolutionary history with invasive predators, they may lack defenses against them. This can lead to population declines and even extinctions, making exotic predators a serious threat to biodiversity. Here, in a community-wide study, we examined the morphological and life-history responses of anuran larvae reared with the invasive red swamp crayfish, Procambarus clarkii, feeding on conspecific tadpoles. We reared tadpoles of nine species until metamorphosis and examined responses in terms of larval morphology, growth, and development, as well as their degree of phenotypic integration. These responses were compared with the ones developed in the presence of a native predator, the larval dragonfly Aeshna sp., also feeding on tadpoles. Eight of the nine species altered their morphology or life history when reared with the fed dragonfly, but only four when reared with the fed crayfish, suggesting among-species variation in the ability to respond to a novel predator. While morphological defenses were generally similar across species (deeper tails) and almost exclusively elicited in the presence of the fed dragonfly, life-history responses were very variable and commonly elicited in the presence of the invasive crayfish. Phenotypes induced in the presence of dragonfly were more integrated than in crayfish presence. The lack of response to the presence of the fed crayfish in five of the study species suggests higher risk of local extinction and ultimately reduced diversity of the invaded amphibian communities. Understanding how native prey species vary in their responses to invasive predators is important in predicting the impacts caused by newly established predator-prey interactions following biological invasions.

  9. Measuring rodent incisors from scats can increase accuracy of predator diet studies. An illustration based on island cats and rats.

    PubMed

    Bonnaud, Elsa; Vidal, Eric; Zarzoso-Lacoste, Diane; Torre, Franck

    2008-09-01

    Non-invasive diet studies, which are a simple but important tool to understand trophic interactions inside ecosystems, need to be as detailed as possible. Determining the precise biomass of ingested prey is a key to obtaining not only a better understanding of the amount of food really ingested but also the predator-prey interactions. It is particularly relevant in the case of rodents, because they are often a predominant prey in carnivores' diet and can differ widely in biomass. This study demonstrates how an original and simple method for measuring rat incisors found in cat scats produces measurements which can be correlated with rat weight. This correlation, used in a field application, made it possible to: (i) calculate a more accurate biomass of rats in cat diets and thus obtain a better estimation of the proportion of rats compared to other prey in cat diets; (ii) show that cats preferentially ate smaller rats, indicating that the use of the mean weight of rodents sampled by trap-lines may induce a significant bias in the biomass calculation. Likewise, a correlation between rat lens weight and incisor measurements was found. Using this correlation, it should be possible to estimate the age of the rats eaten by cats and obtain a better understanding of the impact of predators on prey population dynamics.

  10. The effect of colored noise on spatiotemporal dynamics of biological invasion in a diffusive predator-prey system.

    PubMed

    Wang, Wenting; Li, Wenlong; Li, Zizhen; Zhang, Hui

    2011-04-01

    Spatiotemporal dynamics of a predator-prey system is considered under the assumption that the predator is sensitive to colored noise. Mathematically, the model consists of two coupled diffusion-reactions. By means of extensive numerical simulations, the complex invasion pattern formations of the system are identified. The results show that a geographical invasion emerges without regional persistence when the intensity of colored noise is small. Remarkably, as the noise intensity increases, the species spreads via a patchy invasion only when the system is affected by red noise. Meanwhile, the relationship between local stability and global invasion is also considered. The predator, which becomes extinct in the system without diffusion, could invade locally when the system is affected by white noise. However, the local invasion is not followed by geographical spread.

  11. Native Prey and Invasive Predator Patterns of Foraging Activity: The Case of the Yellow-Legged Hornet Predation at European Honeybee Hives

    PubMed Central

    Monceau, Karine; Arca, Mariangela; Leprêtre, Lisa; Mougel, Florence; Bonnard, Olivier; Silvain, Jean-François; Maher, Nevile; Arnold, Gérard; Thiéry, Denis

    2013-01-01

    Contrary to native predators, which have co-evolved with their prey, alien predators often benefit from native prey naïveté. Vespa velutina, a honeybee predator originating from Eastern China, was introduced into France just before 2004. The present study, based on video recordings of two beehives at an early stage of the invasion process, intends to analyse the alien hornet hunting behaviour on the native prey, Apis mellifera, and to understand the interaction between the activity of the predator and the prey during the day and the season. Chasing hornets spent most of their time hovering facing the hive, to catch flying honeybees returning to the hive. The predation pressure increased during the season confirming previous study based on predator trapping. The number of honeybee captures showed a maximum peak for an intermediate number of V. velutina, unrelated to honeybee activity, suggesting the occurrence of competition between hornets. The number of honeybees caught increased during midday hours while the number of hornets did not vary, suggesting an increase in their efficacy. These results suggest that the impact of V. velutina on honeybees is limited by its own biology and behaviour and did not match the pattern of activity of its prey. Also, it could have been advantageous during the invasion, limiting resource depletion and thus favouring colonisation. This lack of synchronization may also be beneficial for honeybee colonies by giving them an opportunity to increase their activity when the hornets are less effective. PMID:23823754

  12. Native Prey and Invasive Predator Patterns of Foraging Activity: The Case of the Yellow-Legged Hornet Predation at European Honeybee Hives.

    PubMed

    Monceau, Karine; Arca, Mariangela; Leprêtre, Lisa; Mougel, Florence; Bonnard, Olivier; Silvain, Jean-François; Maher, Nevile; Arnold, Gérard; Thiéry, Denis

    2013-01-01

    Contrary to native predators, which have co-evolved with their prey, alien predators often benefit from native prey naïveté. Vespa velutina, a honeybee predator originating from Eastern China, was introduced into France just before 2004. The present study, based on video recordings of two beehives at an early stage of the invasion process, intends to analyse the alien hornet hunting behaviour on the native prey, Apis mellifera, and to understand the interaction between the activity of the predator and the prey during the day and the season. Chasing hornets spent most of their time hovering facing the hive, to catch flying honeybees returning to the hive. The predation pressure increased during the season confirming previous study based on predator trapping. The number of honeybee captures showed a maximum peak for an intermediate number of V. velutina, unrelated to honeybee activity, suggesting the occurrence of competition between hornets. The number of honeybees caught increased during midday hours while the number of hornets did not vary, suggesting an increase in their efficacy. These results suggest that the impact of V. velutina on honeybees is limited by its own biology and behaviour and did not match the pattern of activity of its prey. Also, it could have been advantageous during the invasion, limiting resource depletion and thus favouring colonisation. This lack of synchronization may also be beneficial for honeybee colonies by giving them an opportunity to increase their activity when the hornets are less effective.

  13. Effects of an invasive predator cascade to plants via mutualism disruption

    PubMed Central

    Rogers, Haldre S.; Buhle, Eric R.; HilleRisLambers, Janneke; Fricke, Evan C.; Miller, Ross H.; Tewksbury, Joshua J.

    2017-01-01

    Invasive vertebrate predators are directly responsible for the extinction or decline of many vertebrate species, but their indirect impacts often go unmeasured, potentially leading to an underestimation of their full impact. When invasives extirpate functionally important mutualists, dependent species are likely to be affected as well. Here, we show that the invasive brown treesnake, directly responsible for the extirpation of forest birds from the island of Guam, is also indirectly responsible for a severe decline in plant recruitment as a result of disrupting the fruit-frugivore mutualism. To assess the impact of frugivore loss on plants, we compare seed dispersal and recruitment of two fleshy-fruited tree species on Guam and three nearby islands with intact disperser communities. We conservatively estimate that the loss of frugivorous birds caused by the brown treesnake may have caused a 61–92% decline in seedling recruitment. This case study highlights the potential for predator invasions to cause indirect, pervasive and easily overlooked interaction cascades. PMID:28270682

  14. Modelling disease introduction as biological control of invasive predators to preserve endangered prey.

    PubMed

    Oliveira, Nuno M; Hilker, Frank M

    2010-02-01

    Invasive species are a significant cause of bio-diversity loss particularly in island ecosystems. It has been suggested to release pathogenic parasites as an efficient control measure of these mostly immune-naïve populations. In order to explore the potential impacts of such bio-control approach, we construct and investigate mathematical models describing disease dynamics in a host population that acts as a predator embedded in a simple food chain. The consequences of Feline Immunodeficiency Virus (FIV) introduction into a closed ecosystem are addressed using a bi-trophic system, comprising an indigenous prey (birds) and an introduced predator (cats). Our results show that FIV is unlikely to fully eradicate cats on sub-Antarctic islands, but it can be efficient in depressing their population size, allowing for the recovery of the endangered prey. Depending on the ecological setting and disease transmission mode (we consider proportionate mixing as well as mass action), successful pathogen invasion can induce population oscillations that are not possible in the disease-free predator-prey system. These fluctuations can be seen as a mixed blessing from a management point of view. On the one hand, they may increase the extinction risk of the birds. On the other hand, they provide an opportunity to eradicate cats more easily in combination with other methods such as trapping or culling.

  15. Predation of the newly invasive pest Megacopta cribraria (F.) (Hemiptera: Plataspidae) in soybean habitats adjacent to cotton by a complex of predators

    USDA-ARS?s Scientific Manuscript database

    The kudzu bug, Megacopta cribraria (F.) (Hemiptera: Plataspidae), is a newly-invasive exotic insect found primarily on kudzu, but also on soybean, in the southeastern United States. We used molecular gut-content analysis to document predation on this pest by insects and spiders in soybean; and to d...

  16. Predation of the newly invasive pest Megacopta cribraria (Hemiptera: Plataspidae) in soybean habitats adjacent to cotton by a complex of predators.

    PubMed

    Greenstone, M H; Tillman, P G; Hu, J S

    2014-06-01

    The kudzu bug, Megacopta cribraria (F.) (Hemiptera: Plataspidae),is a newly invasive exotic insect found primarily on kudzu, but also on soybean, in the southeastern United States. We used molecular gut-content analysis to document predation on this pest by insects and spiders in soybean, and to detect remains of crop-specific alternative prey in predators' guts as markers of predator migration between soybean and adjacent cotton. M. cribraria was found exclusively on soybean. Eight native generalist predators over both crops screened positive by specific PCR for DNA of the pest: Geocoris punctipes (Say), Geocoris uliginosus (Say), Orius insidiosus (Say), Podisus maculicentris (Say), Hippodamia convergens Guérin-Méneville, Zelus renardii (Kolenati), Oxyopes salticus Hentz, and Peucetia viridans (Hentz); a ninth predator, the exotic Solenopsis invicta Buren, also screened positive for M. cribraria DNA. P. viridans was the only arthropod that tested positive for DNA of this invasive pest in only one crop, cotton. Two plant-feeding pentatomid species, Piezodorus guildinii (Westwood) and Thyanta custator (F.), were found exclusively on soybean, and another, Euschistus tristigmus (Say), was specific to cotton in the context of this study. Detection of predation on a combination of M. cribraria and P. guildinii and T. custator in cotton and M. cribraria and E. tristigmus in soybean demonstrated that these predators dispersed between crops. These results strongly support the use of soybean habitats adjacent to cotton as part of a conservation biological control strategy against M. cribraria. This is the first report documenting predation on this exotic pest in the field via molecular gut-content analysis.

  17. Morphological and life-history responses of anurans to predation by an invasive crayfish: an integrative approach

    PubMed Central

    Nunes, Ana L; Orizaola, Germán; Laurila, Anssi; Rebelo, Rui

    2014-01-01

    Predator-induced phenotypic plasticity has been widely documented in response to native predators, but studies examining the extent to which prey can respond to exotic invasive predators are scarce. As native prey often do not share a long evolutionary history with invasive predators, they may lack defenses against them. This can lead to population declines and even extinctions, making exotic predators a serious threat to biodiversity. Here, in a community-wide study, we examined the morphological and life-history responses of anuran larvae reared with the invasive red swamp crayfish, Procambarus clarkii, feeding on conspecific tadpoles. We reared tadpoles of nine species until metamorphosis and examined responses in terms of larval morphology, growth, and development, as well as their degree of phenotypic integration. These responses were compared with the ones developed in the presence of a native predator, the larval dragonfly Aeshna sp., also feeding on tadpoles. Eight of the nine species altered their morphology or life history when reared with the fed dragonfly, but only four when reared with the fed crayfish, suggesting among-species variation in the ability to respond to a novel predator. While morphological defenses were generally similar across species (deeper tails) and almost exclusively elicited in the presence of the fed dragonfly, life-history responses were very variable and commonly elicited in the presence of the invasive crayfish. Phenotypes induced in the presence of dragonfly were more integrated than in crayfish presence. The lack of response to the presence of the fed crayfish in five of the study species suggests higher risk of local extinction and ultimately reduced diversity of the invaded amphibian communities. Understanding how native prey species vary in their responses to invasive predators is important in predicting the impacts caused by newly established predator–prey interactions following biological invasions. PMID:24834343

  18. Warming-induced changes in predation, extinction and invasion in an ectotherm food web.

    PubMed

    Seifert, Linda I; Weithoff, Guntram; Gaedke, Ursula; Vos, Matthijs

    2015-06-01

    Climate change will alter the forces of predation and competition in temperate ectotherm food webs. This may increase local extinction rates, change the fate of invasions and impede species reintroductions into communities. Invasion success could be modulated by traits (e.g., defenses) and adaptations to climate. We studied how different temperatures affect the time until extinction of species, using bitrophic and tritrophic planktonic food webs to evaluate the relative importance of predatory overexploitation and competitive exclusion, at 15 and 25 °C. In addition, we tested how inclusion of a subtropical as opposed to a temperate strain in this model food web affects times until extinction. Further, we studied the invasion success of the temperate rotifer Brachionus calyciflorus into the planktonic food web at 15 and 25 °C on five consecutive introduction dates, during which the relative forces of predation and competition differed. A higher temperature dramatically shortened times until extinction of all herbivore species due to carnivorous overexploitation in tritrophic systems. Surprisingly, warming did not increase rates of competitive exclusion among the tested herbivore species in bitrophic communities. Including a subtropical herbivore strain reduced top-down control by the carnivore at high temperature. Invasion attempts of temperate B. calyciflorus into the food web always succeeded at 15 °C, but consistently failed at 25 °C due to voracious overexploitation by the carnivore. Pre-induction of defenses (spines) in B. calyciflorus before the invasion attempt did not change its invasion success at the high temperature. We conclude that high temperatures may promote local extinctions in temperate ectotherms and reduce their chances of successful recovery.

  19. High fecundity and predation pressure of the invasive Gammarus tigrinus cause decline of indigenous gammarids

    NASA Astrophysics Data System (ADS)

    Jänes, Holger; Kotta, Jonne; Herkül, Kristjan

    2015-11-01

    The North American amphipod Gammarus tigrinus is one of the most aggressive invaders recently expanding its distribution in the European waters. The species was detected in the north-eastern Baltic Sea in 2003 and has rapidly expanded its distribution ever since. This invasive amphipod has been notably successful in shallow, soft and mixed bottom habitats becoming one of the most abundant gammarid colonizing such environments. This study carried out two experiments: (1) an outdoor aquarium experiment to assess interspecific competition among the invasive G. tigrinus and the native Gammarus duebeni and compare their reproductive potential, and (2) an in situ meshbag experiment to determine the effect of adult G. tigrinus and native gammarids on juvenile gammarid amphipods. These demonstrated that the adult G. tigrinus had no effects on the adult G. duebeni; however, the invasive amphipod had higher reproductive potential compared to the native species such as G. duebeni. Moreover, almost all adult gammarids exerted a significant predation pressure on juvenile amphipods. Thus, the combined effect of predation on juvenile amphipods and large brood production of G. tigrinus could be plausible explanations describing increased abundance of G. tigrinus and decrease of local gammarid populations in the north-eastern Baltic Sea but plausibly in similar shallow water habitats in other seas.

  20. Reduced seed predation after invasion supports enemy release in a broad biogeographical survey.

    PubMed

    Castells, Eva; Morante, Maria; Blanco-Moreno, José M; Sans, F Xavier; Vilatersana, Roser; Blasco-Moreno, Anabel

    2013-12-01

    The Enemy Release (ER) hypothesis predicts an increase in the plant invasive capacity after being released from their associated herbivores or pathogens in their area of origin. Despite the large number of studies on biological invasions addressing this hypothesis, tests evaluating changes in herbivory on native and introduced populations and their effects on plant reproductive potential at a biogeographical level are relatively rare. Here, we tested the ER hypothesis on the South African species Senecio pterophorus (Asteraceae), which is native to the Eastern Cape, has expanded into the Western Cape, and was introduced into Australia (>70-100 years ago) and Europe (>30 years ago). Insect seed predation was evaluated to determine whether plants in the introduced areas were released from herbivores compared to plants from the native range. In South Africa, 25 % of the seedheads of sampled plants were damaged. Plants from the introduced populations suffered lower seed predation compared to those from the native populations, as expected under the ER hypothesis, and this release was more pronounced in the region with the most recent introduction (Europe 0.2 % vs. Australia 15 %). The insect communities feeding on S. pterophorus in Australia and Europe differed from those found in South Africa, suggesting that the plants were released from their associated fauna after invasion and later established new associations with local herbivore communities in the novel habitats. Our study is the first to provide strong evidence of enemy release in a biogeographical survey across the entire known distribution of a species.

  1. Predators, environment and host characteristics influence the probability of infection by an invasive castrating parasite.

    PubMed

    Gehman, Alyssa-Lois M; Grabowski, Jonathan H; Hughes, A Randall; Kimbro, David L; Piehler, Michael F; Byers, James E

    2017-01-01

    Not all hosts, communities or environments are equally hospitable for parasites. Direct and indirect interactions between parasites and their predators, competitors and the environment can influence variability in host exposure, susceptibility and subsequent infection, and these influences may vary across spatial scales. To determine the relative influences of abiotic, biotic and host characteristics on probability of infection across both local and estuary scales, we surveyed the oyster reef-dwelling mud crab Eurypanopeus depressus and its parasite Loxothylacus panopaei, an invasive castrating rhizocephalan, in a hierarchical design across >900 km of the southeastern USA. We quantified the density of hosts, predators of the parasite and host, the host's oyster reef habitat, and environmental variables that might affect the parasite either directly or indirectly on oyster reefs within 10 estuaries throughout this biogeographic range. Our analyses revealed that both between and within estuary-scale variation and host characteristics influenced L. panopaei prevalence. Several additional biotic and abiotic factors were positive predictors of infection, including predator abundance and the depth of water inundation over reefs at high tide. We demonstrate that in addition to host characteristics, biotic and abiotic community-level variables both serve as large-scale indicators of parasite dynamics.

  2. [Effect of chronic high-fat diet on predation behavior in rats].

    PubMed

    Chen, Wenhao; Jia, Yan; Cao, Shuhui; Chen, Yaru; Duan, Liting; Li, Changqi

    2014-12-01

    To observe the eff ect and mechanism of chronic high-fat diet on predation behavior in rats. Ten female SD rats with 4-week-old were randomly divided into a normal control group (NC group, n=5) and a chronic high-fat diet group (HF group, n=5). The rats in the NC group received the regular diet while rats in the HF group were fed with high-fat diet. Fift een weeks later, the predation behavior of rats was evaluated by open fi eld test and food foraging tests. At the end of experiments, the rats were killed and brain tissues were collected for evaluation of c-Fos protein expression in anterior cingulate cortex by immunohistochemical assay. Th e predation behavior of rats in the HF group was signifi cantly impaired in the competitive or non-competitive food foraging test compared with the control rats (P< 0.001). Th e c-fos protein expression in anterior cingulate cortex of rats from the HF group was signifi cantly decreased (P< 0.001). Long time high-fat diet can aff ect the predation behavior of rats, which is related to dysfunction of neuron in anterior cingulate cortex.

  3. Invasive plant species alters consumer behavior by providing refuge from predation.

    PubMed

    Dutra, Humberto P; Barnett, Kirk; Reinhardt, Jason R; Marquis, Robert J; Orrock, John L

    2011-07-01

    Understanding the effects of invasive plants on native consumers is important because consumer-mediated indirect effects have the potential to alter the dynamics of coexistence in native communities. Invasive plants may promote changes in consumer pressure due to changes in protective cover (i.e., the architectural complexity of the invaded habitat) and in food availability (i.e., subsidies of fruits and seeds). No experimental studies have evaluated the relative interplay of these two effects. In a factorial experiment, we manipulated cover and food provided by the invasive shrub Amur honeysuckle (Lonicera maackii) to evaluate whether this plant alters the foraging activity of native mammals. Using tracking plates to quantify mammalian foraging activity, we found that removal of honeysuckle cover, rather than changes in the fruit resources it provides, reduced the activity of important seed consumers, mice in the genus Peromyscus. Two mesopredators, Procyon lotor and Didelphis virginiana, were also affected. Moreover, we found rodents used L. maackii for cover only on cloudless nights, indicating that the effect of honeysuckle was weather-dependent. Our work provides experimental evidence that this invasive plant species changes habitat characteristics, and in so doing alters the behavior of small- and medium-sized mammals. Changes in seed predator behavior may lead to cascading effects on the seeds that mice consume.

  4. Invasive plant alters community and ecosystem dynamics by promoting native predators.

    PubMed

    Smith-Ramesh, Lauren M

    2017-03-01

    Placing invasion in a more complete food web context expands our understanding of species invasions to reflect the inherent complexity of ecological networks. Garlic mustard (Alliaria petiolata) has traditionally been predicted to dominate native communities through mechanisms embodied in popular hypotheses such as direct plant-plant interactions (allelopathy) and plant-herbivore interactions (enemy escape). However, garlic mustard also interacts directly with native predators by providing habitat for web-building spiders, which colonize the dry fruit structures (siliques) that garlic mustard leaves behind after it senesces. This interaction may lead to altered food web structure, resulting previously unexamined invasion consequences. This idea was tested in a field experiment including three treatments in which garlic mustard siliques were left intact (S+), removed (S-), or native species dominated and garlic mustard was absent (N). When siliques were intact, estimated insect abundance was locally reduced in invaded plots compared to native plots, but this relationship disappeared when siliques were removed. Phosphorus availability and the growth of one native plant species were both elevated in invaded plots where siliques were intact compared to plots where siliques were removed. Results indicate that garlic mustard's close association with web-building spiders initiates cascading invader impacts on the native community and ecosystem properties. This work supports recent theory suggesting that taking a broader food web perspective may help predict invasion impacts in different environmental contexts.

  5. Grass invasion increases top-down pressure on an amphibian via structurally mediated effects on an intraguild predator.

    PubMed

    DeVore, Jayna L; Maerz, John C

    2014-07-01

    Plants serve as both basal resources and ecosystem engineers, so plant invasion may exert trophic influences on consumers both via bottom-up processes and by altering the environmental context in which trophic interactions occur. To determine how these mechanisms affect a native predator we used a mark-recapture study in eight pairs of 58-m2 field enclosures to measure the influence of Japanese stilt grass invasion on 3200 recently metamorphosed American toads. Toad survivorship was lower in invaded habitats despite abiotic effects that favor amphibians. Prey densities were also lower in invaded habitats, but growth was unaffected. Frequent spider predation events in invaded habitats led us to use factorial field cage manipulations of stilt grass and lycosid spiders to determine if invasion increases predation rates. Spiders persisted at higher densities in the presence of stilt grass, and toad survival was lowest in cages with both grass and spiders. Invasion alone did not significantly reduce toad survival. Our results demonstrate that despite prey reductions and abiotic effects, it is increased spider persistence that reduces toad survival in invaded habitats. Invasion therefore affects resident forest floor consumers by modifying trophic interactions between native species, causing structurally mediated reductions in intraguild predation rates among spiders, with cascading implications for toad survival.

  6. Do natural container habitats impede invader dominance? Predator-mediated coexistence of invasive and native container-dwelling mosquitoes.

    PubMed

    Kesavaraju, Banugopan; Damal, Kavitha; Juliano, Steven A

    2008-03-01

    Predator-mediated coexistence of competitors occurs when a species that is superior in competition is also more vulnerable to a shared predator compared to a poorer competitor. The invasive mosquito Aedes albopictus is usually competitively superior to Ochlerotatus triseriatus. Among second instar larvae, A. albopictus show a lesser degree of behavioral modification in response to water-borne cues from predation by the larval midge Corethrella appendiculata than do O. triseriatus, rendering A. albopictus more vulnerable to predation by C. appendiculata than O. triseriatus. The hypothesis that C. appendiculata predation favors coexistence of these competitors predicts that C. appendiculata abundances will be negatively and positively correlated with A. albopictus and O. triseriatus abundances, respectively, and that coexistence will occur where C. appendiculata are common. Actual abundances of O. triseriatus, A. albopictus, and C. appendiculata in three habitats fit this prediction. In natural container habitats like tree holes, C. appendiculata were abundant and competitors co-existed at similar densities. In cemeteries and tires, which occur primarily in non-forested, human-dominated habitats, A. albopictus dominated, with abundances twice those found in tree holes, but C. appendiculata and O. triseriatus were rare or absent. We also tested for whether antipredatory behavioral responses of A. albopictus differed among habitats or populations, or were correlated with local C. appendiculata abundances. We could detect no differences in A. albopictus antipredatory behavioral responses to water-borne cues from predation. Tree hole habitats appear to promote co-existence of O. triseriatus and A. albopictus through interactions with predatory C. appendiculata, and this predator effect appears to limit invasion success of A. albopictus in tree holes. There are many studies on predator-mediated coexistence in natural habitats but to our knowledge this is the first study

  7. Do natural container habitats impede invader dominance? Predator-mediated coexistence of invasive and native container-dwelling mosquitoes

    PubMed Central

    Kesavaraju, Banugopan; Damal, Kavitha; Juliano, Steven A.

    2009-01-01

    Predator-mediated coexistence of competitors occurs when a species that is superior in competition is also more vulnerable to a shared predator compared to a poorer competitor. The invasive mosquito Aedes albopictus is usually competitively superior to Ochlerotatus triseriatus. Among second instar larvae, A. albopictus show a lesser degree of behavioral modiWcation in response to waterborne cues from predation by the larval midge Corethrella appendiculata than do O. triseriatus, rendering A. albopictus more vulnerable to predation by C. appendiculata than O. triseriatus. The hypothesis that C. appendiculata predation favors coexistence of these competitors predicts that C. appendiculata abundances will be negatively and positively correlated with A. albopictus and O. triseriatus abundances, respectively, and that coexistence will occur where C. appendiculata are common. Actual abundances of O. triseriatus, A. albopictus, and C. appendiculata in three habitats Wt this prediction. In natural container habitats like tree holes, C. appendiculata were abundant and competitors co-existed at similar densities. In cemeteries and tires, which occur primarily in non-forested, human-dominated habitats, A. albopictus dominated, with abundances twice those found in tree holes, but C. appendiculata and O. triseriatus were rare or absent. We also tested for whether antipredatory behavioral responses of A. albopictus differed among habitats or populations, or were correlated with local C. appendiculata abundances. We could detect no differences in A. albopictus antipredatory behavioral responses to water-borne cues from predation. Tree hole habitats appear to promote co-existence of O. triseriatus and A. albopictus through interactions with predatory C. appendiculata, and this predator effect appears to limit invasion success of A. albopictus in tree holes. There are many studies on predator-mediated coexistence in natural habitats but to our knowledge this is the first study to

  8. Effects of pre-pubertal social experiences on the responsiveness of juvenile rats to predator odors.

    PubMed

    Siviy, Stephen M

    2008-09-01

    The extent to which social variables may modulate the fear associated with a predator cue was assessed in juvenile rats. Cat odor reduced play to a comparable extent in both socially housed and isolate-housed rats, although socially housed rats exhibited more risk assessment during extinction. Rats that had played previously in the context used for assessing fear hid slightly less when exposed to cat odor than those rats that had not played previously in the testing context. However, no other differences were found between these two groups suggesting that prior social experience with the testing context has minimal effects on fear. In a direct test of a 'social buffering' hypothesis, rats that were tested for contextual fear conditioning in the presence of an unfamiliar partner were less fearful than those rats tested alone. These data are consistent with a social buffering hypothesis and suggest that positive social cues may help animals cope with the threat of predation.

  9. A singular reaction-diffusion system modelling prey-predator interactions: Invasion and co-extinction waves

    NASA Astrophysics Data System (ADS)

    Ducrot, A.; Langlais, M.

    We consider a singular reaction-diffusion system arising in modelling prey-predator interactions in a fragile environment. Since the underlying ODEs system exhibits a complex dynamics including possible finite time quenching, one first provides a suitable notion of global travelling wave weak solution. Then our study focusses on the existence of travelling waves solutions for predator invasion in such environments. We devise a regularized problem to prove the existence of travelling wave solutions for predator invasion followed by a possible co-extinction tail for both species. Under suitable assumptions on the diffusion coefficients and on species growth rates we show that travelling wave solutions are actually positive on a half line and identically zero elsewhere, such a property arising for every admissible wave speeds.

  10. Invasive exotic shrub modifies a classic animal-habitat relationship and alters patterns of vertebrate seed predation.

    PubMed

    Guiden, Peter W; Orrock, John L

    2017-02-01

    Recent evidence suggests that invasive exotic plants can provide novel habitats that alter animal behavior. However, it remains unclear whether classic animal-habitat associations that influence the spatial distribution of plant-animal interactions, such as small mammal use of downed woody debris, persist in invaded habitats. We removed an invasive exotic shrub (buckthorn, Rhamnus cathartica) from 7 of 15 plots in Wisconsin. In each plot, we deployed 200 tagged Quercus rubra seeds in November 2014. After five months, tags were recovered to track spatial patterns of small mammal seed predation. Most recovered tags were associated with consumed seeds (95%); live-trapping, ancillary camera-trapping, and previous behavioral studies suggest that white-footed mice (Peromyscus leucopus) were responsible for most seed predation. In habitats without R. cathartica, most seed predation occurred near woody debris. In habitats with R. cathartica, small mammals rarely consumed seeds near woody debris, and seed predation occurred farther from the plot center and was less spatially clustered. Our results illustrate that invasive exotic shrubs can disrupt an otherwise common animal-habitat relationship. Failing to account for changes in habitat use may diminish our ability to predict animal distributions and outcomes of species interactions in novel habitats created by invasive exotic plants. © 2016 by the Ecological Society of America.

  11. Predatory Functional Response and Prey Choice Identify Predation Differences between Native/Invasive and Parasitised/Unparasitised Crayfish

    PubMed Central

    Haddaway, Neal R.; Wilcox, Ruth H.; Heptonstall, Rachael E. A.; Griffiths, Hannah M.; Mortimer, Robert J. G.; Christmas, Martin; Dunn, Alison M.

    2012-01-01

    Background Invasive predators may change the structure of invaded communities through predation and competition with native species. In Europe, the invasive signal crayfish Pacifastacus leniusculus is excluding the native white clawed crayfish Austropotamobius pallipes. Methodology and Principal Findings This study compared the predatory functional responses and prey choice of native and invasive crayfish and measured impacts of parasitism on the predatory strength of the native species. Invasive crayfish showed a higher (>10%) prey (Gammarus pulex) intake rate than (size matched) natives, reflecting a shorter (16%) prey handling time. The native crayfish also showed greater selection for crustacean prey over molluscs and bloodworm, whereas the invasive species was a more generalist predator. A. pallipes parasitised by the microsporidian parasite Thelohania contejeani showed a 30% reduction in prey intake. We suggest that this results from parasite-induced muscle damage, and this is supported by a reduced (38%) attack rate and increased (30%) prey handling time. Conclusions and Significance Our results indicate that the per capita (i.e., functional response) difference between the species may contribute to success of the invader and extinction of the native species, as well as decreased biodiversity and biomass in invaded rivers. In addition, the reduced predatory strength of parasitized natives may impair their competitive abilities, facilitating exclusion by the invader. PMID:22359673

  12. Predatory functional response and prey choice identify predation differences between native/invasive and parasitised/unparasitised crayfish.

    PubMed

    Haddaway, Neal R; Wilcox, Ruth H; Heptonstall, Rachael E A; Griffiths, Hannah M; Mortimer, Robert J G; Christmas, Martin; Dunn, Alison M

    2012-01-01

    Invasive predators may change the structure of invaded communities through predation and competition with native species. In Europe, the invasive signal crayfish Pacifastacus leniusculus is excluding the native white clawed crayfish Austropotamobius pallipes. This study compared the predatory functional responses and prey choice of native and invasive crayfish and measured impacts of parasitism on the predatory strength of the native species. Invasive crayfish showed a higher (>10%) prey (Gammarus pulex) intake rate than (size matched) natives, reflecting a shorter (16%) prey handling time. The native crayfish also showed greater selection for crustacean prey over molluscs and bloodworm, whereas the invasive species was a more generalist predator. A. pallipes parasitised by the microsporidian parasite Thelohania contejeani showed a 30% reduction in prey intake. We suggest that this results from parasite-induced muscle damage, and this is supported by a reduced (38%) attack rate and increased (30%) prey handling time. Our results indicate that the per capita (i.e., functional response) difference between the species may contribute to success of the invader and extinction of the native species, as well as decreased biodiversity and biomass in invaded rivers. In addition, the reduced predatory strength of parasitized natives may impair their competitive abilities, facilitating exclusion by the invader.

  13. Informing recovery in a human-transformed landscape: Drought-mediated coexistence alters population trends of an imperiled salamander and invasive predators

    USGS Publications Warehouse

    Hossack, Blake R.; Honeycutt, Richard; Sigafus, Brent H.; Muths, Erin L.; Crawford, Catherine L.; Jones, Thomas R.; Sorensen, Jeff A.; Rorabaugh, James C.; Chambert, Thierry

    2017-01-01

    Understanding the additive or interactive threats of habitat transformation and invasive species is critical for conservation, especially where climate change is expected to increase the severity or frequency of drought. In the arid southwestern USA, this combination of stressors has caused widespread declines of native aquatic and semi-aquatic species. Achieving resilience to drought and other effects of climate change may depend upon continued management, so understanding the combined effects of stressors is important. We used Bayesian hierarchical models fitted with 10-years of pond-based monitoring surveys for the federally-endangered Sonoran Tiger Salamander (Ambystoma mavortium stebbinsi) and invasive predators (fishes and American Bullfrogs, Lithobates catesbeianus) that threaten native species. We estimated trends in occupancy of salamanders and invasive predators while accounting for hydrological dynamics of ponds, then used a two-species interaction model to directly estimate how invasive predators affected salamander occupancy. We also tested a conceptual model that predicted that drought, by limiting the distribution of invasive predators, could ultimately benefit native species. Even though occupancy of invasive predators was stationary and their presence in a pond reduced the probability of salamander presence by 23%, occupancy of Sonoran Tiger Salamanders increased, annually, by 2.2%. Occupancy of salamanders and invasive predators both declined dramatically following the 5th consecutive year of drought. Salamander occupancy recovered quickly after return to non-drought conditions, while occupancy of invasive predators remained suppressed. Models that incorporated three time-lagged periods (1 to 4 years) of local moisture conditions confirmed that salamanders and invasive predators responded differently to drought, reflecting how life-history strategies shape responses to disturbances. The positive 10-year trend in salamander occupancy and their

  14. Restoration through eradication? Removal of an invasive bioengineer restores some habitat function for a native predator.

    PubMed

    Holsman, Kirstin K; McDonald, P Sean; Barreyro, Pablo A; Armstrong, David A

    2010-12-01

    Invasive aquatic macrophytes increase structural complexity in recipient systems and alter trophic and physical resources; thus, eradication programs that remove plant structure have potential to restore some impaired ecological functions. In this study we evaluate how an invasive ecosystem engineer, Atlantic smooth cordgrass (Spartina alterniflora), interferes with the movement and foraging activity of a mobile predator, Dungeness crab (Cancer magister), and whether removal of aboveground cordgrass structure rapidly reestablishes access to foraging habitats. By 2004, smooth cordgrass had invaded >25% of crab foraging habitat in Willapa Bay, Washington (USA), and transformed it into a highly structured landscape. However, by 2007 successful eradication efforts had eliminated most meadows of the cordgrass. In order to investigate the effect of smooth cordgrass on the habitat function of littoral areas for foraging crabs, we integrated field, laboratory, and statistical modeling approaches. We conducted trapping surveys at multiple sites and used a hierarchical model framework to examine patterns in catches prior to and following cordgrass removal (i.e., before-after control-impact design, BACI). Prior to eradication, catches of Dungeness crabs in unstructured habitats were 4-19 times higher than catches in adjacent patches of live cordgrass. In contrast, the results of post-eradication trapping in 2007 indicated similar catch rates of crabs in unstructured habitats and areas formerly invaded by the cordgrass. Subsequent laboratory experiments and video observations demonstrated that the rigid physical structure of smooth cordgrass shoots reduces the ability of Dungeness crabs to access prey resources and increases the risk of stranding. Taken together, these findings suggest that eliminating the structural complexity of invasive macrophytes may rapidly restore some ecological function (i.e., foraging area) for migratory predators like Dungeness crab. However

  15. Separate and combined effects of habitat-specific fish predation on the survival of invasive and native gammarids

    NASA Astrophysics Data System (ADS)

    Kotta, Jonne; Orav-Kotta, Helen; Herkül, Kristjan

    2010-10-01

    The North-American amphipod Gammarus tigrinus was observed for the first time in the northern Baltic Sea in 2003. The invasive amphipod has been particularly successful in some habitats (e.g. on pebbles) where it has become one of the most abundant gammarid species. We studied experimentally if the dominant fish Gasterosteus aculeatus preyed differentially on the exotic G. tigrinus and the native Gammarus salinus, if predation differed among habitats, and if one gammarid species facilitated predation on the other. The experiment demonstrated that (1) fish preyed more on the exotic G. tigrinus than the native G. salinus. (2) Predation did not differ among habitats. (3) Gammarus tigrinus facilitated the predation on G. salinus and this facilitation varied among habitats with significant effects on pebbles. Thus, the combined effect of habitat-specific fish predation and competition between gammarid amphipods is a possible explanation of the current range of G. tigrinus in the northern Baltic Sea. G. tigrinus seems to establish in habitats where it can significantly increase fish predation on the native gammarids.

  16. Unintended consequences of invasive predator control in an Australian forest: overabundant wallabies and vegetation change.

    PubMed

    Dexter, Nick; Hudson, Matt; James, Stuart; Macgregor, Christopher; Lindenmayer, David B

    2013-01-01

    Over-abundance of native herbivores is a problem in many forests worldwide. The abundance of native macropod wallabies is extremely high at Booderee National Park (BNP) in south-eastern Australia. This has occurred because of the reduction of exotic predators through an intensive baiting program, coupled with the absence of other predators. The high density of wallabies at BNP may be inhibiting the recruitment of many plant species following fire-induced recruitment events. We experimentally examined the post-fire response of a range of plant species to browsing by wallabies in a forest heavily infested with the invasive species, bitou bush Chrysanthemoides monilifera. We recorded the abundance and size of a range of plant species in 18 unfenced (browsed) and 16 fenced (unbrowsed) plots. We found the abundance and size of bitou bush was suppressed in browsed plots compared to unbrowsed plots. Regenerating seedlings of the canopy or middle storey tree species Eucalyptus pilularis, Acacia implexa, Allocasuarina littoralis, Breynia oblongifolia and Banksia integrifolia were either smaller or fewer in number in grazed plots than treatment plots as were the vines Kennedia rubicunda, Glycine tabacina and Glycine clandestina. In contrast, the understorey fern, Pteridium esculentum increased in abundance in the browsed plots relative to unbrowsed plots probably because of reduced competition with more palatable angiosperms. Twelve months after plots were installed the community structure of the browsed and unbrowsed plots was significantly different (P = 0.023, Global R = 0.091). The relative abundance of C. monilifera and P. esculentum contributed most to the differences. We discuss the possible development of a low diversity bracken fern parkland in Booderee National Park through a trophic cascade, similar to that caused by overabundant deer in the northern hemisphere. We also discuss its implications for broad scale fox control in southern Australian forests.

  17. Unintended Consequences of Invasive Predator Control in an Australian Forest: Overabundant Wallabies and Vegetation Change

    PubMed Central

    Dexter, Nick; Hudson, Matt; James, Stuart; MacGregor, Christopher; Lindenmayer, David B.

    2013-01-01

    Over-abundance of native herbivores is a problem in many forests worldwide. The abundance of native macropod wallabies is extremely high at Booderee National Park (BNP) in south-eastern Australia. This has occurred because of the reduction of exotic predators through an intensive baiting program, coupled with the absence of other predators. The high density of wallabies at BNP may be inhibiting the recruitment of many plant species following fire-induced recruitment events. We experimentally examined the post-fire response of a range of plant species to browsing by wallabies in a forest heavily infested with the invasive species, bitou bush Chrysanthemoides monilifera. We recorded the abundance and size of a range of plant species in 18 unfenced (browsed) and 16 fenced (unbrowsed) plots. We found the abundance and size of bitou bush was suppressed in browsed plots compared to unbrowsed plots. Regenerating seedlings of the canopy or middle storey tree species Eucalyptus pilularis, Acacia implexa, Allocasuarina littoralis, Breynia oblongifolia and Banksia integrifolia were either smaller or fewer in number in grazed plots than treatment plots as were the vines Kennedia rubicunda, Glycine tabacina and Glycine clandestina. In contrast, the understorey fern, Pteridium esculentum increased in abundance in the browsed plots relative to unbrowsed plots probably because of reduced competition with more palatable angiosperms. Twelve months after plots were installed the community structure of the browsed and unbrowsed plots was significantly different (P = 0.023, Global R = 0.091). The relative abundance of C. monilifera and P. esculentum contributed most to the differences. We discuss the possible development of a low diversity bracken fern parkland in Booderee National Park through a trophic cascade, similar to that caused by overabundant deer in the northern hemisphere. We also discuss its implications for broad scale fox control in southern Australian forests

  18. Rats and Seabirds: Effects of Egg Size on Predation Risk and the Potential of Conditioned Taste Aversion as a Mitigation Method

    PubMed Central

    Latorre, Lucía; Larrinaga, Asier R.; Santamaría, Luis

    2013-01-01

    Seabirds nesting on islands are threatened by invasive rodents, such as mice and rats, which may attack eggs, chicks and even adults. The low feasibility of rat eradications on many islands makes the development of alternate control plans necessary. We used a combination of field experiments on a Mediterranean island invaded by black rats (Rattusrattus) to evaluate (1) the predation risk posed to different-sized seabird eggs and (2), the potential of two deterrent methods (electronic and chemical) to reduce its impact. Rats were able to consume eggs of all sizes (12 to 68 g), but survival increased 13 times from the smallest to the largest eggs (which also had more resistant eggshells). Extrapolation to seabird eggs suggests that the smallest species (Hydrobatespelagicus) suffer the most severe predation risk, but even the largest (Larusmichahellis) could suffer >60% mortality. Nest attack was not reduced by the deterrents. However, chemical deterrence (conditioned taste aversion by lithium chloride) slowed the increase in predation rate over time, which resulted in a three-fold increase in egg survival to predation as compared to both control and electronic deterrence. At the end of the experimental period, this effect was confirmed by a treatment swap, which showed that conferred protection remains at least 15 days after cessation of the treatment. Results indicate that small seabird species are likely to suffer severe rates of nest predation by rats and that conditioned taste aversion, but not electronic repellents, may represent a suitable method to protect colonies when eradication or control is not feasible or cost-effective. PMID:24058712

  19. Prenatal exposure to restraint or predator stresses attenuates field excitatory postsynaptic potentials in infant rats.

    PubMed

    Saboory, Ehsan; Ahmadzadeh, Ramin; Roshan-Milani, Shiva

    2011-12-01

    Exposure to stress is known to change synaptic plasticity and results in long-term depression; further, this stress precipitates seizures. In the study described here, the prenatal restraint and predator stress models were used to test the hypothesis that indirect prenatal stresses influence hippocampal synaptic potentiation and may affect seizures susceptibility in infant rats. Pregnant female Wistar rats were divided into 3 groups: control, restraint-stressed, and predator-stressed groups. Both stressed groups were exposed to the stressor on gestation days 15, 16, and 17. The restraint stress involved 1-h sessions twice daily in a Plexiglas tube and the predator stress involved 2-h sessions once daily in a cage placed within the visual range of a caged cat. Blood corticosterone (COS) levels were measured in different time points. Hippocampal slices were prepared and field excitatory postsynaptic potentials (fEPSP) were studied on postnatal day 15. Pilocarpine was administered on postnatal day 25 and mortality rates were measured after 2 and 24h. Restraint and predator stresses resulted in significantly elevated COS blood levels in dams and pups. Both the amplitude and slope of fEPSP in the CA1 area decreased significantly in the stressed groups as compared to the control. Prenatal restraint and predator stresses significantly increased the fatal effect of pilocarpine at 24h after injection. Exposure to prenatal stresses and COS blood levels elevation reduce hippocampal synaptic potentiation and increase mortality rate of seizure in infant rats and may affect on later seizure susceptibility and prognosis.

  20. Amygdala regulates risk of predation in rats foraging in a dynamic fear environment.

    PubMed

    Choi, June-Seek; Kim, Jeansok J

    2010-12-14

    In a natural environment, foragers constantly face the risk of encountering predators. Fear is a defensive mechanism evolved to protect animals from danger by balancing the animals' needs for primary resources with the risk of predation, and the amygdala is implicated in mediating fear responses. However, the functions of fear and amygdala in foraging behavior are not well characterized because of the technical difficulty in quantifying prey-predator interaction with real (unpredictable) predators. Thus, the present study investigated the rat's foraging behavior in a seminaturalistic environment when confronted with a predator-like robot programmed to surge toward the animal seeking food. Rats initially fled into the nest and froze (demonstrating fear) and then cautiously approached and seized the food as a function of decreasing nest-food and increasing food-robot distances. The likelihood of procuring food increased and decreased via lesioning/inactivating and disinhibiting the amygdala, respectively. These results indicate that the amygdala bidirectionally regulates risk behavior in rats foraging in a dynamic fear environment.

  1. Evaluating the Interacting Influences of Pollination, Seed Predation, Invasive Species and Isolation on Reproductive Success in a Threatened Alpine Plant

    PubMed Central

    Krushelnycky, Paul D.

    2014-01-01

    Reproduction in rare plants may be influenced and limited by a complex combination of factors. External threats such as invasive species and landscape characteristics such as isolation may impinge on both pollination and seed predation dynamics, which in turn can strongly affect reproduction. I assessed how patterns in floral visitation, seed predation, invasive ant presence, and plant isolation influenced one another and ultimately affected viable seed production in Haleakalā silverswords (Argyroxiphium sandwicense subsp. macrocephalum) of Hawai’i. Floral visitation was dominated by endemic Hylaeus bees, and patterns of visitation were influenced by floral display size and number of plants clustered together, but not by floral herbivory or nearest flowering neighbor distance. There was also some indication that Argentine ant presence impacted floral visitation, but contradictory evidence and limitations of the study design make this result uncertain. Degree of seed predation was associated only with plant isolation, with the two main herbivores partitioning resources such that one preferentially attacked isolated plants while the other attacked clumped plants; total seed predation was greater in more isolated plants. Net viable seed production was highly variable among individuals (0–55% seed set), and was affected mainly by nearest neighbor distance, apparently owing to low cross-pollination among plants separated by even short distances (>10–20 m). This isolation effect dominated net seed set, with no apparent influence from floral visitation rates, percent seed predation, or invasive ant presence. The measured steep decline in seed set with isolation distance may not be typical of the entire silversword range, and may indicate that pollinators in addition to Hylaeus bees could be important for greater gene flow. Management aimed at maintaining or maximizing silversword reproduction should focus on the spatial context of field populations and outplanting

  2. Evaluating the interacting influences of pollination, seed predation, invasive species and isolation on reproductive success in a threatened alpine plant.

    PubMed

    Krushelnycky, Paul D

    2014-01-01

    Reproduction in rare plants may be influenced and limited by a complex combination of factors. External threats such as invasive species and landscape characteristics such as isolation may impinge on both pollination and seed predation dynamics, which in turn can strongly affect reproduction. I assessed how patterns in floral visitation, seed predation, invasive ant presence, and plant isolation influenced one another and ultimately affected viable seed production in Haleakalā silverswords (Argyroxiphium sandwicense subsp. macrocephalum) of Hawai'i. Floral visitation was dominated by endemic Hylaeus bees, and patterns of visitation were influenced by floral display size and number of plants clustered together, but not by floral herbivory or nearest flowering neighbor distance. There was also some indication that Argentine ant presence impacted floral visitation, but contradictory evidence and limitations of the study design make this result uncertain. Degree of seed predation was associated only with plant isolation, with the two main herbivores partitioning resources such that one preferentially attacked isolated plants while the other attacked clumped plants; total seed predation was greater in more isolated plants. Net viable seed production was highly variable among individuals (0-55% seed set), and was affected mainly by nearest neighbor distance, apparently owing to low cross-pollination among plants separated by even short distances (>10-20 m). This isolation effect dominated net seed set, with no apparent influence from floral visitation rates, percent seed predation, or invasive ant presence. The measured steep decline in seed set with isolation distance may not be typical of the entire silversword range, and may indicate that pollinators in addition to Hylaeus bees could be important for greater gene flow. Management aimed at maintaining or maximizing silversword reproduction should focus on the spatial context of field populations and outplanting

  3. Habitat connectivity and resident shared predators determine the impact of invasive bullfrogs on native frogs in farm ponds.

    PubMed

    Atobe, Takashi; Osada, Yutaka; Takeda, Hayato; Kuroe, Misako; Miyashita, Tadashi

    2014-07-07

    Habitat connectivity is considered to have an important role on the persistence of populations in the face of habitat fragmentation, in particular, for species with conservation concern. However, it can also impose indirect negative effects on native species through the spread of invasive species. Here, we investigated direct and indirect effects of habitat connectivity on populations of invasive bullfrogs and native wrinkled frogs and how these effects are modified by the presence of common carp, a resident shared predator, in a farm pond system in Japan. The distribution pattern analysis using a hierarchical Bayesian modelling indicated that bullfrogs had negative effects on wrinkled frogs, and that these negative effects were enhanced with increasing habitat connectivity owing to the metapopulation structure of bullfrogs. The analysis also suggested that common carp mitigated these impacts, presumably owing to a top-down trophic cascade through preferential predation on bullfrog tadpoles. These presumed interspecific interactions were supported by evidence from laboratory experiments, i.e. predation by carp was more intense on bullfrog tadpoles than on wrinkled frog tadpoles owing to the difference in refuge use. Our results indicate that metacommunity perspectives could provide useful insights for establishing effective management strategies of invasive species living in patchy habitats.

  4. Habitat connectivity and resident shared predators determine the impact of invasive bullfrogs on native frogs in farm ponds

    PubMed Central

    Atobe, Takashi; Osada, Yutaka; Takeda, Hayato; Kuroe, Misako; Miyashita, Tadashi

    2014-01-01

    Habitat connectivity is considered to have an important role on the persistence of populations in the face of habitat fragmentation, in particular, for species with conservation concern. However, it can also impose indirect negative effects on native species through the spread of invasive species. Here, we investigated direct and indirect effects of habitat connectivity on populations of invasive bullfrogs and native wrinkled frogs and how these effects are modified by the presence of common carp, a resident shared predator, in a farm pond system in Japan. The distribution pattern analysis using a hierarchical Bayesian modelling indicated that bullfrogs had negative effects on wrinkled frogs, and that these negative effects were enhanced with increasing habitat connectivity owing to the metapopulation structure of bullfrogs. The analysis also suggested that common carp mitigated these impacts, presumably owing to a top-down trophic cascade through preferential predation on bullfrog tadpoles. These presumed interspecific interactions were supported by evidence from laboratory experiments, i.e. predation by carp was more intense on bullfrog tadpoles than on wrinkled frog tadpoles owing to the difference in refuge use. Our results indicate that metacommunity perspectives could provide useful insights for establishing effective management strategies of invasive species living in patchy habitats. PMID:24827433

  5. Getting ready for invasions: can background level of risk predict the ability of naïve prey to survive novel predators?

    PubMed Central

    Ferrari, Maud C. O.; Crane, Adam L.; Brown, Grant E.; Chivers, Douglas P.

    2015-01-01

    Factors predicting the outcome of predator invasions on native prey communities are critical to our understanding of invasion ecology. Here, we tested whether background level of risk affected the survival of prey to novel predators, both native and invasive, predicting that high-risk environments would better prepare prey for invasions. We used naïve woodfrog as our prey and exposed them to a high or low risk regime either as embryos (prenatal exposure) or as larvae (recent exposure). Tadpoles were then tested for their survival in the presence of 4 novel predators: two dytiscid beetles, crayfish and trout. Survival was affected by both risk level and predator type. High risk was beneficial to prey exposed to the dytiscids larvae (ambush predators), but detrimental to prey exposed to crayfish or trout (pursuit predators). No effect of ontogeny of risk was found. We further documented that high-risk tadpoles were overall more active than their low-risk counterparts, explaining the patterns found with survival. Our results provide insights into the relationship between risk and resilience to predator invasions. PMID:25655436

  6. Can climate change jeopardize predator control of invasive herbivore species? A case study in avocado agro-ecosystems in Spain.

    PubMed

    Montserrat, Marta; Sahún, Rosa María; Guzmán, Celeste

    2013-02-01

    Climate change is one of the most important factors affecting the phenology, distribution, composition and diversity of organisms. In agricultural systems many pests and natural enemies are arthropods. As poikilotherm organisms, their body temperature is highly dependent on environmental conditions. Because higher trophic levels typically have lower tolerance to high temperatures than lower trophic levels, trends towards increasing local or regional temperatures may affect the strength of predator/prey interactions and disrupt pest control. Furthermore, increasing temperatures may create climate corridors that could facilitate the invasion and establishment of invasive species originating from warmer areas. In this study we examined the effect of environmental conditions on the dynamics of an agro-ecosystem community located in southern Spain, using field data on predator/prey dynamics and climate gathered during four consecutive years. The study system was composed of an ever-green tree species (avocado), an exotic tetranychid mite, and two native species of phytoseiid mites found in association with this new pest. We also present a climatological analysis of the temperature trend in the area of study during the last 28 years, as evidence of temperature warming occurring in the area. We found that the range of temperatures with positive per capita growth rates was much wider in prey than in predators, and that relative humidity contributed to explain the growth rate variation in predators, but not in prey. Predator and prey differences in thermal performance curves could explain why natural enemies did not respond numerically to the pest when environmental conditions were harsh.

  7. The enemy of my enemy is my friend: intraguild predation between invaders and natives facilitates coexistence with shared invasive prey

    PubMed Central

    MacNeil, Calum; Dick, Jaimie T. A.

    2014-01-01

    Understanding and predicting the outcomes of biological invasions is challenging where multiple invader and native species interact. We hypothesize that antagonistic interactions between invaders and natives could divert their impact on subsequent invasive species, thus facilitating coexistence. From field data, we found that, when existing together in freshwater sites, the native amphipod Gammarus duebeni celticus and a previous invader G. pulex appear to facilitate the establishment of a second invader, their shared prey Crangonyx pseudogracilis. Indeed, the latter species was rarely found at sites where each Gammarus species was present on its own. Experiments indicated that this may be the result of G. d. celticus and G. pulex engaging in more intraguild predation (IGP) than cannibalism; when the ‘enemy’ of either Gammarus species was present, that is, the other Gammarus species, C. pseudogracilis significantly more often escaped predation. Thus, the presence of mutual enemies and the stronger inter- than intraspecific interactions they engage in can facilitate other invaders. With some invasive species such as C. pseudogracilis having no known detrimental effects on native species, and indeed having some positive ecological effects, we also conclude that some invasions could promote biodiversity and ecosystem functioning. PMID:25122739

  8. The enemy of my enemy is my friend: intraguild predation between invaders and natives facilitates coexistence with shared invasive prey.

    PubMed

    MacNeil, Calum; Dick, Jaimie T A

    2014-08-01

    Understanding and predicting the outcomes of biological invasions is challenging where multiple invader and native species interact. We hypothesize that antagonistic interactions between invaders and natives could divert their impact on subsequent invasive species, thus facilitating coexistence. From field data, we found that, when existing together in freshwater sites, the native amphipod Gammarus duebeni celticus and a previous invader G. pulex appear to facilitate the establishment of a second invader, their shared prey Crangonyx pseudogracilis. Indeed, the latter species was rarely found at sites where each Gammarus species was present on its own. Experiments indicated that this may be the result of G. d. celticus and G. pulex engaging in more intraguild predation (IGP) than cannibalism; when the 'enemy' of either Gammarus species was present, that is, the other Gammarus species, C. pseudogracilis significantly more often escaped predation. Thus, the presence of mutual enemies and the stronger inter- than intraspecific interactions they engage in can facilitate other invaders. With some invasive species such as C. pseudogracilis having no known detrimental effects on native species, and indeed having some positive ecological effects, we also conclude that some invasions could promote biodiversity and ecosystem functioning.

  9. Activation of phenotypically-distinct neuronal subpopulations of the rat amygdala following exposure to predator odor.

    PubMed

    Butler, R K; Sharko, A C; Oliver, E M; Brito-Vargas, P; Kaigler, K F; Fadel, J R; Wilson, M A

    2011-02-23

    Exposure of rats to an odor of a predator can elicit an innate fear response. In addition, such exposure has been shown to activate limbic brain regions such as the amygdala. However, there is a paucity of data on the phenotypic characteristics of the activated amygdalar neurons following predator odor exposure. In the current experiments, rats were exposed to cloth which contained either ferret odor, butyric acid, or no odor for 30 min. Ferret odor-exposed rats displayed an increase in defensive burying versus control rats. Sections of the brains were prepared for dual-labeled immunohistochemistry and counts of c-Fos co-localized with Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), parvalbumin, or calbindin were made in the basolateral (BLA), central (CEA), and medial (MEA) nucleus of the amygdala. Dual-labeled immunohistochemistry showed a significant increase in the percentage of CaMKII-positive neurons also immunoreactive for c-Fos in the BLA, CEA and MEA of ferret odor-exposed rats compared to control and butyric acid-exposed groups. Further results showed a significant decrease in calbindin-immunoreactive neurons that were also c-Fos-positive in the anterior portion of the BLA of ferret odor-exposed rats compared to control and butyric acid-exposed rats, whereas the MEA expressed a significant decrease in calbindin/c-Fos dual-labeled neurons in butyric acid-exposed rats compared to controls and ferret odor-exposed groups. These results enhance our understanding of the functioning of the amygdala following exposure to predator threats by showing phenotypic characteristics of activated amygdalar neurons. With this knowledge, specific neuronal populations could be targeted to further elucidate the fundamental underpinnings of anxiety and could possibly indicate new targets for the therapeutic treatment of anxiety.

  10. Will Climate Change, Genetic and Demographic Variation or Rat Predation Pose the Greatest Risk for Persistence of an Altitudinally Distributed Island Endemic?

    PubMed Central

    Simmons, Catherine Laura; Auld, Tony D.; Hutton, Ian; Baker, William J.; Shapcott, Alison

    2012-01-01

    Species endemic to mountains on oceanic islands are subject to a number of existing threats (in particular, invasive species) along with the impacts of a rapidly changing climate. The Lord Howe Island endemic palm Hedyscepe canterburyana is restricted to two mountains above 300 m altitude. Predation by the introduced Black Rat (Rattus rattus) is known to significantly reduce seedling recruitment. We examined the variation in Hedyscepe in terms of genetic variation, morphology, reproductive output and demographic structure, across an altitudinal gradient. We used demographic data to model population persistence under climate change predictions of upward range contraction incorporating long-term climatic records for Lord Howe Island. We also accounted for alternative levels of rat predation into the model to reflect management options for control. We found that Lord Howe Island is getting warmer and drier and quantified the degree of temperature change with altitude (0.9 °C per 100 m). For H. canterburyana, differences in development rates, population structure, reproductive output and population growth rate were identified between altitudes. In contrast, genetic variation was high and did not vary with altitude. There is no evidence of an upward range contraction as was predicted and recruitment was greatest at lower altitudes. Our models predicted slow population decline in the species and that the highest altitude populations are under greatest threat of extinction. Removal of rat predation would significantly enhance future persistence of this species. PMID:24832517

  11. Cotton Rats Alter Foraging in Response to an Invasive Ant.

    PubMed

    Darracq, Andrea K; Conner, L Mike; Brown, Joel S; McCleery, Robert A

    We assessed the effects of red imported fire ants (Solenopsis invicta; hereafter fire ant) on the foraging of hispid cotton rats (Sigmodon hispidus). We used a manipulative experiment, placing resource patches with a known amount of millet seed within areas with reduced (RIFA [-]) or ambient (RIFA [+]) numbers of fire ants. We measured giving up densities (the amount of food left within each patch) within the resource patches for 4 days to quantify the effects of fire ants on cotton rat foraging. We assessed the effects of fire ant treatment (RIFA), Day, and their interaction on cotton rat giving up densities. Giving up densities on RIFA [+] grids were nearly 2.2 times greater across all foraging days and ranged from 1.6 to 2.3 times greater from day 1 to day 4 than the RIFA [-] grids. From day 1 to day 4, mean giving up densities decreased significantly faster for the RIFA [-] than RIFA [+] treatments, 58% and 13%, respectively. Our results demonstrate that cotton rats perceive a risk of injury from fire ants, which is likely caused by interference competition, rather than direct predation. Envenomation from ants likely decrease the foraging efficiency of cotton rats resulting in more time spent foraging. Increased time spent foraging is likely stressful in terms of the opportunity for direct injury and encounters with other predators. These indirect effects may reduce an individual cotton rat's fitness and translate into lowered population abundances.

  12. Effects of oxytocin on methamphetamine-seeking exacerbated by predator odor pre-exposure in rats.

    PubMed

    Ferland, Chantelle L; Reichel, Carmela M; McGinty, Jacqueline F

    2016-03-01

    The endogenous oxytocin system has emerged as an inhibitor of drug-seeking and stress in preclinical models. The goal of this study was to examine whether systemic oxytocin administration attenuated methamphetamine (METH)-seeking in rats pre-exposed to a predator odor threat. In Experiment 1, rats were exposed for 5 days to the predator odor, 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), or saline before METH self-administration began. After extinction training, rats were injected with 1 mg/kg, ip oxytocin (OXT) or saline 30 min before a cue-induced reinstatement test followed by re-extinction and a TMT-induced reinstatement test. In Experiment 2, TMT pre-exposure was followed by 10 days of 1 mg/kg OXT or saline injections before METH self-administration, extinction, and a TMT-induced reinstatement test. In Experiment 1, TMT pre-exposed rats that were injected with saline 30 min before reinstatement exhibited greater drug-seeking induced by conditioned cues or TMT than that exhibited by saline pre-exposed rats. A single injection of OXT 30 min before reinstatement suppressed METH-seeking in both saline- and TMT pre-exposed rats. In Experiment 2, TMT pre-exposed rats that received saline injections for 10 days prior to METH self-administration exhibited enhanced drug-seeking induced by TMT during stress-induced reinstatement. OXT injections for 10 days prior to METH self-administration blocked only the stress-induced exacerbation of drug-seeking in TMT pre-exposed rats. These results support further research on the development of oxytocin as a novel therapeutic drug that has enduring effects on drug-seeking exacerbated by stress.

  13. Effects of oxytocin on methamphetamine-seeking exacerbated by predator odor pre-exposure in rats

    PubMed Central

    Ferland, Chantelle L.; Reichel, Carmela M.; McGinty, Jacqueline F.

    2016-01-01

    Rationale The endogenous oxytocin system has emerged as an inhibitor of drug-seeking and stress in preclinical models. Objectives The goal of this study was to examine whether systemic oxytocin administration attenuated methamphetamine (METH)–seeking in rats pre-exposed to a predator odor threat. Methods In Experiment 1, rats were exposed for five days to the predator odor, 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), or saline before METH self-administration began. After extinction training, rats were injected with 1 mg/kg, ip oxytocin (OXT) or saline 30 min before a cue-induced reinstatement test followed by re-extinction and a TMT–induced reinstatement test. In Experiment 2, TMT pre-exposure was followed by 10 days of 1 mg/kg OXT or saline injections before METH self-administration, extinction, and a TMT-induced reinstatement test. Results In Experiment 1, TMT pre-exposed rats that were injected with saline 30 min before reinstatement exhibited greater drug-seeking induced by conditioned cues or TMT than that exhibited by saline pre-exposed rats. A single injection of OXT 30 min before reinstatement suppressed METH-seeking in both saline- and TMT pre-exposed rats. In Experiment 2, TMT pre-exposed rats that received saline injections for 10d prior to METH self-administration exhibited enhanced drug-seeking induced by TMT during stress-induced reinstatement. OXT injections for 10d prior to METH self-administration blocked only the stress-induced exacerbation of drug-seeking in TMT pre-exposed rats. Conclusions These results support further research on the development of oxytocin as a novel therapeutic that has enduring effects on drug-seeking exacerbated by stress. PMID:26700240

  14. Cotton Rats Alter Foraging in Response to an Invasive Ant

    PubMed Central

    Darracq, Andrea K.; Conner, L. Mike; Brown, Joel S.; McCleery, Robert A.

    2016-01-01

    We assessed the effects of red imported fire ants (Solenopsis invicta; hereafter fire ant) on the foraging of hispid cotton rats (Sigmodon hispidus). We used a manipulative experiment, placing resource patches with a known amount of millet seed within areas with reduced (RIFA [–]) or ambient (RIFA [+]) numbers of fire ants. We measured giving up densities (the amount of food left within each patch) within the resource patches for 4 days to quantify the effects of fire ants on cotton rat foraging. We assessed the effects of fire ant treatment (RIFA), Day, and their interaction on cotton rat giving up densities. Giving up densities on RIFA [+] grids were nearly 2.2 times greater across all foraging days and ranged from 1.6 to 2.3 times greater from day 1 to day 4 than the RIFA [–] grids. From day 1 to day 4, mean giving up densities decreased significantly faster for the RIFA [–] than RIFA [+] treatments, 58% and 13%, respectively. Our results demonstrate that cotton rats perceive a risk of injury from fire ants, which is likely caused by interference competition, rather than direct predation. Envenomation from ants likely decrease the foraging efficiency of cotton rats resulting in more time spent foraging. Increased time spent foraging is likely stressful in terms of the opportunity for direct injury and encounters with other predators. These indirect effects may reduce an individual cotton rat’s fitness and translate into lowered population abundances. PMID:27655320

  15. Insights into embryo defenses of the invasive apple snail Pomacea canaliculata: egg mass ingestion affects rat intestine morphology and growth.

    PubMed

    Dreon, Marcos S; Fernández, Patricia E; Gimeno, Eduardo J; Heras, Horacio

    2014-06-01

    The spread of the invasive snail Pomacea canaliculata is expanding the rat lungworm disease beyond its native range. Their toxic eggs have virtually no predators and unusual defenses including a neurotoxic lectin and a proteinase inhibitor, presumably advertised by a warning coloration. We explored the effect of egg perivitellin fluid (PVF) ingestion on the rat small intestine morphology and physiology. Through a combination of biochemical, histochemical, histopathological, scanning electron microscopy, cell culture and feeding experiments, we analyzed intestinal morphology, growth rate, hemaglutinating activity, cytotoxicity and cell proliferation after oral administration of PVF to rats. PVF adversely affects small intestine metabolism and morphology and consequently the standard growth rate, presumably by lectin-like proteins, as suggested by PVF hemaglutinating activity and its cytotoxic effect on Caco-2 cell culture. Short-term effects of ingested PVF were studied in growing rats. PVF-supplemented diet induced the appearance of shorter and wider villi as well as fused villi. This was associated with changes in glycoconjugate expression, increased cell proliferation at crypt base, and hypertrophic mucosal growth. This resulted in a decreased absorptive surface after 3 days of treatment and a diminished rat growth rate that reverted to normal after the fourth day of treatment. Longer exposure to PVF induced a time-dependent lengthening of the small intestine while switching to a control diet restored intestine length and morphology after 4 days. Ingestion of PVF rapidly limits the ability of potential predators to absorb nutrients by inducing large, reversible changes in intestinal morphology and growth rate. The occurrence of toxins that affect intestinal morphology and absorption is a strategy against predation not recognized among animals before. Remarkably, this defense is rather similar to the toxic effect of plant antipredator strategies. This defense

  16. Insights into Embryo Defenses of the Invasive Apple Snail Pomacea canaliculata: Egg Mass Ingestion Affects Rat Intestine Morphology and Growth

    PubMed Central

    Gimeno, Eduardo J.; Heras, Horacio

    2014-01-01

    Background The spread of the invasive snail Pomacea canaliculata is expanding the rat lungworm disease beyond its native range. Their toxic eggs have virtually no predators and unusual defenses including a neurotoxic lectin and a proteinase inhibitor, presumably advertised by a warning coloration. We explored the effect of egg perivitellin fluid (PVF) ingestion on the rat small intestine morphology and physiology. Methodology/Principal Findings Through a combination of biochemical, histochemical, histopathological, scanning electron microscopy, cell culture and feeding experiments, we analyzed intestinal morphology, growth rate, hemaglutinating activity, cytotoxicity and cell proliferation after oral administration of PVF to rats. PVF adversely affects small intestine metabolism and morphology and consequently the standard growth rate, presumably by lectin-like proteins, as suggested by PVF hemaglutinating activity and its cytotoxic effect on Caco-2 cell culture. Short-term effects of ingested PVF were studied in growing rats. PVF-supplemented diet induced the appearance of shorter and wider villi as well as fused villi. This was associated with changes in glycoconjugate expression, increased cell proliferation at crypt base, and hypertrophic mucosal growth. This resulted in a decreased absorptive surface after 3 days of treatment and a diminished rat growth rate that reverted to normal after the fourth day of treatment. Longer exposure to PVF induced a time-dependent lengthening of the small intestine while switching to a control diet restored intestine length and morphology after 4 days. Conclusions/Significance Ingestion of PVF rapidly limits the ability of potential predators to absorb nutrients by inducing large, reversible changes in intestinal morphology and growth rate. The occurrence of toxins that affect intestinal morphology and absorption is a strategy against predation not recognized among animals before. Remarkably, this defense is rather similar to

  17. Population-level compensation by an invasive thistle thwarts biological control from seed predators

    USDA-ARS?s Scientific Manuscript database

    Predispersal seed predators are often chosen as biocontrol agents because of their high impacts on plant fitness; however, they have a mixed record in realizing decreased plant population growth. Few studies have experimentally removed agents to explore their impact on weed population growth. Here...

  18. Predator cat odors activate sexual arousal pathways in brains of Toxoplasma gondii infected rats.

    PubMed

    House, Patrick K; Vyas, Ajai; Sapolsky, Robert

    2011-01-01

    Cat odors induce rapid, innate and stereotyped defensive behaviors in rats at first exposure, a presumed response to the evolutionary pressures of predation. Bizarrely, rats infected with the brain parasite Toxoplasma gondii approach the cat odors they typically avoid. Since the protozoan Toxoplasma requires the cat to sexually reproduce, this change in host behavior is thought to be a remarkable example of a parasite manipulating a mammalian host for its own benefit. Toxoplasma does not influence host response to non-feline predator odor nor does it alter behavior on olfactory, social, fear or anxiety tests, arguing for specific manipulation in the processing of cat odor. We report that Toxoplasma infection alters neural activity in limbic brain areas necessary for innate defensive behavior in response to cat odor. Moreover, Toxoplasma increases activity in nearby limbic regions of sexual attraction when the rat is exposed to cat urine, compelling evidence that Toxoplasma overwhelms the innate fear response by causing, in its stead, a type of sexual attraction to the normally aversive cat odor.

  19. Predation on the Invasive Copepod, Pseudodiaptomus forbesi, and Native Zooplankton in the Lower Columbia River: An Experimental Approach to Quantify Differences in Prey-Specific Feeding Rates

    PubMed Central

    Adams, Jesse B.; Bollens, Stephen M.; Bishop, John G.

    2015-01-01

    Invasive planktonic crustaceans have become a prominent feature of aquatic communities worldwide, yet their effects on food webs are not well known. The Asian calanoid copepod, Pseudodiaptomus forbesi, introduced to the Columbia River Estuary approximately 15 years ago, now dominates the late-summer zooplankton community, but its use by native aquatic predators is unknown. We investigated whether three species of planktivorous fishes (chinook salmon, three-spined stickleback, and northern pikeminnow) and one species of mysid exhibited higher feeding rates on native copepods and cladocerans relative to P. forbesi by conducting `single-prey’ feeding experiments and, additionally, examined selectivity for prey types with `two-prey’ feeding experiments. In single-prey experiments individual predator species showed no difference in feeding rates on native cyclopoid copepods (Cyclopidae spp.) relative to invasive P. forbesi, though wild-collected predators exhibited higher feeding rates on cyclopoids when considered in aggregate. In two-prey experiments, chinook salmon and northern pikeminnow both strongly selected native cladocerans (Daphnia retrocurva) over P. forbesi, and moreover, northern pikeminnow selected native Cyclopidae spp. over P. forbesi. On the other hand, in two-prey experiments, chinook salmon, three-spined stickleback and mysids were non- selective with respect to feeding on native cyclopoid copepods versus P. forbesi. Our results indicate that all four native predators in the Columbia River Estuary can consume the invasive copepod, P. forbesi, but that some predators select for native zooplankton over P. forbesi, most likely due to one (or both) of two possible underlying casual mechanisms: 1) differential taxon-specific prey motility and escape responses (calanoids > cyclopoids > daphnids) or 2) the invasive status of the zooplankton prey resulting in naivety, and thus lower feeding rates, of native predators feeding on invasive prey. PMID

  20. Predation on the Invasive Copepod, Pseudodiaptomus forbesi, and Native Zooplankton in the Lower Columbia River: An Experimental Approach to Quantify Differences in Prey-Specific Feeding Rates.

    PubMed

    Adams, Jesse B; Bollens, Stephen M; Bishop, John G

    2015-01-01

    Invasive planktonic crustaceans have become a prominent feature of aquatic communities worldwide, yet their effects on food webs are not well known. The Asian calanoid copepod, Pseudodiaptomus forbesi, introduced to the Columbia River Estuary approximately 15 years ago, now dominates the late-summer zooplankton community, but its use by native aquatic predators is unknown. We investigated whether three species of planktivorous fishes (chinook salmon, three-spined stickleback, and northern pikeminnow) and one species of mysid exhibited higher feeding rates on native copepods and cladocerans relative to P. forbesi by conducting `single-prey' feeding experiments and, additionally, examined selectivity for prey types with `two-prey' feeding experiments. In single-prey experiments individual predator species showed no difference in feeding rates on native cyclopoid copepods (Cyclopidae spp.) relative to invasive P. forbesi, though wild-collected predators exhibited higher feeding rates on cyclopoids when considered in aggregate. In two-prey experiments, chinook salmon and northern pikeminnow both strongly selected native cladocerans (Daphnia retrocurva) over P. forbesi, and moreover, northern pikeminnow selected native Cyclopidae spp. over P. forbesi. On the other hand, in two-prey experiments, chinook salmon, three-spined stickleback and mysids were non- selective with respect to feeding on native cyclopoid copepods versus P. forbesi. Our results indicate that all four native predators in the Columbia River Estuary can consume the invasive copepod, P. forbesi, but that some predators select for native zooplankton over P. forbesi, most likely due to one (or both) of two possible underlying casual mechanisms: 1) differential taxon-specific prey motility and escape responses (calanoids > cyclopoids > daphnids) or 2) the invasive status of the zooplankton prey resulting in naivety, and thus lower feeding rates, of native predators feeding on invasive prey.

  1. Hemolymph Defense against an Invasive Herbivore: Its Breadth of Effectiveness Against Predators

    USDA-ARS?s Scientific Manuscript database

    Defensive characteristics of organisms shape the trophic linkages within food webs and influence the ability of invasive organisms to expand their range. Diabrotica virgifera virgifera is an invasive herbivore in European maize, and its subterranean larval feeding affects the entire maize ecosystem....

  2. What Doesn't Kill You Makes You Wary? Effect of Repeated Culling on the Behaviour of an Invasive Predator

    PubMed Central

    Côté, Isabelle M.; Darling, Emily S.; Malpica-Cruz, Luis; Smith, Nicola S.; Green, Stephanie J.; Curtis-Quick, Jocelyn; Layman, Craig

    2014-01-01

    As a result of being hunted, animals often alter their behaviour in ways that make future encounters with predators less likely. When hunting is carried out for conservation, for example to control invasive species, these behavioural changes can inadvertently impede the success of future efforts. We examined the effects of repeated culling by spearing on the behaviour of invasive predatory lionfish (Pterois volitans/miles) on Bahamian coral reef patches. We compared the extent of concealment and activity levels of lionfish at dawn and midday on 16 coral reef patches off Eleuthera, The Bahamas. Eight of the patches had been subjected to regular daytime removals of lionfish by spearing for two years. We also estimated the distance at which lionfish became alert to slowly approaching divers on culled and unculled reef patches. Lionfish on culled reefs were less active and hid deeper within the reef during the day than lionfish on patches where no culling had occurred. There were no differences at dawn when removals do not take place. Lionfish on culled reefs also adopted an alert posture at a greater distance from divers than lionfish on unculled reefs. More crepuscular activity likely leads to greater encounter rates by lionfish with more native fish species because the abundance of reef fish outside of shelters typically peaks at dawn and dusk. Hiding deeper within the reef could also make remaining lionfish less likely to be encountered and more difficult to catch by spearfishers during culling efforts. Shifts in the behaviour of hunted invasive animals might be common and they have implications both for the impact of invasive species and for the design and success of invasive control programs. PMID:24705447

  3. What doesn't kill you makes you wary? Effect of repeated culling on the behaviour of an invasive predator.

    PubMed

    Côté, Isabelle M; Darling, Emily S; Malpica-Cruz, Luis; Smith, Nicola S; Green, Stephanie J; Curtis-Quick, Jocelyn; Layman, Craig

    2014-01-01

    As a result of being hunted, animals often alter their behaviour in ways that make future encounters with predators less likely. When hunting is carried out for conservation, for example to control invasive species, these behavioural changes can inadvertently impede the success of future efforts. We examined the effects of repeated culling by spearing on the behaviour of invasive predatory lionfish (Pterois volitans/miles) on Bahamian coral reef patches. We compared the extent of concealment and activity levels of lionfish at dawn and midday on 16 coral reef patches off Eleuthera, The Bahamas. Eight of the patches had been subjected to regular daytime removals of lionfish by spearing for two years. We also estimated the distance at which lionfish became alert to slowly approaching divers on culled and unculled reef patches. Lionfish on culled reefs were less active and hid deeper within the reef during the day than lionfish on patches where no culling had occurred. There were no differences at dawn when removals do not take place. Lionfish on culled reefs also adopted an alert posture at a greater distance from divers than lionfish on unculled reefs. More crepuscular activity likely leads to greater encounter rates by lionfish with more native fish species because the abundance of reef fish outside of shelters typically peaks at dawn and dusk. Hiding deeper within the reef could also make remaining lionfish less likely to be encountered and more difficult to catch by spearfishers during culling efforts. Shifts in the behaviour of hunted invasive animals might be common and they have implications both for the impact of invasive species and for the design and success of invasive control programs.

  4. Strong effects of predation by fishes on an invasive macroinvertebrate in a large floodplain river

    USGS Publications Warehouse

    Bartsch, M.R.; Bartsch, L.A.; Gutreuter, S.

    2005-01-01

    We assessed the effects of fish predation on zebra mussels (Dreissena polymorpha) in Navigation Pool 8 of the Upper Mississippi River from 13 May to 5 October, 1998. Concrete-block samplers were deployed at 18 randomly chosen sites in the main-channel border, with 6 sites in the upper, middle, and lower segments of the pool. Two blocks, 1 of which was enclosed in a cage to exclude large predatory fishes, were deployed at each site. After 145 d, blocks were retrieved from 12 of the 18 sites, and zebra mussels were found on all blocks. Densities of zebra mussels were higher on caged blocks than uncaged blocks, and the magnitudes of the differences varied spatially. Mean mussel densities on uncaged blocks were reduced by 66%, 86%, and 20% compared to caged blocks in the upper, middle, and lower pool segments, respectively, over the 145-d interval. Mean daily instantaneous zebra mussel mortality rates from large predators ranged from 0.0016 to 0.0138. Similarly, biomass of zebra mussels was higher on caged than uncaged blocks. Mean mussel biomass on uncaged blocks was reduced by 64% pool-wide, relative to biomass on caged blocks. Zebra mussels were consumed by at least 6 fish taxa including redhorse stickers (Moxostoma spp.), common carp (Cyprinus carpio), bluegill (Lepomis macrochirus), quillback carpsucker (Carpiodes cyprinus), flathead catfish (Pylodictis olivaris), and freshwater drum (Aplodinotus grunniens). Fish predation had an important moderating effect on zebra mussel demography in Pool 8.

  5. Phylogeographic structure of Teretrius nigrescens (Coleoptera: Histeridae) predator of the invasive post harvest pest Prostephanus truncatus (Coleoptera: Bostrichidae).

    PubMed

    Omondi, B A; van den Berg, J; Masiga, D; Schulthess, F

    2011-10-01

    The invasive larger grain borer Prostephanus truncatus (Horn) is the most important pest of farm-stored maize in Africa. It was introduced into the continent from Mesoamerica in the late 1970s and by 2008 had spread to at least 18 countries. Classical biological control using two populations of the predator Teretrius nigrescens Lewis achieved long-term and cost effective control in warm-humid areas, but not in cool and hot-dry zones. The present study investigated the phylogenetic relationships between geographical populations of the predator. Ten populations of T. nigrescens were studied using randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR), sequence analysis of mitochondrial Cytochrme oxydase 1 (mtCOI) gene and ribosomal internally transcribed spacers (ITS) 1, 5.8S and ITS2. The mtCOI variation revealed two clades associated with geographical regions in Central America. It also reveals a significant isolation by distance between populations and considerable genetic shifts in laboratory rearing. RAPD-PCR did not reveal any potential SCAR diagnostic markers. The ITS variation mainly involved insertions and deletions of simple sequence repeats even within individuals. This study reveals the existence of two different mitochondrial lineages of the predator, associated with the geographical origin of populations distinguishable by fixed mutations on the mtCOI gene. The populations of T. nigrescens released in Africa belonged to two different clades from Meso America, namely south (released in West Africa) and north (released in eastern Africa). However, more polymorphic markers are required to clarify the observations in demographic time scales.

  6. Predator odor stress alters corticotropin-releasing factor-1 receptor (CRF1R)-dependent behaviors in rats.

    PubMed

    Roltsch, Emily A; Baynes, Brittni B; Mayeux, Jacques P; Whitaker, Annie M; Baiamonte, Brandon A; Gilpin, Nicholas W

    2014-04-01

    Humans with stress-related anxiety disorders exhibit increases in arousal and alcohol drinking, as well as altered pain processing. Our lab has developed a predator odor stress model that produces reliable and lasting increases in alcohol drinking. Here, we utilize this predator odor stress model to examine stress-induced increases in arousal, nociceptive processing, and alcohol self-administration by rats, and also to determine the effects of corticotropin-releasing factor-1 receptors (CRF1Rs) in mediating these behavioral changes. In a series of separate experiments, rats were exposed to predator odor stress, then tested over subsequent days for thermal nociception in the Hargreaves test, acoustic startle reactivity, or operant alcohol self-administration. In each experiment, rats were systemically injected with R121919, a CRF1R antagonist, and/or vehicle. Predator odor stress increased thermal nociception (i.e., hyperalgesia) and acoustic startle reactivity. Systemic administration of R121919 reduced thermal nociception and hyperarousal in stressed rats but not unstressed controls, and reduced operant alcohol responding over days. Stressed rats exhibited increased sensitivity to the behavioral effects of R121919 in all three tests, suggesting up-regulation of brain CRF1Rs number and/or function in stressed rats. These results suggest that post-stress alcohol drinking may be driven by a high-nociception high-arousal state, and that brain CRF1R signaling mediates these stress effects.

  7. The mother as hunter: significant reduction in foraging costs through enhancements of predation in maternal rats.

    PubMed

    Kinsley, Craig Howard; Blair, Jamie C; Karp, Natalie E; Hester, Naomi W; McNamara, Ilan M; Orthmeyer, Angela L; McSweeney, Molly C; Bardi, Massimo M; Karelina, Kate; Christon, Lillian M; Sirkin, Maxwell R; Victoria, Lindsay W; Skurka, Danielle J; Fyfe, Christian R; Hudepohl, Margaret B; Felicio, Luciano F; Franssen, R Adam; Meyer, Elizabeth E A; da Silva, Ilton S; Lambert, Kelly G

    2014-09-01

    In previous laboratory investigations, we have identified enhanced cognition and reduced stress in parous rats, which are likely adaptations in mothers needing to efficiently exploit resources to maintain, protect and provision their immature offspring. Here, in a series of seven behavioral tests on rats, we examined a natural interface between cognition and resource gathering: predation. Experiment 1 compared predatory behavior (toward crickets) in age-matched nulliparous mothers (NULLs) and postpartum lactating mothers (LACTs), revealing a highly significant enhancement of predation in LACT females (mean = -65s in LACTs, vs. -270s in NULLs). Experiment 2 examined the possibility that LACTs, given their increased metabolic rate, were hungrier, and thus more motivated to hunt; doubling the length of time of food deprivation in NULLs did not decrease their predatory latencies. Experiments 3-5, which examined sensory regulation of the effect, indicated that olfaction (anosmia), audition (blockade with white noise), and somatosensation (trimming the vibrissae) appear to play little role in the behavioral enhancement observed in the LACTs; Experiment 6 examined the possibility that visual augmentations may facilitate the improvements in predation; testing LACTs in a 0-lux environment eliminated the behavioral advantage (increasing their latencies from -65s to -212s), which suggests that temporary augmentation to the visual system may be important, and with hormone-neural alterations therein a likely candidate for further study. In contrast, testing NULLS in the 0-lux environment had the opposite effect, reducing their latency to catch the cricket (from -270s to -200s). Finally, Experiment 7 examined the development of predatory behavior in Early-pregnant (PREG), Mid-PREG, and Late-PREG females. Here, we observed a significant enhancement of predation in Mid-PREG and Late-PREG females--at a time when maternity-associated bodily changes would be expected to diminish

  8. Native bark-foraging birds preferentially forage in infected ash (Fraxinus spp.) and prove effective predators of the invasive emerald ash borer (Agrilus planipennis Fairmaire)

    Treesearch

    Charles E. Flower; Lawrence C. Long; Kathleen S. Knight; Joanne Rebbeck; Joel S. Brown; Miquel A. Gonzalez-Meler; Christopher J. Whelan

    2014-01-01

    Inadvertently introduced into North America in the 1990s, the invasive emerald ash borer (EAB, Agrilus planipennis) has been spreading across the Great Lakes Region resulting in widespread ash tree (Fraxinus spp.) mortality. Native woodpeckers and other bark-foraging insectivores represent one of the few potential natural predators...

  9. Sex-specific impairment of spatial memory in rats following a reminder of predator stress.

    PubMed

    Burke, Hanna M; Robinson, Cristina M; Wentz, Bethany; McKay, Jerel; Dexter, Kyle W; Pisansky, Julia M; Talbot, Jeffery N; Zoladz, Phillip R

    2013-07-01

    It has been suggested that cognitive impairments exhibited by people with post-traumatic stress disorder (PTSD) result from intrusive, flashback memories transiently interfering with ongoing cognitive processing. Researchers have further speculated that females are more susceptible to developing PTSD because they form stronger traumatic memories than males, hence females may be more sensitive to the negative effects of intrusive memories on cognition. We have examined how the reminder of a naturalistic stress experience would affect rat spatial memory and if sex was a contributing factor to such effects. Male and female Sprague-Dawley rats were exposed, without contact, to an adult female cat for 30 min. Five weeks later, the rats were trained to locate a hidden platform in the radial-arm water maze and given a single long-term memory test trial 24 h later. Before long-term memory testing, the rats were given a 30-min reminder of the cat exposure experienced 5 weeks earlier. The results indicated that the stress reminder impaired spatial memory in the female rats only. Control manipulations revealed that this effect was not attributable to the original cat exposure adversely impacting learning that occurred 5 weeks later, or to merely exposing rats to a novel environment or predator-related cues immediately before testing. These findings provide evidence that the reminder of a naturalistic stressful experience can impair cognitive processing in rats; moreover, since female rats were more susceptible to the memory-impairing effects of the stress reminder, the findings could lend insight into the existing sex differences in susceptibility to PTSD.

  10. Divergent induced responses to an invasive predator in marine mussel populations.

    PubMed

    Freeman, Aaren S; Byers, James E

    2006-08-11

    Invasive species may precipitate evolutionary change in invaded communities. In southern New England (USA) the invasive Asian shore crab, Hemigrapsus sanguineus, preys on mussels (Mytlius edulis), but the crab has not yet invaded northern New England. We show that southern New England mussels express inducible shell thickening when exposed to waterborne cues from Hemigrapsus, whereas naïve northern mussel populations do not respond. Yet, both populations thicken their shells in response to a long-established crab, Carcinus maenas. Our findings are consistent with the rapid evolution of an inducible morphological response to Hemigrapsus within 15 years of its introduction.

  11. A novel model of invasive fungal rhinosinusitis in rats.

    PubMed

    Zhang, Fang; An, Yunfang; Li, Zeqing; Zhao, Changqing

    2013-01-01

    Invasive fungal rhinosinusitis (IFRS) is a life-threatening inflammatory disease that affects immunocompromised patients, but animal models of the disease are scarce. This study aimed to develop an IFRS model in neutropenic rats. The model was established in three consecutive steps: unilateral nasal obstruction with Merocel sponges, followed by administration of cyclophosphamide (CPA), and, finally, nasal inoculation with Aspergillus fumigatus. Fifty healthy Wistar rats were randomly divided into five groups, with group I as the controls, group II undergoing unilateral nasal obstruction alone, group III undergoing nasal obstruction with fungal inoculation, group IV undergoing nasal obstruction with administration of CPA, and group V undergoing nasal obstruction with administration of CPA and fungal inoculation. Hematology, histology, and mycology investigations were performed. The changes in the rat absolute neutrophil counts (ANCs) were statistically different across the groups. The administration of CPA decreased the ANCs, whereas nasal obstruction with fungal inoculation increased the ANCs, and nasal obstruction did not change them. Histological examination of the rats in group V revealed the hyphal invasion of sinus mucosa and bone, thrombosis, and tissue infarction. No pathology indicative of IFRS was observed in the remaining groups. Positive rates of fungal culture in tissue homogenates from the maxillary sinus (62.5%) and lung (25%) were found in group V, whereas groups I, II, III, and IV showed no fungal culture in the homogenates. A rat IFRS model was successfully developed through nasal obstruction, CPA-induced neutropenia, and fungal inoculation. The disease model closely mimics the pathophysiology of anthropic IFRS.

  12. Analysis of naticid gastropod predation across the trans-Arctic invasion in the Tjörnes beds, Iceland, and the Red Crag Formation, East Anglia, England

    NASA Astrophysics Data System (ADS)

    Neely, Samuel H.; Kelley, Patricia H.

    2016-04-01

    Invasive species are wreaking havoc on modern ecosystems; however, species invasions are not new threats to ecosystems. The fossil record allows conservationists to acquire deep-time perspectives on long-term effects of natural invasions before anthropogenic impacts. Drill holes from invasive naticid gastropod predators on bivalve prey can be quantified to provide evidence of the impact of these invasive predators on ecosystems. An asymmetrical faunal interchange, known as the trans-Arctic invasion (TAI), occurred between the Pacific and Atlantic oceans during the Pliocene (˜3.5 Ma) because of the opening of the Bering Strait. This interchange could have changed naticid gastropod drilling predation on bivalves due to the migration of Pacific fauna into the Atlantic Ocean. The Tjörnes locality of northeast Iceland well characterizes the TAI because this site has preserved genera in three distinct levels that divide the invasion into the pre-invasion (Tapes and Mactra zones) and the post-invasion (Serripes zone). Temporal comparisons can be made between these pre- and post-invasion zones to analyze drilling predation across the TAI. Spatial comparisons of drilling predation in the post-invasion deposits can be made by correlating the Serripes zone (3.6-2.6 Ma) to the Red Crag Formation (2.54 Ma) of East Anglia, England, because these localities are of similar age and contain similar taxa. Specimens from the Tjörnes Beds, Iceland, were analyzed in collections housed at the Icelandic Institute of Natural History. Red Crag Formation specimens were analyzed at the Academy of Natural Sciences at Drexel University, Philadelphia, PA. Height and length of bivalve specimens were measured. The occurrence of complete and incomplete (unsuccessful) drill holes and drill hole diameter were recorded for all whole bivalves. Drilling frequency (DF = % mortality) and prey effectiveness (PE = % of attempted drill holes that were incomplete) were calculated. Icelandic samples

  13. Exposing rats to a predator impairs spatial working memory in the radial arm water maze.

    PubMed

    Diamond, D M; Park, C R; Heman, K L; Rose, G M

    1999-01-01

    This series of studies investigated the effects of predator exposure on working memory in rats trained on the radial arm water maze (RAWM). The RAWM is a modified Morris water maze that contains four or six swim paths (arms) radiating out of an open central area, with a hidden platform located at the end of one of the arms. The hidden platform was located in the same arm on each trial within a day and was in a different arm across days. Each day rats learned the location of the hidden platform during acquisition trials, and then the rats were removed from the maze for a 30-min delay period. During the delay period, the rats were placed either in their home cage (nonstress condition) or in close proximity to a cat (stress condition). At the end of the delay period, the rats were run on a retention trial, which tested their ability to remember which arm contained the platform that day. The first experiment confirmed that the RAWM is a hippocampal-dependent task. Rats with hippocampal damage were impaired at learning the location of the hidden platform in the easiest RAWM under control (non-stress) conditions. The next three experiments showed that stress had no effect on memory in the easiest RAWM, but stress did impair memory in more difficult versions of the RAWM. These findings indicate that the capacity for stress to impair memory is influenced not only by the brain memory system involved in solving the task (hippocampal versus nonhippocampal), but also by the difficulty of the task. This work should help to resolve some of the confusion in the literature regarding the heterogeneous effects of stress on hippocampal-dependent learning and memory.

  14. Glucocorticoid levels after exposure to predator odor and chronic psychosocial stress with dexamethasone application in rats.

    PubMed

    Starcevic, Ana; Petricevic, Sasa; Radojicic, Zoran; Djulejic, Vuk; Ilankovic, Andrej; Starcevic, Branislav; Filipovic, Branislav

    2016-05-01

    This study was conducted to explore the effects of specific psychosocial paradigm on predator animal posttraumatic stress model and to test the hypothesis that psychosocially stressed rats would exibit abnormal levels of cortisol and a larger suppression of cortisol levels after the application of dexamethasone. Animals were divided in two groups: experimental and control groups. The experimental group was exposed to two types of stressors: acute immobilization stress, and combined predator stress and daily social stress with application of dexamethasone. Blood sampling was performed at three different times. We found statistically significant results after analyzing the differences between cortisol levels in different times of blood sampling in the group of animals exposed to stress with dexamethasone application. Statistical significance was found when we compared the experimental group with the control group in terms of elevated cortisol levels during blood sampling after stress paradigm exposition. Many significant disruptions in the functioning of the hypothalamic-pituitary-adrenal axis were observed, such as decrease in basal cortisol levels and enhanced dexamethasone-induced inhibition of cortisol levels. These findings are important because their impact can translate to human individuals with posttraumatic stress disorder, which is the most important role of every animal model in research. Copyright © 2016. Published by Elsevier Taiwan.

  15. Bartonella species in invasive rats and indigenous rodents from Uganda.

    PubMed

    Billeter, Sarah A; Borchert, Jeff N; Atiku, Linda A; Mpanga, Joseph T; Gage, Kenneth L; Kosoy, Michael Y

    2014-03-01

    The presence of bartonellae in invasive rats (Rattus rattus) and indigenous rodents (Arvicanthis niloticus and Cricetomys gambianus) from two districts in Uganda, Arua and Zombo, was examined by PCR detection and culture. Blood from a total of 228 R. rattus, 31 A. niloticus, and 5 C. gambianus was screened using genus-specific primers targeting the 16S-23S intergenic spacer region. Furthermore, rodent blood was plated on brain heart infusion blood agar, and isolates were verified as Bartonella species using citrate synthase gene- (gltA) specific primers. One hundred and four fleas recovered from R. rattus were also tested for the presence of Bartonella species using the same gltA primer set. An overall prevalence of 1.3% (three of 228) was obtained in R. rattus, whereas 61.3% of 31 A. niloticus and 60% of five C. gambianus were positive for the presence of Bartonella species. Genotypes related to Bartonella elizabethae, a known zoonotic pathogen, were detected in three R. rattus and one C. gambianus. Bartonella strains, similar to bacteria detected in indigenous rodents from other African countries, were isolated from the blood of A. niloticus. Bartonellae, similar to bacteria initially cultured from Ornithodorus sonrai (soft tick) from Senegal, were found in two C. gambianus. Interestingly, bartonellae detected in fleas from invasive rats were similar to bacteria identified in indigenous rodents and not their rat hosts, with an overall prevalence of 6.7%. These results suggest that if fleas are competent vectors of these bartonellae, humans residing in these two districts of Uganda are potentially at greater risk for exposure to Bartonella species from native rodents than from invasive rats. The low prevalence of bartonellae in R. rattus was quite surprising, in contrast, to the detection of these organisms in a large percentage of Rattus species from other geographical areas. A possible reason for this disparity is discussed.

  16. Vespa velutina nest distribution at a local scale: An 8-year survey of the invasive honeybee predator.

    PubMed

    Monceau, Karine; Thiéry, Denis

    2017-08-01

    Vespa velutina is an invasive species that was observed for the first time in France and Europe in 2004, which rapidly threatened domestic honeybees with active predation. For the first time in this study, we analyzed the distribution of V. velutina nests at a local scale to understand the pattern of nesting, and in 8 years of monitoring, a total of 528 nests were surveyed. With the exception of 2 years, the nests of V. velutina were randomly distributed within the monitored area, which suggested that intraspecific competition for nesting sites and/or food was unlikely. When the data for all years were combined, an aggregated distribution of nests at the seafront in the vicinity of the oyster farm and sportfishing activities was observed. This distribution suggested that seafood, attractive to vespids, might provide a valuable alternative food source that favored colony development. We also tested the effect of spring queen trapping of V. velutina on the distribution of nests in 2014, which was the year with the greatest number of colonies within the area; the position of the traps did not influence the distribution of the nests. For the first time, this study showed that (i) intraspecific competition was unlikely to be a mechanism for population regulation, (ii) some areas were more likely favored for hornet nests, and (iii) spring queen wasp trapping was inefficient as a method to limit the distribution of the V. velutina population. © 2016 Institute of Zoology, Chinese Academy of Sciences.

  17. Ethopharmacological evaluation of the rat exposure test: a prey-predator interaction test.

    PubMed

    Campos, Kelciane Ferreira Caetano; Amaral, Vanessa Cristiane Santana; Rico, Javier Leonardo; Miguel, Tarciso Tadeu; Nunes-de-Souza, Ricardo Luiz

    2013-03-01

    The rat exposure test (RET) is a prey (mouse)-predator (rat) situation that activates brain defensive areas and elicits hormonal and defensive behavior in the mouse. Here, we investigated possible correlations between the spatiotemporal [time spent in protected (home chamber and tunnel) and unprotected (surface) compartments and frequency of entries into the three compartments] and ethological [e.g., duration of protected and unprotected stretched-attend postures (SAP), duration of contact with the rat's compartment] measures (Experiment 1). Secondly, we investigated the effects of systemic treatment with pro- or anti-aversive drugs on the behavior that emerged from the factor analysis (Experiment 2). The effects of chronic (21 days) imipramine and fluoxetine on defensive behavior were also investigated (Experiment 3). Exp. 1 revealed that the time in the protected compartment, protected SAP and rat contacts loaded on factor 1 (defensive behavior), while the total entries and unprotected SAP loaded on factor 2 (locomotor activity). Exp. 2 showed that alprazolam (but not diazepam) selectively changed the defensive factor. Caffeine produced a mild proaversive-like effect, whereas yohimbine only decreased locomotor activity (total entries). Fluoxetine (but not imipramine) produced a weak proaversive-like effect. 5-HT(1A)/5-HT(2) receptor ligands did not change any behavioral measure. In Exp. 3, chronic fluoxetine (but not imipramine) attenuated the defensive behavior factor without changing locomotion. Given that the defensive factor was sensitive to drugs known to attenuate (alprazolam and chronic fluoxetine) and induce (caffeine) panic attack, we suggest the RET as a useful test to assess the effects of panicolytic and panicogenic drugs.

  18. FOS EXPRESSION FOLLOWING REGIMENS OF PREDATOR STRESS VERSUS FOOTSHOCK THAT DIFFERENTIALLY AFFECT PREPULSE INHIBITION IN RATS

    PubMed Central

    Baisley, Sarah K.; Cloninger, Christina L.; Bakshi, Vaishali P.

    2011-01-01

    Stress is suggested to exacerbate symptoms and contribute to relapse in patients with schizophrenia and several other psychiatric disorders. A prominent feature of many of these illnesses is an impaired ability to filter information through sensorimotor gating processes. Prepulse inhibition (PPI) is a functional measure of sensorimotor gating, and known to be deficient in schizophrenia and sometimes in post-traumatic stress disorder (PTSD), both of which are also sensitive to stress-induced symptom deterioration. We previously found that a psychological stressor (exposure to a ferret without physical contact), but not footshock, disrupted PPI in rats, suggesting that intense psychological stress/trauma may uniquely model stress-induced sensorimotor gating abnormalities. In the present experiment, we sought to recreate the conditions where we found this behavioral difference, and to explore possible underlying neural substrates. Rats were exposed acutely to ferret stress, footshock, or no stress (control). 90 minutes later, tissue was obtained for Fos immunohistochemistry to assess neuronal activation. Several brain regions (prelimbic, infralimbic, and cingulate cortices, the paraventricular hypothalamic nucleus, the paraventricular thalamic nucleus, and the lateral periaqueductal gray) were equally activated following exposure to either stressor. Interestingly, the medial amygdala and dorsomedial periaqueductal gray had nearly twice as much Fos activation in the ferret-exposed rats as in the footshock-exposed rats, suggesting that higher activation within these structures may contribute to the unique behavioral effects induced by predator stress. These results may have implications for understanding the neural substrates that could participate in sensorimotor gating abnormalities seen in several psychiatric disorders after psychogenic stress. PMID:21843541

  19. Predator odor exposure of rat pups has opposite effects on play by juvenile males and females.

    PubMed

    Stockman, Sara L; McCarthy, Margaret M

    2017-01-01

    Juvenile social play behavior is one of the earliest sexually differentiated behaviors to emerge. In rats, as with most other species that play, males engage in more rough-and-tumble play compared to females. Exposure to early life adversity is a major driver of adult health and can manifest differently in males and females. However, the effects of adverse early life exposure on play behavior in the juvenile period are poorly understood. To address this, male and female neonatal rats were exposed to predator odor (PO), for 5min/day on PN1-PN3. At the time of exposure to PO, both male and female pups suppressed ultrasonic vocalization and displayed more freezing behavior. Circulating corticosterone increased in males immediately following PO exposure but not in females. The enduring effects of PO exposure were opposite in males compared to females in that PO exposed males decreased social play, while PO exposed females increased play behavior compared to same sex controls. PO exposure did not significantly affect cell genesis in the neonatal dentate gyrus of either sex. PO exposure did not affect anxiety-like behavior assessed in the juvenile period or in adulthood, nor did it affect social interactions in adulthood. This work provides new insight into how sex may interact with adverse early life events to contribute to development of the social consequences of such exposures. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Severity of the effects of invasive rats on seabirds: a global review.

    PubMed

    Jones, Holly P; Tershy, Bernie R; Zavaleta, Erika S; Croll, Donald A; Keitt, Bradford S; Finkelstein, Myra E; Howald, Gregg R

    2008-02-01

    Invasive rats are some of the largest contributors to seabird extinction and endangerment worldwide. We conducted a meta-analysis of studies on seabird-rat interactions to examine which seabird phylogenetic, morphological, behavioral, and life history characteristics affect their susceptibility to invasive rats and to identify which rat species have had the largest impact on seabird mortality. We examined 94 manuscripts that demonstrated rat effects on seabirds. All studies combined resulted in 115 independent rat-seabird interactions on 61 islands or island chains with 75 species of seabirds in 10 families affected. Seabirds in the family Hydrobatidae and other small, burrow-nesting seabirds were most affected by invasive rats. Laridae and other large, ground-nesting seabirds were the least vulnerable to rats. Of the 3 species of invasive rats, Rattus rattus had the largest mean impact on seabirds followed by R. norvegicus and R. exulans; nevertheless, these differences were not statistically significant. Our findings should help managers and conservation practitioners prioritize selection of islands for rat eradication based on seabird life history traits, develop testable hypotheses for seabird response to rat eradication, provide justification for rat eradication campaigns, and identify suitable levels of response and prevention measures to rat invasion. Assessment of the effects of rats on seabirds can be improved by data derived from additional experimental studies, with emphasis on understudied seabird families such as Sulidae, Phalacrocoracidae, Spheniscidae, Fregatidae, Pelecanoididae, Phaethontidae, and Diomedeidae and evaluation of rat impacts in tropical regions.

  1. Quantile regression of microgeographic variation in population characteristics of an invasive vertebrate predator

    PubMed Central

    Siers, Shane R.; Savidge, Julie A.; Reed, Robert N.

    2017-01-01

    Localized ecological conditions have the potential to induce variation in population characteristics such as size distributions and body conditions. The ability to generalize the influence of ecological characteristics on such population traits may be particularly meaningful when those traits influence prospects for successful management interventions. To characterize variability in invasive Brown Treesnake population attributes within and among habitat types, we conducted systematic and seasonally-balanced surveys, collecting 100 snakes from each of 18 sites: three replicates within each of six major habitat types comprising 95% of Guam’s geographic expanse. Our study constitutes one of the most comprehensive and controlled samplings of any published snake study. Quantile regression on snake size and body condition indicated significant ecological heterogeneity, with a general trend of relative consistency of size classes and body conditions within and among scrub and Leucaena forest habitat types and more heterogeneity among ravine forest, savanna, and urban residential sites. Larger and more robust snakes were found within some savanna and urban habitat replicates, likely due to relative availability of larger prey. Compared to more homogeneous samples in the wet season, variability in size distributions and body conditions was greater during the dry season. Although there is evidence of habitat influencing Brown Treesnake populations at localized scales (e.g., the higher prevalence of larger snakes—particularly males—in savanna and urban sites), the level of variability among sites within habitat types indicates little ability to make meaningful predictions about these traits at unsampled locations. Seasonal variability within sites and habitats indicates that localized population characterization should include sampling in both wet and dry seasons. Extreme values at single replicates occasionally influenced overall habitat patterns, while pooling

  2. Predation by carabid beetles on the invasive slug Arion vulgaris in an agricultural semi-field experiment.

    PubMed

    Pianezzola, E; Roth, S; Hatteland, B A

    2013-04-01

    Arion vulgaris Moquin-Tandon 1855 is one of the most important invasive species in Europe, affecting both biodiversity and agriculture. The species is spreading in many parts of Europe, inflicting severe damage to horticultural plants and cultivated crops partly due to a lack of satisfactory and effective management solutions. Molluscicides have traditionally been used to manage slug densities, although the effects are variable and some have severe side-effects on other biota. Thus, there is a need to explore potential alternatives such as biological control. The nematode Phasmarhabditis hermaphrodita is the only biological agent that has been applied commercially so far. However, other biological control agents such as carabid beetles have also been found to be promising. In addition, some carabid species have been shown to feed on A. vulgaris in the field as well as in the laboratory. Two species in particular have been found to be important predators of A. vulgaris, and these species are also common in agricultural environments: Pterostichus melanarius and Carabus nemoralis. This study is the first to use semi-field experiments in a strawberry field, manipulating densities, to investigate how P. melanarius and C. nemoralis affect densities of A. vulgaris eggs and juveniles, respectively. Gut contents of C. nemoralis were analysed using multiplex PCR methods to detect DNA of juvenile slugs. Results show that both P. melanarius and C. nemoralis significantly affect densities of slug eggs and juvenile slugs under semi-field conditions and that C. nemoralis seems to prefer slugs smaller than one gram. Carabus nemoralis seems to be especially promising in reducing densities of A. vulgaris, and future studies should investigate the potential of using this species as a biological control agent.

  3. Fear-like biochemical and behavioral responses in rats to the predator odor, TMT, are dependent on the exposure environment.

    PubMed

    Morrow, Bret A; Elsworth, John D; Roth, Robert H

    2002-10-01

    Several laboratories have reported that exposure to predator odor can result in stress-like effects in rodents. While some laboratories have reported fear-like alterations in behavior, other laboratories, including our own, have failed to consistently observe fearful behaviors in rats exposed to the predator odor TMT. One potential contributing factor to this discrepancy is the handling of the rat and its test environment. In the current report, we examine biochemical, endocrinological, and behavioral effects of TMT in two distinct open fields: one small, familiar, and dimly lit, while the other was large, novel, and brightly lit. Only exposure to TMT in the large, novel open field resulted in fearful behavior; however, no increase in dopamine turnover was noted compared to no odor and control odor rats. As expected, the different open fields resulted in some biochemical and behavioral differences, including more horizontal locomotion and less grooming, higher serum corticosterone, and increased dopamine turnover in the ventral prefrontal cortex in the large open field. Finally, compared to the same open field controls, TMT exposure elevated rat serum corticosterone levels in both open fields and dopamine turnover in the dorsal and ventral medial prefrontal cortex and amygdala of rats only in the small, familiar open field. These results indicate that the TMT-induced biochemical activation of may occur without detectable fearful behaviors and may indicate a mechanism that prepares the animal for the expression of a fearful response if additional provocative stimuli are present.

  4. Endocannabinoid Modulation of Predator Stress-Induced Long-Term Anxiety in Rats.

    PubMed

    Lim, James; Igarashi, Miki; Jung, Kwang-Mook; Butini, Stefania; Campiani, Giuseppe; Piomelli, Daniele

    2016-04-01

    Individuals who experience life-threatening psychological trauma are at risk of developing a series of chronic neuropsychiatric pathologies that include generalized anxiety, depression, and drug addiction. The endocannabinoid system has been implicated in the modulation of these responses by regulating the activity of the amygdala and the hypothalamic-pituitary-adrenal axis. However, the relevance of this signaling complex to the long-term consequences of traumatic events is unclear. Here we use an animal model of predatory stress-induced anxiety-like behavior to investigate the role of the endocannabinoid system in the development of persistent anxiety states. Our main finding is that rats exposed to the fox pheromone 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), a life-threatening stimulus for rodents, display a marked and selective increase in the mobilization of the endocannabinoid, 2-arachidonoyl-sn-glycerol (2-AG), in the amygdala. This effect lasts for at least 14 days after the stress has occurred. In addition, systemic or local pharmacological inhibition of monoacylglycerol lipase (MGL)-a lipid hydrolase that degrades 2-AG in presynaptic nerve terminals-elevates 2-AG levels and suppresses the anxiety-like behavior elicited by exposure to TMT. The results suggest that predator threat triggers long-term changes in 2-AG-mediated endocannabinoid signaling in the amygdala, and that pharmacological interventions targeting MGL might provide a therapeutic strategy for the treatment of chronic brain disorders initiated by trauma.

  5. Endocannabinoid Modulation of Predator Stress-Induced Long-Term Anxiety in Rats

    PubMed Central

    Lim, James; Igarashi, Miki; Jung, Kwang-Mook; Butini, Stefania; Campiani, Giuseppe; Piomelli, Daniele

    2016-01-01

    Individuals who experience life-threatening psychological trauma are at risk of developing a series of chronic neuropsychiatric pathologies that include generalized anxiety, depression, and drug addiction. The endocannabinoid system has been implicated in the modulation of these responses by regulating the activity of the amygdala and the hypothalamic–pituitary–adrenal axis. However, the relevance of this signaling complex to the long-term consequences of traumatic events is unclear. Here we use an animal model of predatory stress-induced anxiety-like behavior to investigate the role of the endocannabinoid system in the development of persistent anxiety states. Our main finding is that rats exposed to the fox pheromone 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), a life-threatening stimulus for rodents, display a marked and selective increase in the mobilization of the endocannabinoid, 2-arachidonoyl-sn-glycerol (2-AG), in the amygdala. This effect lasts for at least 14 days after the stress has occurred. In addition, systemic or local pharmacological inhibition of monoacylglycerol lipase (MGL)—a lipid hydrolase that degrades 2-AG in presynaptic nerve terminals—elevates 2-AG levels and suppresses the anxiety-like behavior elicited by exposure to TMT. The results suggest that predator threat triggers long-term changes in 2-AG-mediated endocannabinoid signaling in the amygdala, and that pharmacological interventions targeting MGL might provide a therapeutic strategy for the treatment of chronic brain disorders initiated by trauma. PMID:26361059

  6. Observations of raccoon (Procyon lotor) predation on the invasive Maculata apple snail (Pomacea maculata) in southern Louisiana

    USGS Publications Warehouse

    Carter, Jacoby; Merino, Sergio; Prejean, Drew; LaFleur, Gary Jr.

    2017-01-01

    We used camera traps to determine which predators were responsible for depredated Pomacea maculata (Maculata Apple Snail) shells at 2 different study sites. Evidence of predation at these sites included operculums near the shells with a small amount of flesh attached and shells accumulating a meter or more from the water’s edge with no evidence of recent flooding. In both locations, the most frequently observed potential predators were Procyon lotor (Raccoon), which was the only species directly observed capturing and eating Apple Snails.

  7. Rodents balancing a variety of risks: invasive fire ants and indirect and direct indicators of predation risk.

    SciTech Connect

    Orrock, John, L.; Danielson, Brent, J.

    2004-06-08

    Oecologia (2004) 140: 662 - 667 We used foraging trays to compare how old field mice, Peromyscus polionotus, altered foraging in response to the presence of fire ants, Solenopsisinvicta, and in the presence of direct (predator urine) and indirect (sheltered or exposed micro habitat, moonlight, and precipitation) indicators of predation risk. Foraging reductions elicited by S. invicta were greater than reductions in response to well-documented indicators of risk (i.e., moonlit nights) and the presence of predator urine. The presence of S. invicta always led to reduced foraging, but the overall impact of S. invicta was dependent upon microhabitat and precipitation. When S. invicta was not present, foraging was greater in sheltered microhabitats compared to exposed microhabitats. S. invicta made sheltered microhabitats equivalent to more risky exposed microhabitats, and this effect was especially pronounced on nights without precipitation. The effect of S. invicta suggests that interactions with S. invicta may entail a potentially heavy cost or that presence of S. invicta may represent a more reliable indicator of imminent competition or predation compared to indirect cues of risk and predator urine. The presence of S. invicta led to reduced foraging under situations when foraging activity would otherwise be greatest (i.e., under vegetative cover), potentially reducing habitat quality for P. polionotus and the distribution of seeds consumed by rodents.

  8. Maternal presence and rearing condition affect responses to a live predator in kangaroo rats (Dipodomys heermanni arenae).

    PubMed

    Yoerg, S I; Shier, D M

    1997-12-01

    Experiment 1 compared the responses of wild-caught adult and captive-born adult and juvenile kangaroo rats (Dipodomys heermanni arenae) to a live snake. Wild-caught adult rats were less active and monitored the snake more than during a control condition; captive-born juvenile rats did not behave differently during snake and control tests. Snake-naive adult rats behaved more like the wild-caught adult rats, but not on all measures. In Experiment 2, pups were tested at 25 and 50 days of age in 4 conditions: no-snake control, alone with the snake, with a sibling and the snake, and with the mother and the snake. Pups did not behave differently during control and snake tests, but during tests with the mother, pups faced the snake less and followed the mother. Younger pups were more often near the mother than a sibling and followed the mother more when the snake was present. Development of defensive behavior may depend on both predator experience and maternal influence.

  9. Long-term impacts of invasive species on a native top predator in a large lake system

    USGS Publications Warehouse

    Rush, Scott A.; Paterson, Gordon; Johnson, Tim B.; Drouillard, Ken G.; Haffner, Gordon D.; Hebert, Craig E.; Arts, Michael T.; McGoldrick, Daryl J.; Backus, Sean M.; Lantry, Brian F.; Lantry, Jana R.; Schaner, Ted; Fisk, Aaron T.

    2012-01-01

    1. Declining abundances of forage fish and the introduction and establishment of non-indigenous species have the potential to substantially alter resource and habitat exploitation by top predators in large lakes. 2. We measured stable isotopes of carbon (δ13C) and nitrogen (δ15N) in field-collected and archived samples of Lake Ontario lake trout (Salvelinus namaycush) and five species of prey fish and compared current trophic relationships of this top predator with historical samples. 3. Relationships between δ15N and lake trout age were temporally consistent throughout Lake Ontario and confirmed the role of lake trout as a top predator in this food web. However, δ13C values for age classes of lake trout collected in 2008 ranged from 1.0 to 3.9‰ higher than those reported for the population sampled in 1992. 4. Isotope mixing models predicted that these changes in resource assimilation were owing to the replacement of rainbow smelt (Osmerus mordax) by round goby (Neogobius melanostomus) in lake trout diet and increased reliance on carbon resources derived from nearshore production. This contrasts with the historical situation in Lake Ontario where δ13C values of the lake trout population were dominated by a reliance on offshore carbon production. 5. These results indicate a reduced capacity of the Lake Ontario offshore food web to support the energetic requirements of lake trout and that this top predator has become increasingly reliant on prey resources that are derived from nearshore carbon pathways.

  10. Accessory and main olfactory systems influences on predator odor-induced behavioral and endocrine stress responses in rats

    PubMed Central

    Masini, Cher V.; Garcia, Robert J.; Sasse, Sarah K.; Nyhuis, Tara J.; Day, Heidi E.W.; Campeau, Serge

    2009-01-01

    Exposures to predator odors are very effective methods to evoke a variety of stress responses in rodents. We have previously found that ferret odor exposure leads to changes in endocrine hormones (corticosterone and ACTH) and behavior. To distinguish the contributions of the main and accessory olfactory systems in these responses, studies were designed to interfere with these two systems either independently, or simultaneously. Male Sprague-Dawley rats were treated with 10% zinc sulfate (ZnSO4), which renders rodents anosmic (unable to smell) while leaving the accessory olfactory areas intact, or saline, in experiment 1. In experiment 2, the vomeronasal organs of rats were surgically removed (VNX) to block accessory olfactory processing, while leaving the main olfactory system intact. And in the 3rd experiment both the main and accessory olfactory areas were disrupted by combining the two procedures in the same rats. Neither ZnSO4 treatment or VNX alone reliably reduced the increased corticosterone response to ferret odor compared to strawberry odor, but in combination, they did. This suggests that processing through the main or the accessory olfactory system can elicit the endocrine stress response to ferret odor. VNX alone also did not affect the behavioral responses to the ferret. ZnSO4 treatment, alone and in combination with VNX, led to changes in behavior in response to both ferret and strawberry odor, making the behavioral results less clearly interpretable. Overall these studies suggest that both the main and accessory olfactory systems mediate the neuroendocrine response to predator odor. PMID:19800371

  11. Dendritic morphology of amygdala and hippocampal neurons in more and less predator stress responsive rats and more and less spontaneously anxious handled controls

    PubMed Central

    Adamec, Robert; Hebert, Mark; Blundell, Jacqueline; Mervis, Ronald F.

    2013-01-01

    We investigated the neurobiological bases of variation in response to predator stress (PS). Sixteen days after treatment (PS or handling), rats were grouped according to anxiety in the elevated plus maze (EPM). Acoustic startle was also measured. We examined the structure of dendritic trees of basolateral amygdala (BLA) output neurons (stellate and pyramidal cells) and of dorsal hippocampal (DHC) dentate granule cells of less anxious (LA) and more (extremely) anxious (MA) stressed animals (PSLA and PSMA). Handled controls (HC) which were less anxious (HCLA) and spontaneously more anxious (HCMA) equivalently to predator stressed subgroups were also studied. Golgi analysis revealed BLA output neurons of HCMA rats exhibited longer, more branched dendrites with higher spine density than the other groups of rats, which did not differ. Finally, spine density of DHC granule cells was equally depressed in HCMA and PSMA rats relative to HCLA and PSLA rats. Total dendritic length of BLA pyramidal and stellate cells (positive predictor) and DHC spine density (negative predictor) together accounted for 96% of the variance of anxiety of handled rats. DHC spine density was a negative predictor of PSMA and PSLA anxiety, accounting for 70% of the variance. Data are discussed in the context of morphological differences as phenotypic markers of a genetic predisposition to anxiety in handled controls, and a possible genetic vulnerability to predator stress expressed as reduced spine density in the DHC. Significance of findings for animal models of anxiety and hyperarousal comorbidities of PTSD are discussed. PMID:21925210

  12. Prophylactic and therapeutic effects of acute systemic injections of EMD 281014, a selective serotonin 2A receptor antagonist on anxiety induced by predator stress in rats.

    PubMed

    Adamec, Robert; Creamer, Katherine; Bartoszyk, Gerd D; Burton, Paul

    2004-11-03

    We examined the effect of the selective serotonin 2A (5-HT(2A)) receptor antagonist 7-[4-[2-(4-fluoro-phenyl)-ethyl]-piperazine-1-carbonyl]-1H-indole-3-carbon itrile HCl (EMD 281014) [Bartoszyk, G.D., van Amsterdam, C., Bottcher, H., Seyfried, C.A., 2003. EMD 281014, a new selective serotonin 5-HT2A receptor antagonist. Eur. J. Pharmacol. 473, 229-230.] on change in affect following predator stress. Predator stress involved a 5 min unprotected exposure of rats to a domestic cat. Behavioral effects of stress were evaluated with hole board, plus maze, light/dark box and acoustic startle tests 1 week after stress. Predator stress increased anxiety-like behavior in the plus maze, light/dark box, and elevated response to acoustic startle. EMD 281014 (0.001, 0.01, 0.1, 1 or 10 mg/kg) and vehicle injection (ip) occurred either 10 min after predator stress (prophylactic testing), or 90 min prior to behavioral testing for the effects of predator stress (therapeutic testing 1 week after predator stress). In prophylactic testing, EMD 281014 prevented stress potentiation of startle in a dose dependent manner, though the most effective doses were midrange (0.01 and 0.1 mg/kg). Prophylactic administration of EMD 281014 also prevented stress-induced increase of open arm avoidance in the plus maze in a clear dose dependent manner (from 0.01 mg/kg onward). In therapeutic testing, EMD 281014 had no clear drug dependent effects on stress elevation of startle or on behavior of stressed rats in the elevated plus maze. Finally, EMD 281014 did not block the effects of stress on behavior in the light/dark box when given prophylactically or therapeutically. Findings implicate 5-HT(2A) receptors in initiation of some but not all lasting changes in anxiety-like behavior following predator stress. Potential clinical significance of findings are discussed.

  13. Invasive rats alter woody seedling composition on seabird-dominated islands in New Zealand.

    PubMed

    Grant-Hoffman, Madeline N; Mulder, Christa P; Bellingham, Peter J

    2010-06-01

    Invasive rats (Rattus rattus, R. norvegicus, R. exulans) have large impacts on island habitats through both direct and indirect effects on plants. Rats affect vegetation by extirpating burrowing seabirds through consumption of eggs, chicks, and adults. These seabirds serve as ecosystem engineers, affecting plant communities by burying and trampling seeds and seedlings, and by altering microclimate. Rats also directly affect plant communities by consuming seeds and seedlings. We studied the direct and indirect impacts of rats on the seedlings of woody plants on 21 islands in northern New Zealand. We compared seedling densities and richness on islands which differed in status with respect to rats: nine islands where rats never invaded, seven islands where rats were present at the time of our study, and five islands where rats were either eradicated or where populations were likely to be small as a result of repeated eradications and re-invasions. In addition, we compared plots from a subset of the 21 islands with different burrow densities to examine the effects of burrowing seabirds on plants while controlling for other factors that differ between islands. We categorized plant communities by species composition and seedling density in a cluster analysis. We found that burrow densities explained more variation in seedling communities than rat status. In areas with high seabird burrow density seedling densities were low, especially for the smallest seedlings. Species richness and diversity of seedlings, but not seedling density, were most influenced by changes in microclimate induced by seabirds. Islands where rats had been eradicated or that had low rat populations had the lowest diversity and richness of seedlings (and adults), but the highest seedling density. Seedling communities on these islands were dominated by Pseudopanax lessonii and Coprosma macrocarpa. This indicates lasting effects of rats that may prevent islands from returning to pre-invasion states.

  14. Ant predation on an invasive herbivore: Can an extrafloral nectar-producing plant provide associational resistance to Opuntia individuals?

    USDA-ARS?s Scientific Manuscript database

    The legume Chamaecrista fasciculata attracts ants to its extrafloral nectar (EFN) which can lead to reduced herbivory and increased fecundity for the plant. In Florida, Opuntia stricta and O. humifusa, hosts of the invasive moth Cactoblastis cactorum, are often found growing in close association wit...

  15. Draft Genome Sequences of Six Nontypeable Haemophilus influenzae Strains That Establish Bacteremia in the Infant Rat Model of Invasive Disease

    PubMed Central

    VanWagoner, Timothy M.; Seale, Thomas W.; Mussa, Huda J.; Cole, Brett K.; Whitby, Paul W.; Stull, Terrence L.

    2015-01-01

    Haemophilus influenzae is an important cause of invasive disease. The infant rat is the accepted model of invasive H. influenzae disease. Here, we report the genome sequences of six nontypeable H. influenzae strains that establish bacteremia in the infant rat. PMID:26404588

  16. Effects of systemic injections of vilazodone, a selective serotonin reuptake inhibitor and serotonin 1A receptor agonist, on anxiety induced by predator stress in rats.

    PubMed

    Adamec, Robert; Bartoszyk, Gerd D; Burton, Paul

    2004-11-03

    We examined the effect of Vilazodone, a selective serotonin reuptake inhibitor (SSRI) and serotonin 1A (5-HT(1A)) receptor agonist [Bartoszyk, G.D., Hegenbart, R., Ziegler, H., 1997. EMD 68843, a serotonin reuptake inhibitor with selective presynaptic 5-HT1A receptor agonistic properties. Eur. J. Pharmacol. 322, 147-153.], on change in affect following predator stress. Vilazodone and vehicle injection (intraperitoneal) occurred either 10 min after predator stress (prophylactic testing), or 90 min prior to behavioral testing for the effects of predator stress (therapeutic testing). Predator stress involved unprotected exposure of rats to a domestic cat. Behavioral effects of stress were evaluated with hole board, plus-maze, and acoustic startle tests 1 week after stress. Predator stress increased anxiety-like behavior in the plus-maze and elevated response to acoustic startle. In prophylactic testing, Vilazodone affected stress potentiation of startle at doses above 5 mg/kg. Vilazodone increased stress elevation of startle at 10 mg/kg. Higher doses of Vilazodone (20 and 40 mg/kg) blocked stress potentiation of startle. In contrast, Vilazodone had no effect on stress potentiation of anxiety in the plus-maze. In therapeutic testing, Vilazodone increased stress elevation of startle at all doses. In contrast, therapeutic Vilazodone had no effect on stress potentiation of anxiety in the plus-maze. Taken together, the data suggest a prophylactic potential for Vilazodone in the treatment of changes in hypervigilance following severe stress.

  17. An invasive species induces rapid adaptive change in a native predator: cane toads and black snakes in Australia.

    PubMed

    Phillips, Ben L; Shine, Richard

    2006-06-22

    Rapid environmental change due to human activities has increased rates of extinction, but some species may be able to adapt rapidly enough to deal with such changes. Our studies of feeding behaviour and physiological resistance to toxins reveal surprisingly rapid adaptive responses in Australian black snakes (Pseudechis porphyriacus) following the invasion of a lethally toxic prey item, the cane toad (Bufo marinus). Snakes from toad-exposed localities showed increased resistance to toad toxin and a decreased preference for toads as prey. Separate laboratory experiments suggest that these changes are not attributable to learning (we were unable to teach naive snakes to avoid toxic prey) or to acquired resistance (repeated sub-lethal doses did not enhance resistance). These results strongly suggest that black snake behaviour and physiology have evolved in response to the presence of toads, and have done so rapidly. Toads were brought to Australia in 1935, so these evolved responses have occurred in fewer than 23 snake generations.

  18. An invasive species induces rapid adaptive change in a native predator: cane toads and black snakes in Australia

    PubMed Central

    Phillips, Ben L; Shine, Richard

    2006-01-01

    Rapid environmental change due to human activities has increased rates of extinction, but some species may be able to adapt rapidly enough to deal with such changes. Our studies of feeding behaviour and physiological resistance to toxins reveal surprisingly rapid adaptive responses in Australian black snakes (Pseudechis porphyriacus) following the invasion of a lethally toxic prey item, the cane toad (Bufo marinus). Snakes from toad-exposed localities showed increased resistance to toad toxin and a decreased preference for toads as prey. Separate laboratory experiments suggest that these changes are not attributable to learning (we were unable to teach naive snakes to avoid toxic prey) or to acquired resistance (repeated sub-lethal doses did not enhance resistance). These results strongly suggest that black snake behaviour and physiology have evolved in response to the presence of toads, and have done so rapidly. Toads were brought to Australia in 1935, so these evolved responses have occurred in fewer than 23 snake generations. PMID:16777750

  19. From Human Geography to Biological Invasions: The Black Rat Distribution in the Changing Southeastern of Senegal.

    PubMed

    Lucaccioni, Héloïse; Granjon, Laurent; Dalecky, Ambroise; Fossati, Odile; Le Fur, Jean; Duplantier, Jean-Marc; Handschumacher, Pascal

    In the contemporary context of zoonosis emergence and spread, invasive species are a major issue since they represent potential pathogen hosts. Even though many progresses have been done to understand and predict spatial patterns of invasive species, the challenge to identify the underlying determinants of their distribution remains a central question in invasion biology. This is particularly exacerbated in the case of commensal species that strictly depend on humankind for dispersal and perennial establishment of new populations. The distribution of these species is predicted to be influenced by dispersal opportunities and conditions acting on establishment and proliferation, such as environmental characteristics, including spatio-temporal components of the human societies. We propose to contribute to the understanding of the recent spread of a major invasive rodent species, the black rat (Rattus rattus), in the changing southeastern of Senegal. We address the factors that promote the dispersal and distribution of this invasive rodent from the perspective of human geography. We first describe characteristics of human settlements in terms of social and spatial organization of human societies (i.e. economic activities, commercial and agricultural networks, roads connectivity). We then explore the relationship between these characteristics and the distribution of this invasive rodent. Finally we propose that historical and contemporary dynamics of human societies have contributed to the risk of invasion of the black rat. We argue that the diffusion processes of invasive species cannot be considered as a result of the spatial structure only (i.e. connectivity and distance), but as a part of the human territory that includes the social and spatial organization. Results suggest that the distribution of invasive rodents partly results from the contemporary and inherited human socio-spatial systems, beyond the existence of suitable ecological conditions that are

  20. From Human Geography to Biological Invasions: The Black Rat Distribution in the Changing Southeastern of Senegal

    PubMed Central

    Lucaccioni, Héloïse; Granjon, Laurent; Dalecky, Ambroise; Fossati, Odile; Le Fur, Jean; Duplantier, Jean-Marc; Handschumacher, Pascal

    2016-01-01

    In the contemporary context of zoonosis emergence and spread, invasive species are a major issue since they represent potential pathogen hosts. Even though many progresses have been done to understand and predict spatial patterns of invasive species, the challenge to identify the underlying determinants of their distribution remains a central question in invasion biology. This is particularly exacerbated in the case of commensal species that strictly depend on humankind for dispersal and perennial establishment of new populations. The distribution of these species is predicted to be influenced by dispersal opportunities and conditions acting on establishment and proliferation, such as environmental characteristics, including spatio-temporal components of the human societies. We propose to contribute to the understanding of the recent spread of a major invasive rodent species, the black rat (Rattus rattus), in the changing southeastern of Senegal. We address the factors that promote the dispersal and distribution of this invasive rodent from the perspective of human geography. We first describe characteristics of human settlements in terms of social and spatial organization of human societies (i.e. economic activities, commercial and agricultural networks, roads connectivity). We then explore the relationship between these characteristics and the distribution of this invasive rodent. Finally we propose that historical and contemporary dynamics of human societies have contributed to the risk of invasion of the black rat. We argue that the diffusion processes of invasive species cannot be considered as a result of the spatial structure only (i.e. connectivity and distance), but as a part of the human territory that includes the social and spatial organization. Results suggest that the distribution of invasive rodents partly results from the contemporary and inherited human socio-spatial systems, beyond the existence of suitable ecological conditions that are

  1. Aboriginal and invasive rats of genus Rattus as hosts of infectious agents.

    PubMed

    Kosoy, Michael; Khlyap, Lyudmila; Cosson, Jean-Francois; Morand, Serge

    2015-01-01

    From the perspective of ecology of zoonotic pathogens, the role of the Old World rats of the genus Rattus is exceptional. The review analyzes specific characteristics of rats that contribute to their important role in hosting pathogens, such as host-pathogen relations and rates of rat-borne infections, taxonomy, ecology, and essential factors. Specifically the review addresses recent taxonomic revisions within the genus Rattus that resulted from applications of new genetic tools in understanding relationships between the Old World rats and the infectious agents that they carry. Among the numerous species within the genus Rattus, only three species-the Norway rat (R. norvegicus), the black or roof rat (R. rattus), and the Asian black rat (R. tanezumi)-have colonized urban ecosystems globally for a historically long period of time. The fourth invasive species, R. exulans, is limited to tropical Asia-Pacific areas. One of the points highlighted in this review is the necessity to discriminate the roles played by rats as pathogen reservoirs within the land of their original diversification and in regions where only one or few rat species were introduced during the recent human history.

  2. Lipopolysaccharide-induced biliary factors enhance invasion of Salmonella enteritidis in a rat model.

    PubMed

    Islam, A F; Moss, N D; Dai, Y; Smith, M S; Collins, A M; Jackson, G D

    2000-01-01

    In this study, the role of the hepatobiliary system in the early pathogenesis of Salmonella enteritidis infection was investigated in a rat model. Intravenous (i.v.) challenge with lipopolysaccharide (LPS) has previously been shown to enhance the translocation of normal gut flora. We first confirmed that LPS can similarly promote the invasion of S. enteritidis. Oral infection of outbred Australian Albino Wistar rats with 10(6) to 10(7) CFU of S. enteritidis led to widespread tissue invasion after days. If animals were similarly challenged after intravenous administration of S. enteritidis LPS (3 to 900 microg/kg of body weight), significant invasion of the livers and mesenteric lymph nodes (MLN) occurred within 24 h, with invasion of the liver increasing in a dose-dependent fashion (P < 0.01). If bile was prevented from reaching the intestine by bile duct ligation or cannulation, bacterial invasion of the liver and MLN was almost totally abrogated (P < 0.001). As i.v. challenge with LPS could induce the delivery of inflammatory mediators into the bile, biliary tumor necrosis factor alpha (TNF-alpha) concentrations were measured by bioassay. Biliary concentrations of TNF-alpha rose shortly after LPS challenge, peaked with a mean concentration of 27.0 ng/ml at around 1 h postchallenge, and returned to baseline levels (3.1 ng/ml) after 2.5 h. Although TNF-alpha cannot be directly implicated in the invasion process, we conclude that the invasiveness of the enteric pathogen S. enteritidis is enhanced by the presence of LPS in the blood and that this enhanced invasion is at least in part a consequence of the delivery of inflammatory mediators to the gastrointestinal tract by the hepatobiliary system.

  3. Lipopolysaccharide-Induced Biliary Factors Enhance Invasion of Salmonella enteritidis in a Rat Model

    PubMed Central

    Islam, Abul F. M. W.; Moss, Nathan D.; Dai, Yung; Smith, Murray S. R.; Collins, Andrew M.; Jackson, Graham D. F.

    2000-01-01

    In this study, the role of the hepatobiliary system in the early pathogenesis of Salmonella enteritidis infection was investigated in a rat model. Intravenous (i.v.) challenge with lipopolysaccharide (LPS) has previously been shown to enhance the translocation of normal gut flora. We first confirmed that LPS can similarly promote the invasion of S. enteritidis. Oral infection of outbred Australian Albino Wistar rats with 106 to 107 CFU of S. enteritidis led to widespread tissue invasion after days. If animals were similarly challenged after intravenous administration of S. enteritidis LPS (3 to 900 μg/kg of body weight), significant invasion of the livers and mesenteric lymph nodes (MLN) occurred within 24 h, with invasion of the liver increasing in a dose-dependent fashion (P < 0.01). If bile was prevented from reaching the intestine by bile duct ligation or cannulation, bacterial invasion of the liver and MLN was almost totally abrogated (P < 0.001). As i.v. challenge with LPS could induce the delivery of inflammatory mediators into the bile, biliary tumor necrosis factor alpha (TNF-α) concentrations were measured by bioassay. Biliary concentrations of TNF-α rose shortly after LPS challenge, peaked with a mean concentration of 27.0 ng/ml at around 1 h postchallenge, and returned to baseline levels (3.1 ng/ml) after 2.5 h. Although TNF-α cannot be directly implicated in the invasion process, we conclude that the invasiveness of the enteric pathogen S. enteritidis is enhanced by the presence of LPS in the blood and that this enhanced invasion is at least in part a consequence of the delivery of inflammatory mediators to the gastrointestinal tract by the hepatobiliary system. PMID:10603360

  4. Toxoplasma gondii infection reduces predator aversion in rats through epigenetic modulation in the host medial amygdala.

    PubMed

    Hari Dass, Shantala Arundhati; Vyas, Ajai

    2014-12-01

    Male rats (Rattus novergicus) infected with protozoan Toxoplasma gondii relinquish their innate aversion to the cat odours. This behavioural change is postulated to increase transmission of the parasite to its definitive felid hosts. Here, we show that the Toxoplasma gondii infection institutes an epigenetic change in the DNA methylation of the arginine vasopressin promoter in the medial amygdala of male rats. Infected animals exhibit hypomethylation of arginine vasopressin promoter, leading to greater expression of this nonapeptide. The infection also results in the greater activation of the vasopressinergic neurons after exposure to the cat odour. Furthermore, we show that loss of fear in the infected animals can be rescued by the systemic hypermethylation and recapitulated by directed hypomethylation in the medial amygdala. These results demonstrate an epigenetic proximate mechanism underlying the extended phenotype in the Rattus novergicus-Toxoplasma gondii association.

  5. Efficacy of urine bile acid as a non-invasive indicator of liver damage in rats.

    PubMed

    Kawai, Hiroshi; Kudo, Naomi; Kawashima, Yoichi; Mitsumoto, Atsushi

    2009-02-01

    Estimation of liver damage is important in the pathophysiological and toxicological study of liver disease. As a novel, non-invasive marker of liver damage, we studied the efficacy of urine bile acids (UBA) in a rat model of liver disease. Thioacetamide (TAA)-treated rats were used in this study. Single intraperitoneal administration of high-dose TAA induces severe damage to the liver, and thus is used as a model of acute hepatitis. Continuous administration of low-dose TAA yields mild damage to the liver, and induces cirrhosis and hepatic tumors. In this study, it was found that both acute and chronic administration of TAA was associated with a dose-dependent elevation of UBA. The elevation of UBA content correlated with the alteration of blood biochemical indicators, and UBA screening showed a remarkable ability to distinguish liver-damaged rats from healthy rats. In particular, UBA analysis was found to have high sensitivity, specificity, and positive predictive value for the screening of rats with abnormal serum alkaline phosphatase (ALP) activity due to chronic liver damage, which was confirmed to include cholestasis and subsequent cirrhosis by liver histological analysis. In conclusion, we demonstrated that measurement of UBA is a simple, non-invasive and effective method for the screening of cholestasis in TAA-treated rats. We suggest that UBA analysis may have potent applicability for monitoring the progress of liver damage in animal models of chronic liver disease, such as cirrhosis and hepatic encephalopathy.

  6. Predator Exposure/Psychosocial Stress Animal Model of Post-Traumatic Stress Disorder Modulates Neurotransmitters in the Rat Hippocampus and Prefrontal Cortex

    PubMed Central

    Wilson, C. Brad; Ebenezer, Philip J.; McLaughlin, Leslie D.; Francis, Joseph

    2014-01-01

    Post-Traumatic Stress Disorder (PTSD) can develop in response to a traumatic event involving a threat to life. To date, no diagnostic biomarkers have been identified for PTSD. Recent research points toward physiological abnormalities in the hypothalamic-pituitary-adrenal (HPA) axis, sympathoadrenal medullary and immune system that may be implicated in the disorder. The modulation of neurotransmitters is another possible mechanism, but their role in the progression of PTSD is poorly understood. Low serotonin (5-HT) may be a factor, but it may not be the only neurotransmitter affected as modulation affects levels of other neurotransmitters. In this study, we hypothesized the predator exposure/psychosocial stress rodent model of PTSD may alter levels of 5-HT and other neurotransmitters in the rat hippocampus and prefrontal cortex (PFC). Male Sprague-Dawley rats were used in this experiment. We induced PTSD via a predator exposure/psychosocial stress model, whereby rats were placed in a cage with a cat for 1 hour on days 1 and 11 of the 31-day experiment. Rats also received psychosocial stress via daily cage cohort changes. On day 32, the rats were sacrificed and the brains dissected to remove the hippocampus and PFC. Norepinephrine (NE), 5-Hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), dopamine (DA), and 3,4-Dihydroxyphenylacetic acid (DOPAC), and 5-HT levels in the hippocampus and PFC were measured with high-performance liquid chromatography (HPLC). In the hippocampus, 5-HT and HVA were lower, while NE and DOPAC were higher, in the PTSD group vs. controls. In the PFC, only 5-HT was lower, while NE, DA, and DOPAC were higher, in the PTSD group vs. controls. The rate limiting enzymes tyrosine hydroxylase and tryptophan hydroxylase were also examined and confirmed our findings. These results demonstrate that the predator exposure/psychosocial stress model of PTSD produces neurotransmitter changes similar to those seen in human patients and may cause a

  7. Development of Odor Hedonics: Experience-Dependent Ontogeny of Circuits Supporting Maternal and Predator Odor Responses in Rats

    PubMed Central

    Al Aïn, Syrina; Raineki, Charlis; Sullivan, Regina M.

    2016-01-01

    A major component of perception is hedonic valence: perceiving stimuli as pleasant or unpleasant. Here, we used early olfactory experiences that shape odor preferences and aversions to explore developmental plasticity in circuits mediating odor hedonics. We used 2-deoxyglucose autoradiographic mapping of neural activity to identify circuits differentially activated by biologically relevant preferred and avoided odors across rat development. We then further probed this system by increasing or decreasing hedonic value. Using both region of interest and functional connectivity analyses, we identified regions within primary olfactory, amygdala/hippocampal, and prefrontal cortical networks that were activated differentially by maternal and male odors. Although some activated regions remained stable across development (postnatal days 7–23), there was a developmental emergence of others that resulted in an age-dependent elaboration of hedonic-response-specific circuitry despite stable behavioral responses (approach/avoidance) to the odors across age. Hedonic responses to these biologically important odors were modified through diet suppression of the maternal odor and co-rearing with a male. This allowed assessment of hedonic circuits in isolation of the specific odor quality and/or intensity. Early experience significantly modified odor-evoked circuitry in an age-dependent manner. For example, co-rearing with a male, which induced pup attraction to male odor, reduced activity in amygdala regions normally activated by the unfamiliar avoided male odor, making this region more consistent with maternal odor. Understanding the development of odor hedonics, particularly within the context of altered early life experience, provides insight into the development of sensory processes, food preferences, and the formation of social affiliations, among other behaviors. SIGNIFICANCE STATEMENT Odor hedonic valence controls approach–avoidance behaviors, but also modulates ongoing

  8. Power lines, roads, and avian nest survival: effects on predator identity and predation intensity

    PubMed Central

    DeGregorio, Brett A; Weatherhead, Patrick J; Sperry, Jinelle H

    2014-01-01

    1 Anthropogenic alteration of landscapes can affect avian nest success by influencing the abundance, distribution, and behavior of predators. Understanding avian nest predation risk necessitates understanding how landscapes affect predator distribution and behavior. 2 From a sample of 463 nests of 17 songbird species, we evaluated how landscape features (distance to forest edge, unpaved roads, and power lines) influenced daily nest survival. We also used video cameras to identify nest predators at 137 nest predation events and evaluated how landscape features influenced predator identity. Finally, we determined the abundance and distribution of several of the principal predators using surveys and radiotelemetry. 3 Distance to power lines was the best predictor of predator identity: predation by brown-headed cowbirds (Molothrus ater), corvids (Corvus sp. and Cyanocitta cristata), racers (Coluber constrictor), and coachwhips (Masticophis flagellum) increased with proximity to power lines, whereas predation by rat snakes (Elaphe obsoleta) and raptors decreased. In some cases, predator density may reliably indicate nest predation risk because racers, corvids, and cowbirds frequently used power line right-of-ways. 4 Of five bird species with enough nests to analyze individually, daily nest survival of only indigo buntings (Passerina cyanea) decreased with proximity to power lines, despite predation by most predators at our site being positively associated with power lines. For all nesting species combined, distance to unpaved road was the model that most influenced daily nest survival. This pattern is likely a consequence of rat snakes, the locally dominant nest predator (28% of predation events), rarely using power lines and associated areas. Instead, rat snakes were frequently associated with road edges, indicating that not all edges are functionally similar. 5 Our results suggest that interactions between predators and landscape features are likely to be specific to

  9. Power lines, roads, and avian nest survival: effects on predator identity and predation intensity.

    PubMed

    DeGregorio, Brett A; Weatherhead, Patrick J; Sperry, Jinelle H

    2014-05-01

    1 Anthropogenic alteration of landscapes can affect avian nest success by influencing the abundance, distribution, and behavior of predators. Understanding avian nest predation risk necessitates understanding how landscapes affect predator distribution and behavior. 2 From a sample of 463 nests of 17 songbird species, we evaluated how landscape features (distance to forest edge, unpaved roads, and power lines) influenced daily nest survival. We also used video cameras to identify nest predators at 137 nest predation events and evaluated how landscape features influenced predator identity. Finally, we determined the abundance and distribution of several of the principal predators using surveys and radiotelemetry. 3 Distance to power lines was the best predictor of predator identity: predation by brown-headed cowbirds (Molothrus ater), corvids (Corvus sp. and Cyanocitta cristata), racers (Coluber constrictor), and coachwhips (Masticophis flagellum) increased with proximity to power lines, whereas predation by rat snakes (Elaphe obsoleta) and raptors decreased. In some cases, predator density may reliably indicate nest predation risk because racers, corvids, and cowbirds frequently used power line right-of-ways. 4 Of five bird species with enough nests to analyze individually, daily nest survival of only indigo buntings (Passerina cyanea) decreased with proximity to power lines, despite predation by most predators at our site being positively associated with power lines. For all nesting species combined, distance to unpaved road was the model that most influenced daily nest survival. This pattern is likely a consequence of rat snakes, the locally dominant nest predator (28% of predation events), rarely using power lines and associated areas. Instead, rat snakes were frequently associated with road edges, indicating that not all edges are functionally similar. 5 Our results suggest that interactions between predators and landscape features are likely to be specific to

  10. Changes in Dam and Pup Behavior Following Repeated Postnatal Exposure to a Predator Odor (TMT): A Preliminary Investigation in Long-Evans Rats

    PubMed Central

    Ayers, Luke W.; Asok, Arun; Blaze, Jennifer; Roth, Tania L.; Rosen, Jeffrey B.

    2016-01-01

    The present study investigated whether repeated early postnatal exposure to the predator odor 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) alters behavioral responses to the stimulus later in life, at postnatal day (PN30). Long-Evans rat pups with their mothers were exposed for 20 min daily to TMT, water, or a noxious odor, butyric acid (BTA), during the first three weeks of life. Mothers exposed to TMT displayed more crouching and nursing behavior than those exposed to BTA, and TMT exposed pups emitted more ultrasonic vocalizations than BTA exposed pups. At PN30, rats were tested for freezing to TMT, water, or BTA. Rats exposed to TMT during the postnatal period displayed less freezing to TMT than rats exposed postnatally to water or BTA. Our data indicate that early-life experience with a predator cue has a significant impact on later fear responses to that same cue, highlighting the programming capacity of the postnatal environment on the development of behavior. PMID:26394891

  11. Changes in dam and pup behavior following repeated postnatal exposure to a predator odor (TMT): A preliminary investigation in Long-Evans rats.

    PubMed

    Ayers, Luke W; Asok, Arun; Blaze, Jennifer; Roth, Tania L; Rosen, Jeffrey B

    2016-03-01

    The present study investigated whether repeated early postnatal exposure to the predator odor 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) alters behavioral responses to the stimulus later in life, at postnatal day (PN30). Long-Evans rat pups with their mothers were exposed for 20 min daily to TMT, water, or a noxious odor, butyric acid (BTA), during the first three weeks of life. Mothers exposed to TMT displayed more crouching and nursing behavior than those exposed to BTA, and TMT exposed pups emitted more ultrasonic vocalizations than BTA exposed pups. At PN30, rats were tested for freezing to TMT, water, or BTA. Rats exposed to TMT during the postnatal period displayed less freezing to TMT than rats exposed postnatally to water or BTA. Our data indicate that early-life experience with a predator cue has a significant impact on later fear responses to that same cue, highlighting the programming capacity of the postnatal environment on the development of behavior.

  12. Intravoxel distribution of DWI decay rates reveals C6 glioma invasion in rat brain.

    PubMed

    Bennett, Kevin M; Hyde, James S; Rand, Scott D; Bennett, Raoqiong; Krouwer, Hendrikus G J; Rebro, Kelly J; Schmainda, Kathleen M

    2004-11-01

    The hypothesis was tested that the intravoxel distribution of water diffusion rates, as measured with a stretched-exponential model of diffusion-weighted imaging (DWI), is a marker of brain tumor invasion. Eight rats underwent intracerebral inoculation of C6 glioma cells. In three rats, cells were labeled with a fluorescent dye for microscopy. One rat was inoculated with a saline solution, and five more rats were imaged without inoculation as controls. Five healthy uninoculated rats were also imaged. DWI was performed 14-15 days after inoculation, with diffusion-weighting factor b = 500 to 6500 sec/mm2, and the resulting signal attenuation was fitted with the stretched-exponential model. The heterogeneity index values were significantly lower (P < 0.05) in the peritumor ROI than in normal gray matter and significantly higher than in normal white matter. The distributed diffusion coefficient values were significantly lower than in normal white matter or normal gray matter. Fluorescence microscopy confirmed the presence of tumors in the peritumor region that could be histologically distinguished from the main tumor mass. There was no change in proton density or T2-weighted images in the peritumor region, making vasogenic edema unlikely as a source of contrast. It is therefore thought that the heterogeneity parameter alpha is a marker of brain tumor invasion. (c) 2004 Wiley-Liss, Inc.

  13. Control of invasive rats on islands and priorities for future action.

    PubMed

    Duron, Quiterie; Shiels, Aaron B; Vidal, Eric

    2017-08-01

    Invasive rats are one of the world's most successful animal groups that cause native species extinctions and ecosystem change, particularly on islands. On large islands, rat eradication is often impossible and population control, defined as the local limitation of rat abundance, is now routinely performed on many of the world's islands as an alternative management tool. However, a synthesis of the motivations, techniques, costs, and outcomes of such rat-control projects is lacking. We reviewed the literature, searched relevant websites, and conducted a survey via a questionnaire to synthesize the available information on rat-control projects in island natural areas worldwide to improve rat management and native species conservation. Data were collected from 136 projects conducted over the last 40 years; most were located in Australasia (46%) and the tropical Pacific (25%) in forest ecosystems (65%) and coastal strands (22%). Most of the projects targeted Rattus rattus and most (82%) were aimed at protecting birds and endangered ecosystems. Poisoning (35%) and a combination of trapping and poisoning (42%) were the most common methods. Poisoning allows for treatment of larger areas, and poison projects generally last longer than trapping projects. Second-generation anticoagulants (mainly brodifacoum and bromadiolone) were used most often. The median annual cost for rat-control projects was US$17,262 or US$227/ha. Median project duration was 4 years. For 58% of the projects, rat population reduction was reported, and 51% of projects showed evidence of positive effects on biodiversity. Our data were from few countries, revealing the need to expand rat-control distribution especially in some biodiversity hotspots. Improvement in control methods is needed as is regular monitoring to assess short- and long-term effectiveness of rat-control. © 2016 Society for Conservation Biology.

  14. Pitfalls of invasive blood pressure monitoring using the caudal ventral artery in rats

    PubMed Central

    Ohta, Hiroki; Ohki, Takao; Kanaoka, Yuji; Koizumi, Makoto; Okano, Hirotaka J.

    2017-01-01

    During rodent experiments, the caudal ventral artery (CVA) is useful for blood pressure (BP) measurement. However, CVA measurements may not reflect the true BP. This study was performed to verify the site-specific accuracy of invasive arterial BP monitoring during surgery in rats. Invasive arterial BP was simultaneously measured in rats via the CVA and the common carotid artery (CCA). The BP values were analysed while the rats were subjected to cooling of the head or tail. Additionally, the rats underwent digital subtraction angiography and histological examination of these arteries. The pressure difference was more significant in the tail cooling group than in the head cooling group. Digital subtraction angiography revealed that angiospasms occurred more frequently in the CVA than in the CCA upon cooling. This phenomenon was supported by histological analysis, which showed that the tunica media area was significantly larger in the CVA than in the CCA. CVA pressure is susceptible to environmental changes and may not accurately reflect the true BP without a strictly controlled laboratory environment. Therefore, understanding the pitfalls of this method is necessary to avoid cooling of the tail during BP measurement. PMID:28198822

  15. Human and rat glioma growth, invasion, and vascularization in a novel chick embryo brain tumor model.

    PubMed

    Cretu, Alexandra; Fotos, Joseph S; Little, Brian W; Galileo, Deni S

    2005-01-01

    The mechanisms that control the insidiously invasive nature of malignant gliomas are poorly understood, and their study would be facilitated by an in vivo model that is easy to manipulate and inexpensive. The developing chick embryo brain was assessed as a new xenograft model for the production, growth, and study of human and rat glioma cell lines. Three established glioma lines (U-87 MG, C6, and 9L) were injected into chick embryo brain ventricles on embryonic day (E) 5 and brains were examined after several days to two weeks after injection. All glioma lines survived, produced vascularized intraventricular tumors, and invaded the brain in a manner similar to that in rodents. Rat C6 glioma cells spread along vasculature and also invaded the neural tissue. Human U-87 glioma cells migrated along vasculature and exhibited slight invasion of neural tissue. Rat 9L gliosarcoma cells were highly motile, but migrated only along the vasculature. A derivative of 9L cells that stably expressed the cell surface adhesion molecule NgCAM/L1 was produced and also injected into chick embryo brain ventricles to see if this protein could facilitate tumor cell migration away from the vasculature into areas such as axonal tracts. 9L/NgCAM cells, however, did not migrate away from the vasculature and, thus, this protein alone cannot be responsible for diffuse invasiveness of some gliomas. 9L/NgCAM cell motility was assessed in vitro using sophisticated time-lapse microscopy and quantitative analysis, and was significantly altered compared to parental 9L cells. These studies demonstrate that the chick embryo brain is a successful and novel xenograft model for mammalian gliomas and demonstrate the potential usefulness of this new model for studying glioma tumor cell growth, vascularization, and invasiveness.

  16. Predator-Free New Zealand: Conservation Country.

    PubMed

    Russell, James C; Innes, John G; Brown, Philip H; Byrom, Andrea E

    2015-05-01

    Eradications of invasive species from over 1000 small islands around the world have created conservation arks, but to truly address the threat of invasive species to islands, eradications must be scaled by orders of magnitude. New Zealand has eradicated invasive predators from 10% of its offshore island area and now proposes a vision to eliminate them from the entire country. We review current knowledge of invasive predator ecology and control technologies in New Zealand and the biological research, technological advances, social capacity and enabling policy required. We discuss the economic costs and benefits and conclude with a 50-year strategy for a predator-free New Zealand that is shown to be ecologically obtainable, socially desirable, and economically viable. The proposal includes invasive predator eradication from the two largest offshore islands, mammal-free mainland peninsulas, very large ecosanctuaries, plus thousands of small projects that will together merge eradication and control concepts on landscape scales.

  17. Predator-Free New Zealand: Conservation Country

    PubMed Central

    Russell, James C.; Innes, John G.; Brown, Philip H.; Byrom, Andrea E.

    2015-01-01

    Eradications of invasive species from over 1000 small islands around the world have created conservation arks, but to truly address the threat of invasive species to islands, eradications must be scaled by orders of magnitude. New Zealand has eradicated invasive predators from 10% of its offshore island area and now proposes a vision to eliminate them from the entire country. We review current knowledge of invasive predator ecology and control technologies in New Zealand and the biological research, technological advances, social capacity and enabling policy required. We discuss the economic costs and benefits and conclude with a 50-year strategy for a predator-free New Zealand that is shown to be ecologically obtainable, socially desirable, and economically viable. The proposal includes invasive predator eradication from the two largest offshore islands, mammal-free mainland peninsulas, very large ecosanctuaries, plus thousands of small projects that will together merge eradication and control concepts on landscape scales. PMID:26955079

  18. ENDURING SENSORIMOTOR GATING ABNORMALITIES FOLLOWING PREDATOR EXPOSURE OR CORTICOTROPIN-RELEASING FACTOR IN RATS: A MODEL FOR PTSD-LIKE INFORMATION PROCESSING DEFICITS?

    PubMed Central

    Bakshi, Vaishali P.; Alsene, Karen M.; Roseboom, Patrick H.; Connors, Elenora E.

    2011-01-01

    A deficit in prepulse inhibition (PPI) can be one of the clinically observed features of post traumatic stress disorder (PTSD) that is seen long after the acute traumatic episode has terminated. Thus, reduced PPI may represent an enduring psychophysiological marker of this illness in some patients. PPI is an operational measure of sensorimotor gating and refers to the phenomenon in which a weak stimulus presented immediately before an intense startling stimulus inhibits the magnitude of the subsequent startle response. The effects of stress on PPI have been relatively understudied, and in particular, there is very little information on PPI effects of ethologically relevant psychological stressors. We aimed to develop a paradigm for evaluating stress-induced sensorimotor gating abnormalities by comparing the effects of a purely psychological stressor (predator exposure) to those of a noiciceptive physical stressor (footshock) on PPI and baseline startle responses in rats over an extended period of time following stressor presentation. Male Sprague-Dawley rats were exposed (within a protective cage) to ferrets for 5 min or left in their homecage and then tested for PPI immediately, 24h, 48h, and 9 days after the exposure. The effects of footshock were evaluated in a separate set of rats. The effects seen with stressor presentation were compared to that elicited by corticotropin-releasing factor (CRF; 0.5 and 3μg/6μl, intracerebroventricularly). Finally, the effects of these stressors and CRF administration on plasma corticosterone were measured. PPI was disrupted 24h after ferret exposure; in contrast, footshock failed to affect PPI at any time. CRF mimicked the predator stress profile, with the low dose producing a PPI deficit 24h after infusion. Interestingly, the high dose also produced a PPI deficit 24h after infusion, but with this dose, the PPI deficit was evident even 9d later. Plasma corticosterone levels were elevated acutely (before PPI deficits emerged

  19. Cyclic mechanical stretching promotes migration but inhibits invasion of rat bone marrow stromal cells.

    PubMed

    Zhang, Bingyu; Luo, Qing; Chen, Zhe; Sun, Jinghui; Xu, Baiyao; Ju, Yang; Song, Guanbin

    2015-03-01

    Bone marrow stromal cells (BMSCs, also broadly known as bone marrow-derived mesenchymal stem cells) are multipotent stem cells that have a self-renewal capacity and multilineage differentiation potential. Mechanical stretching plays a vital role in regulating the proliferation and differentiation of BMSCs. However, little is known about the effects of cyclic stretching on BMSC migration and invasion. In this study, using a custom-made cell-stretching device, we studied the effects of cyclic mechanical stretching on rat BMSC migration and invasion using a Transwell Boyden Chamber. The protein secretion of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) was detected by gelatin zymography, and the activation of focal adhesion kinase (FAK) and extracellular signal regulated kinase1/2 (ERK1/2) was measured by western blot. We found that cyclic mechanical stretching with 10% amplitude at 1Hz frequency for 8h promotes BMSC migration, but reduces BMSC invasion. FAK and ERK1/2 signals were activated in BMSCs after exposure to cyclic stretching. In the presence of the FAK phosphorylation blocker PF573228 or the ERK1/2 phosphorylation blocker PD98059, the cyclic-stretch-promoted migration of BMSCs was completely suppressed. On the other hand, cyclic mechanical stretching reduced the secretion of MMP-2 and MMP-9 in BMSCs, and PF573228 suppressed the cyclic-stretch-reduced secretion of MMP-2 and MMP-9. The decrease of BMSC invasion induced by mechanical stretching is partially restored by PF573228 but remained unaffected by PD98059. Taken together, these data show that cyclic mechanical stretching promotes BMSC migration via the FAK-ERK1/2 signalling pathway, but reduces BMSC invasion by decreasing secretion of MMP-2 and MMP-9 via FAK, independent of the ERK1/2 signal.

  20. Differential impact of adults and nymphs of a generalist predator on an exotic invasive pest demonstrated by molecular gut-content analysis

    USDA-ARS?s Scientific Manuscript database

    Generalist predators can regulate herbivore populations through a variety of mechanisms, but food webs are complex and defining the strength of trophic linkages can be difficult. Molecular gut-content analysis has revolutionized our understanding of these systems. Using this technology, we examined ...

  1. Non-invasive Measurement of Renal Blood Flow by Magnetic Resonance Imaging (MRI) in Rats.

    PubMed

    Romero, Cesar A; Cabral, Glauber; Knight, Robert A; Ding, Guangliang; Peterson, Edward L; Carretero, Oscar A

    2017-10-04

    Renal blood flow (RBF) provides important information regarding renal physiology and nephropathies. Arterial spin labeling-magnetic resonance imaging (ASL-MRI) is a non-invasive method of measuring blood flow without exogenous contrast media. However, low signal/noise ratio and respiratory motion artifacts are challenges for RBF measurements in small animals. Our objective was to evaluate the feasibility and reproducibility of RBF measures by ASL-MRI using respiratory-gating and navigator correction methods to reduce motion artifacts. ASL-MRI images were obtained from the kidneys of Sprague-Dawley (SD) rats on a 7 tesla Varian MRI system with a spin-echo imaging sequence. After 4 days, the study was repeated to evaluate its reproducibility. RBF was also measured in animals under unilateral nephrectomy and in renal artery stenosis (RST) to evaluate the sensitivity in high and low RBF models, respectively. RBF was also evaluated in Dahl salt-sensitive (SS) rats and spontaneous hypertensive rats (SHR). In SD rats the cortical RBFs (cRBF) were 305±59 and 271.8±39 ml/min/100 g tissue in the right and left kidneys, respectively. Re-test analysis revealed no differences (p=0.2). The test-retest reliability coefficient was 92±5%. The cRBFs before and after the nephrectomy were 296.8±30 and 428.2±45 ml/min/100 g (p=0.02), respectively. The kidneys with RST exhibited a cRBF decrease compared with sham animals (86±17.6 vs. 198±33.7 ml/min/100 g tissue; p<0.01). The cRBFs in SD, Dahl-ss and SHR rats were not different (p=0.35). We conclude that ASL-MRI performed with navigator correction and respiratory gating is a feasible and reliable non-invasive method for measuring RBF in rats. Copyright © 2017, American Journal of Physiology-Renal Physiology.

  2. A simple and effective semi-invasive method for inducing local hypothermia in rat spinal cord.

    PubMed

    Bazley, Faith A; Pashai, Nikta; Kerr, Candace; Thakor, Nitish; All, Angelo H

    2013-01-01

    Hypothermia has been shown to be an effective treatment for spinal cord injury. Local hypothermia is advantageous because it avoids inducing systemic side effects of general hypothermia while providing the opportunity for greater temperature reduction at the site of injury, which may contribute to increased neuroprotection. We report a new semi-invasive method for inducing local hypothermia in rats' spinal cords. Our method does not require laminectomy or penetration of the dura and is more effective at cooling the cord than transcutaneous approaches. We show that we were successfully able to cool the spinal cord to 30.2 ± 0.3°C for 2 hours with rectal temperature maintained at 37.3 ± 0.3°C after a spinal cord contusion injury. We also validated our method in control rats that received only a laminectomy. Furthermore, this method was able to reliably cool and rewarm the cord at a steady rate (Δ5.5°C in 30 min, or 0.2°C/min). Future work will include validating long-term functional improvements of injured rats after treatment and to apply local cooling to other spinal cord injury models, such as compression injuries.

  3. Pasta Predation.

    ERIC Educational Resources Information Center

    Waugh, Michael L.

    1986-01-01

    Presents a predator-prey simulation which involves students in collecting data, solving problems, and making predictions on the evolution of prey populations. Provides directives on how to perform the chi-square test and also includes an Applesoft BASK program that performs the calculations. (ML)

  4. Predator Arithmetic

    ERIC Educational Resources Information Center

    Shutler, Paul M. E.; Fong, Ng Swee

    2010-01-01

    Modern Hindu-Arabic numeration is the end result of a long period of evolution, and is clearly superior to any system that has gone before, but is it optimal? We compare it to a hypothetical base 5 system, which we dub Predator arithmetic, and judge which of the two systems is superior from a mathematics education point of view. We find that…

  5. Predator Arithmetic

    ERIC Educational Resources Information Center

    Shutler, Paul M. E.; Fong, Ng Swee

    2010-01-01

    Modern Hindu-Arabic numeration is the end result of a long period of evolution, and is clearly superior to any system that has gone before, but is it optimal? We compare it to a hypothetical base 5 system, which we dub Predator arithmetic, and judge which of the two systems is superior from a mathematics education point of view. We find that…

  6. Pasta Predation.

    ERIC Educational Resources Information Center

    Waugh, Michael L.

    1986-01-01

    Presents a predator-prey simulation which involves students in collecting data, solving problems, and making predictions on the evolution of prey populations. Provides directives on how to perform the chi-square test and also includes an Applesoft BASK program that performs the calculations. (ML)

  7. Patterns of Toxoplasma gondii cyst distribution in the forebrain associate with individual variation in predator odor avoidance and anxiety-related behavior in male Long-Evans rats

    PubMed Central

    Evans, Andrew K.; Strassmann, Patrick S.; Lee, I-Ping; Sapolsky, Robert M.

    2014-01-01

    Toxoplasma gondii (T. gondii) is one of the world’s most successful brain parasites. T. gondii engages in parasite manipulation of host behavior and infection has been epidemiologically linked to numerous psychiatric disorders. Mechanisms by which T. gondii alters host behavior are not well understood, but neuroanatomical cyst presence and the localized host immune response to cysts are potential candidates. The aim of these studies was to test the hypothesis that T. gondii manipulation of specific host behaviors is dependent on neuroanatomical location of cysts in a time-dependent function post-infection. We examined neuroanatomical cyst distribution (53 forebrain regions) in infected rats after predator odor aversion behavior and anxiety-related behavior in the elevated plus maze and open field arena, across a 6-week time course. In addition, we examined evidence for microglial response to the parasite across the time course. Our findings demonstrate that while cysts are randomly distributed throughout the forebrain, individual variation in cyst localization, beginning 3 weeks post-infection, can explain individual variation in the effects of T. gondii on behavior. Additionally, not all infected rats develop cysts in the forebrain, and attenuation of predator odor aversion and changes in anxiety-related behavior are linked with cyst presence in specific forebrain areas. Finally, the immune response to cysts is striking. These data provide the foundation for testing hypotheses about proximate mechanisms by which T. gondii alters behavior in specific brain regions, including consequences of establishment of a homeostasis between T. gondii and the host immune response. PMID:24269877

  8. Resistance to DNA Damaging Agents Produced Invasive Phenotype of Rat Glioma Cells-Characterization of a New in Vivo Model.

    PubMed

    Stojković, Sonja; Podolski-Renić, Ana; Dinić, Jelena; Pavković, Željko; Ayuso, Jose M; Fernández, Luis J; Ochoa, Ignacio; Pérez-García, Victor M; Pešić, Vesna; Pešić, Milica

    2016-06-27

    Chemoresistance and invasion properties are severe limitations to efficient glioma therapy. Therefore, development of glioma in vivo models that more accurately resemble the situation observed in patients emerges. Previously, we established RC6 rat glioma cell line resistant to DNA damaging agents including antiglioma approved therapies such as 3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and temozolomide (TMZ). Herein, we evaluated the invasiveness of RC6 cells in vitro and in a new orthotopic animal model. For comparison, we used C6 cells from which RC6 cells originated. Differences in cell growth properties were assessed by real-time cell analyzer. Cells' invasive potential in vitro was studied in fluorescently labeled gelatin and by formation of multicellular spheroids in hydrogel. For animal studies, fluorescently labeled cells were inoculated into adult male Wistar rat brains. Consecutive coronal and sagittal brain sections were analyzed 10 and 25 days post-inoculation, while rats' behavior was recorded during three days in the open field test starting from 25th day post-inoculation. We demonstrated that development of chemoresistance induced invasive phenotype of RC6 cells with significant behavioral impediments implying usefulness of orthotopic RC6 glioma allograft in preclinical studies for the examination of new approaches to counteract both chemoresistance and invasion of glioma cells.

  9. Time-resolved diffuse optical tomography for non-invasive flap viability assessment: pre-clinical tests on rats

    NASA Astrophysics Data System (ADS)

    Di Sieno, L.; Bettega, G.; Berger, M.; Hamou, C.; Aribert, M.; Dalla Mora, A.; Puszka, A.; Grateau, H.; Contini, D.; Hervé, L.; Coll, J.-L.; Dinten, J.-M.; Pifferi, A.; Planat-Chrétien, A.

    2015-07-01

    We present a new setup for time-resolved diffuse optical tomography based on multiple source-detector acquisitions analysed by means of the Mellin-Laplace transform. The proposed setup has been used to perform pre-clinical measurements on rats in order to show its suitability for non-invasive assessment of flap viability.

  10. Predator effects on reef fish settlement depend on predator origin and recruit density.

    PubMed

    Benkwitt, Cassandra E

    2017-04-01

    During major life-history transitions, animals often experience high mortality rates due to predation, making predator avoidance particularly advantageous during these times. There is mixed evidence from a limited number of studies, however, regarding how predator presence influences settlement of coral-reef fishes and it is unknown how other potentially mediating factors, including predator origin (native vs. nonnative) or interactions among conspecific recruits, mediate the non-consumptive effects of predators on reef fish settlement. During a field experiment in the Caribbean, approximately 52% fewer mahogany snapper (Lutjanus mahogoni) recruited to reefs with a native predator (graysby grouper, Cephalopholis cruentata) than to predator-free control reefs and reefs with an invasive predator (red lionfish, Pterois volitans) regardless of predator diet. These results suggest that snapper recruits do not recognize nonnative lionfish as a threat. However, these effects depended on the density of conspecific recruits, with evidence that competition may limit the response of snapper to even native predators at the highest recruit densities. In contrast, there was no effect of predator presence or conspecific density on the recruitment of bicolor damselfish (Stegastes partitus). These context-dependent responses of coral-reef fishes to predators during settlement may influence individual survival and shape subsequent population and community dynamics. © 2017 by the Ecological Society of America.

  11. A non-invasive method to evaluate gastrointestinal transit behavior in rat.

    PubMed

    Bove, Geoffrey M

    2015-01-01

    Many factors alter gastrointestinal transit. Animal models are useful for preclinical studies of gastrointestinal transit, but terminal methods do not allow later study, and stressful assessment methods will likely alter the transit of the animal. To overcome these factors, we developed a new method to assay rat total gastrointestinal transit. Standard plastic cages with their bottoms cut off were placed on wire mesh floors. Custom apparatuses were built to contain fecal pellets as they fell through the floors. Webcams connected to a computer running a security program were placed to image the pellets at regular intervals. Custom food was obtained with and without blue pigment. After habituating to the cages and the non-pigmented food, the pigmented food was administered. The duration to the appearance of the first pigmented pellet was determined by reviewing the photographs. This duration represents the complete gastrointestinal behavior, including feeding. We compared 24-hour fecal pellet counts using images to counts by visual inspection, and also made hourly counts. After establishing baseline transit times and hourly fecal pellet discharge, rats were given buprenorphine, known to alter gastrointestinal transit. Transit times and hourly discharge were obtained again and compared to the baselines. The methods were successful in determining transit times. Baseline measures were consistent between three groups of 8 rats. Visual and image-based counts were highly correlated. Transit times and hourly pellet discharge were reduced by buprenorphine. The described method offers a relatively simple, inexpensive, and non-invasive means to measure rat gastrointestinal behavior. The method has potential for any study where altered total gastrointestinal transit is an experimental concern. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Minimally Invasive Approach to the Lingual and Hypoglossal Nerves in the Adult Rat.

    PubMed

    Doyle, Edward John; Phillips, Grady W; Gratton, Michael Anne; Long, John P; Varvares, Mark A

    2016-06-01

    Surgical manipulation of the sensory and motor nerves of the rat tongue is often employed in studies evaluating the oral cavity functions of mastication and deglutition. A noninvasive, atraumatic approach that will then facilitate sufficient manipulation of these structures is required. In this study, we detail an approach that consistently allows identification of the hypoglossal (motor) and lingual (sensory) nerves of the rat. Six Wistar rats (250-500 g) were anesthetized and dissected either as fresh tissue (N = 3) or following transcardial perfusion with 4% paraformaldehyde (N = 3). Both fixed and non-fixed specimens of the rat head and neck were incised in the right submandibular region. The first animal in each group was used to gain a basic understanding of the regional muscular anatomy with reference to the hypoglossal and lingual nerves. Subsequent animals were used for the development of an efficient and minimally invasive approach to these nerves. The resultant approach begins as an incision through skin and platysma, followed by medial reflection of the digastric muscle. This allows visualization of the hypoglossal nerve in the region of the bifurcation of the common trunk into medial and lateral subdivisions. Next, the lingual nerve dissection is approached by reflection rostrally of the transversus mandibularis muscle and a caudal reflection of the mylohyoid muscle. This dissection reveals the geniohyoid muscle which when separated bluntly using forceps, exposes the lingual nerve. The anatomical approach described and illustrated herein will aid investigators in consistent identification of these two nerves as fundamental methods of their projects.

  13. Biogeographic variation in behavioral and morphological responses to predation risk.

    PubMed

    Large, Scott I; Smee, Delbert L

    2013-04-01

    The expression of prey antipredator defenses is often related to ambient consumer pressure, and prey express greater defenses under intense consumer pressure. Predation is generally greater at lower latitudes, and antipredator defenses often display a biogeographic pattern. Predation pressure may also vary significantly between habitats within latitudes, making biogeographic patterns difficult to distinguish. Furthermore, invasive predators may also influence the expression of prey defenses in ecological time. The purpose of this study was to determine how these factors influence the strength of antipredator responses. To assess patterns in prey antipredator defenses based upon geographic range (north vs. south), habitat type (wave-protected vs. wave-exposed shores), and invasive predators, we examined how native rock (Cancer irroratus) and invasive green (Carcinus maenas) crab predators influence the behavioral and morphological defenses of dogwhelk (Nucella lapillus) prey from habitats that differ in wave exposure across an ~230 km range within the Gulf of Maine. The expression of behavioral and morphological antipredatory responses varied according to wave exposure, geographic location, and predator species. Dogwhelks from areas with an established history with green crabs exhibited the largest behavioral and morphological antipredator responses to green crabs. Dogwhelk behavioral responses to rock crabs did not vary between habitats or geographic regions, although morphological responses were greater further south where predation pressure was greatest. These findings suggest that dogwhelk responses to invasive and native predators vary according to geographic location and habitat, and are strongly affected by ambient predation pressure due to the invasion history of an exotic predator.

  14. Invasive rats and recent colonist birds partially compensate for the loss of endemic New Zealand pollinators

    PubMed Central

    Pattemore, David E.; Wilcove, David S.

    2012-01-01

    Reported declines of pollinator populations around the world have led to increasing concerns about the consequences for pollination as a critical ecosystem function and service. Pollination could be maintained through compensation if remaining pollinators increase their contribution or if novel species are recruited as pollinators, but empirical evidence of this compensation is so far lacking. Using a natural experiment in New Zealand where endemic vertebrate pollinators still occur on one offshore island reserve despite their local extinction on the adjacent North Island, we investigated whether compensation could maintain pollination in the face of pollinator extinctions. We show that two recently arrived species in New Zealand, the invasive ship rat (Rattus rattus) and the recent colonist silvereye (Zosterops lateralis; a passerine bird), at least partly maintain pollination for three forest plant species in northern New Zealand, and without this compensation, these plants would be significantly more pollen-limited. This study provides empirical evidence that widespread non-native species can play an important role in maintaining ecosystem functions, a role that needs to be assessed when planning invasive species control or eradication programmes. PMID:22090388

  15. Cardiac Impairment Evaluated by Transesophageal Echocardiography and Invasive Measurements in Rats Undergoing Sinoaortic Denervation

    PubMed Central

    Sirvente, Raquel A.; Irigoyen, Maria C.; Souza, Leandro E.; Mostarda, Cristiano; La Fuente, Raquel N.; Candido, Georgia O.; Souza, Pamella R. M.; Medeiros, Alessandra; Mady, Charles; Salemi, Vera M. C.

    2014-01-01

    Background Sympathetic hyperactivity may be related to left ventricular (LV) dysfunction and baro- and chemoreflex impairment in hypertension. However, cardiac function, regarding the association of hypertension and baroreflex dysfunction, has not been previously evaluated by transesophageal echocardiography (TEE) using intracardiac echocardiographic catheter. Methods and Results We evaluated exercise tests, baroreflex sensitivity and cardiovascular autonomic control, cardiac function, and biventricular invasive pressures in rats 10 weeks after sinoaortic denervation (SAD). The rats (n = 32) were divided into 4 groups: 16 Wistar (W) with (n = 8) or without SAD (n = 8) and 16 spontaneously hypertensive rats (SHR) with (n = 8) or without SAD (SHRSAD) (n = 8). Blood pressure (BP) and heart rate (HR) did not change between the groups with or without SAD; however, compared to W, SHR groups had higher BP levels and BP variability was increased. Exercise testing showed that SHR had better functional capacity compared to SAD and SHRSAD. Echocardiography showed left ventricular (LV) concentric hypertrophy; segmental systolic and diastolic biventricular dysfunction; indirect signals of pulmonary arterial hypertension, mostly evident in SHRSAD. The end-diastolic right ventricular (RV) pressure increased in all groups compared to W, and the end-diastolic LV pressure increased in SHR and SHRSAD groups compared to W, and in SHRSAD compared to SAD. Conclusions Our results suggest that baroreflex dysfunction impairs cardiac function, and increases pulmonary artery pressure, supporting a role for baroreflex dysfunction in the pathogenesis of hypertensive cardiac disease. Moreover, TEE is a useful and feasible noninvasive technique that allows the assessment of cardiac function, particularly RV indices in this model of cardiac disease. PMID:24828834

  16. Barriers to seed and seedling survival of once-common Hawaiian palms: the role of invasive rats and ungulates.

    PubMed

    Shiels, Aaron B; Drake, Donald R

    2015-05-27

    Mammalian herbivores can limit plant recruitment and affect forest composition. Loulu palms (Pritchardia spp.) once dominated many lowland ecosystems in Hawai'i, and non-native rats (Rattus spp.), ungulates (e.g. pigs Sus scrofa, goats Capra hircus) and humans have been proposed as major causes of their decline. In lowland wet forest, we experimentally determined the vulnerability of seeds and seedlings of two species of Pritchardia, P. maideniana and P. hillebrandii, by measuring their removal by introduced vertebrates; we also used motion-sensing cameras to identify the animals responsible for Pritchardia removal. We assessed potential seed dispersal of P. maideniana by spool-and-line tracking, and conducted captive-feeding trials with R. rattus and seeds and seedlings of both Pritchardia species. Seed removal from the forest floor occurred rapidly for both species: >50 % of Pritchardia seeds were removed from the vertebrate-accessible stations within 6 days and >80 % were removed within 22 days. Although rats and pigs were both common to the study area, motion-sensing cameras detected only rats (probably R. rattus) removing Pritchardia seeds from the forest floor. Captive-feeding trials and spool-and-line tracking revealed that vertebrate seed dispersal is rare; rats moved seeds up to 8 m upon collection and subsequently destroyed them (100 % mortality in 24-48 h in captivity). Surprisingly, seedlings did not suffer vertebrate damage in field trials, and although rats damaged seedlings in captivity, they rarely consumed them. Our findings are consistent with the hypothesis generated from palaeoecological studies, indicating that introduced rats may have assisted in the demise of native insular palm forests. These findings also imply that the seed stage of species in this Pacific genus is particularly vulnerable to rats; therefore, future conservation efforts involving Pritchardia should prioritize the reduction of rat predation on the plant recruitment stages

  17. Barriers to seed and seedling survival of once-common Hawaiian palms: the role of invasive rats and ungulates

    PubMed Central

    Shiels, Aaron B.; Drake, Donald R.

    2015-01-01

    Mammalian herbivores can limit plant recruitment and affect forest composition. Loulu palms (Pritchardia spp.) once dominated many lowland ecosystems in Hawai‘i, and non-native rats (Rattus spp.), ungulates (e.g. pigs Sus scrofa, goats Capra hircus) and humans have been proposed as major causes of their decline. In lowland wet forest, we experimentally determined the vulnerability of seeds and seedlings of two species of Pritchardia, P. maideniana and P. hillebrandii, by measuring their removal by introduced vertebrates; we also used motion-sensing cameras to identify the animals responsible for Pritchardia removal. We assessed potential seed dispersal of P. maideniana by spool-and-line tracking, and conducted captive-feeding trials with R. rattus and seeds and seedlings of both Pritchardia species. Seed removal from the forest floor occurred rapidly for both species: >50 % of Pritchardia seeds were removed from the vertebrate-accessible stations within 6 days and >80 % were removed within 22 days. Although rats and pigs were both common to the study area, motion-sensing cameras detected only rats (probably R. rattus) removing Pritchardia seeds from the forest floor. Captive-feeding trials and spool-and-line tracking revealed that vertebrate seed dispersal is rare; rats moved seeds up to 8 m upon collection and subsequently destroyed them (100 % mortality in 24–48 h in captivity). Surprisingly, seedlings did not suffer vertebrate damage in field trials, and although rats damaged seedlings in captivity, they rarely consumed them. Our findings are consistent with the hypothesis generated from palaeoecological studies, indicating that introduced rats may have assisted in the demise of native insular palm forests. These findings also imply that the seed stage of species in this Pacific genus is particularly vulnerable to rats; therefore, future conservation efforts involving Pritchardia should prioritize the reduction of rat predation on the plant recruitment

  18. Interstellar Predation

    NASA Astrophysics Data System (ADS)

    Cockell, C. S.; Lee, M.

    Although chemosynthesis and photosynthesis can theoretically supply enough energy for intelligence, for reasons elucidated here, heterotrophy and specifically phagotrophy (ingestion of prey) are likely to make predation a characteristic of life and extraterrestrial intelligence (ETI). Here, the Earth's biota is used to consider the nature of interstellar predation. The ability of the ETI to directly ingest a biota will be determined by the chiral preference of the ETI, the compatibility of the biochemistry used in life on Earth with the molecules required by the ETI and the potential toxicity of the macromolecules. If chirality is determined by astrophysical factors and not by the specificities of terrestrial origins of life and if molecules found in terrestrial organisms are also represented in ETIs (which could plausibly include hydrated carbohydrides and many amino acids that are similar or identical to amino acids found in meteoritic or cometary material) then the Earth might represent a universally appreciated resource. The Earth's biota could be used as an energy supply or, if other forms of technology have advanced to the point where bioreactors can be exclusively used to supply a civilization with food, as a culinary curiosity. Even in the absence of metabolic compatibility, technology can be used to extract useful products from an undigestible biota, similarly to the industrial biotransformation of cellulose. The value of the resource will also be determined by the availability of prey. Planets at stages in biological evolution where the surface is dominated by just one or several large (>5kg), abundant, easily captured organisms are particu- larly attractive to predators because harvesting techniques can be standardized. We discuss implications for exobiology and the `Fermi Paradox'.

  19. KCa1.1 inhibition attenuates fibroblast-like synoviocyte invasiveness and ameliorates rat models of rheumatoid arthritis

    PubMed Central

    Tanner, Mark R.; Hu, Xueyou; Huq, Redwan; Tajhya, Rajeev B.; Sun, Liang; Khan, Fatima S.; Laragione, Teresina; Horrigan, Frank T.; Gulko, Pércio S.; Beeton, Christine

    2014-01-01

    Objective Fibroblast-like synoviocytes (FLS) participate in joint inflammation and damage during rheumatoid arthritis (RA) and its animal models. The purpose of this study was to define the importance of KCa1.1 (BK, Maxi-K, Slo1, KCNMA1) channel expression and function in FLS and to establish these channels as potential new targets for RA therapy. Methods We compared KCa1.1 expression levels in FLS from rats with the pristane-induced arthritis (PIA) model of RA and in FLS from healthy rats. We then used ex vivo functional assays combined with siRNA-induced knock-down, over-expression, and functional modulation of KCa1.1 in PIA-FLS. Finally, we determined the effectiveness of modulating KCa1.1 in two rat models of RA, moderate PIA and severe complete Freund’s adjuvant collagen-induced arthritis (CFA-CIA). Results We found that PIA-FLS express the KCa1.1 channel as their major potassium channel, as do FLS from patients with RA. In contrast, FLS from healthy rats expressed fewer of these channels. Inhibiting the function or expression of KCa1.1 ex vivo reduced the proliferation, production of proteases, and invasive properties of PIA-FLS whereas opening native KCa1.1 or over-expressing the channel enhanced the invasiveness of both PIA-FLS and FLS isolated from healthy rats. Treatment with a KCa1.1 channel blocker starting at onset of clinical signs stopped disease progression in both PIA and CFA-CIA, reduced joint and bone damage, and inhibited FLS invasiveness and proliferation. Conclusion Our results demonstrate a critical role for KCa1.1 channels in the regulation of FLS invasiveness and suggest they represent a potential therapeutic target for RA. PMID:25252152

  20. Detailing renal hemodynamics and oxygenation in rats by a combined near-infrared spectroscopy and invasive probe approach.

    PubMed

    Grosenick, Dirk; Cantow, Kathleen; Arakelyan, Karen; Wabnitz, Heidrun; Flemming, Bert; Skalweit, Angela; Ladwig, Mechthild; Macdonald, Rainer; Niendorf, Thoralf; Seeliger, Erdmann

    2015-02-01

    We hypothesize that combining quantitative near-infrared spectroscopy (NIRS) with established invasive techniques will enable advanced insights into renal hemodynamics and oxygenation in small animal models. We developed a NIRS technique to monitor absolute values of oxygenated and deoxygenated hemoglobin and of oxygen saturation of hemoglobin within the renal cortex of rats. This NIRS technique was combined with invasive methods to simultaneously record renal tissue oxygen tension and perfusion. The results of test procedures including occlusions of the aorta or the renal vein, hyperoxia, hypoxia, and hypercapnia demonstrated that the combined approach, by providing different but complementary information, enables a more comprehensive characterization of renal hemodynamics and oxygenation.

  1. Detailing renal hemodynamics and oxygenation in rats by a combined near-infrared spectroscopy and invasive probe approach

    PubMed Central

    Grosenick, Dirk; Cantow, Kathleen; Arakelyan, Karen; Wabnitz, Heidrun; Flemming, Bert; Skalweit, Angela; Ladwig, Mechthild; Macdonald, Rainer; Niendorf, Thoralf; Seeliger, Erdmann

    2015-01-01

    We hypothesize that combining quantitative near-infrared spectroscopy (NIRS) with established invasive techniques will enable advanced insights into renal hemodynamics and oxygenation in small animal models. We developed a NIRS technique to monitor absolute values of oxygenated and deoxygenated hemoglobin and of oxygen saturation of hemoglobin within the renal cortex of rats. This NIRS technique was combined with invasive methods to simultaneously record renal tissue oxygen tension and perfusion. The results of test procedures including occlusions of the aorta or the renal vein, hyperoxia, hypoxia, and hypercapnia demonstrated that the combined approach, by providing different but complementary information, enables a more comprehensive characterization of renal hemodynamics and oxygenation. PMID:25780726

  2. Predators and Prey

    ERIC Educational Resources Information Center

    Kramm, Kenneth R.

    1975-01-01

    Reviews basic concepts of predator-prey interaction, encourages the presentation of the predator's role and describes a model of predator behavior to be used in secondary school or college classes. (LS)

  3. Predator arithmetic

    NASA Astrophysics Data System (ADS)

    Shutler, Paul M. E.; Swee Fong, Ng

    2010-01-01

    Modern Hindu-Arabic numeration is the end result of a long period of evolution, and is clearly superior to any system that has gone before, but is it optimal? We compare it to a hypothetical base 5 system, which we dub Predator arithmetic, and judge which of the two systems is superior from a mathematics education point of view. We find that complex calculations such as long multiplication can be carried out more efficiently in base 5 than in base 10, and that base 5 is in fact close to being optimal in this regard. We also show that base 5 is small enough so that the intuitiveness of simple grouping and the efficiency of fully ciphered numerals can be combined effectively in a single notation, something which Hindu-Arabic numeration tries but fails to achieve. Furthermore, as a consequence of these notational advantages, we show that the basic operations of arithmetic, addition and subtraction, also borrowing and carrying (regrouping), are easier to teach and to learn in base 5 than in base 10. Finally we show that, even though a shift from base 10 to base 5 may not be a realistic possibility, there are many ways in which the teaching of elementary arithmetic could be improved significantly, along the lines of Predator arithmetic, and which could be implemented at little cost within our current Hindu-Arabic system.

  4. Predator odor evokes sex-independent stress responses in male and female Wistar rats and reduces phosphorylation of cyclic-adenosine monophosphate response element binding protein in the male, but not the female hippocampus.

    PubMed

    Homiack, Damek; O'Cinneide, Emma; Hajmurad, Sema; Barrileaux, Brett; Stanley, Mary; Kreutz, Michael R; Schrader, Laura A

    2017-09-01

    Post-traumatic stress disorder (PTSD) is characterized by memory disturbances following trauma. Acute predator threat has emerged as an ethological model of PTSD, yet the effects of predator odor on signaling cascades associated with long-term memory remain poorly understood. In this study, we exposed male and female Wistar rats to the synthetic predator odor 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) to assess behavioral and physiological responses as well as rapid modulation of signal transduction cascades associated with learning and memory in the male and female hippocampus. During exposure to TMT in the homecage, both male and female animals displayed robust immobility, avoidance, and altered activity as a function of time. Physiologically, TMT exposure increased circulating corticosterone and blood glucose in both male and female rodents, suggesting that TMT evokes sex-independent behavioral and physiological responses. With respect to signal transduction, TMT exposure rapidly reduced phosphorylation of cyclic-adenosine monophosphate response element binding protein (CREB) in the male, but not the female hippocampus. Furthermore, TMT exposure reduced phosphorylation of extracellular signal-regulated kinase 1/2 and increased nuclear expression of the synapto-nuclear messenger protein Jacob in the male hippocampus, consistent with activation of the CREB shut-off pathway. In a follow-up behavioral experiment, post-training exposure to TMT did not affect spatial water maze performance of male rats. However, male rats re-introduced to the context in which TMT had previously been presented displayed avoidance and hyperactivity, but not freezing behavior or elevated corticosterone responses, suggesting that TMT exposure supports a form of contextual conditioning which is not characterized by immobility. Taken together, our findings suggest that TMT evokes similar behavioral and physiological responses in male and female Wistar rats, but affects distinct signaling

  5. RhoC is essential for TGF-{beta}1-induced invasive capacity of rat ascites hepatoma cells

    SciTech Connect

    Mukai, M.; Endo, H.; Iwasaki, T.; Tatsuta, M.; Togawa, A.; Nakamura, H.; Inoue, M. . E-mail: inoue-ma2@mc.pref.osaka.jp

    2006-07-21

    Transforming growth factor-{beta}1 (TGF-{beta}1) is a multifunctional growth factor that plays a role in cell proliferation, differentiation, extracellular matrix production, apoptosis, and cell motility. We show here that TGF-{beta}1 increased the invasiveness of MM1 cells, which are a highly invasive clone of rat ascites hepatoma cells. Both mRNA and protein levels of RhoC but not RhoA in TGF-{beta}1-treated MM1 cells increased. In parallel with this increase in expression, RhoC activity was induced by TGF-{beta}1 treatment. When RhoC was overexpressed in MM1 cells, the invasive capacity increased. The RhoC-overexpressing cells formed more nodules than did mock cells when injected into rat peritoneum. Furthermore, when RhoC expression was reduced by transfection with shRNA/RhoC, the invasiveness of MM1 cells decreased with concomitant suppression of RhoC expression. Thus, the induced expression of RhoC by TGF-{beta}1 in MM1 cells plays a critical role in TGF-{beta}1-induced cell migration.

  6. MRI mediated, non-invasive tracking of intratumoral distribution of nanocarriers in rat glioma

    NASA Astrophysics Data System (ADS)

    Karathanasis, Efstathios; Park, Jaekeun; Agarwal, Abhiruchi; Patel, Vijal; Zhao, Fuqiang; Annapragada, Ananth V.; Hu, Xiaoping; Bellamkonda, Ravi V.

    2008-08-01

    Nanocarrier mediated therapy of gliomas has shown promise. The success of systemic nanocarrier-based chemotherapy is critically dependent on the so-called leaky vasculature to permit drug extravasation across the blood-brain barrier. Yet, the extent of vascular permeability in individual tumors varies widely, resulting in a correspondingly wide range of responses to the therapy. However, there exist no tools currently for rationally determining whether tumor blood vessels are amenable to nanocarrier mediated therapy in an individualized, patient specific manner today. To address this need for brain tumor therapy, we have developed a multifunctional 100 nm scale liposomal agent encapsulating a gadolinium-based contrast agent for contrast-enhanced magnetic resonance imaging with prolonged blood circulation. Using a 9.4 T MRI system, we were able to track the intratumoral distribution of the gadolinium-loaded nanocarrier in a rat glioma model for a period of three days due to improved magnetic properties of the contrast agent being packaged in a nanocarrier. Such a nanocarrier provides a tool for non-invasively assessing the suitability of tumors for nanocarrier mediated therapy and then optimizing the treatment protocol for each individual tumor. Additionally, the ability to image the tumor in high resolution can potentially constitute a surgical planning tool for tumor resection.

  7. Alphaxalone inhibits growth, migration and invasion of rat C6 malignant glioma cells.

    PubMed

    Sun, Huawei; Zheng, Xiaoke; Zhou, Yuehan; Zhu, Wenbo; Ou, Yanqiu; Shu, Minfeng; Gao, Xiuren; Leng, Tiandong; Qiu, Pengxin; Yan, Guangmei

    2013-10-01

    Malignant gliomas are the most devastating and aggressive brain tumors affecting the central nervous system. The insidious growth and infiltration are the most prominent characteristics of malignant gliomas, which render the current therapies for malignant gliomas including surgery, radiation and chemotherapy unsuccessful. Inhibition of infiltration as well as proliferation in combination with surgery might be more effective in the treatment of malignant gliomas. In the current study, we demonstrate the alphaxalone (3-hydroxypregnane-11,20-dione) could effectively inhibit the proliferation of C6 glioma cells in a concentration dependent manner. Moreover, this compound could also suppress the migration and invasion of C6 glioma cells at a concentration without causing significant cytotoxicity. Except the in vitro anti-glioma activity, alphaxalone effectively delayed the growth of rat C6 malignant glioma xenografts in vivo. Together, these findings suggest alphaxalone might be a promising candidate for the treatment of malignant gliomas and may also provide helpful clues for anti-glioma drugs development in future.

  8. Invasive non-native species' provision of refugia for endangered native species.

    PubMed

    Chiba, Satoshi

    2010-08-01

    The influence of non-native species on native ecosystems is not predicted easily when interspecific interactions are complex. Species removal can result in unexpected and undesired changes to other ecosystem components. I examined whether invasive non-native species may both harm and provide refugia for endangered native species. The invasive non-native plant Casuarina stricta has damaged the native flora and caused decline of the snail fauna on the Ogasawara Islands, Japan. On Anijima in 2006 and 2009, I examined endemic land snails in the genus Ogasawarana. I compared the density of live specimens and frequency of predation scars (from black rats [Rattus rattus]) on empty shells in native vegetation and Casuarina forests. The density of land snails was greater in native vegetation than in Casuarina forests in 2006. Nevertheless, radical declines in the density of land snails occurred in native vegetation since 2006 in association with increasing predation by black rats. In contrast, abundance of Ogasawarana did not decline in the Casuarina forest, where shells with predation scars from rats were rare. As a result, the density of snails was greater in the Casuarina forest than in native vegetation. Removal of Casuarina was associated with an increased proportion of shells with predation scars from rats and a decrease in the density of Ogasawarana. The thick and dense litter of Casuarina appears to provide refugia for native land snails by protecting them from predation by rats; thus, eradication of rats should precede eradication of Casuarina. Adaptive strategies, particularly those that consider the removal order of non-native species, are crucial to minimizing the unintended effects of eradication on native species. In addition, my results suggested that in some cases a given non-native species can be used to mitigate the impacts of other non-native species on native species.

  9. Adaptive and variable intraguild predators facilitate local coexistence in an intraguild predation module.

    PubMed

    Wu, San-He; Okuyama, Toshinori

    2012-05-24

    Intraguild predation (IGP) is common in nature, but its ecological role is still illusive. A number of studies have investigated a three species IGP module that consists of an intraguild predator, intraguild prey, and resource species in which the intraguild predator and the intraguild prey exploitatively compete for the resource while the intraguild predator also consumes the intraguild prey. A common prediction of models of the IGP module is that the coexistence of the species is difficult, which is considered inconsistent to the ubiquity of IGP in nature. This study revisits the IGP module and provides an alternative coexistence mechanism by focusing on a commonly used analysis method (i.e., invasion analysis) in light of individual variation in adaptive behavior. Invasion analysis underestimates the possibility of coexistence regardless of the presence or absence of adaptive behavior. Coexistence is possible even when invasion analysis predicts otherwise. The underestimation by invasion analysis is pronounced when the intraguild predator forages adaptively, which is even further pronounced when the expression of foraging behavior is variable among intraguild predators. The possibility of coexistence in the IGP module is greater than previously thought, which may have been partly due to how models were analyzed. Inconsistent conclusions may result from the same model depending on how the model is analyzed. Individual variation in adaptive behavior can be an important factor promoting the coexistence of species in IGP modules.

  10. Adaptive and variable intraguild predators facilitate local coexistence in an intraguild predation module

    PubMed Central

    2012-01-01

    Background Intraguild predation (IGP) is common in nature, but its ecological role is still illusive. A number of studies have investigated a three species IGP module that consists of an intraguild predator, intraguild prey, and resource species in which the intraguild predator and the intraguild prey exploitatively compete for the resource while the intraguild predator also consumes the intraguild prey. A common prediction of models of the IGP module is that the coexistence of the species is difficult, which is considered inconsistent to the ubiquity of IGP in nature. This study revisits the IGP module and provides an alternative coexistence mechanism by focusing on a commonly used analysis method (i.e., invasion analysis) in light of individual variation in adaptive behavior. Results Invasion analysis underestimates the possibility of coexistence regardless of the presence or absence of adaptive behavior. Coexistence is possible even when invasion analysis predicts otherwise. The underestimation by invasion analysis is pronounced when the intraguild predator forages adaptively, which is even further pronounced when the expression of foraging behavior is variable among intraguild predators. Conclusions The possibility of coexistence in the IGP module is greater than previously thought, which may have been partly due to how models were analyzed. Inconsistent conclusions may result from the same model depending on how the model is analyzed. Individual variation in adaptive behavior can be an important factor promoting the coexistence of species in IGP modules. PMID:22626442

  11. Behavioral responses of native prey to disparate predators: naiveté and predator recognition.

    PubMed

    Anson, Jennifer R; Dickman, Chris R

    2013-02-01

    It is widely accepted that predator recognition and avoidance are important behaviors in allowing prey to mitigate the impacts of their predators. However, while prey species generally develop anti-predator behaviors through coevolution with predators, they sometimes show accelerated adoption of these behaviors under strong selection pressure from novel species. We used a field manipulation experiment to gauge the ability of the common ringtail possum (Pseudocheirus peregrinus), a semi-arboreal Australian marsupial, to recognize and respond to olfactory cues of different predator archetypes. We predicted that ringtails would display stronger anti-predator behaviors to cues of the invasive European red fox (Vulpes vulpes) in areas where fox impacts had been greatest, and to cues of the native lace monitor (Varanus varius) in areas of sympatry compared with allopatry. We found that ringtails fled quickly and were more alert when exposed to the fecal odors of both predators compared to neutral and pungent control odors, confirming that predator odors are recognized and avoided. However, these aversive responses were similar irrespective of predator presence or level of impact. These results suggest that selection pressure from the fox has been sufficient for ringtails to develop anti-predator behaviors over the few generations since foxes have become established. In contrast, we speculate that aversive responses by ringtails to the lace monitor in areas where this predator is absent reflect recent coexistence of the two species. We conclude that rapid evolution of anti-predator behaviors may occur when selection is strong. The maintenance of these behaviors should allow re-establishment of predator-prey relationships if the interactants regain sympatry via range shifts or management actions to reintroduce them to their former ranges.

  12. Spatial dynamics of specialist seed predators on synchronized and intermittent seed production of host plants.

    PubMed

    Satake, Akiko; Bjørnstad, Ottar N

    2004-04-01

    Masting, the synchronized and intermittent seed production by plant populations, provides highly variable food resources for specialist seed predators. Such a reproductive mode helps minimize seed losses through predator satiation and extinction of seed predator populations. The seed predators can buffer the resource variation through dispersal or extended diapause. We developed a spatially explicit resource-consumer model to understand the effect of masting on specialist seed predators. The masting dynamics were assumed to follow a resource-based model for plant reproduction, and the population dynamics of the predator were represented by a spatially extended Nicholson-Bailey model. The resultant model demonstrated that when host plants reproduce intermittently, seed predator populations go locally extinct, but global persistence of the predator is facilitated by dispersal or extended diapause. Global extinction of the predator resulted when the intermittent reproduction is highly synchronized among plants. An approximate invasion criterion for the predators showed that negative lag-1 autocorrelation in seeding reduces invasibility, and positive lag-1 cross-correlation enhances invasibility. Spatial synchronization in seeding at local scale caused by pollen coupling (or climate forcing) further prevented invasion of the predators. If the predators employed extended diapause, extremely high temporal variability in reproduction was required for plants to evade the predators.

  13. Combination therapy of advanced invasive pulmonary aspergillosis in transiently neutropenic rats using human pharmacokinetic equivalent doses of voriconazole and anidulafungin.

    PubMed

    van de Sande, Wendy W J; Mathot, Ron A A; ten Kate, Marian T; van Vianen, Wim; Tavakol, Mehri; Rijnders, Bart J A; Bakker-Woudenberg, Irma A J M

    2009-05-01

    At present, voriconazole (VOR) is the drug of first choice for treating invasive pulmonary aspergillosis (IPA). However, particularly in advanced stages of disease and in the severely immunocompromised host, the mortality remains substantial. The combination of VOR with an echinocandin may improve the therapeutic outcome. We investigate here whether combining VOR and anidulafungin (ANI) in advanced IPA in transiently neutropenic rats results in a higher therapeutic efficacy. Since VOR is metabolized more rapidly in rodents than in humans, dosage adjustment for VOR is necessary to obtain an area under the plasma concentration-time curve (AUC) in rodents that is equivalent to that of humans. In this study, the pharmacokinetics of VOR and ANI in rats were elucidated, and dosage schedules were applied that produced AUCs similar to those of humans. The developed dose schedules were well tolerated by the rats, without effects on renal and hepatic functions. VOR showed excellent efficacy in early IPA (100% rat survival). In advanced IPA, VOR was less efficacious (50% rat survival), whereas a significant decrease in galactomannan concentrations in lungs and sera was found in surviving rats. ANI administered in advanced IPA resulted in 22% rat survival, and the serum concentrations of fungal galactomannan were slightly but not significantly decreased. The addition of ANI to VOR did not result in significantly increased therapeutic efficacy in advanced IPA, resulting in 67% rat survival and a significant decrease in galactomannan concentration in serum. In conclusion, VOR monotherapy is therapeutically effective in the treatment of advanced-stage IPA and superior to the use of ANI. Combining both agents does not significantly improve the therapeutic outcome.

  14. Molecular survey of rodent-borne Trypanosoma in Niger with special emphasis on T. lewisi imported by invasive black rats.

    PubMed

    Dobigny, Gauthier; Poirier, Philippe; Hima, Karmadine; Cabaret, Odile; Gauthier, Philippe; Tatard, Caroline; Costa, Jean-Marc; Bretagne, Stéphane

    2011-03-01

    Invading rodent species can harbor parasites with potential transmission to native rodents and/or humans. To investigate trypanosomes prevalence in rodents, the spleen of 76 rodents from Niger identified by their karyotype was used as a DNA source for Trypanosoma detection using a newly developed qPCR assay. Of the invasive black rat, Rattus rattus, 71% (10/14) were PCR positive as well as 6% (4/62) of native African rodents. Sequences of ~400bp of the SSU rDNA gene identified phylogenetically close Trypanosoma lineages. Trypanosoma lewisi was present in all positive black rats and the sequences displayed 100% similarity with T. lewisi-infected humans in Senegal. T. lewisi was also detected in one Acomys johannis, suggesting a possible transmission to native species. In addition to improved knowledge of Trypanosoma diversity in rodents, our data underscore the introduction of the potentially pathogenic T. lewisi kinetoplastid through the human-mediated invasion of black rats all over West Africa.

  15. Stress triangle: do introduced predators exert indirect costs on native predators and prey?

    PubMed

    Anson, Jennifer R; Dickman, Chris R; Boonstra, Rudy; Jessop, Tim S

    2013-01-01

    Non-consumptive effects of predators on each other and on prey populations often exceed the effects of direct predation. These effects can arise from fear responses elevating glucocorticoid (GC) hormone levels (predator stress hypothesis) or from increased vigilance that reduces foraging efficiency and body condition (predator sensitive foraging hypothesis); both responses can lead to immunosuppression and increased parasite loads. Non-consumptive effects of invasive predators have been little studied, even though their direct impacts on local species are usually greater than those of their native counterparts. To address this issue, we explored the non-consumptive effects of the invasive red fox Vulpes vulpes on two native species in eastern Australia: a reptilian predator, the lace monitor Varanus varius and a marsupial, the ringtail possum Pseudocheirus peregrinus. In particular, we tested predictions derived from the above two hypotheses by comparing the basal glucocorticoid levels, foraging behaviour, body condition and haemoparasite loads of both native species in areas with and without fox suppression. Lace monitors showed no GC response or differences in haemoparasite loads but were more likely to trade safety for higher food rewards, and had higher body condition, in areas of fox suppression than in areas where foxes remained abundant. In contrast, ringtails showed no physiological or behavioural differences between fox-suppressed and control areas. Predator sensitive foraging is a non-consumptive cost for lace monitors in the presence of the fox and most likely represents a response to competition. The ringtail's lack of response to the fox potentially represents complete naiveté or strong and rapid selection to the invasive predator. We suggest evolutionary responses are often overlooked in interactions between native and introduced species, but must be incorporated if we are to understand the suite of forces that shape community assembly and function

  16. Stress Triangle: Do Introduced Predators Exert Indirect Costs on Native Predators and Prey?

    PubMed Central

    Anson, Jennifer R.; Dickman, Chris R.; Boonstra, Rudy; Jessop, Tim S.

    2013-01-01

    Non-consumptive effects of predators on each other and on prey populations often exceed the effects of direct predation. These effects can arise from fear responses elevating glucocorticoid (GC) hormone levels (predator stress hypothesis) or from increased vigilance that reduces foraging efficiency and body condition (predator sensitive foraging hypothesis); both responses can lead to immunosuppression and increased parasite loads. Non-consumptive effects of invasive predators have been little studied, even though their direct impacts on local species are usually greater than those of their native counterparts. To address this issue, we explored the non-consumptive effects of the invasive red fox Vulpes vulpes on two native species in eastern Australia: a reptilian predator, the lace monitor Varanus varius and a marsupial, the ringtail possum Pseudocheirus peregrinus. In particular, we tested predictions derived from the above two hypotheses by comparing the basal glucocorticoid levels, foraging behaviour, body condition and haemoparasite loads of both native species in areas with and without fox suppression. Lace monitors showed no GC response or differences in haemoparasite loads but were more likely to trade safety for higher food rewards, and had higher body condition, in areas of fox suppression than in areas where foxes remained abundant. In contrast, ringtails showed no physiological or behavioural differences between fox-suppressed and control areas. Predator sensitive foraging is a non-consumptive cost for lace monitors in the presence of the fox and most likely represents a response to competition. The ringtail’s lack of response to the fox potentially represents complete naiveté or strong and rapid selection to the invasive predator. We suggest evolutionary responses are often overlooked in interactions between native and introduced species, but must be incorporated if we are to understand the suite of forces that shape community assembly and function

  17. Frequency, efficiency, and physical characteristics of predation by generalist predators of brown marmorated stink bug (Hemiptera: Pentatomidae) eggs

    USDA-ARS?s Scientific Manuscript database

    The native generalist predator community of Halyomorpha halys, an invasive species in the United States and Europe, remains poorly studied. The aims of the current study were to determine which generalist predators that are commonly found in mid-Atlantic orchards and vegetable crops are capable of ...

  18. Manganese superoxide dismutase promotes interaction of actin, S100A4 and Talin, and enhances rat gastric tumor cell invasion

    PubMed Central

    Indo, Hiroko P.; Matsui, Hirofumi; Chen, Jing; Zhu, Haining; Hawkins, Clare L.; Davies, Michael J.; Yarana, Chontida; St. Clair, Daret K.; Majima, Hideyuki J.

    2015-01-01

    It has been demonstrated that cancer cells are under high levels of oxidative stress and express high levels of Manganese superoxide dismutase (MnSOD) to protect themselves and support the anabolic metabolism needed for growth and cell motility. The aim of this study was to identify proteins that may have a correlation with invasion and redox regulation by mitochondrial reactive oxygen species (ROS). MnSOD scavenges superoxide anions generated from mitochondria and is an important regulator of cellular redox status. Oxidative posttranslational modification of cysteine residues is a key mechanism that regulates protein structure and function. We hypothesized that MnSOD regulates intracellular reduced thiol status and promotes cancer invasion. A proteomic thiol-labeling approach with 5-iodoacetamidofluorescein was used to identify changes in intracellular reduced thiol-containing proteins. Our results demonstrate that overexpression of MnSOD maintained the major structural protein, actin, in a reduced state, and enhanced the invasion ability in gastric mucosal cancer cells, RGK1. We also found that the expression of Talin and S100A4 were increased in MnSOD-overexpressed RGK1 cells. Moreover, Talin bound not only with actin but also with S100A4, suggesting that the interaction of these proteins may, in part, contribute to the invasive ability of rat gastric cancer. PMID:26236095

  19. Evidence of indirect impacts of introduced trout on native amphibians via facilitation of a shared predator

    Treesearch

    Karen L. Pope; Justin M. Garwood; Hartwell H. Welsh Jr.; Sharon P. Lawler

    2008-01-01

    Hyperpredation occurs when non-native prey facilitate invasive predators, which then suppress native prey. Direct impacts of introduced fish on amphibians are well studied, but the role of fish in supporting shared predators has not been considered. We present evidence for indirect effects of trout on amphibians through snake predation. Analyses of the diet,...

  20. On local(ly) ESS of a pair of prey-predator system with predatory switching.

    PubMed

    Mukherjee, D; Roy, A B

    1998-08-01

    This paper concentrates on the study of ecological stability for guaranteeing evolutionary stable strategies (ESS) in a two pre-predator system taking into consideration of handling time, with predatory switching. Here predators are polyphagous in nature. The conditions for ESS of the model system are obtained at the equivalence point. We also derive the invasion conditions of a mutant predator.

  1. Non-Invasive Imaging Demonstrates Clinical Features of Ankylosing Spondylitis in a Rat Adjuvant Model: a Case Study

    PubMed Central

    Dawson, J.; Kolbinger, F.; Kramer, I.; Beckmann, N.

    2016-01-01

    Main features of ankylosing spondylitis like inflammatory erosive osteopenia and bony overgrowth are recapitulated in rats challenged with complete Freund’s adjuvant. In vivo changes induced in the rat spine were followed longitudinally by magnetic resonance imaging (MRI) and assessed terminally by micro-computerized tomography (micro-CT) and histology. Signals reflecting inflammation were detected by MRI at levels L5-L6 throughout the experiment, peaking at day 27 after adjuvant. Bone erosion and formation occurred from this time point onward, as confirmed by micro-CT. Histology confirmed the inflammation and bone remodeling. The present study demonstrates the potential of imaging for longitudinal assessments of spinal changes in this animal model and the excellent correlation between in vivo images and histology underlines its fundamental role in the validation of non-invasive imaging. PMID:28076929

  2. Predation at the Shore.

    ERIC Educational Resources Information Center

    Cook, Helen M.; Matthews, Catherine E.; Hildreth, David P.; Couch, Emma

    2003-01-01

    Describes 10 predator/prey relationships that occur on the coast. Predators are compared to criminals and prey to their victims along with details of crime scenes. Accurately describes the habits and habitats of the criminals and presents games and activities that feature the relationships between predators and their prey. (Author/SOE)

  3. Predation at the Shore.

    ERIC Educational Resources Information Center

    Cook, Helen M.; Matthews, Catherine E.; Hildreth, David P.; Couch, Emma

    2003-01-01

    Describes 10 predator/prey relationships that occur on the coast. Predators are compared to criminals and prey to their victims along with details of crime scenes. Accurately describes the habits and habitats of the criminals and presents games and activities that feature the relationships between predators and their prey. (Author/SOE)

  4. Exploiting interspecific olfactory communication to monitor predators.

    PubMed

    Garvey, Patrick M; Glen, Alistair S; Clout, Mick N; Wyse, Sarah V; Nichols, Margaret; Pech, Roger P

    2017-03-01

    Olfaction is the primary sense of many mammals and subordinate predators use this sense to detect dominant species, thereby reducing the risk of an encounter and facilitating coexistence. Chemical signals can act as repellents or attractants and may therefore have applications for wildlife management. We devised a field experiment to investigate whether dominant predator (ferret Mustela furo) body odor would alter the behavior of three common mesopredators: stoats (Mustela erminea), hedgehogs (Erinaceus europaeus), and ship rats (Rattus rattus). We predicted that apex predator odor would lead to increased detections, and our results support this hypothesis as predator kairomones (interspecific olfactory messages that benefit the receiver) provoked "eavesdropping" behavior by mesopredators. Stoats exhibited the most pronounced responses, with kairomones significantly increasing the number of observations and the time spent at a site, so that their occupancy estimates changed from rare to widespread. Behavioral responses to predator odors can therefore be exploited for conservation and this avenue of research has not yet been extensively explored. A long-life lure derived from apex predator kairomones could have practical value, especially when there are plentiful resources that reduce the efficiency of food-based lures. Our results have application for pest management in New Zealand and the technique of using kairomones to monitor predators could have applications for conservation efforts worldwide.

  5. Inhibitory effect of coffee on hepatoma proliferation and invasion in culture and on tumor growth, metastasis and abnormal lipoprotein profiles in hepatoma-bearing rats.

    PubMed

    Miura, Yutaka; Ono, Kanako; Okauchi, Rieko; Yagasaki, Kazumi

    2004-02-01

    We have already reported that instant coffee powder (ICP) and ICP-loaded rat sera could suppress proliferation and invasion of rat ascites hepatoma cell line of AH109A in vitro. In this report, we examined the mechanisms for suppression of tumor cell proliferation and invasion by ICP, and the effect of ICP on in vivo tumor growth, metastasis and abnormal lipoprotein profiles in hepatoma-bearing rats. ICP, when directly added to the culture media, induced cell cycle arrest (elongation of S phase) at a lower concentration (0.3 mg/mL) and apoptosis at a higher concentration (0.6-1.2 mg/mL). ICP and ICP-loaded rat sera showed reactive oxygen species (ROS)-scavenging property and canceled the enhancement of invasive activity of hepatoma cells induced by ROS in vitro. These results suggest that ICP suppresses the proliferation by inducing cell cycle arrest and apoptosis, and the invasion by scavenging ROS and that ICP could retain these properties after their gastrointestinal absorption. The hepatoma-bearing rats were fed with a 20% casein diet (20C) or 20C supplemented with 0.1%, ICP for 14 d. Dietary ICP significantly reduced solid tumor growth and tended to reduce hepatoma metastases to lung and lymphatic nodes, suggesting that ICP could suppress tumor cell proliferation and invasion in vivo. In addition, dietary ICP significantly increased serum high-density lipoprotein (HDL)-cholesterol and tended to reduce very low-density and low-density lipoprotein (VLDL+LDL)-cholesterol, resulting in amelioration of abnormal lipoprotein profiles occurred in hepatoma-bearing rats. In conclusion, ICP has the ability to induce cell cycle arrest and apoptosis in hepatoma cells and to suppress tumor cell invasion by reducing oxidative stresses in vitro, and it could also exhibit these effects in vivo, leading to the inhibition of tumor growth and metastases.

  6. Rat hepatic stellate cells alter the gene expression profile and promote the growth, migration and invasion of hepatocellular carcinoma cells.

    PubMed

    Wang, Zhi-Ming; Zhou, Le-Yuan; Liu, Bin-Bin; Jia, Qin-An; Dong, Yin-Ying; Xia, Yun-Hong; Ye, Sheng-Long

    2014-10-01

    The aim of the present study was to examine the effects of activated hepatic stellate cells (HSCs) and their paracrine secretions, on hepatocellular cancer cell growth and gene expression in vitro and in vivo. Differentially expressed genes in McA-RH7777 hepatocellular carcinoma (HCC) cells following non-contact co-culture with activated stellate cells, were identified by a cDNA microarray. The effect of the co-injection of HCC cells and activated HSCs on tumor size in rats was also investigated. Non-contact co-culture altered the expression of 573 HCC genes by >2-fold of the control levels. Among the six selected genes, ELISA revealed increased protein levels of hepatic growth factor, matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9). Incubation of HCC cells with medium conditioned by activated HSCs significantly increased the proliferation rate (P<0.001), migration rate and the number of invasive HCC cells (P=0.001). Co-injection of HCC cells and activated HSCs into rats significantly increased the weight of the resulting HCC tumors (P<0.01). The paracrine activity of activated HSCs markedly altered the gene expression profile of HCC cells and affected their growth, migration and invasiveness. The results from the present study indicate that the interaction between the activated HSCs and HCC has an important role in the development of HCC.

  7. Automated determination of wakefulness and sleep in rats based on non-invasively acquired measures of movement and respiratory activity.

    PubMed

    Zeng, Tao; Mott, Christopher; Mollicone, Daniel; Sanford, Larry D

    2012-03-15

    The current standard for monitoring sleep in rats requires labor intensive surgical procedures and the implantation of chronic electrodes which have the potential to impact behavior and sleep. With the goal of developing a non-invasive method to determine sleep and wakefulness, we constructed a non-contact monitoring system to measure movement and respiratory activity using signals acquired with pulse Doppler radar and from digitized video analysis. A set of 23 frequency and time-domain features were derived from these signals and were calculated in 10s epochs. Based on these features, a classification method for automated scoring of wakefulness, non-rapid eye movement sleep (NREM) and REM in rats was developed using a support vector machine (SVM). We then assessed the utility of the automated scoring system in discriminating wakefulness and sleep by comparing the results to standard scoring of wakefulness and sleep based on concurrently recorded EEG and EMG. Agreement between SVM automated scoring based on selected features and visual scores based on EEG and EMG were approximately 91% for wakefulness, 84% for NREM and 70% for REM. The results indicate that automated scoring based on non-invasively acquired movement and respiratory activity will be useful for studies requiring discrimination of wakefulness and sleep. However, additional information or signals will be needed to improve discrimination of NREM and REM episodes within sleep. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Automated determination of wakefulness and sleep in rats based on non-invasively acquired measures of movement and respiratory activity

    PubMed Central

    Zeng, Tao; Mott, Christopher; Mollicone, Daniel; Sanford, Larry D.

    2012-01-01

    The current standard for monitoring sleep in rats requires labor intensive surgical procedures and the implantation of chronic electrodes which have the potential to impact behavior and sleep. With the goal of developing a non-invasive method to determine sleep and wakefulness, we constructed a non-contact monitoring system to measure movement and respiratory activity using signals acquired with pulse Doppler radar and from digitized video analysis. A set of 23 frequency and time-domain features were derived from these signals and were calculated in 10 s epochs. Based on these features, a classification method for automated scoring of wakefulness, non-rapid eye movement sleep (NREM) and REM in rats was developed using a support vector machine (SVM). We then assessed the utility of the automated scoring system in discriminating wakefulness and sleep by comparing the results to standard scoring of wakefulness and sleep based on concurrently recorded EEG and EMG. Agreement between SVM automated scoring based on selected features and visual scores based on EEG and EMG were approximately 91% for wakefulness, 84% for NREM and 70% for REM. The results indicate that automated scoring based on non-invasively acquired movement and respiratory activity will be useful for studies requiring discrimination of wakefulness and sleep. However, additional information or signals will be needed to improve discrimination of NREM and REM episodes within sleep. PMID:22178621

  9. Nest Predation by Commensal Rodents in Urban Bushland Remnants

    PubMed Central

    2016-01-01

    Exotic predators are a major threat to native wildlife in many parts of the world. Developing and implementing effective strategies to mitigate their effects requires robust quantitative data so that management can be evidence-based, yet in many ecosystems this is missing. Birds in particular have been severely impacted by exotic mammalian predators, and a plethora of studies on islands record predation of bird eggs, fledglings and adults by exotic species such as rodents, stoats and cats. By comparison, few studies have examined nest predation around mainland urban centres which often act as dispersal hubs, especially for commensal species such as rodents. Here, we experimentally examine nest predation rates in habitat patches with varying black rat (Rattus rattus) densities in Sydney, Australia and test whether these exotic rats have the effects expected of exotic predators using effect size benchmarks. In the case where black rats have replaced native Rattus spp., we expected that black rats, being more arboreal than native Rattus spp., would be a significant source of predation on birds because they can readily access the arboreal niche where many birds nest. We tested this idea using above-ground artificial nests to represent those of typical small bird species such as the New Holland honeyeater (Phylidonyris novaehollandiae). We found that fewer eggs were depredated by rodents on sites where we removed black rats compared to unmanipulated sites, and that the effect size calculated from the total number of eggs surviving beyond the typical incubation period was similar to that expected for an exotic predator. Our results suggest that, although Australian birds have co-evolved with native Rattus species, in the case where black rats have replaced native Rattus species, exotic black rats appear to pose an additive source of predation on birds in remnant habitats, most likely due to their ability to climb more efficiently than their native counterparts

  10. Nest Predation by Commensal Rodents in Urban Bushland Remnants.

    PubMed

    Smith, Helen M; Dickman, Chris R; Banks, Peter B

    2016-01-01

    Exotic predators are a major threat to native wildlife in many parts of the world. Developing and implementing effective strategies to mitigate their effects requires robust quantitative data so that management can be evidence-based, yet in many ecosystems this is missing. Birds in particular have been severely impacted by exotic mammalian predators, and a plethora of studies on islands record predation of bird eggs, fledglings and adults by exotic species such as rodents, stoats and cats. By comparison, few studies have examined nest predation around mainland urban centres which often act as dispersal hubs, especially for commensal species such as rodents. Here, we experimentally examine nest predation rates in habitat patches with varying black rat (Rattus rattus) densities in Sydney, Australia and test whether these exotic rats have the effects expected of exotic predators using effect size benchmarks. In the case where black rats have replaced native Rattus spp., we expected that black rats, being more arboreal than native Rattus spp., would be a significant source of predation on birds because they can readily access the arboreal niche where many birds nest. We tested this idea using above-ground artificial nests to represent those of typical small bird species such as the New Holland honeyeater (Phylidonyris novaehollandiae). We found that fewer eggs were depredated by rodents on sites where we removed black rats compared to unmanipulated sites, and that the effect size calculated from the total number of eggs surviving beyond the typical incubation period was similar to that expected for an exotic predator. Our results suggest that, although Australian birds have co-evolved with native Rattus species, in the case where black rats have replaced native Rattus species, exotic black rats appear to pose an additive source of predation on birds in remnant habitats, most likely due to their ability to climb more efficiently than their native counterparts

  11. Minimally invasive method for determining the effective lymphatic pumping pressure in rats using near-infrared imaging

    PubMed Central

    Nelson, Tyler S.; Akin, Ryan E.; Weiler, Michael J.; Kassis, Timothy; Kornuta, Jeffrey A.

    2014-01-01

    The ability to quantify collecting vessel function in a minimally invasive fashion is crucial to the study of lymphatic physiology and the role of lymphatic pump function in disease progression. Therefore, we developed a highly sensitive, minimally invasive research platform for quantifying the pumping capacity of collecting lymphatic vessels in the rodent tail and forelimb. To achieve this, we have integrated a near-infrared lymphatic imaging system with a feedback-controlled pressure cuff to modulate lymph flow. After occluding lymphatic flow by inflating a pressure cuff on the limb or tail, we gradually deflate the cuff while imaging flow restoration proximal to the cuff. Using prescribed pressure applications and automated image processing of fluorescence intensity levels in the vessels, we were able to noninvasively quantify the effective pumping pressure (Peff, pressure at which flow is restored after occlusion) and vessel emptying rate (rate of fluorescence clearance during flow occlusion) of lymphatics in the rat. To demonstrate the sensitivity of this system to changes in lymphatic function, a nitric oxide (NO) donor cream, glyceryl trinitrate ointment (GTNO), was applied to the tails. GTNO decreased Peff of the vessels by nearly 50% and the average emptying rate by more than 60%. We also demonstrate the suitability of this approach for acquiring measurements on the rat forelimb. Thus, this novel research platform provides the first minimally invasive measurements of Peff and emptying rate in rodents. This experimental platform holds strong potential for future in vivo studies that seek to evaluate changes in lymphatic health and disease. PMID:24430884

  12. Biocontrol in an impulsive predator-prey model.

    PubMed

    Terry, Alan J

    2014-10-01

    We study a model for biological pest control (or "biocontrol") in which a pest population is controlled by a program of periodic releases of a fixed yield of predators that prey on the pest. Releases are represented as impulsive increases in the predator population. Between releases, predator-pest dynamics evolve according to a predator-prey model with some fairly general properties: the pest population grows logistically in the absence of predation; the predator functional response is either of Beddington-DeAngelis type or Holling type II; the predator per capita birth rate is bounded above by a constant multiple of the predator functional response; and the predator per capita death rate is allowed to be decreasing in the predator functional response and increasing in the predator population, though the special case in which it is constant is permitted too. We prove that, when the predator functional response is of Beddington-DeAngelis type and the predators are not sufficiently voracious, then the biocontrol program will fail to reduce the pest population below a particular economic threshold, regardless of the frequency or yield of the releases. We prove also that our model possesses a pest-eradication solution, which is both locally and globally stable provided that predators are sufficiently voracious and that releases occur sufficiently often. We establish, curiously, that the pest-eradication solution can be locally stable whilst not being globally stable, the upshot of which is that, if we delay a biocontrol response to a new pest invasion, then this can change the outcome of the response from pest eradication to pest persistence. Finally, we state a number of specific examples for our model, and, for one of these examples, we corroborate parts of our analysis by numerical simulations.

  13. Effectiveness of rodenticides for managing invasive roof rats and native deer mice in orchards.

    PubMed

    Baldwin, Roger A; Quinn, Niamh; Davis, David H; Engeman, Richard M

    2014-05-01

    Roof rats (Rattus rattus) and deer mice (Peromyscus maniculatus) are occasional pests of nut and tree fruit orchards throughout California and in many other parts of the USA and beyond. In general, the most practical and cost-effective control method for rodents in many agricultural environments is the use of rodenticides (toxic baits), but little or no information exists on the efficacy of current rodenticides in controlling roof rats and deer mice in orchards. Therefore, our goals were to develop an index of rodent activity to monitor efficacy of rodenticides and to subsequently test the efficacy of three California Department of Food and Agriculture rodenticide baits (0.005 % chlorophacinone treated oats, 0.005 % diphacinone treated oats, and 0.005 % diphacinone wax block) to determine their utility for controlling roof rats and deer mice in agricultural orchards. We determined that a general index using the number of roof rat photos taken at a minimum of a 5-min interval was strongly correlated to the minimum number known estimate of roof rats; this approach was used to monitor roof rat and deer mouse populations pre- and post-treatment. Of the baits tested, the 0.005 % diphacinone treated oats was most effective for both species; 0.005 % chlorophacinone grain was completely ineffective against roof rats. Our use of elevated bait stations proved effective at providing bait to target species and should substantially limit access to rodenticides by many non-target species.

  14. Effects of invasive rats and burrowing seabirds on seeds and seedlings on New Zealand islands.

    PubMed

    Grant-Hoffman, Madeline N; Mulder, Christa P H; Bellingham, Peter J

    2010-04-01

    Rats (Rattus rattus, Rattus norvegicus, Rattus exulans) are important invaders on islands. They alter vegetation indirectly by preying on burrowing seabirds. These seabirds affect vegetation through nutrient inputs from sea to land and physical disturbance through trampling and burrowing. Rats also directly affect vegetation though consumption of seeds and seedlings. Seedling communities on northern New Zealand islands differ in composition and densities among islands which have never been invaded by rats, are currently invaded by rats, or from which rats have been eradicated. We conducted experimental investigations to determine the mechanisms driving these patterns. When the physical disturbance of seabirds was removed, in soils collected from islands and inside exclosures, seedling densities increased with seabird burrow density. For example, seedling densities inside exclosures were 10 times greater than those outside. Thus the negative effects of seabirds on seedlings, by trampling and uprooting, overwhelm the potentially beneficial effects of high levels of seed germination, seedling emergence, and possibly seed production, which result from seed burial and nutrient additions. Potential seedling density was reduced on an island where rats were present, germination of seeds from soils of this island was approximately half that found on other islands, but on this island seedling density inside exclosures was 7 times the density outside. Although the total negative effects of seabirds and rats on seedling densities are similar (reduced seedling density), the differences in mechanisms and life stages affected result in very different filters on the plant community.

  15. Shikonin inhibits TNF-α-induced growth and invasion of rat aortic vascular smooth muscle cells.

    PubMed

    Zhang, Xuemin; Hu, Wenyu; Wu, Fang; Yuan, Xue; Hu, Jian

    2015-08-01

    Shikonin is a naphthoquinone compound extracted from the Chinese herb purple gromwell. Shikonin has broad antibacterial, anti-inflammatory, and antitumor activities. The tumor necrosis factor-α (TNF-α)-induced proliferation and invasion of vascular smooth muscle cells (VSMCs) is an important factor that contributes to atherosclerosis. The effects of shikonin on the proliferation and apoptosis of VSMCs have been reported; however, the function of shikonin on TNF-α-mediated growth and invasion of VSMCs during atherosclerosis remains unclear. In this study, we used Western blot, flow cytometry, real-time quantitative PCR, and enzyme-linked immunosorbent assay to investigate the effect of shikonin on the TNF-α-induced growth and invasion of VSMCs and to determine the underlying mechanism. Our results showed that shikonin inhibits the TNF-α-mediated growth and invasion. Further study revealed that shikonin regulates the activation of nuclear factor kappa B and phosphatidyl inositol 3-kinase signaling pathways; modulates the expression of cyclin D1, cyclin E, B-cell lymphoma 2, and Bax; activates caspase-3 and caspase-9; induces cell cycle arrest; and promotes the apoptosis of VSMCs. Together, our results indicate that shikonin may become a promising agent for the treatment of atherosclerosis and they also establish foundation for the development of anti-atherosclerosis drugs.

  16. Monitoring hemodynamics and oxygenation of the kidney in rats by a combined near-infrared spectroscopy and invasive probe approach

    NASA Astrophysics Data System (ADS)

    Grosenick, Dirk; Cantow, Kathleen; Arakelyan, Karen; Wabnitz, Heidrun; Flemming, Bert; Skalweit, Angela; Ladwig, Mechthild; Macdonald, Rainer; Niendorf, Thoralf; Seeliger, Erdmann

    2015-07-01

    We have developed a hybrid approach to investigate the dynamics of perfusion and oxygenation in the kidney of rats under pathophysiologically relevant conditions. Our approach combines near-infrared spectroscopy to quantify hemoglobin concentration and oxygen saturation in the renal cortex, and an invasive probe method for measuring total renal blood flow by an ultrasonic probe, perfusion by laser-Doppler fluxmetry, and tissue oxygen tension via fluorescence quenching. Hemoglobin concentration and oxygen saturation were determined from experimental data by a Monte Carlo model. The hybrid approach was applied to investigate and compare temporal changes during several types of interventions such as arterial and venous occlusions, as well as hyperoxia, hypoxia and hypercapnia induced by different mixtures of the inspired gas. The approach was also applied to study the effects of the x-ray contrast medium iodixanol on the kidney.

  17. Blood and tissue distribution of posaconazole in a rat model of invasive pulmonary aspergillosis.

    PubMed

    Cendejas-Bueno, E; Forastiero, A; Ruiz, I; Mellado, E; Gavaldà, J; Gomez-Lopez, A

    2017-02-01

    Posaconazole is the recommended prophylactic agent in patients at high risk of invasive fungal infection, since adequate drug levels seem to be reached in target sites despite the relatively low levels detected in blood. The objective of this study is to obtain pharmacokinetic (PK) information associated to blood and tissue distribution of posaconazole in an animal model of invasive pulmonary aspergillosis. The PK parameters in lung samples were systematically higher than in serum. After multiple-dose administration of posaconazole, a significant accumulation of the drug was evident in lung tissue. The PK behavior of posaconazole in this particular experimental model is similar to that observed in humans. Thus, we believe this model could be a valid tool to evaluate posaconazole exposure-response relationship.

  18. Stress-induced visceral analgesia assessed non-invasively in rats is enhanced by prebiotic diet

    PubMed Central

    Larauche, Muriel; Mulak, Agata; Yuan, Pu-Qing; Kanauchi, Osamu; Taché, Yvette

    2012-01-01

    AIM: To investigate the influence of repeated water avoidance stress (rWAS) on the visceromotor response (VMR) to colorectal distension (CRD) and the modulation of the response by a prebiotic diet in rats using a novel surgery-free method of solid-state manometry. METHODS: Male Wistar rats fed a standard diet with or without 4% enzyme-treated rice fiber (ERF) for 5 wk were subjected to rWAS (1 h daily x 10 d) or no stress. The VMR to graded phasic CRD was assessed by intraluminal colonic pressure recording on days 0 (baseline), 1 and 10 (45 min) and 11 (24 h) after rWAS and expressed as percentage change from baseline. Cecal content of short chain fatty acids and distal colonic histology were assessed on day 11. RESULTS: WAS on day 1 reduced the VMR to CRD at 40 and 60 mmHg similarly by 28.9% ± 6.6% in both diet groups. On day 10, rWAS-induced reduction of VMR occurred only at 40 mmHg in the standard diet group (36.2% ± 17.8%) while in the ERF group VMR was lowered at 20, 40 and 60 mmHg by 64.9% ± 20.9%, 49.3% ± 11.6% and 38.9% ± 7.3% respectively. The visceral analgesia was still observed on day 11 in ERF- but not in standard diet-fed rats. By contrast the non-stressed groups (standard or ERF diet) exhibited no changes in VMR to CRD. In standard diet-fed rats, rWAS induced mild colonic histological changes that were absent in ERF-fed rats exposed to stress compared to non-stressed rats. The reduction of cecal content of isobutyrate and total butyrate, but not butyrate alone, was correlated with lower visceral pain response. Additionally, ERF diet increased rWAS-induced defecation by 26% and 75% during the first 0-15 min and last 15-60 min, respectively, compared to standard diet, and reduced rats’ body weight gain by 1.3 fold independently of their stress status. CONCLUSION: These data provide the first evidence of psychological stress-related visceral analgesia in rats that was enhanced by chronic intake of ERF prebiotic. PMID:22294825

  19. Sleep and rhythm changes at the time of Trypanosoma brucei invasion of the brain parenchyma in the rat.

    PubMed

    Seke Etet, Paul F; Palomba, Maria; Colavito, Valeria; Grassi-Zucconi, Gigliola; Bentivoglio, Marina; Bertini, Giuseppe

    2012-05-01

    Human African trypanosomiasis (HAT), or sleeping sickness, is a severe disease caused by Trypanosoma brucei (T.b.). The disease hallmark is sleep alterations. Brain involvement in HAT is a crucial pathogenetic step for disease diagnosis and therapy. In this study, a rat model of African trypanosomiasis was used to assess changes of sleep-wake, rest-activity, and body temperature rhythms in the time window previously shown as crucial for brain parenchyma invasion by T.b. to determine potential biomarkers of this event. Chronic radiotelemetric monitoring in Sprague-Dawley rats was used to continuously record electroencephalogram, electromyogram, rest-activity, and body temperature in the same animals before (baseline recording) and after infection. Rats were infected with T.b. brucei. Data were acquired from 1 to 20 d after infection (parasite neuroinvasion initiates at 11-13 d post-infection in this model), and were compared to baseline values. Sleep parameters were manually scored from electroencephalographic-electromyographic tracings. Circadian rhythms of sleep time, slow-wave activity, rest-activity, and body temperature were studied using cosinor rhythmometry. Results revealed alterations of most of the analyzed parameters. In particular, sleep pattern and sleep-wake organization plus rest-activity and body temperature rhythms exhibited early quantitative and qualitative alterations, which became marked around the time interval crucial for parasite neuroinvasion or shortly after. Data derived from actigrams showed close correspondence with those from hypnograms, suggesting that rest-activity could be useful to monitor sleep-wake alterations in African trypanosomiasis.

  20. Near-infrared oxymeter biosensor prototype for non-invasive in vivo analysis of rat brain oxygenation: effects of drugs of abuse

    NASA Astrophysics Data System (ADS)

    Crespi, F.; Donini, M.; Bandera, A.; Congestri, F.; Formenti, F.; Sonntag, V.; Heidbreder, C.; Rovati, L.

    2006-07-01

    The feasibility of non-invasive analysis of brain activities was studied in the attempt to overcome the major limitation of actual in vivo methodologies, i.e. invasiveness. Optic fibre probes were used as the optical head of a novel, highly sensitive near-infrared continuous wave spectroscopy (CW-NIR) instrument. This prototype was designed for non-invasive analysis of the two main forms of haemoglobin: oxy-haemoglobin (HbO2) and deoxy-haemoglobin (Hb), chromophores present in biological tissues. It was tested in peripheral tissue (human gastrocnemius muscle) and then reset to perform the measurement on rat brain. In animal studies, the optical head was firmly placed using stereotaxic apparatus upon the sagittal line of the head of anaesthetized adult rats, without any surgery. Then pharmacological treatments with saline (300 µl s.c.) amphetamine (2 mg kg-1) or nicotine (0.4 mg kg-1) were performed. Within 10-20 min amphetamine substantially increased HbO2 and reduced Hb control levels. Nicotine produced a rapid initial increase followed by a decrease in HbO2. In contrast to amphetamine, nicotine treatment also reduced Hb and blood volume. These results support the capacity of our CW-NIR prototype to measure non-invasively HbO2 and Hb levels in the rat brain, that are markers of the degree of tissue oxygenation, thus providing an index of blood levels and therefore of brain metabolism.

  1. Cascading top-down effects of changing oceanic predator abundances.

    PubMed

    Baum, Julia K; Worm, Boris

    2009-07-01

    1. Top-down control can be an important determinant of ecosystem structure and function, but in oceanic ecosystems, where cascading effects of predator depletions, recoveries, and invasions could be significant, such effects had rarely been demonstrated until recently. 2. Here we synthesize the evidence for oceanic top-down control that has emerged over the last decade, focusing on large, high trophic-level predators inhabiting continental shelves, seas, and the open ocean. 3. In these ecosystems, where controlled manipulations are largely infeasible, 'pseudo-experimental' analyses of predator-prey interactions that treat independent predator populations as 'replicates', and temporal or spatial contrasts in predator populations and climate as 'treatments', are increasingly employed to help disentangle predator effects from environmental variation and noise. 4. Substantial reductions in marine mammals, sharks, and piscivorous fishes have led to mesopredator and invertebrate predator increases. Conversely, abundant oceanic predators have suppressed prey abundances. Predation has also inhibited recovery of depleted species, sometimes through predator-prey role reversals. Trophic cascades have been initiated by oceanic predators linking to neritic food webs, but seem inconsistent in the pelagic realm with effects often attenuating at plankton. 5. Top-down control is not uniformly strong in the ocean, and appears contingent on the intensity and nature of perturbations to predator abundances. Predator diversity may dampen cascading effects except where nonselective fisheries deplete entire predator functional groups. In other cases, simultaneous exploitation of predator and prey can inhibit prey responses. Explicit consideration of anthropogenic modifications to oceanic foodwebs should help inform predictions about trophic control. 6. Synthesis and applications. Oceanic top-down control can have important socio-economic, conservation, and management implications as

  2. Efficacy of PTX3 and Posaconazole Combination in a Rat Model of Invasive Pulmonary Aspergillosis

    PubMed Central

    Sousa, Vitor L.; Gaziano, Roberta; Pacello, M. Lucrezia; Arseni, Brunilde; Aurisicchio, Luigi; De Santis, Rita; Salvatori, Giovanni

    2014-01-01

    Posaconazole is currently used for the prophylaxis of invasive pulmonary aspergillosis (IPA). Limitations to posaconazole usage are drug-drug interactions and side effects. PTX3 is an innate immunity glycoprotein with opsonic activity, proven to be protective in IPA animal models. This study investigated the combination of posaconazole with PTX3. The results indicate synergy between PTX3 and posaconazole against aspergillosis, suggesting that a combination of reduced doses of posaconazole with the immune response enhancer PTX3 might represent a treatment option with a higher therapeutic index than posaconazole. PMID:25070103

  3. Efficacy of PTX3 and posaconazole combination in a rat model of invasive pulmonary aspergillosis.

    PubMed

    Marra, Emanuele; Sousa, Vitor L; Gaziano, Roberta; Pacello, M Lucrezia; Arseni, Brunilde; Aurisicchio, Luigi; De Santis, Rita; Salvatori, Giovanni

    2014-10-01

    Posaconazole is currently used for the prophylaxis of invasive pulmonary aspergillosis (IPA). Limitations to posaconazole usage are drug-drug interactions and side effects. PTX3 is an innate immunity glycoprotein with opsonic activity, proven to be protective in IPA animal models. This study investigated the combination of posaconazole with PTX3. The results indicate synergy between PTX3 and posaconazole against aspergillosis, suggesting that a combination of reduced doses of posaconazole with the immune response enhancer PTX3 might represent a treatment option with a higher therapeutic index than posaconazole.

  4. Bioinsecticide-predator interactions: azadirachtin behavioral and reproductive impairment of the coconut mite predator Neoseiulus baraki.

    PubMed

    Lima, Debora B; Melo, José Wagner S; Guedes, Nelsa Maria P; Gontijo, Lessando M; Guedes, Raul Narciso C; Gondim, Manoel Guedes C

    2015-01-01

    Synthetic pesticide use has been the dominant form of pest control since the 1940s. However, biopesticides are emerging as sustainable pest control alternatives, with prevailing use in organic agricultural production systems. Foremost among botanical biopesticides is the limonoid azadirachtin, whose perceived environmental safety has come under debate and scrutiny in recent years. Coconut production, particularly organic coconut production, is one of the agricultural systems in which azadirachtin is used as a primary method of pest control for the management of the invasive coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae). The management of this mite species also greatly benefits from predation by Neoseiulus baraki (Athias-Henriot) (Acari: Phytoseiidae). Here, we assessed the potential behavioral impacts of azadirachtin on the coconut mite predator, N. baraki. We explored the effects of this biopesticide on overall predator activity, female searching time, and mating behavior and fecundity. Azadirachtin impairs the overall activity of the predator, reducing it to nearly half; however, female searching was not affected. In contrast, mating behavior was compromised by azadirachtin exposure particularly when male predators were exposed to the biopesticide. Consequently, predator fecundity was also compromised by azadirachtin, furthering doubts about its environmental safety and selectivity towards biological control agents.

  5. Bioinsecticide-Predator Interactions: Azadirachtin Behavioral and Reproductive Impairment of the Coconut Mite Predator Neoseiulus baraki

    PubMed Central

    Lima, Debora B.; Melo, José Wagner S.; Guedes, Nelsa Maria P.; Gontijo, Lessando M.; Guedes, Raul Narciso C.; Gondim, Manoel Guedes C.

    2015-01-01

    Synthetic pesticide use has been the dominant form of pest control since the 1940s. However, biopesticides are emerging as sustainable pest control alternatives, with prevailing use in organic agricultural production systems. Foremost among botanical biopesticides is the limonoid azadirachtin, whose perceived environmental safety has come under debate and scrutiny in recent years. Coconut production, particularly organic coconut production, is one of the agricultural systems in which azadirachtin is used as a primary method of pest control for the management of the invasive coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae). The management of this mite species also greatly benefits from predation by Neoseiulus baraki (Athias-Henriot) (Acari: Phytoseiidae). Here, we assessed the potential behavioral impacts of azadirachtin on the coconut mite predator, N. baraki. We explored the effects of this biopesticide on overall predator activity, female searching time, and mating behavior and fecundity. Azadirachtin impairs the overall activity of the predator, reducing it to nearly half; however, female searching was not affected. In contrast, mating behavior was compromised by azadirachtin exposure particularly when male predators were exposed to the biopesticide. Consequently, predator fecundity was also compromised by azadirachtin, furthering doubts about its environmental safety and selectivity towards biological control agents. PMID:25679393

  6. Predator richness has no effect in a diverse marine food web.

    PubMed

    O'Connor, Mary I; Bruno, John F

    2009-07-01

    1. In many ecosystems, predator abundance, composition and diversity vary naturally among seasons and habitats. In addition, predator assemblages are changing due to overharvesting, habitat destruction and species invasions. 2. Predator species composition and richness can influence prey community structure and these effects can cascade to influence plant abundance and composition. 3. To test the effects of predator presence, composition and species richness on prey abundance, species richness and composition, we conducted three experiments in a subtidal marine food web. Experimental food webs were drawn from species pools of 5-7 predator species, 19-52 prey species, benthic micro-algae and 5 macro-algae. 4. Predators reduced prey abundance in the mesocosm experiment, but this effect was diminished or absent in field experiments. Predator species differed in their effects on prey, but we found no effect of predator richness (via complementarity or selection) on any aspect of prey community structure. 5. The absence of a predator richness effect could be due to several factors including potentially opposing effects of individual predator species, intraguild predation, or greater importance of colonization relative to competition in structuring prey assemblages. Although predators can have strong top-down effects in this system, selection or resource-use complementarity among predators do not affect prey community structure.

  7. Predator identity can explain nest predation patterns. Chapter 11

    Treesearch

    Jennifer L. Reidy; Frank R., III Thompson

    2012-01-01

    Knowledge of dominant predators is necessary to identify predation patterns and mitigate losses to nest predation, especially for endangered songbirds. We monitored songbird nests with timelapse infrared video cameras at Fort Hood Military Reservation, Texas, from 1997 to 2002 and 2005, and in Austin, Texas, during 2005, 2006, 2008, and 2009. Predation was the most...

  8. Capsaicin-induced mucus secretion in rat airways assessed in vivo and non-invasively by magnetic resonance imaging

    PubMed Central

    Karmouty-Quintana, H; Cannet, C; Sugar, R; Fozard, J R; Page, C P; Beckmann, N

    2007-01-01

    Background and purpose: An up-regulation of the sensory neural pathways in the lung has been implicated in asthma and chronic obstructive pulmonary disease (COPD) and is thought to contribute to mucus hypersecretion, an essential feature of both diseases. The aim of this study was to assess non-invasively the acute effects (up to 60 min) of sensory nerve stimulation by capsaicin in the lung, using magnetic resonance imaging (MRI). Experimental approach: Male Brown Norway rats were imaged prior to and 10, 30 and 60 min after intra-tracheal challenge with capsaicin (30 μgkg−1) or vehicle (0.5% ethanol solution). In subsequent studies, pre-treatment with the transient receptor potential vanilloid (TRPV)-1 antagonist, capsazepine; the dual neurokinin (NK) 1 and NK2 receptor antagonist, DNK333 and the mast cell stabilizer, di-sodium cromoglycate (DSCG) was used to modulate the effects of capsaicin. Key results: Diffuse fluid signals were detected by MRI in the lung as early as 10 min after capsaicin, remaining constant 30 and 60 min after treatment. Broncho-alveolar lavage (BAL) fluid analysis performed 60 min after capsaicin revealed increased mucin concentration. Capsazepine (3.5 mgkg−1), DNK333 (10 mgkg−1) but not DSCG (10 mgkg−1) administered prophylactically were able to block the effect of capsaicin in the airways. Conclusions and implications: These observations suggest that the fluid signals detected by MRI after capsaicin administration reflected predominantly the release of mucus following activation of sensory nerves. They point to the opportunity of non-invasively assessing with MRI the influence of neuronal mechanisms in animal models of asthma and COPD. PMID:17351665

  9. Overexpression of protein kinase C-zeta (PKC-zeta) inhibits invasive and metastatic abilities of Dunning R-3327 MAT-LyLu rat prostate cancer cells.

    PubMed

    Powell, C T; Gschwend, J E; Fair, W R; Brittis, N J; Stec, D; Huryk, R

    1996-09-15

    Previously, we reported that protein kinase C (PKC)-zeta mRNA levels are reduced markedly in metastatic Dunning R-3327 rat prostate tumors relative to the nonmetastatic Dunning H tumor and normal rat prostate (C.T. Powell et al., Cell Growth & Differ., 5: 143-149, 1994). To examine the effect of PKC-zeta on metastatic and invasive abilities of an aggressive Dunning R-3327 cell line, we generated stably transfected clones of MAT-LyLu cells that overexpress active PKC-zeta. PKC-zeta-overexpressing MAT-LyLu cells exhibited tumorigenicity and growth rates in syngeneic rats similar to those of MAT-LyLu cells transfected with vector alone or untransfected MAT-LyLu. However, nine independent clones of PKC-zeta-expressing cells exhibited an average 2-fold lower tendency to metastasize to lungs relative to vector-transfected MAT-LyLu cell clones, with about 2-fold and 4.5-fold fewer metastases per rat in two separate protocols. In addition, the ability of four PKC-zeta overexpressing MAT-LyLu clones to invade through Matrigel in a Boyden chamber assay was reduced an average of 12-fold relative to three vector-transfected clones. These results indicate that increased PKC-zeta expression can substantially suppress invasion and metastasis by an aggressive rat prostate tumor.

  10. Effect of PTX3 and Voriconazole Combination in a Rat Model of Invasive Pulmonary Aspergillosis

    PubMed Central

    Lo Giudice, Pietro; Campo, Silvia; De Santis, Rita

    2012-01-01

    This study evaluated the pharmacological activity of PTX3, administered in combination with voriconazole, in a rat model of pulmonary aspergillosis. The data indicated additive therapeutic activities of these compounds, as demonstrated by the amelioration of respiratory function changes, reduction of lung fungal burden, and increased survival. Overall, we provide clear evidence that the combination of PTX3 with a suboptimal dose of voriconazole might represent a therapeutic option under those clinical conditions where the use of voriconazole alone is not warranted for efficacy and tolerability reasons. PMID:23006752

  11. Endovascular trophoblast invasion and associated structural changes in uterine spiral arteries of the pregnant rat.

    PubMed

    Caluwaerts, S; Vercruysse, L; Luyten, C; Pijnenborg, R

    2005-08-01

    The involvement of endovascular trophoblast in fibrinoid deposition, replacement of the endothelium and vascular smooth muscle breakdown is studied in spiral arteries of the mesometrial triangle from day 15 to day 21 of rat pregnancy, by examining arterial cross sections after staining for cytokeratin, PAS, CD31 and alpha-actin. From day 15 to day 18 of pregnancy, fibrinoid deposition underneath the endovascular trophoblast increases gradually, whereas the amount of endovascular trophoblast in invaded arteries remains constant. CD31 staining is significantly reduced in sub-ET (= underlying the endovascular trophoblast) as compared to extra-ET (= outside the endovascular trophoblast) and no-ET (= non-invaded arterial sections) at each time-point of pregnancy examined (P < 0.005 and P < 0.0005 at each day of pregnancy), whereas alpha-actin staining is reduced both in sub-ET and in extra-ET as compared to no-ET. During pregnancy, CD31 staining in sub-ET initially declines, but increases significantly on day 21 (P < 0.001 versus d20) suggesting re-endothelialization of the vascular wall. In conclusion, changes in spiral arteries of pregnant rats reveal striking similarities with physiological changes seen in human pregnancy, thus emphasizing the usefulness of this species as an experimental model for studying normal and complicated pregnancies in humans.

  12. Non-invasive transcranial stimulation of rat abducens nerve by focused ultrasound

    PubMed Central

    Kim, Hyungmin; Taghados, Seyed Javid; Fischer, Krisztina; Maeng, Lee-So; Park, Shinsuk; Yoo, Seung-Schik

    2012-01-01

    Non-pharmacological and non-surgical transcranial modulation of the nerve function may provide new opportunities in evaluation and treatment of cranial nerve diseases. This study investigates the possibility of using low-intensity transcranial focused ultrasound (FUS) to selectively stimulate the rat abducens nerve located above the base of the skull. FUS (frequencies of 350 kHz and 650 kHz) operating in a pulsed mode was applied to the abducens nerve of Sprague-Dawley rats under stereotactic guidance. The abductive eyeball movement ipsilateral to the side of sonication was observed at 350 kHz, using the 0.36 msec tone burst duration (TBD), 1.5 kHz pulse repetition frequency (PRF), and the overall sonication duration of 200 msec. Histological and behavioral monitoring showed no signs of disruption in the blood brain barrier (BBB) as well as no damage to the nerves and adjacent brain tissue resulting from the sonication. As a novel functional neuro-modulatory modality, the pulsed application of FUS has potential in diagnostic and therapeutic applications in diseases of the peripheral nervous system. PMID:22763009

  13. A non-invasive method to produce pressure ulcers of varying severity in a spinal cord-injured rat model.

    PubMed

    Ahmed, A K; Goodwin, C R; Sarabia-Estrada, R; Lay, F; Ansari, A M; Steenbergen, C; Pang, C; Cohen, R; Born, L J; Matsangos, A E; Ng, C; Marti, G P; Abu-Bonsrah, N; Phillips, N A; Suk, I; Sciubba, D M; Harmon, J W

    2016-12-01

    Experimental study. The objective of this study was to establish a non-invasive model to produce pressure ulcers of varying severity in animals with spinal cord injury (SCI). The study was conducted at the Johns Hopkins Hospital in Baltimore, Maryland, USA. A mid-thoracic (T7-T9) left hemisection was performed on Sprague-Dawley rats. At 7 days post SCI, rats received varying degrees of pressure on the left posterior thigh region. Laser Doppler Flowmetry was used to record blood flow. Animals were killed 12 days after SCI. A cardiac puncture was performed for blood chemistry, and full-thickness tissue was harvested for histology. Doppler blood flow after SCI prior to pressure application was 237.808±16.175 PFUs at day 7. Following pressure application, there was a statistically significant decrease in blood flow in all pressure-applied groups in comparison with controls with a mean perfusion of 118.361±18.223 (P<0.001). White blood cell counts and creatine kinase for each group were statistically significant from the control group (P=0.0107 and P=0.0028, respectively). We have created a novel animal model of pressure ulcer formation in the setting of a SCI. Histological analysis revealed different stages of injury corresponding to the amount of pressure the animals were exposed to with decreased blood flow immediately after the insult along with a subsequent marked increase in blood flow the next day, conducive to an ischemia-reperfusion injury (IRI) and a possible inflammatory response following tissue injury. Following ischemia and hypoxia secondary to microcirculation impairment, free radicals generate lipid peroxidation, leading to ischemic tissue damage. Future studies should be aimed at measuring free radicals during this period of increased blood flow, following tissue ischemia.

  14. The Predator-Prey Relationship

    ERIC Educational Resources Information Center

    Mitchell, Charles W.

    1977-01-01

    Many children develop a mistaken attitude about the predator-prey relationship in the ecosystem. Fairy tales portray the predator as evil or worthless. This article attempts to clarify the role of the predator by giving numerous examples of the value of predators. (MA)

  15. Predator interference and stability of predator-prey dynamics.

    PubMed

    Přibylová, Lenka; Berec, Luděk

    2015-08-01

    Predator interference, that is, a decline in the per predator consumption rate as predator density increases, is generally thought to promote predator-prey stability. Indeed, this has been demonstrated in many theoretical studies on predator-prey dynamics. In virtually all of these studies, the stabilization role is demonstrated as a weakening of the paradox of enrichment. With predator interference, stable limit cycles that appear as a result of environmental enrichment occur for higher values of the environmental carrying capacity of prey, and even a complete absence of the limit cycles can happen. Here we study predator-prey dynamics using the Rosenzweig-MacArthur-like model in which the Holling type II functional response has been replaced by a predator-dependent family which generalizes many of the commonly used descriptions of predator interference. By means of a bifurcation analysis we show that sufficiently strong predator interference may bring about another stabilizing mechanism. In particular, hysteresis combined with (dis)appearance of stable limit cycles imply abrupt increases in both the prey and predator densities and enhanced persistence and resilience of the predator-prey system. We encourage refitting the previously collected data on predator consumption rates as well as for conducting further predation experiments to see what functional response from the explored family is the most appropriate.

  16. Influence of diet conditions on predation response of a predatory mite to a polyphagous insect pest

    USDA-ARS?s Scientific Manuscript database

    Chilli thrips, Scirtothrips dorsalis Hood (Thysanoptera: Thripidae), an invasive polyphagous species, is an economically important pest. A modified standard petri dish assay method was employed to examine the functional response and predation capacity of predatory mites (Amblyseius swirskii Anthias-...

  17. Linking non-invasive parametric MRI with invasive physiological measurements (MR-PHYSIOL): towards a hybrid and integrated approach for investigation of acute kidney injury in rats.

    PubMed

    Pohlmann, A; Cantow, K; Hentschel, J; Arakelyan, K; Ladwig, M; Flemming, B; Hoff, U; Persson, P B; Seeliger, E; Niendorf, T

    2013-04-01

    Acute kidney injury of various origins shares a common link in the pathophysiological chain of events: imbalance between renal medullary oxygen delivery and oxygen demand. For in vivo assessment of kidney haemodynamics and oxygenation in animals, quantitative but invasive physiological methods are established. A very limited number of studies attempted to link these invasive methods with parametric Magnetic Resonance Imaging (MRI) of the kidney. Moreover, the validity of parametric MRI (pMRI) as a surrogate marker for renal tissue perfusion and renal oxygenation has not been systematically examined yet. For this reason, we set out to combine invasive techniques and non-invasive MRI in an integrated hybrid setup (MR-PHYSIOL) with the ultimate goal to calibrate, monitor and interpret parametric MR and physiological parameters by means of standardized interventions. Here we present a first report on the current status of this multi-modality approach. For this purpose, we first highlight key characteristics of renal perfusion and oxygenation. Second, concepts for in vivo characterization of renal perfusion and oxygenation are surveyed together with the capabilities of MRI for probing blood oxygenation-dependent tissue stages. Practical concerns evoked by the use of strong magnetic fields in MRI and interferences between MRI and invasive physiological probes are discussed. Technical solutions that balance the needs of in vivo physiological measurements together with the constraints dictated by small bore MR scanners are presented. An early implementation of the integrated MR-PHYSIOL approach is demonstrated including brief interventions of hypoxia and hyperoxia. Acta Physiologica © 2013 Scandinavian Physiological Society.

  18. Development of a Non-Invasive Biomonitoring Approach to Determine Exposure to the Organophosphorus Insecticide Chlorpyrifos in Rat Saliva

    SciTech Connect

    Timchalk, Chuck; Campbell, James A.; Liu, Guodong; Lin, Yuehe; Kousba, Ahmed A.

    2007-03-01

    Abstract Non-invasive biomonitoring approaches are being developed using reliable portable analytical systems to quantify dosimetry utilizing readily obtainable body fluids, such as saliva. In the current study, rats were given single oral gavage doses (1, 10 or 50 mg/kg) of the insecticide chlorpyrifos (CPF), saliva and blood were collected from groups of animals (4/time-point) at 3, 6, and 12 hr post-dosing, and the samples were analyzed for the CPF metabolite trichlorpyridinol (TCP). Trichlorpyridinol was detected in both blood and saliva at all doses and the TCP concentration in blood exceeded saliva, although the kinetics in blood and saliva were comparable. A physiologically based pharmacokinetic and pharmacodynamic (PBPK/PD) model for CPF incorporated a compartment model to describe the time-course of TCP in blood and saliva. The model adequately simulated the experimental results over the dose ranges evaluated. A rapid and sensitive sequential injection (SI) electrochemical immunoassay was developed to monitor TCP, and the reported detection limit for TCP in water was 6 ng/L. Computer model simulation in the range of the Allowable Daily Intake (ADI) or Reference Dose (RfD) for CPF (0.01-0.003 mg/kg/day) suggest that the electrochemical immunoassay had adequate sensitivity to detect and quantify TCP in saliva at these low exposure levels. To validate this approach further studies are needed to more fully understand the pharmacokinetics of CPF and TCP excretion in saliva. The utilization of saliva as a biomonitoring matrix, coupled to real-time quantitation and PBPK/PD modeling represents a novel approach with broad application for evaluating both occupational and environmental exposures to insecticides.

  19. Non-invasive detection and quantification of brain microvascular deficits by near-infrared spectroscopy in a rat model of Vascular Cognitive Impairment

    NASA Astrophysics Data System (ADS)

    Hallacoglu, Bertan; Sassaroli, Angelo M.; Rosenberg, Irwin H.; Troen, Aron; Fantini, Sergio

    2011-02-01

    Structural abnormalities in brain microvasculature are commonly associated with Alzheimer's Disease and other dementias. However, the extent to which structural microvascular abnormalities cause functional impairments in brain circulation and thereby to cognitive impairment is unclear. Non-invasive, near-infrared spectroscopy (NIRS) methods can be used to determine the absolute hemoglobin concentration and saturation in brain tissue, from which additional parameters such as cerebral blood volume (a theoretical correlate of brain microvascular density) can be derived. Validating such NIRS parameters in animal models, and understanding their relationship to cognitive function is an important step in the ultimate application of these methods to humans. To this end we applied a non-invasive multidistance NIRS method to determine the absolute concentration and saturation of cerebral hemoglobin in rat, by separately measuring absorption and reduced scattering coefficients without relying on pre- or post-correction factors. We applied this method to study brain circulation in folate deficient rats, which express brain microvascular pathology1 and which we have shown to develop cognitive impairment.2 We found absolute brain hemoglobin concentration ([HbT]) and oxygen saturation (StO2) to be significantly lower in folate deficient rats (n=6) with respect to control rats (n=5) (for [HbT]: 73+/-10 μM vs. 95+/-14 μM for StO2: 55%+/-7% vs. 66% +/-4%), implicating microvascular pathology and diminished oxygen delivery as a mechanism of cognitive impairment. More generally, our study highlights how noninvasive, absolute NIRS measurements can provide unique insight into the pathophysiology of Vascular Cognitive Impairment. Applying this method to this and other rat models of cognitive impairment will help to validate physiologically meaningful NIRS parameters for the ultimate goal of studying cerebral microvascular disease and cognitive decline in humans.

  20. Efficacy of aerosolized amphotericin B desoxycholate and liposomal amphotericin B in the treatment of invasive pulmonary aspergillosis in severely immunocompromised rats.

    PubMed

    Ruijgrok, E J; Vulto, A G; Van Etten, E W

    2001-07-01

    The effects of treatment with aerosolized amphotericin B desoxycholate and aerosolized liposomal amphotericin B were evaluated in severely immunosuppressed rats with invasive pulmonary aspergillosis. Aerosol treatment with amphotericin B desoxycholate consisted of a single dose (60 min) with amphotericin B concentrations in the nebulizer reservoir of 1, 2 and 4 mg/mL, respectively. For liposomal amphotericin B, aerosol treatment consisted of single, double or quadruple doses with a nebulizer reservoir concentration of 4 mg/mL of amphotericin B. Treatment, started at 30 h after inoculation, with aerosolized amphotericin B desoxycholate (nebulizer reservoir concentration 2 mg/mL) significantly prolonged survival of rats as compared with placebo-treated rats, whereas treatment with aerosolized amphotericin B desoxycholate with nebulizer reservoir concentration of 1 or 4 mg/mL did not have a significant effect on survival. Treatment with aerosolized liposomal amphotericin B significantly prolonged survival with all treatment regimens when compared with placebo-treated animals. Aerosol treatment did not prevent dissemination of the infection. The effects of amphotericin B desoxycholate and liposomal amphotericin B on pulmonary surfactant function were also evaluated in vitro. Amphotericin B desoxycholate inhibited surfactant function in a dose-dependent fashion. Liposomal amphotericin B had no detrimental effect on surface activity of surfactant. These results indicate that aerosol administration of amphotericin B, especially the liposomal formulation, could be an additional approach to optimizing treatment of invasive pulmonary aspergillosis.

  1. Behavioural responses of feral and domestic guppies (Poecilia reticulata) to predators and their cues.

    PubMed

    Swaney, William T; Cabrera-Álvarez, María J; Reader, Simon M

    2015-09-01

    Predation is an important factor during adaptation to novel environments, and the feralisation of introduced domestic species often involves responding appropriately to allopatric predators despite a background of domestication and inbreeding. Twenty years ago, domestic guppies were introduced to a semi-natural environment at Burgers' Zoo in the Netherlands, where they have since been exposed to avian predation. We compared predation-linked behaviours in this feral population and in domestic guppies akin to the original founders. We found that both populations responded to a novel predator and to conspecific alarm cues. However, shoaling, an important anti-predator behaviour, was higher among feral guppies both at baseline and when exposed to the novel predator. We did not observe a linked suite of anti-predator behaviours across shoaling, predator inspection, alarm substance sensitivity and boldness, suggesting that these responses may be decoupled from one another depending on local predation regimes. As we compared two populations, we cannot identify the causal factors determining population differences, however, our results do suggest that shoaling is either a particularly consequential anti-predator adaptation or the most labile of the behaviours we tested. Finally, the behavioural adaptability of domestic guppies may help to explain their success as an invasive species.

  2. Exposure to a Predator Scent Induces Chronic Behavioral Changes in Rats Previously Exposed to Low-level Blast: Implications for the Relationship of Blast-Related TBI to PTSD

    PubMed Central

    Perez-Garcia, Georgina; Gama Sosa, Miguel A.; De Gasperi, Rita; Lashof-Sullivan, Margaret; Maudlin-Jeronimo, Eric; Stone, James R.; Haghighi, Fatemeh; Ahlers, Stephen T.; Elder, Gregory A.

    2016-01-01

    Blast-related mild traumatic brain injury (mTBI) has been unfortunately common in veterans who served in the recent conflicts in Iraq and Afghanistan. The postconcussion syndrome associated with these mTBIs has frequently appeared in combination with post-traumatic stress disorder (PTSD). The presence of PTSD has complicated diagnosis, since clinically, PTSD and the postconcussion syndrome of mTBI have many overlapping symptoms. In particular, establishing how much of the symptom complex can be attributed to the psychological trauma associated with PTSD in contrast to the physical injury of traumatic brain injury has proven difficult. Indeed, some have suggested that much of what is now being called blast-related postconcussion syndrome is better explained by PTSD. The relationship between the postconcussion syndrome of mTBI and PTSD is complex. Association of the two disorders might be viewed as additive effects of independent psychological and physical traumas suffered in a war zone. However, we previously found that rats exposed to repetitive low-level blast exposure in the absence of a psychological stressor developed a variety of anxiety and PTSD-related behavioral traits that were present months following the last blast exposure. Here, we show that a single predator scent challenge delivered 8 months after the last blast exposure induces chronic anxiety related changes in blast-exposed rats that are still present 45 days later. These observations suggest that in addition to independently inducing PTSD-related traits, blast exposure sensitizes the brain to react abnormally to a subsequent psychological stressor. These studies have implications for conceptualizing the relationship between blast-related mTBI and PTSD and suggest that blast-related mTBI in humans may predispose to the later development of PTSD in reaction to subsequent psychological stressors. PMID:27803688

  3. Exposure to a Predator Scent Induces Chronic Behavioral Changes in Rats Previously Exposed to Low-level Blast: Implications for the Relationship of Blast-Related TBI to PTSD.

    PubMed

    Perez-Garcia, Georgina; Gama Sosa, Miguel A; De Gasperi, Rita; Lashof-Sullivan, Margaret; Maudlin-Jeronimo, Eric; Stone, James R; Haghighi, Fatemeh; Ahlers, Stephen T; Elder, Gregory A

    2016-01-01

    Blast-related mild traumatic brain injury (mTBI) has been unfortunately common in veterans who served in the recent conflicts in Iraq and Afghanistan. The postconcussion syndrome associated with these mTBIs has frequently appeared in combination with post-traumatic stress disorder (PTSD). The presence of PTSD has complicated diagnosis, since clinically, PTSD and the postconcussion syndrome of mTBI have many overlapping symptoms. In particular, establishing how much of the symptom complex can be attributed to the psychological trauma associated with PTSD in contrast to the physical injury of traumatic brain injury has proven difficult. Indeed, some have suggested that much of what is now being called blast-related postconcussion syndrome is better explained by PTSD. The relationship between the postconcussion syndrome of mTBI and PTSD is complex. Association of the two disorders might be viewed as additive effects of independent psychological and physical traumas suffered in a war zone. However, we previously found that rats exposed to repetitive low-level blast exposure in the absence of a psychological stressor developed a variety of anxiety and PTSD-related behavioral traits that were present months following the last blast exposure. Here, we show that a single predator scent challenge delivered 8 months after the last blast exposure induces chronic anxiety related changes in blast-exposed rats that are still present 45 days later. These observations suggest that in addition to independently inducing PTSD-related traits, blast exposure sensitizes the brain to react abnormally to a subsequent psychological stressor. These studies have implications for conceptualizing the relationship between blast-related mTBI and PTSD and suggest that blast-related mTBI in humans may predispose to the later development of PTSD in reaction to subsequent psychological stressors.

  4. Production of coleopteran predators

    USDA-ARS?s Scientific Manuscript database

    The research literature reveals moderate advances in technology to produce coleopteran predators especially lady beetles. We have several factitious prey/foods and insect-free artificial diets for polyphagous species. It might be more time and cost effective to develop artificial diet-based producti...

  5. Production of heteropteran predators

    USDA-ARS?s Scientific Manuscript database

    This chapter treats several key aspects of rearing procedures for predatory bugs. The value of natural, factitious, and artificial foods for the major species used in biological control is reviewed. Whereas several types of factitious foods are routinely used in the production of heteropteran predat...

  6. Prey-predator system with parental care for predators.

    PubMed

    Wang, Wendi; Takeuchi, Yasuhiro; Saito, Yasuhisa; Nakaoka, Shinji

    2006-08-07

    A stage structure is incorporated into a prey-predator model in which predators are split into immature predators and mature predators. It is assumed that immature predators are raised by their parents in the sense that they cannot catch the prey and their foods are provided by parents. Further, it is assumed that the maturation rate of immature predators is a function of the food availability for one immature individual. It is found that the model admits periodic solutions which are produced from the stage structure. Further, it is shown that two stability switches of positive equilibria may occur due to the transition rate incorporating the influence of nutrient, and that the enrichment of adult predators may lead to the catastrophe of the ecological system.

  7. Hierarchical levels of seed predation variation by introduced beetles on an endemic Mediterranean palm.

    PubMed

    Rodríguez, Marta; Delibes, Miguel; Fedriani, José M

    2014-01-01

    Seed predators can limit plant recruitment and thus profoundly impinge the dynamics of plant populations, especially when diverse seed predators (e.g., native and introduced) attack particular plant populations. Surprisingly, however, we know little concerning the potential hierarchy of spatial scales (e.g., region, population, patch) and coupled ecological correlates governing variation in the overall impact that native and introduced seed predators have on plant populations. We investigated several spatial scales and ecological correlates of pre-dispersal seed predation by invasive borer beetles in Chamaerops humilis (Arecaceae), a charismatic endemic palm of the Mediteranean basin. To this end, we considered 13 palm populations (115 palms) within four geographical regions of the Iberian Peninsula. The observed interregional differences in percentages of seed predation by invasive beetles were not significant likely because of considerable variation among populations within regions. Among population variation in seed predation was largely related to level of human impact. In general, levels of seed predation were several folds higher in human-altered populations than in natural populations. Within populations, seed predation declined significantly with the increase in amount of persisting fruit pulp, which acted as a barrier against seed predators. Our results revealed that a native species (a palm) is affected by the introduction of related species because of the concurrent introduction of seed predators that feed on both the introduced and native palms. We also show how the impact of invasive seed predators on plants can vary across a hierarchy of levels ranging from variation among individuals within local populations to large scale regional divergences.

  8. Predator diversity, intraguild predation, and indirect effects drive parasite transmission.

    PubMed

    Rohr, Jason R; Civitello, David J; Crumrine, Patrick W; Halstead, Neal T; Miller, Andrew D; Schotthoefer, Anna M; Stenoien, Carl; Johnson, Lucinda B; Beasley, Val R

    2015-03-10

    Humans are altering biodiversity globally and infectious diseases are on the rise; thus, there is interest in understanding how changes to biodiversity affect disease. Here, we explore how predator diversity shapes parasite transmission. In a mesocosm experiment that manipulated predator (larval dragonflies and damselflies) density and diversity, non-intraguild (non-IG) predators that only consume free-living cercariae (parasitic trematodes) reduced metacercarial infections in tadpoles, whereas intraguild (IG) predators that consume both parasites and tadpole hosts did not. This likely occurred because IG predators reduced tadpole densities and anticercarial behaviors, increasing per capita exposure rates of the surviving tadpoles (i.e., via density- and trait-mediated effects) despite the consumption of parasites. A mathematical model demonstrated that non-IG predators reduce macroparasite infections, but IG predation weakens this "dilution effect" and can even amplify parasite burdens. Consistent with the experiment and model, a wetland survey revealed that the diversity of IG predators was unrelated to metacercarial burdens in amphibians, but the diversity of non-IG predators was negatively correlated with infections. These results are strikingly similar to generalities that have emerged from the predator diversity-pest biocontrol literature, suggesting that there may be general mechanisms for pest control and that biocontrol research might inform disease management and vice versa. In summary, we identified a general trait of predators--where they fall on an IG predation continuum--that predicts their ability to reduce infections and possibly pests in general. Consequently, managing assemblages of predators represents an underused tool for the management of human and wildlife diseases and pest populations.

  9. Granivory of invasive, naturalized, and native plants in communities differentially susceptible to invasion.

    PubMed

    Connolly, B M; Pearson, D E; Mack, R N

    2014-07-01

    Seed predation is an important biotic filter that can influence abundance and spatial distributions of native species through differential effects on recruitment. This filter may also influence the relative abundance of nonnative plants within habitats and the communities' susceptibility to invasion via differences in granivore identity, abundance, and food preference. We evaluated the effect of postdispersal seed predators on the establishment of invasive, naturalized, and native species within and between adjacent forest and steppe communities of eastern Washington, USA that differ in severity of plant invasion. Seed removal from trays placed within guild-specific exclosures revealed that small mammals were the dominant seed predators in both forest and steppe. Seeds of invasive species (Bromus tectorum, Cirsium arvense) were removed significantly less than the seeds of native (Pseudoroegneria spicata, Balsamorhiza sagittata) and naturalized (Secale cereale, Centaurea cyanus) species. Seed predation limited seedling emergence and establishment in both communities in the absence of competition in a pattern reflecting natural plant abundance: S. cereale was most suppressed, B. tectorum was least suppressed, and P. spicata was suppressed at an intermediate level. Furthermore, seed predation reduced the residual seed bank for all species. Seed mass correlated with seed removal rates in the forest and their subsequent effects on plant recruitment; larger seeds were removed at higher rates than smaller seeds. Our vegetation surveys indicate higher densities and canopy cover of nonnative species occur in the steppe compared with the forest understory, suggesting the steppe may be more susceptible to invasion. Seed predation alone, however, did not result in significant differences in establishment for any species between these communities, presumably due to similar total small-mammal abundance between communities. Consequently, preferential seed predation by small

  10. Predator-prey system with strong Allee effect in prey.

    PubMed

    Wang, Jinfeng; Shi, Junping; Wei, Junjie

    2011-03-01

    Global bifurcation analysis of a class of general predator-prey models with a strong Allee effect in prey population is given in details. We show the existence of a point-to-point heteroclinic orbit loop, consider the Hopf bifurcation, and prove the existence/uniqueness and the nonexistence of limit cycle for appropriate range of parameters. For a unique parameter value, a threshold curve separates the overexploitation and coexistence (successful invasion of predator) regions of initial conditions. Our rigorous results justify some recent ecological observations, and practical ecological examples are used to demonstrate our theoretical work.

  11. Selective predation and productivity jointly drive complex behavior in host-parasite systems.

    PubMed

    Hall, Spencer R; Duffy, Meghan A; Cáceres, Carla E

    2005-01-01

    Successful invasion of a parasite into a host population and resulting host-parasite dynamics can depend crucially on other members of a host's community such as predators. We do not fully understand how predation intensity and selectivity shape host-parasite dynamics because the interplay between predator density, predator foraging behavior, and ecosystem productivity remains incompletely explored. By modifying a standard susceptible-infected model, we show how productivity can modulate complex behavior induced by saturating and selective foraging behavior of predators in an otherwise stable host-parasite system. When predators strongly prefer parasitized hosts, the host-parasite system can oscillate, but predators can also create alternative stable states, Allee effects, and catastrophic extinction of parasites. In the latter three cases, parasites have difficulty invading and/or persisting in ecosystems. When predators are intermediately selective, these more complex behaviors become less important, but the host-parasite system can switch from stable to oscillating and then back to stable states along a gradient of predator control. Surprisingly, at higher productivity, predators that neutrally select or avoid parasitized hosts can catalyze extinction of both hosts and parasites. Thus, synergy between two enemies can end disastrously for the host. Such diverse outcomes underscore the crucial importance of the community and ecosystem context in which host-parasite interactions occur.

  12. Rodent seed predation as a biotic filter influencing exotic plant abundance and distribution

    Treesearch

    D. E. Pearson; J. L. Hierro; M. Chiuffo; D. Villarreal

    2014-01-01

    Biotic resistance is commonly invoked to explain why many exotic plants fail to thrive in introduced ranges, but the role of seed predation as an invasion filter is understudied. Abiotic conditions may also influence plant populations and can interact with consumers to determine plant distributions, but how these factors jointly influence invasions is poorly understood...

  13. Efficacy and toxicity of a tropically stable lipid-based formulation of amphotericin B (iCo-010) in a rat model of invasive candidiasis.

    PubMed

    Ibrahim, Fady; Gershkovich, Pavel; Sivak, Olena; Wasan, Ellen K; Bartlett, Karen; Wasan, Kishor M

    2012-10-15

    The objective of this work was to assess the antifungal activity of a tropically stable formulation of amphotericin B (AmB) (iCo-010) over short period of treatment in a rat model of invasive candidiasis. The rats were infected with Candida albicans (ATCC 18804); 48 h later, the animals were assigned either to a control group, AmBisome(®) group (5 mg/kg QD), or iCo-010 groups (0.5, 1, 2.5, 5 and 10 mg/kg TID). The animals were treated for two days and then sacrificed 18 h following the completion of the treatment. The blood, liver, lungs, kidneys and spleen were harvested to assess the colony forming units in the samples. There was no significant difference in the reduction of the fungal burden in the organs between the AmBisome(®) and iCo-010 groups except in the spleen and liver. There was a linear correlation between the antifungal activity in renal tissues and the administered doses of iCo-010. The plasma creatinine levels were not significantly different among the control and all the treatment groups. Oral iCo-010 has high efficacy against invasive candidiasis in renal and pulmonary tissues. Longer treatment period than the two-days regimen should be considered for higher therapeutic efficacy of iCo-010 in all the tissues. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. A Comparison of Surgical Invasions for Spinal Nerve Ligation with or without Paraspinal Muscle Removal in a Rat Neuropathic Pain Model

    PubMed Central

    Huang, Yi-Gang; Zhang, Qing; Wu, Hao

    2016-01-01

    L5 spinal nerve ligation (SNL) in rats is one of the most popular models for studying neuropathic pain because of its high reproducibility. During the surgery, a part of the L5 paraspinal muscle is usually removed, which produces extra trauma and may potentially affect the physiological processes involved in neuropathic pain. To reduce the surgical trauma, the paraspinal muscle retraction was developed for exposure of the spinal nerve. The current study was aimed at comparing the surgical invasions between the L5 SNL models with paraspinal muscle removal or retraction. The results showed that both methods induced similar neuropathic pain behavior. However, the paraspinal muscle retraction group exhibited an average of 2.7 mg less blood loss than the muscle removal group. This group also showed a significantly lower increase in serum myoglobin and creatine phosphokinase levels on postoperative days 1 and 2, as well as a lower increase in interleukin-1β and interleukin-6 levels on postoperative day 1. The paraspinal muscle maintained normal morphological features following paraspinal muscle retraction. Our results indicate that the SNL rat model with paraspinal muscle retraction is a reliable physiological model that is reproducible, readily available, and less invasive than the model with muscle removal. PMID:27597970

  15. Non-Invasive In Vivo Imaging and Quantification of Tumor Growth and Metastasis in Rats Using Cells Expressing Far-Red Fluorescence Protein.

    PubMed

    Christensen, Jon; Vonwil, Daniel; Shastri, V Prasad

    2015-01-01

    Non-invasive in vivo imaging is emerging as an important tool for basic and preclinical research. Near-infrared (NIR) fluorescence dyes and probes have been used for non-invasive optical imaging since in the NIR region absorption and auto fluorescence by body tissue is low, thus permitting for greater penetration depths and high signal to noise ratio. Currently, cell tracking systems rely on labeling cells prior to injection or administering probes targeting the cell population of choice right before imaging. These approaches do not enable imaging of tumor growth, as the cell label is diluted during cell division. In this study we have developed cell lines stably expressing the far-red fluorescence protein E2-Crimson, thus enabling continuous detection and quantification of tumor growth. In a xenograft rat model, we show that E2-Crimson expressing cells can be detected over a 5 week period using optical imaging. Fluorescence intensities correlated with tumor volume and weight and allowed for a reliable and robust quantification of the entire tumor compartment. Using a novel injection regime, the seeding of MDA-MB-231 breast cancer cells in the lungs in a rat model was established and verified.

  16. Predator Avoidance in Extremophile Fish

    PubMed Central

    Bierbach, David; Schulte, Matthias; Herrmann, Nina; Zimmer, Claudia; Arias-Rodriguez, Lenin; Indy, Jeane Rimber; Riesch, Rüdiger; Plath, Martin

    2013-01-01

    Extreme habitats are often characterized by reduced predation pressures, thus representing refuges for the inhabiting species. The present study was designed to investigate predator avoidance of extremophile populations of Poecilia mexicana and P. sulphuraria that either live in hydrogen sulfide-rich (sulfidic) springs or cave habitats, both of which are known to have impoverished piscine predator regimes. Focal fishes that inhabited sulfidic springs showed slightly weaker avoidance reactions when presented with several naturally occurring predatory cichlids, but strongest differences to populations from non-sulfidic habitats were found in a decreased shoaling tendency with non-predatory swordtail (Xiphophorus hellerii) females. When comparing avoidance reactions between P. mexicana from a sulfidic cave (Cueva del Azufre) and the adjacent sulfidic surface creek (El Azufre), we found only slight differences in predator avoidance, but surface fish reacted much more strongly to the non-predatory cichlid Vieja bifasciata. Our third experiment was designed to disentangle learned from innate effects of predator recognition. We compared laboratory-reared (i.e., predator-naïve) and wild-caught (i.e., predator-experienced) individuals of P. mexicana from a non-sulfidic river and found no differences in their reaction towards the presented predators. Overall, our results indicate (1) that predator avoidance is still functional in extremophile Poecilia spp. and (2) that predator recognition and avoidance reactions have a strong genetic basis. PMID:25371337

  17. Predator diversity, intraguild predation, and indirect effects drive parasite transmission

    PubMed Central

    Rohr, Jason R.; Civitello, David J.; Crumrine, Patrick W.; Halstead, Neal T.; Miller, Andrew D.; Schotthoefer, Anna M.; Stenoien, Carl; Johnson, Lucinda B.; Beasley, Val R.

    2015-01-01

    Humans are altering biodiversity globally and infectious diseases are on the rise; thus, there is interest in understanding how changes to biodiversity affect disease. Here, we explore how predator diversity shapes parasite transmission. In a mesocosm experiment that manipulated predator (larval dragonflies and damselflies) density and diversity, non-intraguild (non-IG) predators that only consume free-living cercariae (parasitic trematodes) reduced metacercarial infections in tadpoles, whereas intraguild (IG) predators that consume both parasites and tadpole hosts did not. This likely occurred because IG predators reduced tadpole densities and anticercarial behaviors, increasing per capita exposure rates of the surviving tadpoles (i.e., via density- and trait-mediated effects) despite the consumption of parasites. A mathematical model demonstrated that non-IG predators reduce macroparasite infections, but IG predation weakens this “dilution effect” and can even amplify parasite burdens. Consistent with the experiment and model, a wetland survey revealed that the diversity of IG predators was unrelated to metacercarial burdens in amphibians, but the diversity of non-IG predators was negatively correlated with infections. These results are strikingly similar to generalities that have emerged from the predator diversity–pest biocontrol literature, suggesting that there may be general mechanisms for pest control and that biocontrol research might inform disease management and vice versa. In summary, we identified a general trait of predators—where they fall on an IG predation continuum—that predicts their ability to reduce infections and possibly pests in general. Consequently, managing assemblages of predators represents an underused tool for the management of human and wildlife diseases and pest populations. PMID:25713379

  18. Developments in the rat adjuvant arthritis model and its use in therapeutic evaluation of novel non-invasive treatment by SOD in Transfersomes.

    PubMed

    Simões, S I; Delgado, T C; Lopes, R M; Jesus, S; Ferreira, A A; Morais, J A; Cruz, M E M; Corvo, M L; Martins, M B F

    2005-03-21

    The aim of this study was firstly to refine a rat model of arthritis, the adjuvant arthritis (AA) model, by studying the time course of the disease, introducing new evaluation methods such as haematological and biochemical parameters in order to identify the main stages of the disease. An optimisation of treatment schedule and evaluation criteria was developed. This refinement provided novel non-invasive anti-inflammatory treatment of the AA with SOD by using mixed lipid vesicles specially developed for transdermal delivery, Transfersomes (Tfs), this being the second major aim. The time course of AA includes a first stage: 1 day after the disease induction, the induced paw volume more than doubled and the paw circumference increased by approx. 50%. Two weeks later, another stage occurred where the disease shifted from the local arthritis form towards polyarthritis: an additional increase of volume and circumference of the induced and non-induced paws, occurred. The animals also started to loose weight around day 14 after the disease induction. Radiographic observable lesions increased correspondingly. Treatment of animals, started at day 1 after induction, by epicutaneous application of SOD-Tfs showed that 1 mg SOD/kg body weight is more efficient than 0.66 mg SOD /kg body weight. As a positive control, SOD liposomes intravenously injected were used for comparison and confirmed the biological efficiency of epicutaneously applied SOD in Tfs. SOD solution and empty Tfs epicutaneously applied exerted no effect. In addition, epicutaneous application of SOD-Tfs used prophylactically was able to suppress the induced rat paw oedema. Radiographic images showed less joint lesions in SOD-Tfs treated animals in comparison with control and placebo treated rats. It was shown for the first time that SOD incorporated into Tfs and applied onto a skin area not necessarily close to the inflamed tissue is able to promote non-invasive treatment of induced arthritis.

  19. Cadmium-induced malignant transformation of rat liver cells: Potential key role and regulatory mechanism of altered apolipoprotein E expression in enhanced invasiveness.

    PubMed

    Suzuki, Masayo; Takeda, Shuso; Teraoka-Nishitani, Noriko; Yamagata, Akane; Tanaka, Takahiro; Sasaki, Marika; Yasuda, Natsuki; Oda, Makiko; Okano, Tatsuji; Yamahira, Kazuhiro; Nakamura, Yuta; Kobayashi, Takanobu; Kino, Katsuhito; Miyazawa, Hiroshi; Waalkes, Michael P; Takiguchi, Masufumi

    2017-05-01

    Cadmium is a transition metal that is classified as human carcinogen by the International Agency for Research on Cancer (IARC) with multiple target sites. Many studies using various model systems provide evidence of cadmium-induced malignancy formation in vivo or malignant cell transformation in vitro. Nonetheless, further studies are needed to completely understand the mechanisms of cadmium carcinogenicity. Our prior studies have utilized a rat liver epithelial cell line (TRL 1215) as a model for cadmium-induced malignant transformation. In the present study, we focused on the molecular mechanisms of this malignant transformation, especially with regard to hyper-invasiveness stimulated by cadmium transformation. By performing a series of biochemical analyses on cadmium transformed cells, it was determined that cadmium had significantly down-regulated the expression of apolipoprotein E (ApoE). ApoE was recently established as a suppressor of cell invasion. A key factor in the suppression of ApoE by cadmium appeared to be that the metal evoked a 5-aza-2'-deoxycytidine-sensitive hypermethylation of the regulatory region of ApoE, coupled with interference of the action of liver X receptor α (LXRα), a transcriptional regulator for ApoE. Furthermore, the expression of LXRα itself was suppressed by cadmium-mediated epigenetic modification. Re-expression of ApoE clearly abrogated the cell invasion stimulated by cadmium-induced malignant transformation. Together, the current results suggest that the cadmium-mediated enhanced cell invasion is linked to down-regulation of ApoE during malignant transformation these liver cells. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Patterns of avian nest predators and a brood parasite among restored riparian habitats in agricultural watersheds.

    PubMed

    Maul, Jonathan D; Smiley, Peter C; Cooper, Charles M

    2005-09-01

    In fragmented edge-dominated landscapes, nest predation and brood parasitism may reduce avian reproductive success and, ultimately, populations of some passerine species. In the fragmented agroecosystem of northwest Mississippi, placement of drop-pipe structures has been used as a restoration technique for abating gully erosion along stream banks. These actions have formed small herbaceous and woody habitat extensions into former agricultural lands. We quantified species relative abundances, species richness, and evenness of avian nest predators and a brood parasite within four categories of constructed habitat resulting from drop-pipe installation. Differences in the abundance of two nest predators, cotton mouse (Peromyscus gossypinus) and blue jay (Cyanocitta cristata), were observed among constructed habitats. However, relative abundances of other predators such as common grackle (Quiscalus quiscula), American crow (Corvus brachyrhynchos), and hispid cotton rat (Sigmodon hispidus), and the obligate brood parasite brown-headed cowbird (Molothrus ater) did not differ among four habitat categories. Although species richness, abundance, and evenness of potential nest predators were generally similar among the constructed habitats, predator species composition varied, suggesting that these habitats supported different predator communities. This difference is important because as each predator species is added to or deleted from the community, variation may occur in the framework of prey search methods, predator strategies, and potentially overall predation pressure. We suggest that land managers using drop-pipes as part of stream restoration projects allow for the development of the constructed habitat with the largest area and greatest vegetative structure.

  1. Understanding predation: implications toward forest management

    Treesearch

    Harvey R. Smith

    1991-01-01

    It is generally accepted that when gypsy moths rest in the litter survival is low due to predation by ground-foraging generalist predators and that predation can maintain these populations indefinitely. Forest Service research on predators of gypsy moth continues to focus on population dynamics, the mechanisms of predation and forest management implications.

  2. Non-invasive Monitoring of L-2-Oxothiazolidine-4-Carboxylate Metabolism in the Rat Brain by In vivo 13C Magnetic Resonance Spectroscopy

    PubMed Central

    Clark, M. Daniel; Ludeman, Susan M.; Springer, James B.; D’Alessandro, Michael A.; Simpson, Nicholas E.; Pourdeyhimi, Roxana; Johnson, C. Bryce; Teeter, Stephanie D.; Blackband, Stephen J.; Thelwall, Peter E.

    2011-01-01

    The cysteine precursor L-2-oxothiazolidine-4-carboxylate (OTZ, procysteine) can raise cysteine concentration, and thus glutathione levels, in some tissues. OTZ has therefore been proposed as a prodrug for combating oxidative stress. We have synthesized stable isotope labeled OTZ (i.e. L-2-oxo-[5-13C]-thiazolidine-4-carboxylate, 13C-OTZ) and tracked its uptake and metabolism in vivo in rat brain by 13C magnetic resonance spectroscopy. Although uptake and clearance of 13C-OTZ was detectable in rat brain following a bolus dose by in vivo spectroscopy, no incorporation of isotope label into brain glutathione was detectable. Continuous infusion of 13C-OTZ over 20 h, however, resulted in 13C-label incorporation into glutathione, taurine, hypotaurine and lactate at levels sufficient for detection by in vivo magnetic resonance spectroscopy. Examination of brain tissue extracts by mass spectrometry confirmed only low levels of isotope incorporation into glutathione in rats treated with a bolus dose and much higher levels after 20 h of continuous infusion. In contrast to some previous studies, bolus administration of OTZ did not alter brain glutathione levels. Even a continuous infusion of OTZ over 20 h failed to raise brain glutathione levels. These studies demonstrate the utility of in vivo magnetic resonance for non-invasive monitoring of antioxidant uptake and metabolism in intact brain. These types of experiments can be used to evaluate the efficacy of various interventions for maintenance of brain glutathione. PMID:21161591

  3. Behavioural responses of larval container mosquitoes to a size-selective predator.

    PubMed

    Kesavaraju, Banugopan; Alto, Barry W; Lounibos, L Philip; Juliano, Steven A

    2007-06-01

    The hypothesis that size-selective predation and species-specific prey behaviours facilitate the coexistence between larvae of invasive Aedes albopictus (Skuse) and U.S.A.-native Ochlerotatus triseriatus (Say) was tested experimentally with the predator Corethrella appendiculata (Grabham).Larval behaviours associated with a higher risk of predation were identified, and prey behavioural responses were tested in either the physical presence of predators or in water containing predation cues. Larvae that thrashed on container bottoms had a higher risk of being captured by fourth instar C. appendiculata than did larvae resting on the water surface. Ochlerotatus triseriatus, but not A. albopictus, adopted low-risk behaviours in response to water-borne cues to predation. Both prey species reduced risky behaviours in the physical presence of the predator, but O. triseriatus showed a stronger response.The vulnerability of 2nd and 3rd instar prey to predation was compared, and behavioural responses were correlated with prey vulnerability. Second instars of both species were more vulnerable to predation by C. appendiculata than were 3rd instars, and the 3rd instar A. albopictus was more vulnerable than O. triseriatus of the same stage. All instars of O. triseriatus showed a similar reduction of risky behaviours in response to the presence of C. appendiculata despite 4th instar prey being relatively invulnerable to size-selective predation.Weaker predator avoidance, coupled with superior competitive ability, of invasive A. albopictus is likely to contribute to its coexistence with O. triseriatus in containers of the south-eastern U.S.A., where C. appendiculata can be abundant.

  4. Optimal Culling and Biocontrol in a Predator-Prey Model.

    PubMed

    Numfor, Eric; Hilker, Frank M; Lenhart, Suzanne

    2017-01-01

    Invasive species cause enormous problems in ecosystems around the world. Motivated by introduced feral cats that prey on bird populations and threaten to drive them extinct on remote oceanic islands, we formulate and analyze optimal control problems. Their novelty is that they involve both scalar and time-dependent controls. They represent different forms of control, namely the initial release of infected predators on the one hand and culling as well as trapping, infecting, and returning predators on the other hand. Combinations of different control methods have been proposed to complement their respective strengths in reducing predator numbers and thus protecting endangered prey. Here, we formulate and analyze an eco-epidemiological model, provide analytical results on the optimal control problem, and use a forward-backward sweep method for numerical simulations. By taking into account different ecological scenarios, initial conditions, and control durations, our model allows to gain insight how the different methods interact and in which cases they could be effective.

  5. Bat Predation by Spiders

    PubMed Central

    Nyffeler, Martin; Knörnschild, Mirjam

    2013-01-01

    In this paper more than 50 incidences of bats being captured by spiders are reviewed. Bat-catching spiders have been reported from virtually every continent with the exception of Antarctica (∼90% of the incidences occurring in the warmer areas of the globe between latitude 30° N and 30° S). Most reports refer to the Neotropics (42% of observed incidences), Asia (28.8%), and Australia-Papua New Guinea (13.5%). Bat-catching spiders belong to the mygalomorph family Theraphosidae and the araneomorph families Nephilidae, Araneidae, and Sparassidae. In addition to this, an attack attempt by a large araneomorph hunting spider of the family Pisauridae on an immature bat was witnessed. Eighty-eight percent of the reported incidences of bat catches were attributable to web-building spiders and 12% to hunting spiders. Large tropical orb-weavers of the genera Nephila and Eriophora in particular have been observed catching bats in their huge, strong orb-webs (of up to 1.5 m diameter). The majority of identifiable captured bats were small aerial insectivorous bats, belonging to the families Vespertilionidae (64%) and Emballonuridae (22%) and usually being among the most common bat species in their respective geographic area. While in some instances bats entangled in spider webs may have died of exhaustion, starvation, dehydration, and/or hyperthermia (i.e., non-predation death), there were numerous other instances where spiders were seen actively attacking, killing, and eating the captured bats (i.e., predation). This evidence suggests that spider predation on flying vertebrates is more widespread than previously assumed. PMID:23516436

  6. Bat predation by spiders.

    PubMed

    Nyffeler, Martin; Knörnschild, Mirjam

    2013-01-01

    In this paper more than 50 incidences of bats being captured by spiders are reviewed. Bat-catching spiders have been reported from virtually every continent with the exception of Antarctica (≈ 90% of the incidences occurring in the warmer areas of the globe between latitude 30° N and 30° S). Most reports refer to the Neotropics (42% of observed incidences), Asia (28.8%), and Australia-Papua New Guinea (13.5%). Bat-catching spiders belong to the mygalomorph family Theraphosidae and the araneomorph families Nephilidae, Araneidae, and Sparassidae. In addition to this, an attack attempt by a large araneomorph hunting spider of the family Pisauridae on an immature bat was witnessed. Eighty-eight percent of the reported incidences of bat catches were attributable to web-building spiders and 12% to hunting spiders. Large tropical orb-weavers of the genera Nephila and Eriophora in particular have been observed catching bats in their huge, strong orb-webs (of up to 1.5 m diameter). The majority of identifiable captured bats were small aerial insectivorous bats, belonging to the families Vespertilionidae (64%) and Emballonuridae (22%) and usually being among the most common bat species in their respective geographic area. While in some instances bats entangled in spider webs may have died of exhaustion, starvation, dehydration, and/or hyperthermia (i.e., non-predation death), there were numerous other instances where spiders were seen actively attacking, killing, and eating the captured bats (i.e., predation). This evidence suggests that spider predation on flying vertebrates is more widespread than previously assumed.

  7. Invasive predatory crayfish do not trigger inducible defences in tadpoles

    PubMed Central

    Gomez-Mestre, Ivan; Díaz-Paniagua, Carmen

    2011-01-01

    Invasive species cause deep impacts on ecosystems worldwide, contributing to the decline and extinction of indigenous species. Effective defences against native biological threats in indigenous species, whether structural or inducible, often seem inoperative against invasive species. Here, we show that tadpoles of the Iberian green frog detect chemical cues from indigenous predators (dragonfly nymphs) and respond by reducing their activity and developing an efficient defensive morphology against them (increased tail depth and pigmentation). Those defensive responses, however, were not activated against a highly damaging invasive predator (red swamp crayfish). Induced defences increased tadpole survival when faced against either indigenous dragonflies or invasive crayfish, so its inactivation in the presence of the invasive predator seems to be due to failure in cue recognition. Furthermore, we tested for local adaptation to the invasive predator by comparing individuals from ponds either exposed to or free from crayfish. In both cases, tadpoles failed to express inducible defences against crayfish, indicating that ca 30 years of contact with the invasive species (roughly 10–15 frog generations) have been insufficient for the evolution of recognition of invasive predator cues. PMID:21450734

  8. Intraguild predation in pioneer predator communities of alpine glacier forelands

    PubMed Central

    Raso, Lorna; Sint, Daniela; Mayer, Rebecca; Plangg, Simon; Recheis, Thomas; Brunner, Silvia; Kaufmann, Rüdiger; Traugott, Michael

    2014-01-01

    Pioneer communities establishing themselves in the barren terrain in front of glacier forelands consist principally of predator species such as carabid beetles and lycosid spiders. The fact that so many different predators can co-inhabit an area with no apparent primary production was initially explained by allochthonous material deposited in these forelands. However, whether these populations can be sustained on allochthonous material alone is questionable and recent studies point towards this assumption to be flawed. Intraguild predation (IGP) might play an important role in these pioneer predator assemblages, especially in the very early successional stages where other prey is scarce. Here, we investigated IGP between the main predator species and their consumption of Collembola, an important autochthonous alternative prey, within a glacier foreland in the Ötztal (Austrian Alps). Multiplex PCR and stable isotope analysis were used to characterize the trophic niches in an early and late pioneer stage over 2 years. Results showed that intraguild prey was consumed by all invertebrate predators, particularly the larger carabid species. Contrary to our initial hypothesis, the DNA detection frequency of IGP prey was not significantly higher in early than in late pioneer stage, which was corroborated by the stable isotope analysis. Collembola were the most frequently detected prey in all of the predators, and the overall prey DNA detection patterns were consistent between years. Our findings show that IGP appears as a constant in these pioneer predator communities and that it remains unaffected by successional changes. PMID:24383765

  9. Quantitative Analysis of Lysobacter Predation

    PubMed Central

    Seccareccia, Ivana; Kost, Christian

    2015-01-01

    Bacteria of the genus Lysobacter are considered to be facultative predators that use a feeding strategy similar to that of myxobacteria. Experimental data supporting this assumption, however, are scarce. Therefore, the predatory activities of three Lysobacter species were tested in the prey spot plate assay and in the lawn predation assay, which are commonly used to analyze myxobacterial predation. Surprisingly, only one of the tested Lysobacter species showed predatory behavior in the two assays. This result suggested that not all Lysobacter strains are predatory or, alternatively, that the assays were not appropriate for determining the predatory potential of this bacterial group. To differentiate between the two scenarios, predation was tested in a CFU-based bioassay. For this purpose, defined numbers of Lysobacter cells were mixed together with potential prey bacteria featuring phenotypic markers, such as distinctive pigmentation or antibiotic resistance. After 24 h, cocultivated cells were streaked out on agar plates and sizes of bacterial populations were individually determined by counting the respective colonies. Using the CFU-based predation assay, we observed that Lysobacter spp. strongly antagonized other bacteria under nutrient-deficient conditions. Simultaneously, the Lysobacter population was increasing, which together with the killing of the cocultured bacteria indicated predation. Variation of the predator/prey ratio revealed that all three Lysobacter species tested needed to outnumber their prey for efficient predation, suggesting that they exclusively practiced group predation. In summary, the CFU-based predation assay not only enabled the quantification of prey killing and consumption by Lysobacter spp. but also provided insights into their mode of predation. PMID:26231654

  10. Using consumption rate to assess potential predators for biological control of white perch

    USGS Publications Warehouse

    Gosch, N.J.C.; Pope, K.L.

    2011-01-01

    Control of undesirable fishes is important in aquatic systems, and using predation as a tool for biological control is an attractive option to fishery biologists. However, determining the appropriate predators for biological control is critical for success. The objective of this study was to evaluate the utility of consumption rate as an index to determine the most effective predators for biological control of an invasive fish. Consumption rate values were calculated for nine potential predators that prey on white perch Morone americana in Branched Oak and Pawnee reservoirs, Nebraska. The consumption rate index provided a unique and insightful means of determining the potential effectiveness of each predator species in controlling white perch. Cumulative frequency distributions facilitated interpretation by providing a graphical presentation of consumption rates by all individuals within each predator species. Largemouth bass Micropterus salmoides, walleye Sander vitreus and sauger S. canadensis were the most efficient white perch predators in both reservoirs; however, previous attempts to increase biomass of these predators have failed suggesting that successful biological control is unlikely using existing predator species in these Nebraska reservoirs. ?? 2011 ONEMA.

  11. Bioluminescent Imaging Reveals Novel Patterns of Colonization and Invasion in Systemic Escherichia coli K1 Experimental Infection in the Neonatal Rat

    PubMed Central

    Witcomb, Luci A.; Collins, James W.; McCarthy, Alex J.; Frankel, Gadi

    2015-01-01

    Key features of Escherichia coli K1-mediated neonatal sepsis and meningitis, such as a strong age dependency and development along the gut-mesentery-blood-brain course of infection, can be replicated in the newborn rat. We examined temporal and spatial aspects of E. coli K1 infection following initiation of gastrointestinal colonization in 2-day-old (P2) rats after oral administration of E. coli K1 strain A192PP and a virulent bioluminescent derivative, E. coli A192PP-lux2. A combination of bacterial enumeration in the major organs, two-dimensional bioluminescence imaging, and three-dimensional diffuse light imaging tomography with integrated micro-computed tomography indicated multiple sites of colonization within the alimentary canal; these included the tongue, esophagus, and stomach in addition to the small intestine and colon. After invasion of the blood compartment, the bacteria entered the central nervous system, with restricted colonization of the brain, and also invaded the major organs, in line with increases in the severity of symptoms of infection. Both keratinized and nonkeratinized surfaces of esophagi were colonized to a considerably greater extent in susceptible P2 neonates than in corresponding tissues from infection-resistant 9-day-old rat pups; the bacteria appeared to damage and penetrate the nonkeratinized esophageal epithelium of infection-susceptible P2 animals, suggesting the esophagus represents a portal of entry for E. coli K1 into the systemic circulation. Thus, multimodality imaging of experimental systemic infections in real time indicates complex dynamic patterns of colonization and dissemination that provide new insights into the E. coli K1 infection of the neonatal rat. PMID:26351276

  12. Bioluminescent imaging reveals novel patterns of colonization and invasion in systemic Escherichia coli K1 experimental infection in the neonatal rat.

    PubMed

    Witcomb, Luci A; Collins, James W; McCarthy, Alex J; Frankel, Gadi; Taylor, Peter W

    2015-12-01

    Key features of Escherichia coli K1-mediated neonatal sepsis and meningitis, such as a strong age dependency and development along the gut-mesentery-blood-brain course of infection, can be replicated in the newborn rat. We examined temporal and spatial aspects of E. coli K1 infection following initiation of gastrointestinal colonization in 2-day-old (P2) rats after oral administration of E. coli K1 strain A192PP and a virulent bioluminescent derivative, E. coli A192PP-lux2. A combination of bacterial enumeration in the major organs, two-dimensional bioluminescence imaging, and three-dimensional diffuse light imaging tomography with integrated micro-computed tomography indicated multiple sites of colonization within the alimentary canal; these included the tongue, esophagus, and stomach in addition to the small intestine and colon. After invasion of the blood compartment, the bacteria entered the central nervous system, with restricted colonization of the brain, and also invaded the major organs, in line with increases in the severity of symptoms of infection. Both keratinized and nonkeratinized surfaces of esophagi were colonized to a considerably greater extent in susceptible P2 neonates than in corresponding tissues from infection-resistant 9-day-old rat pups; the bacteria appeared to damage and penetrate the nonkeratinized esophageal epithelium of infection-susceptible P2 animals, suggesting the esophagus represents a portal of entry for E. coli K1 into the systemic circulation. Thus, multimodality imaging of experimental systemic infections in real time indicates complex dynamic patterns of colonization and dissemination that provide new insights into the E. coli K1 infection of the neonatal rat.

  13. Intraguild predation and competition impacts on a subordinate predator.

    PubMed

    Björklund, Heidi; Santangeli, Andrea; Blanchet, F Guillaume; Huitu, Otso; Lehtoranta, Hannu; Lindén, Harto; Valkama, Jari; Laaksonen, Toni

    2016-05-01

    Intraguild (IG) predation and interspecific competition may affect the settlement and success of species in their habitats. Using data on forest-dwelling hawks from Finland, we addressed the impact of an IG predator, the northern goshawk Accipiter gentilis (goshawk), on the breeding of an IG prey, the common buzzard Buteo buteo. We hypothesized that the subordinate common buzzard avoids breeding in the proximity of goshawks and that interspecific competitors, mainly Strix owls, may also disturb common buzzards by competing for nests and food. Our results show that common buzzards more frequently occupied territories with a low IG predation threat and with no interspecific competitors. We also observed that common buzzards avoided territories with high levels of grouse, the main food of goshawks, possibly due to a risk of IG predation since abundant grouse can attract goshawks. High levels of small rodents attracted interspecific competitors to common buzzard territories and created a situation where there was not only an abundance of food but also an abundance of competitors for the food. These results suggest interplay between top-down and bottom-up processes which influence the interactions between avian predator species. We conclude that the common buzzard needs to balance the risks of IG predation and interference competition with the availability of its own resources. The presence of other predators associated with high food levels may impede a subordinate predator taking full advantage of the available food. Based on our results, it appears that interspecific interactions with dominant predators have the potential to influence the distribution pattern of subordinate predators.

  14. Introduced rats indirectly change marine rocky intertidal communities from algae- to invertebrate-dominated.

    PubMed

    Kurle, Carolyn M; Croll, Donald A; Tershy, Bernie R

    2008-03-11

    It is widely recognized that trophic interactions structure ecological communities, but their effects are usually only demonstrated on a small scale. As a result, landscape-level documentations of trophic cascades that alter entire communities are scarce. Islands invaded by animals provide natural experiment opportunities both to measure general trophic effects across large spatial scales and to determine the trophic roles of invasive species within native ecosystems. Studies addressing the trophic interactions of invasive species most often focus on their direct effects. To investigate both the presence of a landscape-level trophic cascade and the direct and indirect effects of an invasive species, we examined the impacts of Norway rats (Rattus norvegicus) introduced to the Aleutian Islands on marine bird densities and marine rocky intertidal community structures through surveys conducted on invaded and rat-free islands throughout the entire 1,900-km archipelago. Densities of birds that forage in the intertidal were higher on islands without rats. Marine intertidal invertebrates were more abundant on islands with rats, whereas fleshy algal cover was reduced. Our results demonstrate that invasive rats directly reduce bird densities through predation and significantly affect invertebrate and marine algal abundance in the rocky intertidal indirectly via a cross-community trophic cascade, unexpectedly changing the intertidal community structure from an algae- to an invertebrate-dominated system.

  15. Introduced rats indirectly change marine rocky intertidal communities from algae- to invertebrate-dominated

    PubMed Central

    Kurle, Carolyn M.; Croll, Donald A.; Tershy, Bernie R.

    2008-01-01

    It is widely recognized that trophic interactions structure ecological communities, but their effects are usually only demonstrated on a small scale. As a result, landscape-level documentations of trophic cascades that alter entire communities are scarce. Islands invaded by animals provide natural experiment opportunities both to measure general trophic effects across large spatial scales and to determine the trophic roles of invasive species within native ecosystems. Studies addressing the trophic interactions of invasive species most often focus on their direct effects. To investigate both the presence of a landscape-level trophic cascade and the direct and indirect effects of an invasive species, we examined the impacts of Norway rats (Rattus norvegicus) introduced to the Aleutian Islands on marine bird densities and marine rocky intertidal community structures through surveys conducted on invaded and rat-free islands throughout the entire 1,900-km archipelago. Densities of birds that forage in the intertidal were higher on islands without rats. Marine intertidal invertebrates were more abundant on islands with rats, whereas fleshy algal cover was reduced. Our results demonstrate that invasive rats directly reduce bird densities through predation and significantly affect invertebrate and marine algal abundance in the rocky intertidal indirectly via a cross-community trophic cascade, unexpectedly changing the intertidal community structure from an algae- to an invertebrate-dominated system. PMID:18308929

  16. Corridors cause differential seed predation.

    SciTech Connect

    Orrock, John L.; Damschen, Ellen I.

    2005-06-01

    Orrock, John, L., and Ellen I. Damschen. 2005. Corridors cause differential seed predation. Ecol. Apps. 15(3):793-798. Abstract. Corridors that connect disjunct populations are heavily debated in conservation, largely because the effects of corridors have rarely been evaluated by replicated, large-scale studies. Using large-scale experimental landscapes, we found that, in addition to documented positive effects, corridors also have negative impacts on bird-dispersed plants by affecting seed predation, and that overall predation is a function of the seeds primary consumer (rodents or arthropods). Both large-seeded Prunus serotina and small-seeded Rubus allegheniensis experienced greater predation in connected patches. However, P. serotina experienced significantly less seed predation compared to R. allegheniensis in unconnected patches, due to decreased impacts of rodent seed predators on this large-seeded species. Viewed in light of previous evidence that corridors have beneficial impacts by increasing pollination and seed dispersal, this work demonstrates that corridors may have both positive and negative effects for the same plant species at different life stages. Moreover, these effects may differentially affect plant species within the same community: seeds primarily consumed by rodents suffer less predation in unconnected patches. By shifting the impact of rodent and arthropod seed predators, corridors constructed for plant conservation could lead to shifts in the seed bank.

  17. Alien mink predation induces prolonged declines in archipelago amphibians

    PubMed Central

    Ahola, Markus; Nordström, Mikael; Banks, Peter B; Laanetu, Nikolai; Korpimäki, Erkki

    2006-01-01

    Amphibians are undergoing enigmatic global declines variously attributed to a complex web of anthropogenic forces. Alien predators pose a fundamental threat to biodiversity generally that is predicted to be most acute in island ecosystems. While amphibian eggs and tadpoles are vulnerable to aquatic predators, the effect of predators on adult, reproducing frogs, which most influence amphibian population processes, is unknown. Here, we report on the responses of amphibian populations in the outer Finnish Archipelago to a long-term, large-scale removal of American mink (Mustela vison Schreb.), an invasive predator linked to recent biodiversity loss across Europe. Removal increased both the densities and distribution of common frogs (Rana temporaria L.) but not those of common toads (Bufo bufo L.), which appear to escape mink predation because of their unpalatable skin. Importantly, the largest benefits of mink removal to frog recovery were slow to appear as frogs apparently have a delayed maturation in these harsh environments, which means we must be cautious about reliance upon short-term results. PMID:16720400

  18. The influence of sulindac on diabetic cardiomyopathy: a non-invasive evaluation by Doppler echocardiography in streptozotocin-induced diabetic rats.

    PubMed

    Krishna, Kota M; Gopal, Gopisetty S; Chalam, Chitrapu R V; Madan, Kalagara; Kumar, Veeravalli K; Prakash, Gomedhikam J; Annapurna, Akula

    2005-08-01

    The aim of the present study was to investigate the cardioprotective activity of sulindac as an aldose reductase inhibitor in the development of cardiomyopathy by non-invasive techniques; M-mode and Doppler echocardiography. Diabetes was induced by streptozotocin (45 mg/kg, iv) in the Sprague-Dawley rats. Echocardiography, biochemical and histological studies were carried out in normal control, diabetic untreated, diabetic vehicle (sodium carboxy methyl cellulose, 1%, po) and sulindac (6 mg/kg and 20 mg/kg, po) treated animals at varying time intervals. In the diabetic untreated and vehicle treated rats at 12 weeks after induction of diabetes, there was a significant decrease in the E-wave, an increase in the A-wave and corresponding decrease in the E/A ratio was observed. Significant decrease in the Eat was found after 12 weeks (P < 0.05). Whereas systolic function variables; ejection fraction and fractional shortening were significantly decreased (P < 0.05) after 12 weeks compared to their baseline data. In the sulindac treated animals, there were no significant alterations in the systolic and diastolic parameters were found throughout the study period. Myocardial fructose levels were significantly increased in the diabetic untreated animals compared to normal control rats (P < 0.05), whereas these were significantly decreased in the sulindac (6 mg/kg and 20 mg/kg) treated animals (301.11+/-37.98, 214.11+/-25.31, vs. 914.88+/-56.01 nmol/g) compared to diabetic vehicle treated group (P < 0.05). Extensive focal ischemic myocyte degeneration was observed in the diabetic untreated and vehicle treated rats, whereas in the sulindac (6 mg/kg) treated rats, minimal necrosis was found, with no evidence of necrosis in sulindac (20 mg/kg) group. Our results show for the first time that sulindac has a cardioprotective activity as this agent prevented the development of left ventricular dysfunction in STZ-induced diabetic rats in the 12-week chronic study.

  19. Dynamics of a plant-herbivore-predator system with plant-toxicity

    USGS Publications Warehouse

    Feng, Zhilan; Qiu, Zhipeng; Liu, Rongsong; DeAngelis, Donald L.

    2011-01-01

    A system of ordinary differential equations is considered that models the interactions of two plant species populations, an herbivore population, and a predator population. We use a toxin-determined functional response to describe the interactions between plant species and herbivores and use a Holling Type II functional response to model the interactions between herbivores and predators. In order to study how the predators impact the succession of vegetation, we derive invasion conditions under which a plant species can invade into an environment in which another plant species is co-existing with a herbivore population with or without a predator population. These conditions provide threshold quantities for several parameters that may play a key role in the dynamics of the system. Numerical simulations are conducted to reinforce the analytical results. This model can be applied to a boreal ecosystem trophic chain to examine the possible cascading effects of predator-control actions when plant species differ in their levels of toxic defense.

  20. Risk induced by a native top predator reduces alien mink movements.

    PubMed

    Salo, Pälvi; Nordström, Mikael; Thomson, Robert L; Korpimäki, Erkki

    2008-11-01

    1. Nonlethal predation effects may have stronger impacts on prey populations than direct predation impacts, and this should also apply to intraguild predation. The consequences of such interactions become especially important if invasive, and potentially destructive alien predators act as intraguild prey. 2. We studied the predation-risk impacts of a re-colonizing native top predator, Haliaeetus albicilla (white-tailed sea eagle), on the movements of Mustela vison (American mink), an alien predator in Europe. We radiocollared 20 mink in two study areas in the outer archipelago of the Baltic Sea, South-west Finland, during 2004 and 2005. In the archipelago, mink home ranges incorporate many islands, and mink are most predisposed to eagle predation while swimming between islands. Observed swimming distances of mink were compared to distances expected at random, and deviations from random swimming were explained by mink distance from nearest eagle nest, number of eagle observations near mink location, and mink home-range size. 3. Mink reduced their swimming distances with increasing sea eagle predation risk: for females, the reduction was 10% for an increase of 10 eagle observations, and 5% for each kilometre towards an eagle nest. Conclusions for males were restricted by their small sample size. 4. Our results suggest that female mink modify their behaviour according to eagle predation risk, which may reduce their population growth and have long-term cascading effects on lower trophic levels including bird, mammal and amphibian populations in the archipelago. Ecosystem restoration by bringing back the top predators may be one way of mitigating alien predator effects on native biota.

  1. Spreading and vanishing in the diffusive prey-predator model with a free boundary

    NASA Astrophysics Data System (ADS)

    Wang, Mingxin

    2015-06-01

    This paper deals with the diffusive Lotka-Volterra type prey-predator model with a free boundary over a one dimensional habitat. This problem may be used to describe the interaction between indigenous species and invasive species and the spreading of such two species, with the free boundary representing the expanding front. Our main purpose is to study the spreading and vanishing phenomena and long time behaviors of prey and predator.

  2. Stability of an intraguild predation system with mutual predation

    NASA Astrophysics Data System (ADS)

    Wang, Yuanshi; DeAngelis, Donald L.

    2016-04-01

    We examine intraguild predation (IGP), in which species both compete for resources or space and prey on each other. The IGP system is modeled here by a lattice gas model of the mean-field theory. First, we consider the IGP system of one species in which individuals of the same species cannibalize each other. The dynamical behavior of the model demonstrates a mechanism by which the intraspecific predation promotes persistence of the species. Then we consider the IGP system of two species with mutual predation. Global dynamics of the model exhibit basic properties of IGP: (i) When both species' efficiencies in converting the consumptions into fitness are large, the outcome of their interaction is mutualistic in form and the IGP promotes persistence of both species. (ii) When one species' efficiency is large but the other's is small, the interaction outcomes become parasitic in nature, in which an obligate species can survive through the mutual predation with a facultative one. (iii) When both species' efficiencies are small, the interaction outcomes are competitive in nature and the IGP leads to extinction of one of the species. A novel result of this work is that varying one parameter or population density of the species can lead to transition of interaction outcomes between mutualism, parasitism and competition. On the other hand, dynamics of the models demonstrate that over-predation or under-predation will result in extinction of one/both species, while intermediate predation is favorable under certain parameter ranges.

  3. The paradox of the long-term positive effects of a North American crayfish on a European community of predators.

    PubMed

    Tablado, Zulima; Tella, José L; Sánchez-Zapata, José A; Hiraldo, Fernando

    2010-10-01

    Invasions of non-native species are one of the major causes of losses of native species. In some cases, however, non-natives may also have positive effects on native species. We investigated the potential facilitative effects of the North American red swamp crayfish (Procambarus clarkii) on the community of predators in southwestern Spain. To do so, we examined the diets of predators in the area and their population trends since introduction of the crayfish. Most predator species consumed red swamp crayfish, which sometimes occurred in over 50% of their diet samples. Moreover, the abundance of species preying on crayfish increased significantly in the area as opposed to the abundance of herbivores and to predator populations in other areas of Europe, where those predators are even considered threatened. Thus, we report the first case in which one non-native species is both beneficial because it provides prey for threatened species and detrimental because it can drive species at lower trophic levels to extinction. Increases in predator numbers that are associated with non-native species of prey, especially when some of these predators are also invasive non-natives, may increase levels of predation on other species and produce cascading effects that threaten native biota at longer temporal and larger spatial scales. Future management plans should include the complexity of interactions between invasive non-natives and the entire native community, the feasibility of successful removal of non-native species, and the potential social and economic interests in the area.

  4. Eating the competition speeds up invasions.

    PubMed

    Hall, Richard J

    2011-04-23

    Many introduced species engage in intraguild predation (IGP), the consumption of species with which they compete for shared resources. While the factors influencing local persistence of IG predator and prey species are well-understood, using these factors to predict the invasion speed of an introduced IG predator has received less attention. Existing theory predicts that native competitors slow invasions via depletion of shared resources, but this fails to account for additional resources acquired when an invader consumes competitors. Here, I outline a general framework for understanding the effect of IGP on invasion speeds. I find that invaders that consume native competitors may be able to spread where invasion by pure competitors would fail, and that invasion speed increases with increasing levels of IGP. Notably, if the benefit from consuming competitors outweighs the loss of shared resources to competitors, invasion proceeds faster than invasion in the absence of competitors. This may explain empirical observations of rapid spread rates of invaders that feed at multiple trophic levels.

  5. Prenatal low-dose bisphenol A enhances behavioral responses induced by a predator odor.

    PubMed

    Fujimoto, Tetsuya; Kubo, Kazuhiko; Nishikawa, Yasuo; Aou, Shuji

    2015-01-01

    Bisphenol A (BPA) is an environmental endocrine disrupter (EED). Previous studies by our group showed that pre- and postnatal administration of low-level BPA induced depression-like behavior in rats. In this study, we evaluated the effects of prenatal BPA on behavioral responses to a predator odor by using a novel cross-form apparatus consisting of 4 plastic chambers. On the first day, nothing was placed into the chambers (Session 1). On the second day, a predator odor (fox odor) was located in separate chambers at 2 opposite corners of the apparatus (Session 2). Pregnant Wistar rats were exposed to low-dose BPA (less than the reference dose) during the 7 days just before birth, and the offspring of the treated rats were evaluated as adults. The locomotor activity and avoidance response of each rat on both test days were compared. The control and BPA groups showed reduced locomotor activity in the presence of the predator odor, but the odor-avoidance response was significant only in the BPA rats. The BPA-exposed rats were obviously sensitive to the predator odor. These results suggest that prenatal BPA exposure has an amplifying effect on avoidance responses to predator odor stress.

  6. Induced changes in island fox (Urocyon littoralis) activity do not mitigate the extinction threat posed by a novel predator.

    PubMed

    Hudgens, Brian R; Garcelon, David K

    2011-03-01

    Prey response to novel predators influences the impacts on prey populations of introduced predators, bio-control efforts, and predator range expansion. Predicting the impacts of novel predators on native prey requires an understanding of both predator avoidance strategies and their potential to reduce predation risk. We examine the response of island foxes (Urocyon littoralis) to invasion by golden eagles (Aquila chrysaetos). Foxes reduced daytime activity and increased night time activity relative to eagle-naïve foxes. Individual foxes reverted toward diurnal tendencies following eagle removal efforts. We quantified the potential population impact of reduced diurnality by modeling island fox population dynamics. Our model predicted an annual population decline similar to what was observed following golden eagle invasion and predicted that the observed 11% reduction in daytime activity would not reduce predation risk sufficiently to reduce extinction risk. The limited effect of this behaviorally plastic predator avoidance strategy highlights the importance of linking behavioral change to population dynamics for predicting the impact of novel predators on resident prey populations.

  7. Species coexistence of communities with intraguild predation: the role of refuges used by the resource and the intraguild prey.

    PubMed

    Liu, Zhiguang; Zhang, Fengpan

    2013-10-01

    In this paper, we develop a three-species intraguild predation model which incorporates refuges used by the resource and the intraguild prey, and focus on the effects of refuges on the three species coexistence. The invasion condition and parameter region for coexistence are obtained using invasion analysis. The new invasion condition requires that all boundary states with one missing species can be invaded by the missing species. Numerical simulations show that refuges have a major influence on species coexistence of intraguild predation system, and the results strongly depend on the types of refuges introduced into the model. Our study also shows that prey's refuges are detrimental to species coexistence except the resource using refuges. In contrast to previous research, we find that spatial structure may play an important role in effects of refuges on species coexistence of intraguild predation systems. Our results may shed new light on understanding the mechanisms and the persistence of multi-species predators-prey system.

  8. Non-invasive assessment of liver fibrosis in a rat model: shear wave elasticity imaging versus real-time elastography.

    PubMed

    Lin, Sen-Hao; Ding, Hong; Mao, Feng; Xue, Li-Yun; Lv, Wei-Wei; Zhu, Hong-Guang; Huang, Bei-Jian; Wang, Wen-Ping

    2013-07-01

    The purpose of this study was to investigate the diagnostic value of shear wave elasticity imaging (SWEI) and real-time elastography (RTE) in liver fibrosis induced by dimethylnitrosamine (DMN) and to compare the accuracy of these methods. Seventy male Wistar rats given a single intra-peritoneal injection of DMN and 10 control rats given a saline injection underwent SWEI and RTE to determine their shear wave velocity (V(s)) and liver fibrosis (LF) index, respectively. Correlations between V(s) or the LF index and histologic stage of liver fibrosis (S0-S4) were analyzed, and the diagnostic values of the techniques were assessed using a receiver operating characteristic curve. A positive correlation was found between V(s) and stage of liver fibrosis (r = 0.947, p < 0.001) and between LF index and stage (S) of liver fibrosis (r = 0.662, p < 0.001). For Vs, the areas under the receiver operating characteristic curve for the diagnosis of fibrosis, S ≥ S1, S ≥ S2, S ≥ S3 and S = S4, were 0.983, 0.995, 0.999 and 0.964, respectively; for the LF index, the values were 0.871, 0.887, 0.761 and 0.839, respectively (all p < 0.001). Vs and the LF index values in rats with severe inflammatory activity were significantly higher than those in controls (p < 0.001). In conclusion, positive correlations exist between V(s) or the LF index and the severity of liver fibrosis in rats. Vs is more accurate than the LF index in predicting liver fibrosis in rats. However, severe inflammatory activity may reduce the accuracy of both techniques.

  9. Presence of Native Prey Does Not Divert Predation on Exotic Pests by Harmonia axyridis in Its Indigenous Range.

    PubMed

    Zhang, Gui Fen; Lövei, Gábor L; Wu, Xia; Wan, Fang Hao

    2016-01-01

    In China, two invasive pests, Bemisia tabaci MEAM1 (Gennadius) and Frankliniella occidentalis (Pergande), often co-occur with the native pest, Aphis gossypii (Glover), on plants of Malvaceae and Cucurbitaceae. All three are preyed on by the native ladybird, Harmonia axyridis (Pallas); however, the native predator might be expected to prefer native prey to the exotic ones due to a shared evolutionary past. In order to clarify whether the presence of native prey affected the consumption of these two invasive species by the native predator, field-cage experiments were conducted. A duplex qPCR was used to simultaneously detect both non-native pests within the gut of the predator. H. axyridis readily accepted both invasive prey species, but preferred B. tabaci. With all three prey species available, H. axyridis consumption of B. tabaci was 39.3±2.2% greater than consumption of F. occidentalis. The presence of A. gossypii reduced (by 59.9% on B. tabaci, and by 60.6% on F. occidentalis), but did not stop predation on the two exotic prey when all three were present. The consumption of B. tabaci was similar whether it was alone or together with A. gossypii. However, the presence of aphids reduced predation on the invasive thrips. Thus, some invasive prey may be incorporated into the prey range of a native generalist predator even in the presence of preferred native prey.

  10. Presence of Native Prey Does Not Divert Predation on Exotic Pests by Harmonia axyridis in Its Indigenous Range

    PubMed Central

    Zhang, Gui Fen; Lövei, Gábor L; Wu, Xia; Wan, Fang Hao

    2016-01-01

    In China, two invasive pests, Bemisia tabaci MEAM1 (Gennadius) and Frankliniella occidentalis (Pergande), often co-occur with the native pest, Aphis gossypii (Glover), on plants of Malvaceae and Cucurbitaceae. All three are preyed on by the native ladybird, Harmonia axyridis (Pallas); however, the native predator might be expected to prefer native prey to the exotic ones due to a shared evolutionary past. In order to clarify whether the presence of native prey affected the consumption of these two invasive species by the native predator, field-cage experiments were conducted. A duplex qPCR was used to simultaneously detect both non-native pests within the gut of the predator. H. axyridis readily accepted both invasive prey species, but preferred B. tabaci. With all three prey species available, H. axyridis consumption of B. tabaci was 39.3±2.2% greater than consumption of F. occidentalis. The presence of A. gossypii reduced (by 59.9% on B. tabaci, and by 60.6% on F. occidentalis), but did not stop predation on the two exotic prey when all three were present. The consumption of B. tabaci was similar whether it was alone or together with A. gossypii. However, the presence of aphids reduced predation on the invasive thrips. Thus, some invasive prey may be incorporated into the prey range of a native generalist predator even in the presence of preferred native prey. PMID:27391468

  11. Predator behaviour and predation risk in the heterogeneous Arctic environment.

    PubMed

    Lecomte, Nicolas; Careau, Vincent; Gauthier, Gilles; Giroux, Jean-François

    2008-05-01

    1. Habitat heterogeneity and predator behaviour can strongly affect predator-prey interactions but these factors are rarely considered simultaneously, especially when systems encompass multiple predators and prey. 2. In the Arctic, greater snow geese Anser caerulescens atlanticus L. nest in two structurally different habitats: wetlands that form intricate networks of water channels, and mesic tundra where such obstacles are absent. In this heterogeneous environment, goose eggs are exposed to two types of predators: the arctic fox Vulpes lagopus L. and a diversity of avian predators. We hypothesized that, contrary to birds, the hunting ability of foxes would be impaired by the structurally complex wetland habitat, resulting in a lower predation risk for goose eggs. 3. In addition, lemmings, the main prey of foxes, show strong population cycles. We thus further examined how their fluctuations influenced the interaction between habitat heterogeneity and fox predation on goose eggs. 4. An experimental approach with artificial nests suggested that foxes were faster than avian predators to find unattended goose nests in mesic tundra whereas the reverse was true in wetlands. Foxes spent 3.5 times more time between consecutive attacks on real goose nests in wetlands than in mesic tundra. Their attacks on goose nests were also half as successful in wetlands than in mesic tundra whereas no difference was found for avian predators. 5. Nesting success in wetlands (65%) was higher than in mesic tundra (56%) but the difference between habitats increased during lemming crashes (15%) compared to other phases of the cycle (5%). Nests located at the edge of wetland patches were also less successful than central ones, suggesting a gradient in accessibility of goose nests in wetlands for foxes. 6. Our study shows that the structural complexity of wetlands decreases predation risk from foxes but not avian predators in arctic-nesting birds. Our results also demonstrate that cyclic

  12. Intraguild predation in pioneer predator communities of alpine glacier forelands.

    PubMed

    Raso, Lorna; Sint, Daniela; Mayer, Rebecca; Plangg, Simon; Recheis, Thomas; Brunner, Silvia; Kaufmann, Rüdiger; Traugott, Michael

    2014-08-01

    Pioneer communities establishing themselves in the barren terrain in front of glacier forelands consist principally of predator species such as carabid beetles and lycosid spiders. The fact that so many different predators can co-inhabit an area with no apparent primary production was initially explained by allochthonous material deposited in these forelands. However, whether these populations can be sustained on allochthonous material alone is questionable and recent studies point towards this assumption to be flawed. Intraguild predation (IGP) might play an important role in these pioneer predator assemblages, especially in the very early successional stages where other prey is scarce. Here, we investigated IGP between the main predator species and their consumption of Collembola, an important autochthonous alternative prey, within a glacier foreland in the Ötztal (Austrian Alps). Multiplex PCR and stable isotope analysis were used to characterize the trophic niches in an early and late pioneer stage over 2 years. Results showed that intraguild prey was consumed by all invertebrate predators, particularly the larger carabid species. Contrary to our initial hypothesis, the DNA detection frequency of IGP prey was not significantly higher in early than in late pioneer stage, which was corroborated by the stable isotope analysis. Collembola were the most frequently detected prey in all of the predators, and the overall prey DNA detection patterns were consistent between years. Our findings show that IGP appears as a constant in these pioneer predator communities and that it remains unaffected by successional changes. © 2014 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd.

  13. Do intraspecific or interspecific interactions determine responses to predators feeding on a shared size-structured prey community?

    PubMed

    ten Brink, Hanna; Mazumdar, Abul Kalam Azad; Huddart, Joseph; Persson, Lennart; Cameron, Tom C

    2015-03-01

    Coexistence of predators that share the same prey is common. This is still the case in size-structured predator communities where predators consume prey species of different sizes (interspecific prey responses) or consume different size classes of the same species of prey (intraspecific prey responses). A mechanism has recently been proposed to explain coexistence between predators that differ in size but share the same prey species, emergent facilitation, which is dependent on strong intraspecific responses from one or more prey species. Under emergent facilitation, predators can depend on each other for invasion, persistence or success in a size-structured prey community. Experimental evidence for intraspecific size-structured responses in prey populations remains rare, and further questions remain about direct interactions between predators that could prevent or limit any positive effects between predators [e.g. intraguild predation (IGP)]. Here, we provide a community-wide experiment on emergent facilitation including natural predators. We investigate both the direct interactions between two predators that differ in body size (fish vs. invertebrate predator), and the indirect interaction between them via their shared prey community (zooplankton). Our evidence supports the most likely expectation of interactions between differently sized predators that IGP rates are high, and interspecific interactions in the shared prey community dominate the response to predation (i.e. predator-mediated competition). The question of whether emergent facilitation occurs frequently in nature requires more empirical and theoretical attention, specifically to address the likelihood that its pre-conditions may co-occur with high rates of IGP.

  14. Ocean acidification alters predator behaviour and reduces predation rate.

    PubMed

    Watson, Sue-Ann; Fields, Jennifer B; Munday, Philip L

    2017-02-01

    Ocean acidification poses a range of threats to marine invertebrates; however, the emerging and likely widespread effects of rising carbon dioxide (CO2) levels on marine invertebrate behaviour are still little understood. Here, we show that ocean acidification alters and impairs key ecological behaviours of the predatory cone snail Conus marmoreus Projected near-future seawater CO2 levels (975 µatm) increased activity in this coral reef molluscivore more than threefold (from less than 4 to more than 12 mm min(-1)) and decreased the time spent buried to less than one-third when compared with the present-day control conditions (390 µatm). Despite increasing activity, elevated CO2 reduced predation rate during predator-prey interactions with control-treated humpbacked conch, Gibberulus gibberulus gibbosus; 60% of control predators successfully captured and consumed their prey, compared with only 10% of elevated CO2 predators. The alteration of key ecological behaviours of predatory invertebrates by near-future ocean acidification could have potentially far-reaching implications for predator-prey interactions and trophic dynamics in marine ecosystems. Combined evidence that the behaviours of both species in this predator-prey relationship are altered by elevated CO2 suggests food web interactions and ecosystem structure will become increasingly difficult to predict as ocean acidification advances over coming decades. © 2017 The Author(s).

  15. Deciphering Scavenging Propensity Among Arthropod Predators.

    USDA-ARS?s Scientific Manuscript database

    Scavenging is a well documented feeding behavior among many arthrop predators. However, quantifying scavenging feeding activity is not well understood because many predators are small elusive. This makes directly observing predation events in nature almost impossible. If predators prefer dead prey ...

  16. Top predators affect the composition of naive protist communities, but only in their early-successional stage.

    PubMed

    Zander, Axel; Gravel, Dominique; Bersier, Louis-Félix; Gray, Sarah M

    2016-02-01

    Introduced top predators have the potential to disrupt community dynamics when prey species are naive to predation. The impact of introduced predators may also vary depending on the stage of community development. Early-succession communities are likely to have small-bodied and fast-growing species, but are not necessarily good at defending against predators. In contrast, late-succession communities are typically composed of larger-bodied species that are more predator resistant relative to small-bodied species. Yet, these aspects are greatly neglected in invasion studies. We therefore tested the effect of top predator presence on early- and late-succession communities that were either naive or non-naive to top predators. We used the aquatic community held within the leaves of Sarracenia purpurea. In North America, communities have experienced the S. purpurea top predator and are therefore non-naive. In Europe, this predator is not present and its niche has not been filled, making these communities top-predator naive. We collected early- and late-succession communities from two non-naive and two naive sites, which are climatically similar. We then conducted a common-garden experiment, with and without the presence of the top predator, in which we recorded changes in community composition, body size spectra, bacterial density, and respiration. We found that the top predator had no statistical effect on global measures of community structure and functioning. However, it significantly altered protist composition, but only in naive, early-succession communities, highlighting that the state of community development is important for understanding the impact of invasion.

  17. Investigating Invasives

    ERIC Educational Resources Information Center

    Lightbody, Mary

    2008-01-01

    Invasive species, commonly known as "invasives," are nonnative plants, animals, and microbes that completely take over and change an established ecosystem. The consequences of invasives' spread are significant. In fact, many of the species that appear on the Endangered Species list are threatened by invasives. Therefore, the topic of invasive…

  18. Investigating Invasives

    ERIC Educational Resources Information Center

    Lightbody, Mary

    2008-01-01

    Invasive species, commonly known as "invasives," are nonnative plants, animals, and microbes that completely take over and change an established ecosystem. The consequences of invasives' spread are significant. In fact, many of the species that appear on the Endangered Species list are threatened by invasives. Therefore, the topic of invasive…

  19. Predation on Japanese quail vs. house sparrow eggs in artificial nests: small eggs reveal small predators

    Treesearch

    Thomas J. Maier; Richard M. DeGraaf

    2000-01-01

    Nest predation studies frequently use eggs such as Japanese Quail (Coturnix japonica) to identify potential predators of Neotropical migrants' eggs, but such eggs may be too large or thick-shelled to identify the full complement of potential predators. We compared predation events and predators of Japanese Quail and smaller House Sparrow (

  20. Over-invasion by functionally equivalent invasive species.

    PubMed

    Russell, James C; Sataruddin, Nurul S; Heard, Allison D

    2014-08-01

    Multiple invasive species have now established at most locations around the world, and the rate of new species invasions and records of new invasive species continue to grow. Multiple invasive species interact in complex and unpredictable ways, altering their invasion success and impacts on biodiversity. Incumbent invasive species can be replaced by functionally similar invading species through competitive processes; however the generalized circumstances leading to such competitive displacement have not been well investigated. The likelihood of competitive displacement is a function of the incumbent advantage of the resident invasive species and the propagule pressure of the colonizing invasive species. We modeled interactions between populations of two functionally similar invasive species and indicated the circumstances under which dominance can be through propagule pressure and incumbent advantage. Under certain circumstances, a normally subordinate species can be incumbent and reject a colonizing dominant species, or successfully colonize in competition with a dominant species during simultaneous invasion. Our theoretical results are supported by empirical studies of the invasion of islands by three invasive Rattus species. Competitive displacement is prominent in invasive rats and explains the replacement of R. exulans on islands subsequently invaded by European populations of R. rattus and R. norvegicus. These competition outcomes between invasive species can be found in a broad range of taxa and biomes, and are likely to become more common. Conservation management must consider that removing an incumbent invasive species may facilitate invasion by another invasive species. Under very restricted circumstances of dominant competitive ability but lesser impact, competitive displacement may provide a novel method of biological control.

  1. Chemotactic predator-prey dynamics

    NASA Astrophysics Data System (ADS)

    Sengupta, Ankush; Kruppa, Tobias; Löwen, Hartmut

    2011-03-01

    A discrete chemotactic predator-prey model is proposed in which the prey secrets a diffusing chemical which is sensed by the predator and vice versa. Two dynamical states corresponding to catching and escaping are identified and it is shown that steady hunting is unstable. For the escape process, the predator-prey distance is diffusive for short times but exhibits a transient subdiffusive behavior which scales as a power law t1/3 with time t and ultimately crosses over to diffusion again. This allows us to classify the motility and dynamics of various predatory microbes and phagocytes. In particular, there is a distinct region in the parameter space where they prove to be infallible predators.

  2. Habitat segregation mediates predation by the benthic fish Cottus gobio on the exotic amphipod species Gammarus roeseli

    NASA Astrophysics Data System (ADS)

    Kaldonski, Nicolas; Lagrue, Clément; Motreuil, Sébastien; Rigaud, Thierry; Bollache, Loïc

    2008-09-01

    Predation is often considered as one of the most important biotic factor determining the success of exotic species. The freshwater amphipod Gammarus roeseli has widely colonized Western Europe, where it is frequently found in sympatry with the native species ( Gammarus pulex). Previous laboratory experiments revealed that G. roeseli may have an advantage over G. pulex through differential predation by native fish (brown trout). Morphological anti-predator defences (spines) were found responsible for lower rates of predation on the invasive G. roeseli. Here, using both field surveys and laboratory experiments, we tested if a differential of predation exists with other fish predators naturally encountered by gammarids. The main predators present in our field site were nocturnal benthic feeders (mainly bullheads, Cottus gobio). Fish diet analysis showed that, compared to its global availability in the river, G. roeseli was less consumed than G. pulex. In the field, however, G. roeseli was found mainly in the aquatic vegetation whereas G. pulex was found in all habitat types. Laboratory experiments in microcosms revealed that G. roeseli was less prone to predation by C. gobio only when vegetation was present. Depending on the type of predator, the differential of predation could therefore be mediated by antipredator behaviour, and a better usage of refuges, rather than by morphological defences.

  3. On Predation of Symbiotic Systems

    NASA Astrophysics Data System (ADS)

    Chatterjee, Samrat; Venturino, Ezio

    2011-09-01

    In this study we investigate an ecosystem in which a predator population hunts two different prey who live in symbiosis. Under the assumptions we take, the effect of the predators on the symbiotic system does not reveal any substantial change in the system dynamics, except that in sufficient numbers they can drive the ecosystem to extinction, although the prey in their absence might grow unboundedly.

  4. Integrated management of Scotch broom, Cytisus scoparius: is control enhanced when seed predation is combined with prescribed fire or mowing?

    USDA-ARS?s Scientific Manuscript database

    Integrated weed management (IWM) strategies are being advocated and employed to control invasive plants species. Prescribed fire, mechanical removal, and biological control (seed predator Exapion fuscirostre) are used to manage the invasive plant, Cytisus scoparius, in prairies at Fort Lewis, Washi...

  5. Predators of the Whitetail

    USGS Publications Warehouse

    Fagre, Daniel B.

    1994-01-01

    white-tailed deer have long been important prey for large predators. Before Europeans colonized North America, deer roaming the forested region east of the Great Plains and areas along the Gulf of Mexico were hunted by wolves and mountain lions, and by Native Americans for food and clothing materials. Today, wolves and mountain lions are largely gone from the white-tailed deer range of the eastern United States. Deer still face the threat of wolves in northern Minnesota, Michigan, and Wisconsin, and of mountain lions, to a limited extent, in Texas and south Florida. Relatively small populations of whitetails have expanded westward, showing up in the Great Plains and several areas west of the Continental Divide such as northwestern Montana, northern Idaho, and eastern Washington. More than half the prey killed by recolonizing wolves in northwestern Montana are white-tailed deer. Although it has not been well documented, these western whitetails undoubtedly also are preyed on by mountain lions. Wolves and mountain lions have evolved as effective killers of deer but with very different physical characteristics and hunting behaviors. Of course, for their part, whitetails have found ways to protect themselves.

  6. Invasive ants influence native lizard populations

    USDA-ARS?s Scientific Manuscript database

    The red imported fire ant (Solenopsis invicta; hereafter RIFA) is an invasive predator found on four continents, including South America, North America, Australia, and Asia. RIFAs are implicated in the decline of native invertebrates and vertebrates throughout their invaded range. We used the easter...

  7. Modelling landscape-level numerical responses of predators to prey: the case of cats and rabbits.

    PubMed

    Cruz, Jennyffer; Glen, Alistair S; Pech, Roger P

    2013-01-01

    Predator-prey systems can extend over large geographical areas but empirical modelling of predator-prey dynamics has been largely limited to localised scales. This is due partly to difficulties in estimating predator and prey abundances over large areas. Collection of data at suitably large scales has been a major problem in previous studies of European rabbits (Oryctolagus cuniculus) and their predators. This applies in Western Europe, where conserving rabbits and predators such as Iberian lynx (Lynx pardinus) is important, and in other parts of the world where rabbits are an invasive species supporting populations of introduced, and sometimes native, predators. In pastoral regions of New Zealand, rabbits are the primary prey of feral cats (Felis catus) that threaten native fauna. We estimate the seasonal numerical response of cats to fluctuations in rabbit numbers in grassland-shrubland habitat across the Otago and Mackenzie regions of the South Island of New Zealand. We use spotlight counts over 1645 km of transects to estimate rabbit and cat abundances with a novel modelling approach that accounts simultaneously for environmental stochasticity, density dependence and varying detection probability. Our model suggests that cat abundance is related consistently to rabbit abundance in spring and summer, possibly through increased rabbit numbers improving the fecundity and juvenile survival of cats. Maintaining rabbits at low abundance should therefore suppress cat numbers, relieving predation pressure on native prey. Our approach provided estimates of the abundance of cats and rabbits over a large geographical area. This was made possible by repeated sampling within each season, which allows estimation of detection probabilities. A similar approach could be applied to predator-prey systems elsewhere, and could be adapted to any method of direct observation in which there is no double-counting of individuals. Reliable estimates of numerical responses are essential

  8. Modelling Landscape-Level Numerical Responses of Predators to Prey: The Case of Cats and Rabbits

    PubMed Central

    Cruz, Jennyffer; Glen, Alistair S.; Pech, Roger P.

    2013-01-01

    Predator-prey systems can extend over large geographical areas but empirical modelling of predator-prey dynamics has been largely limited to localised scales. This is due partly to difficulties in estimating predator and prey abundances over large areas. Collection of data at suitably large scales has been a major problem in previous studies of European rabbits (Oryctolagus cuniculus) and their predators. This applies in Western Europe, where conserving rabbits and predators such as Iberian lynx (Lynx pardinus) is important, and in other parts of the world where rabbits are an invasive species supporting populations of introduced, and sometimes native, predators. In pastoral regions of New Zealand, rabbits are the primary prey of feral cats (Felis catus) that threaten native fauna. We estimate the seasonal numerical response of cats to fluctuations in rabbit numbers in grassland–shrubland habitat across the Otago and Mackenzie regions of the South Island of New Zealand. We use spotlight counts over 1645 km of transects to estimate rabbit and cat abundances with a novel modelling approach that accounts simultaneously for environmental stochasticity, density dependence and varying detection probability. Our model suggests that cat abundance is related consistently to rabbit abundance in spring and summer, possibly through increased rabbit numbers improving the fecundity and juvenile survival of cats. Maintaining rabbits at low abundance should therefore suppress cat numbers, relieving predation pressure on native prey. Our approach provided estimates of the abundance of cats and rabbits over a large geographical area. This was made possible by repeated sampling within each season, which allows estimation of detection probabilities. A similar approach could be applied to predator-prey systems elsewhere, and could be adapted to any method of direct observation in which there is no double-counting of individuals. Reliable estimates of numerical responses are essential

  9. Function of the Blood-Brain Barrier and Restriction of Drug Delivery to Invasive Glioma Cells: Findings in an Orthotopic Rat Xenograft Model of Glioma

    PubMed Central

    Agarwal, Sagar; Manchanda, Pooja; Vogelbaum, Michael A.; Ohlfest, John R.

    2013-01-01

    Despite aggressive treatment with radiation and chemotherapy, recurrence of glioblastoma multiforme (GBM) is inevitable. The objective of this study was to show that the blood-brain barrier (BBB), through a combination of tight junctions and active efflux transporters in the brain microvasculature, can significantly restrict delivery of molecularly targeted agents to invasive glioma cells. Transgenic mice lacking P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) were used to study efflux of erlotinib at the BBB. A U87 rat xenograft model of GBM was used to investigate the regional distribution of erlotinib to the tumor, and brain regions surrounding the tumor. The effect of concurrent administration of elacridar on regional tumor distribution of erlotinib was evaluated. We show that erlotinib transport across an intact BBB is significantly restricted due to P-gp- and Bcrp-mediated efflux transport. We then show that the BBB is sufficiently intact in areas of brain adjacent to the tumor core to significantly restrict erlotinib delivery. Inhibition of P-gp and Bcrp by the dual inhibitor elacridar dramatically increased erlotinib delivery to the tumor core, rim, and normal brain. These results provide conclusive evidence of the impact that active efflux at the BBB has on the delivery of molecularly targeted therapy to different tumor regions in glioma. These data also support the possibility that the repeated failure of clinical trials of new drugs for gliomas may be in part due to a failure to achieve effective concentrations in invasive tumor cells that reside behind an intact BBB. PMID:23014761

  10. Behavioral Hypervolumes of Predator Groups and Predator-Predator Interactions Shape Prey Survival Rates and Selection on Prey Behavior.

    PubMed

    Pruitt, Jonathan N; Howell, Kimberly A; Gladney, Shaniqua J; Yang, Yusan; Lichtenstein, James L L; Spicer, Michelle Elise; Echeverri, Sebastian A; Pinter-Wollman, Noa

    2017-03-01

    Predator-prey interactions often vary on the basis of the traits of the individual predators and prey involved. Here we examine whether the multidimensional behavioral diversity of predator groups shapes prey mortality rates and selection on prey behavior. We ran individual sea stars (Pisaster ochraceus) through three behavioral assays to characterize individuals' behavioral phenotype along three axes. We then created groups that varied in the volume of behavioral space that they occupied. We further manipulated the ability of predators to interact with one another physically via the addition of barriers. Prey snails (Chlorostome funebralis) were also run through an assay to evaluate their predator avoidance behavior before their use in mesocosm experiments. We then subjected pools of prey to predator groups and recorded the number of prey consumed and their behavioral phenotypes. We found that predator-predator interactions changed survival selection on prey traits: when predators were prevented from interacting, more fearful snails had higher survival rates, whereas prey fearfulness had no effect on survival when predators were free to interact. We also found that groups of predators that occupied a larger volume in behavioral trait space consumed 35% more prey snails than homogeneous predator groups. Finally, we found that behavioral hypervolumes were better predictors of prey survival rates than single behavioral traits or other multivariate statistics (i.e., principal component analysis). Taken together, predator-predator interactions and multidimensional behavioral diversity determine prey survival rates and selection on prey traits in this system.

  11. Is naïveté forever? Alien predator and aggressor recognition by two endemic island reptiles.

    PubMed

    Gérard, A; Jourdan, H; Cugnière, C; Millon, A; Vidal, E

    2014-11-01

    The disproportionate impacts of invasive predators are often attributed to the naïveté (i.e., inefficient or non-existing anti-predator behavior) of island native species having evolved without such predators. Naïveté has long been regarded as a fixed characteristic, but a few recent studies indicate a capacity for behavioral adaptation in native species in contact with alien predators. Here, we tested whether two reptiles endemic to New Caledonia, a skink, Caledoniscincus austrocaledonicus, and a gecko, Bavayia septuiclavis, recognized and responded to the odor of six introduced species (two rodents, the feral cat, and three species of ants). We used an experimental design in which reptiles had a choice of retreat sites with or without the odor of predators or aggressors. Skinks avoided two or three of the predators, whereas geckos avoided at most one. These results suggest that diurnal skinks are more responsive than nocturnal geckos to the odor of introduced predators. Neither skinks nor geckos avoided the three species of ants. Thus, the odors of alien predators are shown to influence retreat site selection by two native island reptiles. Moreover, the study suggests that this loss of naïveté varies among native species, probably as a consequence of the intensity of the threat and of time since introduction. These findings argue for re-thinking the behavioral flexibility of ectothermic reptiles in terms of their responses to biological invasion.

  12. Mutualism Between Fire Ants and Mealybugs Reduces Lady Beetle Predation.

    PubMed

    Cheng, Shoujie; Zeng, Ling; Xu, Yijuan

    2015-08-01

    Solenopsis invicta Buren is an important invasive pest that has a negative impact on biodiversity. However, current knowledge regarding the ecological effects of its interaction with honeydew-producing hemipteran insects is inadequate. To partially address this problem, we assessed whether the interaction between the two invasive species S. invicta and Phenacoccus solenopsis Tinsley mediated predation of P. solenopsis by Propylaea japonica Thunbery lady beetles using field investigations and indoor experiments. S. invicta tending significantly reduced predation by the Pr. japonica lady beetle, and this response was more pronounced for lady beetle larvae than for adults. A field investigation showed that the species richness and quantity of lady beetle species in plots with fire ants were much lower than in those without fire ants. In an olfaction bioassay, lady beetles preferred to move toward untended rather than tended mealybugs. Overall, these results suggest that mutualism between S. invicta and P. solenopsis may have a serious impact on predation of P. solenopsis by lady beetles, which could promote growth of P. solenopsis populations.

  13. Mismatched anti-predator behavioral responses in predator-naïve larval anurans

    PubMed Central

    Vance-Chalcraft, Heather D.

    2015-01-01

    Organisms are adept at altering behaviors to balance the tradeoff between foraging and predation risk in spatially and temporally shifting predator environments. In order to optimize this tradeoff, prey need to be able to display an appropriate response based on degree of predation risk. To be most beneficial in the earliest life stages in which many prey are vulnerable to predation, innate anti-predator responses should scale to match the risk imposed by predators until learned anti-predator responses can occur. We conducted an experiment that examined whether tadpoles with no previous exposure to predators (i.e., predator-naive) exhibit innate antipredator behavioral responses (e.g., via refuge use and spatial avoidance) that match the actual risk posed by each predator. Using 7 treatments (6 free-roaming, lethal predators plus no-predator control), we determined the predation rates of each predator on Lithobates sphenocephalus tadpoles. We recorded behavioral observations on an additional 7 nonlethal treatments (6 caged predators plus no-predator control). Tadpoles exhibited innate responses to fish predators, but not non-fish predators, even though two non-fish predators (newt and crayfish) consumed the most tadpoles. Due to a mismatch between innate response and predator consumption, tadpoles may be vulnerable to greater rates of predation at the earliest life stages before learning can occur. Thus, naïve tadpoles in nature may be at a high risk to predation in the presence of a novel predator until learned anti-predator responses provide additional defenses to the surviving tadpoles. PMID:26664805

  14. Effect of nanostructured thin film on minimally invasive surgery devices applications: characterization, cell cytotoxicity evaluation and an animal study in rat.

    PubMed

    Ou, Keng-Liang; Weng, Chao-Chia; Sugiatno, Erwan; Ruslin, Muhammad; Lin, Yun-Ho; Cheng, Han-Yi

    2016-07-01

    Minimally invasive surgery is performed using an endoscope and other instruments including the electrosurgical units. However, concerns including surgical smoke, tissue sticking and thermal injury are remaining in electrosurgery. Accordingly, a newly developed electrosurgical electrode coating with hydrogenated Cu-incorporated diamond-like carbon (DLC-Cu) film is purposed to improve the instrument performance. The morphologies of DLC-Cu surfaces were characterized using transmission electron microscopy, scanning electron microscopy and atomic force microscopy. In this study, lesions were made on the liver lobes of adult rats, using a monopolar electrosurgical unit equipped with untreated stainless steel electrodes or treated-electrodes. Animals were killed for evaluations at 0, 3, 7 and 28 days postoperatively. Treated-electrodes generate less sticking tissues and adhesive blood cells. Thermography revealed that the surgical temperature in liver tissue from the treated-electrode was significantly lower than the untreated-electrode. Total injury area of livers treated with treated-electrodes was significantly smaller than the untreated-electrodes treatment. Moreover, treated-electrodes caused a relatively smaller area of lateral thermal injury, a smaller area of fibrotic tissue and a faster process of remodeling than the untreated-electrodes. Western blot analysis showed that rats treated with treated-electrode expressed lower levels of NF-κB, caspase-3 and MMP-9 than untreated-electrode. Immunofluorescence staining for caspase-3 revealed that the untreated-electrode caused more serious injury. This study reveals that the plating of electrodes with hydrogenated Cu-incorporated diamond-like carbon film is an efficient method for improving the performance of electrosurgical units, and should benefit wound remodeling. However, more tests must be carried out to confirm these promising findings in human patients.

  15. Introduced Predator Elicits Deficient Brood Defence Behaviour in a Crater Lake Fish

    PubMed Central

    Lehtonen, Topi K.; McCrary, Jeffrey K.; Meyer, Axel

    2012-01-01

    Introduced species represent one of the most serious global threats to biodiversity. In this field-based study, we assessed behavioural responses of brood tending cichlid fish to an invasive predator of their offspring. This was achieved by comparing parental defence responses of the endangered arrow cichlid (Amphilophus zaliosus), a fish species endemic to the crater lake Apoyo in Nicaragua, towards the bigmouth sleeper (Gobiomorus dormitor), a formidable predator of cichlid fry, and all other potential fish predators of offspring. The bigmouth sleeper was recently introduced into Apoyo but naturally co-exists with cichlids in a few other Nicaraguan lakes. Arrow cichlid parents allowed bigmouth sleepers to advance much closer to their fry than other predators before initiating aggressive brood defence behaviours. Interestingly, parents of a very closely related species, A. sagittae, which has coevolved with bigmouth sleepers in crater lake Xiloá, reacted to approaching bigmouth sleepers at comparable distances as to other predators of cichlid fry. These results provide a novel demonstration of the specific mechanism (i.e. naive parental behaviour) by which invasive predators may negatively affect species that lack the adequate behavioural repertoire. PMID:22253881

  16. Adaptation of prey and predators between patches.

    PubMed

    Wang, Wendi; Takeuchi, Yasuhiro

    2009-06-21

    Mathematical models are proposed to simulate migrations of prey and predators between patches. In the absence of predators, it is shown that the adaptation of prey leads to an ideal spatial distribution in the sense that the maximal capacity of each patch is achieved. With the introduction of co-adaptation of predators, it is proved that both prey and predators achieve ideal spatial distributions when the adaptations are weak. Further, it is shown that the adaptation of prey and predators increases the survival probability of predators from the extinction in both patches to the persistence in one patch. It is also demonstrated that there exists a pattern that prey and predators cooperate well through adaptations such that predators are permanent in every patch in the case that predators become extinct in each patch in the absence of adaptations. For strong adaptations, it is proved that the model admits periodic cycles and multiple stability transitions.

  17. Local genetic adaptation generates latitude-specific effects of warming on predator-prey interactions.

    PubMed

    De Block, Marjan; Pauwels, Kevin; Van Den Broeck, Maarten; De Meester, Luc; Stoks, Robby

    2013-03-01

    Temperature effects on predator-prey interactions are fundamental to better understand the effects of global warming. Previous studies never considered local adaptation of both predators and prey at different latitudes, and ignored the novel population combinations of the same predator-prey species system that may arise because of northward dispersal. We set up a common garden warming experiment to study predator-prey interactions between Ischnura elegans damselfly predators and Daphnia magna zooplankton prey from three source latitudes spanning >1500 km. Damselfly foraging rates showed thermal plasticity and strong latitudinal differences consistent with adaptation to local time constraints. Relative survival was higher at 24 °C than at 20 °C in southern Daphnia and higher at 20 °C than at 24 °C, in northern Daphnia indicating local thermal adaptation of the Daphnia prey. Yet, this thermal advantage disappeared when they were confronted with the damselfly predators of the same latitude, reflecting also a signal of local thermal adaptation in the damselfly predators. Our results further suggest the invasion success of northward moving predators as well as prey to be latitude-specific. We advocate the novel common garden experimental approach using predators and prey obtained from natural temperature gradients spanning the predicted temperature increase in the northern populations as a powerful approach to gain mechanistic insights into how community modules will be affected by global warming. It can be used as a space-for-time substitution to inform how predator-prey interaction may gradually evolve to long-term warming.

  18. Are lemmings prey or predators?

    NASA Astrophysics Data System (ADS)

    Turchin, P.; Oksanen, L.; Ekerholm, P.; Oksanen, T.; Henttonen, H.

    2000-06-01

    Large oscillations in the populations of Norwegian lemmings have mystified both professional ecologists and lay public. Ecologists suspect that these oscillations are driven by a trophic mechanism: either an interaction between lemmings and their food supply, or an interaction between lemmings and their predators. If lemming cycles are indeed driven by a trophic interaction, can we tell whether lemmings act as the resource (`prey') or the consumer (`predator')? In trophic interaction models, peaks of resource density generally have a blunt, rounded shape, whereas peaks of consumer density are sharp and angular. Here we have applied several statistical tests to three lemming datasets and contrasted them with comparable data for cyclic voles. We find that vole peaks are blunt, consistent with their cycles being driven by the interaction with predators. In contrast, the shape of lemming peaks is consistent with the hypothesis that lemmings are functional predators, that is, their cycles are driven by their interaction with food plants. Our findings suggest that a single mechanism, such as interaction between rodents and predators, is unlikely to provide the `universal' explanation of all cyclic rodent dynamics.

  19. Invasive Candidiasis

    MedlinePlus

    ... Invasive candidiasis is an infection caused by a yeast (a type of fungus) called Candida . Unlike Candida ... mouth and throat (also called “thrush”) or vaginal “yeast infections,” invasive candidiasis is a serious infection that ...

  20. Invasive Species

    EPA Pesticide Factsheets

    Invasive species have significantly changed the Great Lakes ecosystem. An invasive species is a plant or animal that is not native to an ecosystem, and whose introduction is likely to cause economic, human health, or environmental damage.

  1. Geometric optimization for prey-predator strategies.

    PubMed

    Alshamary, Bader; Calin, Ovidiu

    2011-11-01

    This paper investigates several strategies for prey and predator in both bounded and unbounded domains, assuming they have the same speed. The work describes how the prey should move to escape from the predator and how predator should move to catch the prey. The approach is agent-based and explicitly tracks movement of individuals as prey and predator. We show that the prey escapes one or two competing predators, while might be caught in the case of three predators. The paper also describes a strategy for finding a well camouflaged static prey which emits signals.

  2. Behavioral refuges and predator-prey coexistence.

    PubMed

    Křivan, Vlastimil

    2013-12-21

    The effects of a behavioral refuge caused either by the predator optimal foraging or prey adaptive antipredator behavior on the Gause predator-prey model are studied. It is shown that both of these mechanisms promote predator-prey coexistence either at an equilibrium, or along a limit cycle. Adaptive prey refuge use leads to hysteresis in prey antipredator behavior which allows predator-prey coexistence along a limit cycle. Similarly, optimal predator foraging leads to sigmoidal functional responses with a potential to stabilize predator-prey population dynamics at an equilibrium, or along a limit cycle.

  3. Predation by signal crayfish Pacifastacus leniusculus on fish eggs and its consequences for coregonid recruitment.

    PubMed

    Karjalainen, J; Ruokonen, T J; MarjomäKi, T J; Martikainen, A; Pursiainen, M; Sarvala, J; Tarvainen, M; Ventelä, A-M

    2015-01-21

    The character and magnitude of predation by the invasive, ectothermic Pacifastacus leniusculus, a crayfish widely introduced to Europe and Japan from North America, on the eggs of coregonid fishes, vendace Coregonus albula and whitefish Coregonus lavaretus were examined by experimentation, modelling and field data. The present results showed that P. leniusculus has the potential to be very efficient predator of fish eggs under winter conditions, but the predation by P. leniusculus did not significantly decrease production of coregonid larvae during the years with a high P. leniusculus population in the study lake. Hence, the mortality caused by the novel invertebrate predator appeared to compensate for other yet unexplored mortality factors instead of having an additive effect on the present salmonids.

  4. Time-dependent effects of rapamycin on consolidation of predator stress-induced hyperarousal.

    PubMed

    Fifield, Kathleen; Hebert, Mark; Williams, Kimberly; Linehan, Victoria; Whiteman, Jesse D; Mac Callum, Phillip; Blundell, Jacqueline

    2015-06-01

    Previous studies have indicated that rapamycin, a potent inhibitor of the mammalian target of rapamycin (mTOR) pathway, blocks consolidation of shock-induced associative fear memories. Moreover, rapamycin's block of associative fear memories is time-dependent. It is unknown, however, if rapamycin blocks consolidation of predator stress-induced non-associative fear memories. Furthermore, the temporal pattern of mTOR activation following predator stress is unknown. Thus, the goal of the current studies was to determine if rapamycin blocks consolidation of predator stress-induced fear memories and if so, whether rapamycin's effect is time-dependent. Male rats were injected systemically with rapamycin at various time points following predator stress. Predator stress involves an acute, unprotected exposure of a rat to a cat, which causes long-lasting non-associative fear memories manifested as generalized hyperarousal and increased anxiety-like behaviour. We show that rapamycin injected immediately after predator stress blocked consolidation of stress-induced startle. However, rapamycin injected 9, 24 or 48h post predator stress potentiated stress-induced startle. Consistent with shock-induced associative fear memories, we show that mTOR signalling is essential for consolidation of predator stress-induced hyperarousal. However, unlike shock-induced fear memories, a second, persistent, late phase mTOR-dependent process following predator stress actually dampens startle. Consistent with previous findings, our data support the potential role for rapamycin in treatment of stress related disorders such as posttraumatic stress disorder. However, our data suggest timing of rapamycin administration is critical.

  5. Predation by Red Foxes (Vulpes vulpes) at an Outdoor Piggery

    PubMed Central

    Fleming, Patricia A.; Dundas, Shannon J.; Lau, Yvonne Y. W.; Pluske, John R.

    2016-01-01

    Simple Summary Predation of piglets by red foxes is a significant risk for outdoor/free-range pork producers, but is often difficult to quantify. Using remote sensing cameras, we recorded substantial evidence of red foxes taking piglets from around farrowing huts, and found that piglets were most likely to be recorded as “missing” over their first week. These data suggest that fox predation contributed to the marked production differences between this outdoor farm and a similar-sized intensive farm under the same management, and warrant greater control of this introduced, invasive predator. Abstract Outdoor pig operations are an alternative to intensive systems of raising pigs; however for the majority of outdoor pork producers, issues of biosecurity and predation control require significant management and (or) capital investment. Identifying and quantifying predation risk in outdoor pork operations has rarely been done, but such data would be informative for these producers as part of their financial and logistical planning. We quantified potential impact of fox predation on piglets bred on an outdoor pork operation in south-western Australia. We used remote sensor cameras at select sites across the farm as well as above farrowing huts to record interactions between predators and pigs (sows and piglets). We also identified animal losses from breeding records, calculating weaning rate as a proportion of piglets born. Although only few piglets were recorded lost to fox predation (recorded by piggery staff as carcasses that are “chewed”), it is likely that foxes were contributing substantially to the 20% of piglets that were reported “missing”. Both sets of cameras recorded a high incidence of fox activity; foxes appeared on camera soon after staff left for the day, were observed tracking and taking live piglets (despite the presence of sows), and removed dead carcasses from in front of the cameras. Newly born and younger piglets appeared to be the most

  6. Diel patterns in sea urchin activity and predation on sea urchins on the Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Young, M. A. L.; Bellwood, D. R.

    2011-09-01

    Understanding diel patterns in sea urchin activity is important when assessing sea urchin populations and when interpreting their interactions with predators. Here we employ a combination of surveys and a non-invasive tethering technique to examine these patterns in an intact coral reef system on the Great Barrier Reef (GBR). We also assess local scale variation in relative diurnal predation pressure. Surveys revealed that sea urchins were active and exposed at night. Echinometra mathaei and Echinothrix calamaris were the most abundant species with significantly higher night densities (0.21 and 0.03 ind. m-2, respectively), than daytime densities (0.05 and 0.001, respectively). Bioassays revealed that exposed adult E. mathaei (the most abundant sea urchin species) were 30.8 times more likely to be eaten during the day than at night when controlling for sites. This observation concurs with widely held assumptions that nocturnal activity is a risk-related adaptive response to diurnal predation pressure. Despite relatively intact predator communities on the GBR, potential predation pressure on diurnally exposed E. mathaei assays was variable at a local scale and the biomass of potential fish predators at each site was a poor predictive measure of this variation. Patterns in predation appear to be more complex and variable than we may have assumed.

  7. Experimental evidence for emergent facilitation: promoting the existence of an invertebrate predator by killing its prey.

    PubMed

    Huss, Magnus; Nilsson, Karin A

    2011-05-01

    1. Recent theoretical insights have shown that predator species may help each other to persist by size-selective foraging on a shared prey. By feeding on a certain prey stage, a predator may induce a compensatory response in another stage of the same prey species, thereby favouring other predators; a phenomenon referred to as emergent facilitation. 2. To test whether emergent facilitation may occur in a natural system, we performed an enclosure experiment where we mimicked fish predation by selectively removing large zooplankton and subsequently following the response of the invertebrate predator Bythotrephes longimanus. 3. Positive responses to harvest were observed in the biomass of juvenile individuals of the dominant zooplankton Holopedium gibberum and in Bythotrephes densities. Hence, by removing large prey, we increased the biomass of small prey, i.e. stage-specific biomass overcompensation was present in the juvenile stage of Holopedium. This favoured Bythotrephes, which preferentially feed on small Holopedium. 4. We argue that the stage-specific overcompensation occurred as a result of increased per capita fecundity of adult Holopedium and as a result of competitive release following harvest. If shown to be common, emergent facilitation may be a major mechanism behind observed predator extinctions and patterns of predator invasions.

  8. Spatiotemporal Analysis of Predation by Carabid Beetles (Carabidae) on Nematode Infected and Uninfected Slugs in the Field

    PubMed Central

    Hatteland, Bjørn Arild; Haukeland, Solveig; Roth, Steffen; Brurberg, May Bente; Vaughan, Ian P.; Symondson, William O. C.

    2013-01-01

    The dynamics of predation on parasites within prey has received relatively little attention despite the profound effects this is likely to have on both prey and parasite numbers and hence on biological control programmes where parasites are employed. The nematode Phasmarhabditis hermaphrodita is a commercially available biological agent against slugs. Predation on these slugs may, at the same time, result in intraguild predation on slug-parasitic nematodes. This study describes, for the first time, predation by carabid beetles on slugs and their nematode parasites on both spatial and temporal scales, using PCR-based methods. The highest nematode infection levels were found in the slugs Deroceras reticulatum and Arion silvaticus. Numbers of infected slugs decreased over time and no infected slugs were found four months after nematode application. The density of the most abundant slug, the invasive Arion vulgaris, was positively related to the activity-density of the carabid beetle, Carabus nemoralis. Predation on slugs was density and size related, with highest predation levels also on A. vulgaris. Predation on A. vulgaris decreased significantly in summer when these slugs were larger than one gram. Predation by C. nemoralis on slugs was opportunistic, without any preferences for specific species. Intraguild predation on the nematodes was low, suggesting that carabid beetles such as C. nemoralis probably do not have a significant impact on the success of biological control using P. hermaphrodita. PMID:24349202

  9. Spatiotemporal analysis of predation by carabid beetles (Carabidae) on nematode infected and uninfected slugs in the field.

    PubMed

    Hatteland, Bjørn Arild; Haukeland, Solveig; Roth, Steffen; Brurberg, May Bente; Vaughan, Ian P; Symondson, William O C

    2013-01-01

    The dynamics of predation on parasites within prey has received relatively little attention despite the profound effects this is likely to have on both prey and parasite numbers and hence on biological control programmes where parasites are employed. The nematode Phasmarhabditis hermaphrodita is a commercially available biological agent against slugs. Predation on these slugs may, at the same time, result in intraguild predation on slug-parasitic nematodes. This study describes, for the first time, predation by carabid beetles on slugs and their nematode parasites on both spatial and temporal scales, using PCR-based methods. The highest nematode infection levels were found in the slugs Deroceras reticulatum and Arion silvaticus. Numbers of infected slugs decreased over time and no infected slugs were found four months after nematode application. The density of the most abundant slug, the invasive Arion vulgaris, was positively related to the activity-density of the carabid beetle, Carabus nemoralis. Predation on slugs was density and size related, with highest predation levels also on A. vulgaris. Predation on A. vulgaris decreased significantly in summer when these slugs were larger than one gram. Predation by C. nemoralis on slugs was opportunistic, without any preferences for specific species. Intraguild predation on the nematodes was low, suggesting that carabid beetles such as C. nemoralis probably do not have a significant impact on the success of biological control using P. hermaphrodita.

  10. Ficus whitefly, Singhiella simplex, and its predation by a coccinellid beetle, Delphastus catalinae

    USDA-ARS?s Scientific Manuscript database

    Ficus whitefly, Singhiella simplex, is a pest of ficus plant such as Ficus benjamina, F. altissima, F. bengalensis and others. This invasive pest causes plants to exhibit leaf yellowing, wilting, and eventually, leaf drop. There is little information on the effectiveness of insect predators to contr...

  11. Hunting cooperation and Allee effects in predators.

    PubMed

    Teixeira Alves, Mickaël; Hilker, Frank M

    2017-04-21

    Cooperation is a ubiquitous behavior in many biological systems and is well-known for promoting Allee effects. However, few studies have paid attention to mechanisms inducing Allee effects in predators. Here, we focus on hunting cooperation and use a classical predator-prey system for identifying the impact of this mechanism. We add a cooperation term to the attack rate of the predator population, and investigate the equilibrium stability in phase plane and bifurcation diagrams. We show that hunting cooperation can be beneficial to the predator population by increasing the attack rate. We identify a scenario in which hunting cooperation produces Allee effects in predators and allows the latter to persist when the prey population does not sustain them in the absence of hunting cooperation. However, hunting cooperation can turn detrimental to predators when prey density drastically decreases because of increased predation pressure, which in turn decreases the predator intake. Hunting cooperation can also destabilize the system and promote a sudden collapse of the predator population. We generalize the model and prove that demographic Allee effects always occur when (1) the attack rate increases with the predator density, and (2) the functional response increases with the attack rate. We conclude that Allee effects in predators might be more widespread than expected. Mechanisms inducing such effects may strongly influence not only predators, but also the fate of ecosystems involving predators as in biological control programs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Non-invasive parenchymal, vascular and metabolic high-frequency ultrasound and photoacoustic rat deep brain imaging.

    PubMed

    Giustetto, Pierangela; Filippi, Miriam; Castano, Mauro; Terreno, Enzo

    2015-03-02

    Photoacoustics and high frequency ultrasound stands out as powerful tools for neurobiological applications enabling high-resolution imaging on the central nervous system of small animals. However, transdermal and transcranial neuroimaging is frequently affected by low sensitivity, image aberrations and loss of space resolution, requiring scalp or even skull removal before imaging. To overcome this challenge, a new protocol is presented to gain significant insights in brain hemodynamics by photoacoustic and high-frequency ultrasounds imaging with the animal skin and skull intact. The procedure relies on the passage of ultrasound (US) waves and laser directly through the fissures that are naturally present on the animal cranium. By juxtaposing the imaging transducer device exactly in correspondence to these selected areas where the skull has a reduced thickness or is totally absent, one can acquire high quality deep images and explore internal brain regions that are usually difficult to anatomically or functionally describe without an invasive approach. By applying this experimental procedure, significant data can be collected in both sonic and optoacoustic modalities, enabling to image the parenchymal and the vascular anatomy far below the head surface. Deep brain features such as parenchymal convolutions and fissures separating the lobes were clearly visible. Moreover, the configuration of large and small blood vessels was imaged at several millimeters of depth, and precise information were collected about blood fluxes, vascular stream velocities and the hemoglobin chemical state. This repertoire of data could be crucial in several research contests, ranging from brain vascular disease studies to experimental techniques involving the systemic administration of exogenous chemicals or other objects endowed with imaging contrast enhancement properties. In conclusion, thanks to the presented protocol, the US and PA techniques become an attractive noninvasive

  13. Non-invasive Parenchymal, Vascular and Metabolic High-frequency Ultrasound and Photoacoustic Rat Deep Brain Imaging

    PubMed Central

    Giustetto, Pierangela; Filippi, Miriam; Castano, Mauro; Terreno, Enzo

    2015-01-01

    Photoacoustics and high frequency ultrasound stands out as powerful tools for neurobiological applications enabling high-resolution imaging on the central nervous system of small animals. However, transdermal and transcranial neuroimaging is frequently affected by low sensitivity, image aberrations and loss of space resolution, requiring scalp or even skull removal before imaging. To overcome this challenge, a new protocol is presented to gain significant insights in brain hemodynamics by photoacoustic and high-frequency ultrasounds imaging with the animal skin and skull intact. The procedure relies on the passage of ultrasound (US) waves and laser directly through the fissures that are naturally present on the animal cranium. By juxtaposing the imaging transducer device exactly in correspondence to these selected areas where the skull has a reduced thickness or is totally absent, one can acquire high quality deep images and explore internal brain regions that are usually difficult to anatomically or functionally describe without an invasive approach. By applying this experimental procedure, significant data can be collected in both sonic and optoacoustic modalities, enabling to image the parenchymal and the vascular anatomy far below the head surface. Deep brain features such as parenchymal convolutions and fissures separating the lobes were clearly visible. Moreover, the configuration of large and small blood vessels was imaged at several millimeters of depth, and precise information were collected about blood fluxes, vascular stream velocities and the hemoglobin chemical state. This repertoire of data could be crucial in several research contests, ranging from brain vascular disease studies to experimental techniques involving the systemic administration of exogenous chemicals or other objects endowed with imaging contrast enhancement properties. In conclusion, thanks to the presented protocol, the US and PA techniques become an attractive noninvasive

  14. Predicting invasive species impacts: a community module functional response approach reveals context dependencies.

    PubMed

    Paterson, Rachel A; Dick, Jaimie T A; Pritchard, Daniel W; Ennis, Marilyn; Hatcher, Melanie J; Dunn, Alison M

    2015-03-01

    Predatory functional responses play integral roles in predator-prey dynamics, and their assessment promises greater understanding and prediction of the predatory impacts of invasive species. Other interspecific interactions, however, such as parasitism and higher-order predation, have the potential to modify predator-prey interactions and thus the predictive capability of the comparative functional response approach. We used a four-species community module (higher-order predator; focal native or invasive predators; parasites of focal predators; native prey) to compare the predatory functional responses of native Gammarus duebeni celticus and invasive Gammarus pulex amphipods towards three invertebrate prey species (Asellus aquaticus, Simulium spp., Baetis rhodani), thus, quantifying the context dependencies of parasitism and a higher-order fish predator on these functional responses. Our functional response experiments demonstrated that the invasive amphipod had a higher predatory impact (lower handling time) on two of three prey species, which reflects patterns of impact observed in the field. The community module also revealed that parasitism had context-dependent influences, for one prey species, with the potential to further reduce the predatory impact of the invasive amphipod or increase the predatory impact of the native amphipod in the presence of a higher-order fish predator. Partial consumption of prey was similar for both predators and occurred increasingly in the order A. aquaticus, Simulium spp. and B. rhodani. This was associated with increasing prey densities, but showed no context dependencies with parasitism or higher-order fish predator. This study supports the applicability of comparative functional responses as a tool to predict and assess invasive species impacts incorporating multiple context dependencies.

  15. Selective Predation of a Stalking Predator on Ungulate Prey.

    PubMed

    Heurich, Marco; Zeis, Klara; Küchenhoff, Helmut; Müller, Jörg; Belotti, Elisa; Bufka, Luděk; Woelfing, Benno

    2016-01-01

    Prey selection is a key factor shaping animal populations and evolutionary dynamics. An optimal forager should target prey that offers the highest benefits in terms of energy content at the lowest costs. Predators are therefore expected to select for prey of optimal size. Stalking predators do not pursue their prey long, which may lead to a more random choice of prey individuals. Due to difficulties in assessing the composition of available prey populations, data on prey selection of stalking carnivores are still scarce. We show how the stalking predator Eurasian lynx (Lynx lynx) selects prey individuals based on species identity, age, sex and individual behaviour. To address the difficulties in assessing prey population structure, we confirm inferred selection patterns by using two independent data sets: (1) data of 387 documented kills of radio-collared lynx were compared to the prey population structure retrieved from systematic camera trapping using Manly's standardized selection ratio alpha and (2) data on 120 radio-collared roe deer were analysed using a Cox proportional hazards model. Among the larger red deer prey, lynx selected against adult males-the largest and potentially most dangerous prey individuals. In roe deer lynx preyed selectively on males and did not select for a specific age class. Activity during high risk periods reduced the risk of falling victim to a lynx attack. Our results suggest that the stalking predator lynx actively selects for size, while prey behaviour induces selection by encounter and stalking success rates.

  16. Selective Predation of a Stalking Predator on Ungulate Prey

    PubMed Central

    Heurich, Marco; Zeis, Klara; Küchenhoff, Helmut; Müller, Jörg; Belotti, Elisa; Bufka, Luděk; Woelfing, Benno

    2016-01-01

    Prey selection is a key factor shaping animal populations and evolutionary dynamics. An optimal forager should target prey that offers the highest benefits in terms of energy content at the lowest costs. Predators are therefore expected to select for prey of optimal size. Stalking predators do not pursue their prey long, which may lead to a more random choice of prey individuals. Due to difficulties in assessing the composition of available prey populations, data on prey selection of stalking carnivores are still scarce. We show how the stalking predator Eurasian lynx (Lynx lynx) selects prey individuals based on species identity, age, sex and individual behaviour. To address the difficulties in assessing prey population structure, we confirm inferred selection patterns by using two independent data sets: (1) data of 387 documented kills of radio-collared lynx were compared to the prey population structure retrieved from systematic camera trapping using Manly’s standardized selection ratio alpha and (2) data on 120 radio-collared roe deer were analysed using a Cox proportional hazards model. Among the larger red deer prey, lynx selected against adult males—the largest and potentially most dangerous prey individuals. In roe deer lynx preyed selectively on males and did not select for a specific age class. Activity during high risk periods reduced the risk of falling victim to a lynx attack. Our results suggest that the stalking predator lynx actively selects for size, while prey behaviour induces selection by encounter and stalking success rates. PMID:27548478

  17. Granivory of invasive, naturalized, and native plants in communities differentially susceptible to invasion

    Treesearch

    B. M. Connolly; D. E. Pearson; R. N. Mack

    2014-01-01

    Seed predation is an important biotic filter that can influence abundance and spatial distributions of native species through differential effects on recruitment. This filter may also influence the relative abundance of nonnative plants within habitats and the communities' susceptibility to invasion via differences in granivore identity, abundance, and food...

  18. Functional traits determine formation of mutualism and predation interactions in seed-rodent dispersal system of a subtropical forest

    NASA Astrophysics Data System (ADS)

    Chang, Gang; Zhang, Zhibin

    2014-02-01

    Network structure in plant-animal systems has been widely investigated but the roles of functional traits of plants and animals in formation of mutualism and predation interactions and community structure are still not fully understood. In this study, we quantitatively assessed interaction strength of mutualism and predation between 5 tree species and 7 rodent species by using semi-natural enclosures in a subtropical forest in southwest China. Seeds with high handling-time and nutrition traits (for both rat and mouse species) or high tannin trait (for mouse species) show high mutualism but low predation with rodents; while seeds with low handling-time and low nutrition traits show high predation but low mutualism with rodents. Large-sized rat species are more linked to seeds with high handling-time and high nutrition traits, while small-sized mouse species are more connected with seeds with low handling-time, low nutrition value and high tannin traits. Anti-predation seed traits tend to increase chance of mutualism instead of reducing predation by rodents, suggesting formation of mutualism may be connected with that of predation. Our study demonstrates that seed and animal traits play significant roles in the formation of mutualism and predation and network structure of the seed-rodent dispersal system.

  19. Predators and the public trust.

    PubMed

    Treves, Adrian; Chapron, Guillaume; López-Bao, Jose V; Shoemaker, Chase; Goeckner, Apollonia R; Bruskotter, Jeremy T

    2017-02-01

    Many democratic governments recognize a duty to conserve environmental resources, including wild animals, as a public trust for current and future citizens. These public trust principles have informed two centuries of U.S.A. Supreme Court decisions and environmental laws worldwide. Nevertheless numerous populations of large-bodied, mammalian carnivores (predators) were eradicated in the 20th century. Environmental movements and strict legal protections have fostered predator recoveries across the U.S.A. and Europe since the 1970s. Now subnational jurisdictions are regaining management authority from central governments for their predator subpopulations. Will the history of local eradication repeat or will these jurisdictions adopt public trust thinking and their obligation to broad public interests over narrower ones? We review the role of public trust principles in the restoration and preservation of controversial species. In so doing we argue for the essential roles of scientists from many disciplines concerned with biological diversity and its conservation. We look beyond species endangerment to future generations' interests in sustainability, particularly non-consumptive uses. Although our conclusions apply to all wild organisms, we focus on predators because of the particular challenges they pose for government trustees, trust managers, and society. Gray wolves Canis lupus L. deserve particular attention, because detailed information and abundant policy debates across regions have exposed four important challenges for preserving predators in the face of interest group hostility. One challenge is uncertainty and varied interpretations about public trustees' responsibilities for wildlife, which have created a mosaic of policies across jurisdictions. We explore how such mosaics have merits and drawbacks for biodiversity. The other three challenges to conserving wildlife as public trust assets are illuminated by the biology of predators and the interacting

  20. Living with the enemy: parasites and pathogens of the invasive alien ladybird Harmonia axyridis

    USDA-ARS?s Scientific Manuscript database

    Harmonia axyridis is an invasive alien predator in many countries across the world. The rapid establishment and spread of this species is of concern because of the threat it poses to biodiversity as a generalist predator. Understanding the mechanisms that contribute to the success of this species ...

  1. Increasing the intestinal resistance of rats to the invasive pathogen Salmonella enteritidis: additive effects of dietary lactulose and calcium.

    PubMed Central

    Bovee-Oudenhoven, I M; Termont, D S; Heidt, P J; Van der Meer, R

    1997-01-01

    BACKGROUND AND AIMS: Lactulose fermentation by the intestinal microflora acidifies the gut contents, resulting in an increased resistance to colonisation by acid sensitive pathogens. The extent of fermentation should be controlled to prevent acid induced epithelial cell damage. Considering the buffering capacity of calcium phosphate and its intestinal cytoprotective effects, whether supplemental calcium phosphate adds to the increased resistance to intestinal infections by lactulose fermentations was studied. METHODS: In a strictly controlled experiment, rats were fed a purified low calcium control diet, a low calcium/lactulose diet, or a high calcium/lactulose diet, and subsequently infected orally with Salmonella enteritidis. RESULTS: Lactulose fermentation lowered the pH and increased the lactic acid concentration of the intestinal contents, which significantly reduced excretion of this pathogen in faeces; thus it improved the resistance to colonisation. This agreed with the high sensitivity of S enteritidis to lactic acid (main metabolite of lactulose fermentation) in vitro. Calcium phosphate decreased translocation of S enteritidis to the systemic circulation, an effect independent of lactulose. The unfavourable increased cytotoxicity of faecal water caused by lactulose fermentation was more than counteracted by supplemental calcium phosphate. Moreover, calcium phosphate stimulated lactulose fermentation, as judged by the reduced lactulose excretion in faeces and increased lactic acid, ammonia, and faecal nitrogen excretion. CONCLUSION: Extra calcium phosphate added to a lactulose diet improves the resistance to colonisation and translocation of S enteritidis. This is probably mediated by a calcium induced stimulation of lactulose fermentation by the intestinal microflora and reversion of the lactulose mediated increased luminal cytotoxicity, which reduces damage inflicted on the intestinal mucosa. PMID:9176078

  2. Telemetry monitoring for non-invasive assessment of changes in core temperature after spinal drug administration in freely moving rats.

    PubMed

    Safrany-Fark, A; Petrovszki, Z; Kekesi, G; Keresztes, C; Benedek, G; Horvath, G

    2015-01-01

    There are no data available about the effects of spinally administered drugs on thermoregulation in freely moving animals. The first goal of the present study was to throw light on the consequences of intrathecally administered saline as a vehicle on core temperature and motor activity in unrestrained conditions. The second goal was to characterize the effects of morphine on these parameters as a widely used antinociceptive drug in spinal anesthesia, and reveal the potential role of the N-methyl-d-aspartate (NMDA) receptors in these processes. For these purposes, male Wistar rats were catheterized intrathecally, and E-Mitter battery-free transponders were implanted intraabdominally to continuously monitor core temperature and locomotor activity. Saline induced a short-lasting hyperactivity accompanied by significant and prolonged hyperthermia that was blunted by systemic paracetamol administration. Morphine had no impact on motor activity; however, it caused high but equivalent degree hyperthermia in a wide dose range (1-15 μg), suggesting that it reached its peak effect. In the highest applied dose (25 μg), the NMDA receptor antagonist kynurenic acid blunted the saline-induced hyperthermia, and all doses caused higher hyperactivity compared to vehicle or morphine injections. In combination, kynurenic acid significantly inhibited the morphine-induced hyperthermia. These data suggest that this method might be a valuable tool for investigating the thermoregulatory and locomotor effects of different drugs at spinal level; however, the prolonged effects of intrathecal vehicle injections should also be considered. The results point out that morphine is a very potent hyperthermic drug that may act primarily on the efferent limb of thermoregulation, at least partially, via an indirect NMDA-receptor mediated action mechanism. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. Predation of Songbird Nests Differs By Predator and Between Field and Forest Habitats

    Treesearch

    Frank R., III Thompson; Dirk E. Burhans

    2003-01-01

    Our understanding of factors affecting nest predation and ability to mitigate high nest predation rates is hampered by a lack of information on the importance of various nest predator species in different habitats and landscapes. We identified predators of songbird nests in old-field and forest habitats in central Missouri, USA, with miniature video cameras. We used an...

  4. Intraguild Predation and Native Lady Beetle Decline

    PubMed Central

    Gardiner, Mary M.; O'Neal, Matthew E.; Landis, Douglas A.

    2011-01-01

    Coccinellid communities across North America have experienced significant changes in recent decades, with declines in several native species reported. One potential mechanism for these declines is interference competition via intraguild predation; specifically, increased predation of native coccinellid eggs and larvae following the introduction of exotic coccinellids. Our previous studies have shown that agricultural fields in Michigan support a higher diversity and abundance of exotic coccinellids than similar fields in Iowa, and that the landscape surrounding agricultural fields across the north central U.S. influences the abundance and activity of coccinellid species. The goal of this study was to quantify the amount of egg predation experienced by a native coccinellid within Michigan and Iowa soybean fields and explore the influence of local and large-scale landscape structure. Using the native lady beetle Coleomegilla maculata as a model, we found that sentinel egg masses were subject to intense predation within both Michigan and Iowa soybean fields, with 60.7% of egg masses attacked and 43.0% of available eggs consumed within 48 h. In Michigan, the exotic coccinellids Coccinella septempunctata and Harmonia axyridis were the most abundant predators found in soybean fields whereas in Iowa, native species including C. maculata, Hippodamia parenthesis and the soft-winged flower beetle Collops nigriceps dominated the predator community. Predator abundance was greater in soybean fields within diverse landscapes, yet variation in predator numbers did not influence the intensity of egg predation observed. In contrast, the strongest predictor of native coccinellid egg predation was the composition of edge habitats bordering specific fields. Field sites surrounded by semi-natural habitats including forests, restored prairies, old fields, and pasturelands experienced greater egg predation than fields surrounded by other croplands. This study shows that intraguild

  5. Predators of the Southern Pine Beetle

    Treesearch

    John D. Reeve

    2011-01-01

    This chapter of the Southern Pine Beetle II reviews the overall influence of predators on southern pine beetle (SPB) population dynamics, as well as recent research on specific predators such as the clerid beetle Thanasimus dubius. Several lines of evidence suggest that predators and other natural enemies generate significant SPB mortality that contributes to outbreak...

  6. OVIGENY IN SELECTED GENERALIST PREDATORS

    USDA-ARS?s Scientific Manuscript database

    “Ovigeny” refers to the process of egg production in adult insects. “Pro-ovigenic” adult insects emerge with a fixed complement of mature eggs; whereas, “synovigenic” species continuously produce and develop eggs throughout adulthood. Very little work has been done on ovigeny in insect predators. W...

  7. Herbivory, Predation, and Biological Control.

    ERIC Educational Resources Information Center

    Murphy, Terence M.; And Others

    1992-01-01

    Authors describe a set of controlled ecosystems that can be used to demonstrate the effects of herbivory on the health and growth of a plant population and of predation on the growth of a primary consumer population. The system also shows the effectiveness of biological pest control measures in a dramatic way. The construction of the ecosystems is…

  8. Differential predation of forage seed

    USDA-ARS?s Scientific Manuscript database

    In recent field experiments we observed that the main invertebrate seed predators of overseeded tall fescue (Festuca arundinacea Schreb.) or Italian ryegrass (Lolium multiflorum Lam.) seed in unimproved pastures were harvester ants (Pogonomyrmex sp.) and common field crickets (Gryllus sp.) To determ...

  9. Herbivory, Predation, and Biological Control.

    ERIC Educational Resources Information Center

    Murphy, Terence M.; And Others

    1992-01-01

    Authors describe a set of controlled ecosystems that can be used to demonstrate the effects of herbivory on the health and growth of a plant population and of predation on the growth of a primary consumer population. The system also shows the effectiveness of biological pest control measures in a dramatic way. The construction of the ecosystems is…

  10. Prey attack and predators defend: counterattacking prey trigger parental care in predators

    PubMed Central

    Magalhães, Sara; Janssen, Arne; Montserrat, Marta; Sabelis, Maurice W

    2005-01-01

    That predators attack and prey defend is an oversimplified view. When size changes during development, large prey may be invulnerable to predators, and small juvenile predators vulnerable to attack by prey. This in turn may trigger a defensive response in adult predators to protect their offspring. Indeed, when sizes overlap, one may wonder ‘who is the predator and who is the prey’! Experiments with ‘predatory’ mites and thrips ‘prey’ showed that young, vulnerable prey counterattack by killing young predators and adult predators respond by protective parental care, killing young prey that attack their offspring. Thus, young individuals form the Achilles' heel of prey and predators alike, creating a cascade of predator attack, prey counterattack and predator defence. Therefore, size structure and relatedness induce multiple ecological role reversals. PMID:16191599

  11. Neural circuit changes mediating lasting brain and behavioral response to predator stress.

    PubMed

    Adamec, Robert E; Blundell, Jacqueline; Burton, Paul

    2005-01-01

    This paper reviews recent work which points to critical neural circuitry involved in lasting changes in anxiety like behavior following unprotected exposure of rats to cats (predator stress). Predator stress may increase anxiety like behavior in a variety of behavioral tests including: elevated plus maze, light dark box, acoustic startle, and social interaction. Studies of neural transmission in two limbic pathways, combined with path and covariance analysis relating physiology to behavior, suggest long term potentiation like changes in one or both of these pathways in the right hemisphere accounts for stress induced changes in all behaviors changed by predator stress except light dark box and social interaction. Findings will be discussed within the context of what is known about neural substrates activated by predator odor.

  12. Nonconsumptive effects in a multiple predator system reduce the foraging efficiency of a keystone predator.

    PubMed

    Davenport, Jon M; Chalcraft, David R

    2013-09-01

    Many studies have demonstrated that the nonconsumptive effect (NCE) of predators on prey traits can alter prey demographics in ways that are just as strong as the consumptive effect (CE) of predators. Less well studied, however, is how the CE and NCE of multiple predator species can interact to influence the combined effect of multiple predators on prey mortality. We examined the extent to which the NCE of one predator altered the CE of another predator on a shared prey and evaluated whether we can better predict the combined impact of multiple predators on prey when accounting for this influence. We conducted a set of experiments with larval dragonflies, adult newts (a known keystone predator), and their tadpole prey. We quantified the CE and NCE of each predator, the extent to which NCEs from one predator alters the CE of the second predator, and the combined effect of both predators on prey mortality. We then compared the combined effect of both predators on prey mortality to four predictive models. Dragonflies caused more tadpoles to hide under leaf litter (a NCE), where newts spend less time foraging, which reduced the foraging success (CE) of newts. Newts altered tadpole behavior but not in a way that altered the foraging success of dragonflies. Our study suggests that we can better predict the combined effect of multiple predators on prey when we incorporate the influence of interactions between the CE and NCE of multiple predators into a predictive model. In our case, the threat of predation to prey by one predator reduced the foraging efficiency of a keystone predator. Consequently, the ability of a predator to fill a keystone role could be compromised by the presence of other predators.

  13. A predator-prey model with generic birth and death rates for the predator.

    PubMed

    Terry, Alan J

    2014-02-01

    We propose and study a predator-prey model in which the predator has a Holling type II functional response and generic per capita birth and death rates. Given that prey consumption provides the energy for predator activity, and that the predator functional response represents the prey consumption rate per predator, we assume that the per capita birth and death rates for the predator are, respectively, increasing and decreasing functions of the predator functional response. These functions are monotonic, but not necessarily strictly monotonic, for all values of the argument. In particular, we allow the possibility that the predator birth rate is zero for all sufficiently small values of the predator functional response, reflecting the idea that a certain level of energy intake is needed before a predator can reproduce. Our analysis reveals that the model exhibits the behaviours typically found in predator-prey models - extinction of the predator population, convergence to a periodic orbit, or convergence to a co-existence fixed point. For a specific example, in which the predator birth and death rates are constant for all sufficiently small or large values of the predator functional response, we corroborate our analysis with numerical simulations. In the unlikely case where these birth and death rates equal the same constant for all sufficiently large values of the predator functional response, the model is capable of structurally unstable behaviour, with a small change in the initial conditions leading to a more pronounced change in the long-term dynamics.

  14. Predation risk increases dispersal distance in prey

    NASA Astrophysics Data System (ADS)

    Otsuki, Hatsune; Yano, Shuichi

    2014-06-01

    Understanding the ecological factors that affect dispersal distances allows us to predict the consequences of dispersal. Although predator avoidance is an important cause of prey dispersal, its effects on dispersal distance have not been investigated. We used simple experimental setups to test dispersal distances of the ambulatory dispersing spider mite ( Tetranychus kanzawai) in the presence or absence of a predator ( Neoseiulus womersleyi). In the absence of predators, most spider mites settled in adjacent patches, whereas the majority of those dispersing in the presence of predators passed through adjacent patches and settled in distant ones. This is the first study to experimentally demonstrate that predators induce greater dispersal distance in prey.

  15. Predator Mimicry: Metalmark Moths Mimic Their Jumping Spider Predators

    PubMed Central

    Rota, Jadranka; Wagner, David L.

    2006-01-01

    Cases of mimicry provide many of the nature's most convincing examples of natural selection. Here we report evidence for a case of predator mimicry in which metalmark moths in the genus Brenthia mimic jumping spiders, one of their predators. In controlled trials, Brenthia had higher survival rates than other similarly sized moths in the presence of jumping spiders and jumping spiders responded to Brenthia with territorial displays, indicating that Brenthia were sometimes mistaken for jumping spiders, and not recognized as prey. Our experimental results and a review of wing patterns of other insects indicate that jumping spider mimicry is more widespread than heretofore appreciated, and that jumping spiders are probably an important selective pressure shaping the evolution of diurnal insects that perch on vegetation. PMID:17183674

  16. Cannibalism and intraguild predation of eggs within a diverse predator assemblage.

    PubMed

    Takizawa, Tadashi; Snyder, William E

    2011-02-01

    Greater biodiversity among aphid predators sometimes leads to greater predator reproductive success. This could occur if cannibalism of predator eggs is consistently stronger than intraguild predation, such that diversity dilutes cannibalism risk when total predator densities remain constant across diversity levels. We compared the frequency of cannibalism versus intraguild predation by adult predators of four species [the lady beetles Coccinella septempunctata L. and Hippodamia convergens Guerin-Meneville, and the predatory bugs Geocoris bullatus (Say) and Nabis alternatus Parshley] on the eggs of three predator species (all of these predators but Nabis). For both coccinellid species, egg predation averaged across all intraguild predators was less frequent than cannibalism. In contrast, Geocoris eggs were generally more likely to be consumed by intraguild predators than by conspecifics. Closer inspection of the data revealed that Geocoris consistently consumed fewer eggs than the other species, regardless of egg species. Indeed, for lady beetle eggs it was relatively infrequent egg predation by Geocoris that brought down the average across all heterospecific predators, masking the fact that adults of the two lady beetles were no more likely to act as egg cannibals than as intraguild predators. Nabis ate eggs of the two beetles at approximately equal rates, but rarely ate Geocoris eggs. Female predators generally consumed more eggs than did males, but this did not alter any of the patterns described above. Altogether, our results suggest that species-specific differences in egg predation rates determined the relative intensity of egg intraguild-predation versus cannibalism, rather than any more general trend for egg cannibalism to always exceed intraguild predation.

  17. Innate predator recognition in giant pandas.

    PubMed

    Du, Yiping; Huang, Yan; Zhang, Hemin; Li, Desheng; Yang, Bo; Wei, Ming; Zhou, Yingmin; Liu, Yang

    2012-02-01

    Innate predator recognition confers a survival advantage to prey animals. We investigate whether giant pandas exhibit innate predator recognition. We analyzed behavioral responses of 56 naive adult captive giant pandas (Ailuropoda melanoleuca), to urine from predators and non-predators and water control. Giant pandas performed more chemosensory investigation and displayed flehmen behaviors more frequently in response to predator urine compared to both non-predator urine and water control. Subjects also displayed certain defensive behaviors, as indicated by vigilance, and in certain cases, fleeing behaviors. Our results suggest that there is an innate component to predator recognition in captive giant pandas, although such recognition was only slight to moderate. These results have implications that may be applicable to the conservation and reintroduction of this endangered species.

  18. Chronic effects of an invasive species on an animal community.

    PubMed

    Doody, J Sean; Rhind, David; Green, Brian; Castellano, Christina; McHenry, Colin; Clulow, Simon

    2017-08-01

    Invasive species can trigger trophic cascades in animal communities, but published cases involving their removal of top predators are extremely rare. An exception is the invasive cane toad (Rhinella marina) in Australia, which has caused severe population declines in monitor lizards, triggering trophic cascades that facilitated dramatic and sometimes unexpected increases in several prey of the predators, including smaller lizards, snakes, turtles, crocodiles, and birds. Persistence of isolated populations of these predators with a decades-long sympatry with toads suggests the possibility of recovery, but alternative explanations are possible. Confirming predator recovery requires longer-term study of populations with both baseline and immediate post-invasion densities. Previously, we quantified short-term impacts of invasive cane toads on animal communities over seven years at two sites in tropical Australia. Herein, we test the hypothesis that predators have begun to recover by repeating the study 12 yr after the initial toad invasion. The three predatory lizards that experienced 71-97% declines in the short-term study showed no sign of recovery, and indeed a worse fate: two of the three species were no longer detectable in 630 km of river surveys, suggesting local extirpation. Two mesopredators that had increased markedly in the short term due to these predator losses showed diverse responses in the medium term; a small lizard species increased by ~500%, while populations of a snake species showed little change. Our results indicate a system still in ecological turmoil, having not yet reached a "new equilibrium" more than a decade after the initial invasion; predator losses due to this toxic invasive species, and thus downstream effects, were not transient. Given that cane toads have proven too prolific to eradicate or control, we suggest that recovery of impacted predators must occur unassisted by evolutionary means: dispersal into extinction sites from

  19. Modelling the dynamics of traits involved in fighting-predators-prey system.

    PubMed

    Kooi, B W

    2015-12-01

    We study the dynamics of a predator-prey system where predators fight for captured prey besides searching for and handling (and digestion) of the prey. Fighting for prey is modelled by a continuous time hawk-dove game dynamics where the gain depends on the amount of disputed prey while the costs for fighting is constant per fighting event. The strategy of the predator-population is quantified by a trait being the proportion of the number of predator-individuals playing hawk tactics. The dynamics of the trait is described by two models of adaptation: the replicator dynamics (RD) and the adaptive dynamics (AD). In the RD-approach a variant individual with an adapted trait value changes the population's strategy, and consequently its trait value, only when its payoff is larger than the population average. In the AD-approach successful replacement of the resident population after invasion of a rare variant population with an adapted trait value is a step in a sequence changing the population's strategy, and hence its trait value. The main aim is to compare the consequences of the two adaptation models. In an equilibrium predator-prey system this will lead to convergence to a neutral singular strategy, while in the oscillatory system to a continuous singular strategy where in this endpoint the resident population is not invasible by any variant population. In equilibrium (low prey carrying capacity) RD and AD-approach give the same results, however not always in a periodically oscillating system (high prey carrying-capacity) where the trait is density-dependent. For low costs the predator population is monomorphic (only hawks) while for high costs dimorphic (hawks and doves). These results illustrate that intra-specific trait dynamics matters in predator-prey dynamics.

  20. Predator attack rate evolution in space: the role of ecology mediated by complex emergent spatial structure and self-shading.

    PubMed

    Messinger, Susanna M; Ostling, Annette

    2013-11-01

    Predation interactions are an important element of ecological communities. Population spatial structure has been shown to influence predator evolution, resulting in the evolution of a reduced predator attack rate; however, the evolutionary role of traits governing predator and prey ecology is unknown. The evolutionary effect of spatial structure on a predator's attack rate has primarily been explored assuming a fixed metapopulation spatial structure, and understood in terms of group selection. But endogenously generated, emergent spatial structure is common in nature. Furthermore, the evolutionary influence of ecological traits may be mediated through the spatial self-structuring process. Drawing from theory on pathogens, the evolutionary effect of emergent spatial structure can be understood in terms of self-shading, where a voracious predator limits its long-term invasion potential by reducing local prey availability. Here we formalize the effects of self-shading for predators using spatial moment equations. Then, through simulations, we show that in a spatial context self-shading leads to relationships between predator-prey ecology and the predator's attack rate that are not expected in a non-spatial context. Some relationships are analogous to relationships already shown for host-pathogen interactions, but others represent new trait dimensions. Finally, since understanding the effects of ecology using existing self-shading theory requires simplifications of the emergent spatial structure that do not apply well here, we also develop metrics describing the complex spatial structure of the predator and prey populations to help us explain the evolutionary effect of predator and prey ecology in the context of self-shading. The identification of these metrics may provide a step towards expansion of the predictive domain of self-shading theory to more complex spatial dynamics. Copyright © 2013 Elsevier Inc. All rights reserved.

  1. Predator-prey body size relationships when predators can consume prey larger than themselves.

    PubMed

    Nakazawa, Takefumi; Ohba, Shin-Ya; Ushio, Masayuki

    2013-06-23

    As predator-prey interactions are inherently size-dependent, predator and prey body sizes are key to understanding their feeding relationships. To describe predator-prey size relationships (PPSRs) when predators can consume prey larger than themselves, we conducted field observations targeting three aquatic hemipteran bugs, and assessed their body masses and those of their prey for each hunting event. The data revealed that their PPSR varied with predator size and species identity, although the use of the averaged sizes masked these effects. Specifically, two predators had slightly decreased predator-prey mass ratios (PPMRs) during growth, whereas the other predator specialized on particular sizes of prey, thereby showing a clear positive size-PPMR relationship. We discussed how these patterns could be different from fish predators swallowing smaller prey whole.

  2. Landscape heterogeneity shapes predation in a newly restored predator-prey system

    USGS Publications Warehouse

    Kauffman, M.J.; Varley, N.; Smith, D.W.; Stahler, D.R.; MacNulty, D.R.; Boyce, M.S.

    2007-01-01

    Because some native ungulates have lived without top predators for generations, it has been uncertain whether runaway predation would occur when predators are newly restored to these systems. We show that landscape features and vegetation, which influence predator detection and capture of prey, shape large-scale patterns of predation in a newly restored predator-prey system. We analysed the spatial distribution of wolf (Canis lupus) predation on elk (Cervus elaphus) on the Northern Range of Yellowstone National Park over 10 consecutive winters. The influence of wolf distribution on kill sites diminished over the course of this study, a result that was likely caused by territorial constraints on wolf distribution. In contrast, landscape factors strongly influenced kill sites, creating distinct hunting grounds and prey refugia. Elk in this newly restored predator-prey system should be able to mediate their risk of predation by movement and habitat selection across a heterogeneous risk landscape. ?? 2007 Blackwell Publishing Ltd/CNRS.

  3. Predators reduce abundance and species richness of coral reef fish recruits via non-selective predation

    NASA Astrophysics Data System (ADS)

    Heinlein, J. M.; Stier, A. C.; Steele, M. A.

    2010-06-01

    Predators have important effects on coral reef fish populations, but their effects on community structure have only recently been investigated and are not yet well understood. Here, the effect of predation on the diversity and abundance of young coral reef fishes was experimentally examined in Moorea, French Polynesia. Effects of predators were quantified by monitoring recruitment of fishes onto standardized patch reefs in predator-exclosure cages or uncaged reefs. At the end of the 54-day experiment, recruits were 74% less abundant on reefs exposed to predators than on caged ones, and species richness was 42% lower on reefs exposed to predators. Effects of predators varied somewhat among families, however, rarefaction analysis indicated that predators foraged non-selectively among species. These results indicate that predation can alter diversity of reef fish communities by indiscriminately reducing the abundance of fishes soon after settlement, thereby reducing the number of species present on reefs.

  4. Landscape heterogeneity shapes predation in a newly restored predator-prey system.

    PubMed

    Kauffman, Matthew J; Varley, Nathan; Smith, Douglas W; Stahler, Daniel R; MacNulty, Daniel R; Boyce, Mark S

    2007-08-01

    Because some native ungulates have lived without top predators for generations, it has been uncertain whether runaway predation would occur when predators are newly restored to these systems. We show that landscape features and vegetation, which influence predator detection and capture of prey, shape large-scale patterns of predation in a newly restored predator-prey system. We analysed the spatial distribution of wolf (Canis lupus) predation on elk (Cervus elaphus) on the Northern Range of Yellowstone National Park over 10 consecutive winters. The influence of wolf distribution on kill sites diminished over the course of this study, a result that was likely caused by territorial constraints on wolf distribution. In contrast, landscape factors strongly influenced kill sites, creating distinct hunting grounds and prey refugia. Elk in this newly restored predator-prey system should be able to mediate their risk of predation by movement and habitat selection across a heterogeneous risk landscape.

  5. Predator hunting mode and habitat domain alter nonconsumptive effects in predator-prey interactions.

    PubMed

    Preisser, Evan L; Orrock, John L; Schmitz, Oswald J

    2007-11-01

    Predators can affect prey populations through changes in traits that reduce predation risk. These trait changes (nonconsumptive effects, NCEs) can be energetically costly and cause reduced prey activity, growth, fecundity, and survival. The strength of nonconsumptive effects may vary with two functional characteristics of predators: hunting mode (actively hunting, sit-and-pursue, sit-and-wait) and habitat domain (the ability to pursue prey via relocation in space; can be narrow or broad). Specifically, cues from fairly stationary sit-and-wait and sit-and-pursue predators should be more indicative of imminent predation risk, and thereby evoke stronger NCEs, compared to cues from widely ranging actively hunting predators. Using a meta-analysis of 193 published papers, we found that cues from sit-and-pursue predators evoked stronger NCEs than cues from actively hunting predators. Predator habitat domain was less indicative of NCE strength, perhaps because habitat domain provides less reliable information regarding imminent risk to prey than does predator hunting mode. Given the importance of NCEs in determining the dynamics of prey communities, our findings suggest that predator characteristics may be used to predict how changing predator communities translate into changes in prey. Such knowledge may prove particularly useful given rates of local predator change due to habitat fragmentation and the introduction of novel predators.

  6. Effects of a Synthetic Predator Odor (TMT) on Freezing, Analgesia, Stereotypy, and Spatial Memory.

    ERIC Educational Resources Information Center

    Williams, Jon L.; Baez, Catherine; Hladky, Katherine J.; Camacho, Cheri A.

    2005-01-01

    Exposing rats to the predator odor of trimethylthiazoline (TMT), obtained from the red fox, was compared to exposure to the novel control odor of citronella. In Experiment 1, TMT produced defensive freezing and an analgesic reaction that was reversed by an opiate antagonist. In Experiment 2, TMT augmented response stereotypy induced by an…

  7. Effects of a Synthetic Predator Odor (TMT) on Freezing, Analgesia, Stereotypy, and Spatial Memory.

    ERIC Educational Resources Information Center

    Williams, Jon L.; Baez, Catherine; Hladky, Katherine J.; Camacho, Cheri A.

    2005-01-01

    Exposing rats to the predator odor of trimethylthiazoline (TMT), obtained from the red fox, was compared to exposure to the novel control odor of citronella. In Experiment 1, TMT produced defensive freezing and an analgesic reaction that was reversed by an opiate antagonist. In Experiment 2, TMT augmented response stereotypy induced by an…

  8. A tour de force by Hawaii’s invasive mammals: Establishment, takeover, and ecosystem restoration through eradication

    USGS Publications Warehouse

    Hess, Steve

    2016-01-01

    Invasive mammals have irreversibly altered ecosystems of Hawai‘i and other tropical Pacific islands in numerous cases through novel herbivory, predation, and diseases, thereby causing the disproportionate extinction of flora and fauna that occur nowhere else on Earth. The control and eradication of invasive mammals is the single most expensive management activity necessary for restoring ecological integrity to many natural areas of Hawai‘i and other Pacific Islands, and have already advanced the restoration of native biota by removing herbivorous ungulates from >750 km2. Rodenticides which have been tested and registered for hand and aerial broadcast in Hawai‘i have been used to eradicate rats from remote islands to protect nesting seabirds and are now being applied to larger islands to protect forest birds. The exclusion of other invasive mammals is now being undertaken with more sophisticated control techniques and fences. New fence designs are capable of excluding all mammals from areas to protect endangered native birds. Although the eradication of mammals from large areas has resulted in the restoration of some ecosystem processes such as natural forest regeneration, changes in other processes such as fire regimes, nutrient cycling, and invasive plant proliferation remain more difficult to reverse at larger landscape scales.

  9. Scaphiopus couchii (Couch's spadefoot). Predation

    USGS Publications Warehouse

    Dayton, Gage H.; Jung, R.E.

    1999-01-01

    The observation described in this note appears to be the first record of ant predation upon anuran eggs. At an ephemeral pool in Big Bend National Park, Texas, we observed ants (Forelius mccooki) walking along a blade of grass onto the gelatin of a Couch?s spadefoot (Scaphiopus couchii) egg mass on the water surface. The ants had eaten through the gelatinous envelope and were harvesting the ovum and returning to their nest.

  10. Optimal control of native predators

    USGS Publications Warehouse

    Martin, Julien; O'Connell, Allan F.; Kendall, William L.; Runge, Michael C.; Simons, Theodore R.; Waldstein, Arielle H.; Schulte, Shiloh A.; Converse, Sarah J.; Smith, Graham W.; Pinion, Timothy; Rikard, Michael; Zipkin, Elise F.

    2010-01-01

    We apply decision theory in a structured decision-making framework to evaluate how control of raccoons (Procyon lotor), a native predator, can promote the conservation of a declining population of American Oystercatchers (Haematopus palliatus) on the Outer Banks of North Carolina. Our management objective was to maintain Oystercatcher productivity above a level deemed necessary for population recovery while minimizing raccoon removal. We evaluated several scenarios including no raccoon removal, and applied an adaptive optimization algorithm to account for parameter uncertainty. We show how adaptive optimization can be used to account for uncertainties about how raccoon control may affect Oystercatcher productivity. Adaptive management can reduce this type of uncertainty and is particularly well suited for addressing controversial management issues such as native predator control. The case study also offers several insights that may be relevant to the optimal control of other native predators. First, we found that stage-specific removal policies (e.g., yearling versus adult raccoon removals) were most efficient if the reproductive values among stage classes were very different. Second, we found that the optimal control of raccoons would result in higher Oystercatcher productivity than the minimum levels recommended for this species. Third, we found that removing more raccoons initially minimized the total number of removals necessary to meet long term management objectives. Finally, if for logistical reasons managers cannot sustain a removal program by removing a minimum number of raccoons annually, managers may run the risk of creating an ecological trap for Oystercatchers.

  11. Age and sex-selective predation moderate the overall impact of predators.

    PubMed

    Hoy, Sarah R; Petty, Steve J; Millon, Alexandre; Whitfield, D Philip; Marquiss, Michael; Davison, Martin; Lambin, Xavier

    2015-05-01

    Currently, there is no general agreement about the extent to which predators impact prey population dynamics and it is often poorly predicted by predation rates and species abundances. This could, in part be caused by variation in the type of selective predation occurring. Notably, if predation is selective on categories of individuals that contribute little to future generations, it may moderate the impact of predation on prey population dynamics. However, despite its prevalence, selective predation has seldom been studied in this context. Using recoveries of ringed tawny owls (Strix aluco) predated by 'superpredators', northern goshawks (Accipiter gentilis) as they colonized the area, we investigated the extent to which predation was sex and age-selective. Predation of juvenile owls was disproportionately high. Amongst adults, predation was strongly biased towards females and predation risk appeared to increase with age. This implies age-selective predation may shape the decline in survival with age, observed in tawny owls. To determine whether selective predation can modulate the overall impact of predation, age-based population matrix models were used to simulate the impact of five different patterns of age-selective predation, including the pattern actually observed in the study site. The overall impact on owl population size varied by up to 50%, depending on the pattern of selective predation. The simulation of the observed pattern of predation had a relatively small impact on population size, close to the least harmful scenario, predation on juveniles only. The actual changes in owl population size and structure observed during goshawk colonization were also analysed. Owl population size and immigration were unrelated to goshawk abundance. However, goshawk abundance appeared to interact with owl food availability to have a delayed effect on recruitment into the population. This study provides strong evidence to suggest that predation of other predators is

  12. Coevolution can reverse predator-prey cycles.

    PubMed

    Cortez, Michael H; Weitz, Joshua S

    2014-05-20

    A hallmark of Lotka-Volterra models, and other ecological models of predator-prey interactions, is that in predator-prey cycles, peaks in prey abundance precede peaks in predator abundance. Such models typically assume that species life history traits are fixed over ecologically relevant time scales. However, the coevolution of predator and prey traits has been shown to alter the community dynamics of natural systems, leading to novel dynamics including antiphase and cryptic cycles. Here, using an eco-coevolutionary model, we show that predator-prey coevolution can also drive population cycles where the opposite of canonical Lotka-Volterra oscillations occurs: predator peaks precede prey peaks. These reversed cycles arise when selection favors extreme phenotypes, predator offense is costly, and prey defense is effective against low-offense predators. We present multiple datasets from phage-cholera, mink-muskrat, and gyrfalcon-rock ptarmigan systems that exhibit reversed-peak ordering. Our results suggest that such cycles are a potential signature of predator-prey coevolution and reveal unique ways in which predator-prey coevolution can shape, and possibly reverse, community dynamics.

  13. Improving the assessment of predator functional responses by considering alternate prey and predator interactions.

    PubMed

    Chan, K; Boutin, S; Hossie, T J; Krebs, C J; O'Donoghue, M; Murray, D L

    2017-07-01

    To improve understanding of the complex and variable patterns of predator foraging behavior in natural systems, it is critical to determine how density-dependent predation and predator hunting success are mediated by alternate prey or predator interference. Despite considerable theory and debate seeking to place predator-prey interactions in a more realistic context, few empirical studies have quantified the role of alternate prey or intraspecific interactions on predator-prey dynamics. We assessed functional responses of two similarly sized, sympatric carnivores, lynx (Lynx canadensis) and coyotes (Canis latrans), foraging on common primary (snowshoe hares; Lepus americanus) and alternate (red squirrels; Tamiasciurus hudsonicus) prey in a natural system. Lynx exhibited a hyperbolic prey-dependent response to changes in hare density, which is characteristic of predators relying primarily on a single prey species. In contrast, the lynx-squirrel response was found to be linear ratio dependent, or inversely dependent on hare density. The coyote-hare and coyote-squirrel interactions also were linear and influenced by predator density. We explain these novel results by apparent use of spatial and temporal refuges by prey, and the likelihood that predators commonly experience interference and lack of satiation when foraging. Our study provides empirical support from a natural predator-prey system that (1) predation rate may not be limited at high prey densities when prey are small or rarely captured; (2) interference competition may influence the predator functional response; and (3) predator interference has a variable role across different prey types. Ultimately, distinct functional responses of predators to different prey types illustrates the complexity associated with predator-prey interactions in natural systems and highlights the need to investigate predator behavior and predation rate in relation to the broader ecological community. © 2017 by the Ecological

  14. Shoaling behaviour enhances risk of predation from multiple predator guilds in a marine fish.

    PubMed

    Ford, John R; Swearer, Stephen E

    2013-06-01

    Predicting the consequences of predator biodiversity loss on prey requires an understanding of multiple predator interactions. Predators are often assumed to have independent and additive effects on shared prey survival; however, multiple predator effects can be non-additive if predators foraging together reduce prey survival (risk enhancement) or increase prey survival through interference (risk reduction). In marine communities, juvenile reef fish experience very high mortality from two predator guilds with very different hunting modes and foraging domains-benthic and pelagic predator guilds. The few previous predator manipulation studies have found or assumed that mortality is independent and additive. We tested whether interacting predator guilds result in non-additive prey mortality and whether the detection of such effects change over time as prey are depleted. To do so, we examined the roles of benthic and pelagic predators on the survival of a juvenile shoaling zooplanktivorous temperate reef fish, Trachinops caudimaculatus, on artificial patch reefs over 2 months in Port Phillip Bay, Australia. We observed risk enhancement in the first 7 days, as shoaling behaviour placed prey between predator foraging domains with no effective refuge. At day 14 we observed additive mortality, and risk enhancement was no longer detectable. By days 28 and 62, pelagic predators were no longer significant sources of mortality and additivity was trivial. We hypothesize that declines in prey density led to reduced shoaling behaviour that brought prey more often into the domain of benthic predators, resulting in limited mortality from pelagic predators. Furthermore, pelagic predators may have spent less time patrolling reefs in response to declines in prey numbers. Our observation of the changing interaction between predators and prey has important implications for assessing the role of predation in regulating populations in complex communities.

  15. Dynamics of a intraguild predation model with generalist or specialist predator.

    PubMed

    Kang, Yun; Wedekin, Lauren

    2013-11-01

    Intraguild predation (IGP) is a combination of competition and predation which is the most basic system in food webs that contains three species where two species that are involved in a predator/prey relationship are also competing for a shared resource or prey. We formulate two intraguild predation (IGP: resource, IG prey and IG predator) models: one has generalist predator while the other one has specialist predator. Both models have Holling-Type I functional response between resource-IG prey and resource-IG predator; Holling-Type III functional response between IG prey and IG predator. We provide sufficient conditions of the persistence and extinction of all possible scenarios for these two models, which give us a complete picture on their global dynamics. In addition, we show that both IGP models can have multiple interior equilibria under certain parameters range. These analytical results indicate that IGP model with generalist predator has "top down" regulation by comparing to IGP model with specialist predator. Our analysis and numerical simulations suggest that: (1) Both IGP models can have multiple attractors with complicated dynamical patterns; (2) Only IGP model with specialist predator can have both boundary attractor and interior attractor, i.e., whether the system has the extinction of one species or the coexistence of three species depending on initial conditions; (3) IGP model with generalist predator is prone to have coexistence of three species.

  16. Predator-prey interactions mediated by prey personality and predator hunting mode.

    PubMed

    Belgrad, Benjamin A; Griffen, Blaine D

    2016-04-13

    Predator-prey interactions are important drivers in structuring ecological communities. However, despite widespread acknowledgement that individual behaviours and predator species regulate ecological processes, studies have yet to incorporate individual behavioural variations in a multipredator system. We quantified a prevalent predator avoidance behaviour to examine the simultaneous roles of prey personality and predator hunting mode in governing predator-prey interactions. Mud crabs, Panopeus herbstii, reduce their activity levels and increase their refuge use in the presence of predator cues. We measured mud crab mortality and consistent individual variations in the strength of this predator avoidance behaviour in the presence of predatory blue crabs, Callinectes sapidus, and toadfish, Opsanus tau We found that prey personality and predator species significantly interacted to affect mortality with blue crabs primarily consuming bold mud crabs and toadfish preferentially selecting shy crabs. Additionally, the strength of the predator avoidance behaviour depended upon the predation risk from the predator species. Consequently, the personality composition of populations and predator hunting mode may be valuable predictors of both direct and indirect predator-prey interaction strength. These findings support theories postulating mechanisms for maintaining intraspecies diversity and have broad implications for community dynamics.

  17. Antagonistic interactions between an invasive alien and a native coccinellid species may promote coexistence.

    PubMed

    Hentley, William T; Vanbergen, Adam J; Beckerman, Andrew P; Brien, Melanie N; Hails, Rosemary S; Jones, T Hefin; Johnson, Scott N

    2016-07-01

    Despite the capacity of invasive alien species to alter ecosystems, the mechanisms underlying their impact remain only partly understood. Invasive alien predators, for example, can significantly disrupt recipient communities by consuming prey species or acting as an intraguild predator (IGP). Behavioural interactions are key components of interspecific competition between predators, yet these are often overlooked invasion processes. Here, we show how behavioural, non-lethal IGP interactions might facilitate the establishment success of an invading alien species. We experimentally assessed changes in feeding behaviour (prey preference and consumption rate) of native UK coccinellid species (Adalia bipunctata and Coccinella septempunctata), whose populations are, respectively, declining and stable, when exposed to the invasive intraguild predator, Harmonia axyridis. Using a population dynamics model parameterized with these experimental data, we predicted how intraguild predation, accommodating interspecific behavioural interactions, might impact the abundance of the native and invasive alien species over time. When competing for the same aphid resource, the feeding rate of A. bipunctata significantly increased compared to the feeding in isolation, while the feeding rate of H. axyridis significantly decreased. This suggests that despite significant declines in the UK, A. bipunctata is a superior competitor to the intraguild predator H. axyridis. In contrast, the behaviour of non-declining C. septempunctata was unaltered by the presence of H. axyridis. Our experimental data show the differential behavioural plasticity of competing native and invasive alien predators, but do not explain A. bipunctata declines observed in the UK. Using behavioural plasticity as a parameter in a population dynamic model for A. bipunctata and H. axyridis, coexistence is predicted between the native and invasive alien following an initial period of decline in the native species. We

  18. Using the functional response of a consumer to predict biotic resistance to invasive prey.

    PubMed

    Twardochleb, Laura A; Novak, Mark; Moore, Jonathan W

    2012-06-01

    Predators sometimes provide biotic resistance against invasions by nonnative prey. Understanding and predicting the strength of biotic resistance remains a key challenge in invasion biology. A predator's functional response to nonnative prey may predict whether a predator can provide biotic resistance against nonnative prey at different prey densities. Surprisingly, functional responses have not been used to make quantitative predictions about biotic resistance. We parameterized the functional response of signal crayfish (Pacifastacus leniusculus) to invasive New Zealand mud snails (Potamopyrgus antipodarum; NZMS) and used this functional response and a simple model of NZMS population growth to predict the probability of biotic resistance at different predator and prey densities. Signal crayfish were effective predators of NZMS, consuming more than 900 NZMS per predator in a 12-h period, and Bayesian model fitting indicated their consumption rate followed a type 3 functional response to NZMS density. Based on this functional response and associated parameter uncertainty, we predict that NZMS will be able to invade new systems at low crayfish densities (< 0.2 crayfish/m2) regardless of NZMS density. At intermediate to high crayfish densities (> 0.2 crayfish/m2), we predict that low densities of NZMS will be able to establish in new communities; however, once NZMS reach a threshold density of -2000 NZMS/m2, predation by crayfish will drive negative NZMS population growth. Further, at very high densities, NZMS overwhelm predation by crayfish and invade. Thus, interacting thresholds of propagule pressure and predator densities define the probability of biotic resistance. Quantifying the shape and uncertainty of predator functional responses to nonnative prey may help predict the outcomes of invasions.

  19. Inhibition of mTOR kinase via rapamycin blocks persistent predator stress-induced hyperarousal.

    PubMed

    Fifield, Kathleen; Hebert, Mark; Angel, Rebecca; Adamec, Robert; Blundell, Jacqueline

    2013-11-01

    Traumatic, stressful life events are thought to trigger acquired anxiety disorders such as post-traumatic stress disorder (PTSD). Recent data suggests that the mammalian target of rapamycin (mTOR) plays a key role in the formation of traumatic memories. The predator stress paradigm allows us to determine whether mTOR mediates the formation of both context-dependent (associative) and context-independent (non-associative) fear memories. Predator stress involves an acute, unprotected exposure of a rat to a cat which causes long-lasting non-associative fear memories manifested as generalized hyperarousal and increased anxiety-like behavior. Here, we show that rapamycin, an mTOR inhibitor, attenuates predator stress-induced hyperarousal, lasting at least three weeks. In addition, rapamycin blocks a subset of anxiety-like behaviors as measured in the elevated plus maze and hole board. Furthermore, when re-exposed to the predator stress context, rapamycin-treated stressed rats showed increased activity compared to vehicle controls suggesting that rapamycin blocks predator stress-induced associative fear memory. Taken together with past research, our results indicate that mTOR regulation of protein translation is required for the formation of both associative and non-associative fear memories. Overall, these data suggest that mTOR activation may contribute to the development of acquired anxiety disorders such as PTSD.

  20. Phase transitions in predator-prey systems

    NASA Astrophysics Data System (ADS)

    Nagano, Seido; Maeda, Yusuke

    2012-01-01

    The relationship between predator and prey plays an important role in ecosystem conservation. However, our understanding of the principles underlying the spatial distribution of predators and prey is still poor. Here we present a phase diagram of a predator-prey system and investigate the lattice formation in such a system. We show that the production of stable lattice structures depends on the limited diffusion or migration of prey as well as higher carrying capacity for the prey. In addition, when the prey's growth rate is lower than the birth rate of the predator, global prey lattice formation is initiated by microlattices at the center of prey spirals. The predator lattice is later formed in the predator spirals. But both lattice formations proceed together as the prey growth rate increases.

  1. Predator diversity and density affect levels of predation upon strongly interactive species in temperate rocky reefs.

    PubMed

    Guidetti, Paolo

    2007-12-01

    Indirect effects of predators in the classic trophic cascade theory involve the effects of basal species (e.g. primary producers) mediated by predation upon strongly interactive consumers (e.g. grazers). The diversity and density of predators, and the way in which they interact, determine whether and how the effects of different predators on prey combine. Intraguild predation, for instance, was observed to dampen the effects of predators on prey in many ecosystems. In marine systems, species at high trophic levels are particularly susceptible to extinction (at least functionally). The loss of such species, which is mainly attributed to human activities (mostly fishing), is presently decreasing the diversity of marine predators in many areas of the world. Experimental studies that manipulate predator diversity and investigate the effects of this on strongly interactive consumers (i.e. those potentially capable of causing community-wide effects) in marine systems are scant, especially in the rocky sublittoral. I established an experiment that utilised cage enclosures to test whether the diversity and density of fish predators (two sea breams and two wrasses) would affect predation upon juvenile and adult sea urchins, the most important grazers in Mediterranean sublittoral rocky reefs. Changes in species identity (with sea breams producing major effects) and density of predators affected predation upon sea urchins more than changes in species richness per se. Predation upon adult sea urchins decreased in the presence of multiple predators, probably due to interference competition between sea breams and wrasses. This study suggests that factors that influence both fish predator diversity and density in Mediterranean rocky reefs (e.g. fishing and climate change) may have the potential to affect the predators' ability to control sea urchin population density, with possible repercussions for the whole benthic community structure.

  2. Impacts of foraging facilitation among predators on predator-prey dynamics.

    PubMed

    Berec, Ludek

    2010-01-01

    Whereas impacts of predator interference on predator-prey dynamics have received considerable attention, the "inverse" process-foraging facilitation among predators-have not been explored yet. Here we show, via mathematical models, that impacts of foraging facilitation on predator-prey dynamics depend on the way this process is modeled. In particular, foraging facilitation destabilizes predator-prey dynamics when it affects the encounter rate between predators and prey. By contrast, it might have a stabilizing effect if the predator handling time of prey is affected. Foraging facilitation is an Allee effect mechanism among predators and we show that for many parameters, it gives rise to a demographic Allee effect or a critical predator density in need to be crossed for predators to persist. We explore also the effects of predator interference, to make the picture "symmetric" and complete. Predator interference is shown to stabilize predator-prey dynamics once its strength is not too high, and thus corroborates results of others. On the other hand, there is a wide range of model parameters for which predator interference gives rise to three co-occurring co-existence equilibria. Such a multi-equilibrial regime is rather robust as we observe it for all the functional response types we explore. This is a previously unreported phenomenon which we show cannot occur for the Beddington-DeAngelis functional response. An interesting topic for future research thus might be to seek for general conditions on predator functional responses that would produce multiple co-existence equilibria in a predator-prey model.

  3. Predicting invasive species impacts: a community module functional response approach reveals context dependencies

    PubMed Central

    Paterson, Rachel A; Dick, Jaimie T A; Pritchard, Daniel W; Ennis, Marilyn; Hatcher, Melanie J; Dunn, Alison M

    2015-01-01

    Summary Predatory functional responses play integral roles in predator–prey dynamics, and their assessment promises greater understanding and prediction of the predatory impacts of invasive species. Other interspecific interactions, however, such as parasitism and higher-order predation, have the potential to modify predator–prey interactions and thus the predictive capability of the comparative functional response approach. We used a four-species community module (higher-order predator; focal native or invasive predators; parasites of focal predators; native prey) to compare the predatory functional responses of native Gammarus duebeni celticus and invasive Gammarus pulex amphipods towards three invertebrate prey species (Asellus aquaticus, Simulium spp., Baetis rhodani), thus, quantifying the context dependencies of parasitism and a higher-order fish predator on these functional responses. Our functional response experiments demonstrated that the invasive amphipod had a higher predatory impact (lower handling time) on two of three prey species, which reflects patterns of impact observed in the field. The community module also revealed that parasitism had context-dependent influences, for one prey species, with the potential to further reduce the predatory impact of the invasive amphipod or increase the predatory impact of the native amphipod in the presence of a higher-order fish predator. Partial consumption of prey was similar for both predators and occurred increasingly in the order A. aquaticus, Simulium spp. and B. rhodani. This was associated with increasing prey densities, but showed no context dependencies with parasitism or higher-order fish predator. This study supports the applicability of comparative functional responses as a tool to predict and assess invasive species impacts incorporating multiple context dependencies. PMID:25265905

  4. Ecology of invasive mosquitoes: effects on resident species and on human health

    PubMed Central

    Juliano, Steven A.; Lounibos, L. Philip

    2007-01-01

    Investigations of biological invasions focus on patterns and processes that are related to introduction, establishment, spread and impacts of introduced species. This review focuses on the ecological interactions operating during invasions by the most prominent group of insect vectors of disease, mosquitoes. First, we review characteristics of non-native mosquito species that have established viable populations, and those invasive species that have spread widely and had major impacts, testing whether biotic characteristics are associated with the transition from established non-native to invasive. Second, we review the roles of interspecific competition, apparent competition, predation, intraguild predation and climatic limitation as causes of impacts on residents or as barriers to invasion. We concentrate on the best-studied invasive mosquito, Aedes albopictus, evaluating the application of basic ecological theory to invasions by Aedes albopictus. We develop a model based on observations of Aedes albopictus for effects of resource competition and predation as barriers to invasion, evaluating which community and ecosystem characteristics favour invasion. Third, we evaluate the ways in which invasive mosquitoes have contributed to outbreaks of human and animal disease, considering specifically whether invasive mosquitoes create novel health threats, or modify disease transmission for existing pathogen–host systems. PMID:17637849

  5. Molecular forensics in avian conservation: a DNA-based approach for identifying mammalian predators of ground-nesting birds and eggs.

    PubMed

    Hopken, Matthew W; Orning, Elizabeth K; Young, Julie K; Piaggio, Antoinette J

    2016-01-07

    The greater sage-grouse (Centrocercus urophasianus) is a ground-nesting bird from the Northern Rocky Mountains and a species at risk of extinction in in multiple U.S. states and Canada. Herein we report results from a proof of concept that mitochondrial and nuclear DNAs from mammalian predator saliva could be non-invasively collected from depredated greater sage-grouse eggshells and carcasses and used for predator species identification. Molecular forensic approaches have been applied to identify predators from depredated remains as one strategy to better understand predator-prey dynamics and guide management strategies. This can aid conservation efforts by correctly identifying predators most likely to impact threatened and endangered species. DNA isolated from non-invasive samples around nesting sites (e.g. fecal or hair samples) is one method that can increase the success and accuracy of predator species identification when compared to relying on nest remains alone. Predator saliva DNA was collected from depredated eggshells and carcasses using swabs. We sequenced two partial fragments of two mitochondrial genes and obtained microsatellite genotypes using canid specific primers for species and individual identification, respectively. Using this multilocus approach we were able to identify predators, at least down to family, from 11 out of 14 nests (79%) and three out of seven carcasses (47%). Predators detected most frequently were canids (86%), while other taxa included rodents, a striped skunk, and cattle. We attempted to match the genotypes of individual coyotes obtained from eggshells and carcasses with those obtained from fecal samples and coyotes collected in the areas, but no genotype matches were found. Predation is a main cause of nest failure in ground-nesting birds and can impact reproduction and recruitment. To inform predator management for ground-nesting bird conservation, accurate identification of predator species is necessary. Considering

  6. Wanted dead or alive: scavenging versus predation by three insect predators

    USDA-ARS?s Scientific Manuscript database

    Many generalist insect predators may engage in facultative scavenging. If an apparent predator frequently consumes dead prey instead of live prey then the biological control services provided by that predator may be overestimated. The use of unique protein markers on live and dead prey of the same s...

  7. Higher nest predation risk in association with a top predator: mesopredator attraction?

    PubMed

    Morosinotto, Chiara; Thomson, Robert L; Hänninen, Mikko; Korpimäki, Erkki

    2012-10-01

    Breeding close to top predators is a widespread reproductive strategy. Breeding animals may gain indirect benefits if proximity to top predators results in a reduction of predation due to suppression of mesopredators. We tested if passerine birds gain protection from mesopredators by nesting within territories of a top predator, the Ural owl (Strix uralensis). We placed nest boxes for pied flycatchers (Ficedula hypoleuca) in Ural owl nest sites and in control sites (currently unoccupied by owls). The nest boxes were designed so that nest predation risk could be altered (experimentally increased) after flycatcher settlement; we considered predation rate as a proxy of mesopredator abundance. Overall, we found higher nest predation rates in treatment than in control sites. Flycatcher laying date did not differ between sites, but smaller clutches were laid in treatment sites compared to controls, suggesting a response to perceived predation risk. Relative nest predation rate varied between years, being higher in owl nest sites in 2 years but similar in another; this variation might be indirectly influenced by vole abundance. Proximity to Ural owl nests might represent a risky habitat for passerines. High predation rates within owl territories could be because small mesopredators that do not directly threaten owl nests are attracted to owl nest sites. This could be explained if some mesopredators use owl territories to gain protection from their own predators, or if top predators and mesopredators independently seek similar habitats.

  8. Maternal intraguild predation risk affects offspring anti-predator behavior and learning in mites.

    PubMed

    Seiter, Michael; Schausberger, Peter

    2015-10-09

    Predation risk is a strong selective force shaping prey morphology, life history and behavior. Anti-predator behaviors may be innate, learned or both but little is known about the transgenerational behavioral effects of maternally experienced predation risk. We examined intraguild predation (IGP) risk-induced maternal effects on offspring anti-predator behavior, including learning, in the predatory mite Phytoseiulus persimilis. We exposed predatory mite mothers during egg production to presence or absence of the IG predator Amblyseius andersoni and assessed whether maternal stress affects the anti-predator behavior, including larval learning ability, of their offspring as protonymphs. Protonymphs emerging from stressed or unstressed mothers, and having experienced IGP risk as larvae or not, were subjected to choice situations with and without IG predator traces. Predator-experienced protonymphs from stressed mothers were the least active and acted the boldest in site choice towards predator cues. We argue that the attenuated response of the protonymphs to predator traces alone represents optimized risk management because no immediate risk existed. Such behavioral adjustment could reduce the inherent fitness costs of anti-predator behaviors. Overall, our study suggests that P. persimilis mothers experiencing IGP risk may prime their offspring to behave more optimally in IGP environments.

  9. Maternal intraguild predation risk affects offspring anti-predator behavior and learning in mites

    PubMed Central

    Seiter, Michael; Schausberger, Peter

    2015-01-01

    Predation risk is a strong selective force shaping prey morphology, life history and behavior. Anti-predator behaviors may be innate, learned or both but little is known about the transgenerational behavioral effects of maternally experienced predation risk. We examined intraguild predation (IGP) risk-induced maternal effects on offspring anti-predator behavior, including learning, in the predatory mite Phytoseiulus persimilis. We exposed predatory mite mothers during egg production to presence or absence of the IG predator Amblyseius andersoni and assessed whether maternal stress affects the anti-predator behavior, including larval learning ability, of their offspring as protonymphs. Protonymphs emerging from stressed or unstressed mothers, and having experienced IGP risk as larvae or not, were subjected to choice situations with and without IG predator traces. Predator-experienced protonymphs from stressed mothers were the least active and acted the boldest in site choice towards predator cues. We argue that the attenuated response of the protonymphs to predator traces alone represents optimized risk management because no immediate risk existed. Such behavioral adjustment could reduce the inherent fitness costs of anti-predator behaviors. Overall, our study suggests that P. persimilis mothers experiencing IGP risk may prime their offspring to behave more optimally in IGP environments. PMID:26449645

  10. Positive solutions of a prey-predator model with predator saturation and competition

    NASA Astrophysics Data System (ADS)

    Wang, Mingxin; Wu, Qiang

    2008-09-01

    In this paper, we study the existence, multiplicity, bifurcation and stability of positive solutions to a prey-predator model with predator saturation and competition where and parameters are all positive constants, and u and v are the densities of the prey and predator, respectively.

  11. Effects of a disease affecting a predator on the dynamics of a predator-prey system.

    PubMed

    Auger, Pierre; McHich, Rachid; Chowdhury, Tanmay; Sallet, Gauthier; Tchuente, Maurice; Chattopadhyay, Joydev

    2009-06-07

    We study the effects of a disease affecting a predator on the dynamics of a predator-prey system. We couple an SIRS model applied to the predator population, to a Lotka-Volterra model. The SIRS model describes the spread of the disease in a predator population subdivided into susceptible, infected and removed individuals. The Lotka-Volterra model describes the predator-prey interactions. We consider two time scales, a fast one for the disease and a comparatively slow one for predator-prey interactions and for predator mortality. We use the classical "aggregation method" in order to obtain a reduced equivalent model. We show that there are two possible asymptotic behaviors: either the predator population dies out and the prey tends to its carrying capacity, or the predator and prey coexist. In this latter case, the predator population tends either to a "disease-free" or to a "disease-endemic" state. Moreover, the total predator density in the disease-endemic state is greater than the predator density in the "disease-free" equilibrium (DFE).

  12. Intraguild interactions among three spider mite predators: predation preference and effects on juvenile development and oviposition.

    PubMed

    Rahmani, Hasan; Daneshmandi, Aliakbar; Walzer, Andreas

    2015-12-01

    A first step to evaluate potential negative effects of intraguild predation (IGP) when using multiple predators against a pest species is the determination of the predation behavior of the predators and the nutritional value of intraguild (IG) prey in terms of development and oviposition. Here, we investigated the predation preference of the female predatory mites Neoseiulus californicus, Typhlodromus bagdasarjani and Phytoseius plumifer, when having choice between larvae of the two other predatory mite species (IG prey) with and without extraguild prey, the spider mite Tetranychus urticae (EG prey). Additionally, we evaluated the juvenile development and oviposition of the three predator species when provided with larvae from each other species. Irrespective of EG prey, IG prey species affected neither the first attack nor attack times of the three female IG predator species. The IG predation rates of the predator females, however, were influenced by prey species in the absence of EG prey. Neoseiulus californicus females killed more P. plumifer than T. bagdasarjani larvae, whereas T. bagdasarjani and P. plumifer females killed more N. californicus than P. plumifer and T. bagdasarjani larvae, respectively. All IG predator species consumed significantly more EG than IG prey. IG prey species did not influence juvenile and adult survival probabilities of the IG predators. We conclude that IGP is a weak force among the three predators and the potential consequences of IGP should not result in the elimination of one by another tested predatory mite species at least in the presence of spider mites.

  13. Landscape forest cover and edge effects on songbird nest predation vary by nest predator

    Treesearch

    W. Andrew Cox; Frank R. III Thompson; John. Faaborg

    2012-01-01

    Rates of nest predation for birds vary between and within species across multiple spatial scales, but we have a poor understanding of which predators drive such patterns. We video-monitored nests and identified predators at 120 nests of the Acadian Flycatcher (Empidonax virescens) and the Indigo Bunting (Passerina cyanea) at eight...

  14. Learning to distinguish between predators and non-predators: understanding the critical role of diet cues and predator odours in generalisation

    PubMed Central

    Mitchell, Matthew D.; Chivers, Douglas P.; McCormick, Mark I.; Ferrari, Maud C.O.

    2015-01-01

    It is critical for prey to recognise predators and distinguish predators from non-threatening species. Yet, we have little understanding of how prey develop effective predator recognition templates. Recent studies suggest that prey may actually learn key predator features which can be used to recognise novel species with similar characteristics. However, non-predators are sometimes mislabelled as predators when generalising recognition. Here, we conduct the first comprehensive investigation of how prey integrate information on predator odours and predator diet cues in generalisation, allowing them to discriminate between predators and non-predators. We taught lemon damselfish to recognise a predator fed a fish diet, and tested them for their response to the known predator and a series of novel predators (fed fish diet) and non-predators (fed squid diet) distributed across a phylogenetic gradient. Our findings show that damselfish distinguish between predators and non-predators when generalising recognition. Additional experiments revealed that generalised recognition did not result from recognition of predator odours or diet cues, but that damselfish based recognition on what they learned during the initial conditioning. Incorporating multiple sources of information enables prey to develop highly plastic and accurate recognition templates that will increase survival in patchy environments where they have little prior knowledge. PMID:26358861

  15. Species and temporal factors affect predator-specific rates of nest predation for forest songbirds in the midwest

    Treesearch

    W. Andrew Cox; Frank R. III Thompson; John. Faaborg

    2012-01-01

    Knowledge of the relative contributions of predator species to overall rates of nest predation can improve our understanding of why predation risk varies, but the identity of predators is seldom known. We used video technology to identify nest predators of the tree-nesting Acadian Flycatcher (Empidonax virescens) and the shrub-nesting Indigo Bunting...

  16. Predicted responses of invasive mammal communities to climate-related changes in mast frequency in forest ecosystems.

    PubMed

    Tompkins, Daniel M; Byrom, Andrea E; Pech, Roger P

    2013-07-01

    Predicting the dynamics and impacts of multiple invasive species can be complex because ecological relationships, which occur among several trophic levels, are often incompletely understood. Further, the complexity of these trophic relationships exacerbates our inability to predict climate change effects on invaded ecosystems. We explore the hypothesis that interactions between two global change drivers, invasive vertebrates and climate change, will potentially make matters worse for native biodiversity. In New Zealand beech (Nothofagus spp.) forests, a highly irruptive invasive mammal community is driven by multi-annual resource pulses of beech seed (masting). Because mast frequency is predicted to increase with climate change, we use this as a model system to explore the extent to which such effects may influence invasive vertebrate communities, and the implications of such interactions for native biodiversity and its management. We build on an established model of trophic interactions in the system, combining it with a logistic probability mast function, the parameters of which were altered to simulate either contemporary conditions or conditions of more or less frequent masting. The model predicts that increased mast frequency will lead to populations of a top predator (the stoat) and a mesopredator (the ship rat) becoming less irruptive and being maintained at appreciably higher average abundances in this forest type. In addition, the ability of both current and in-development management approaches to suppress invasive mammals is predicted to be compromised. Because invasive mammals are key drivers of native fauna extinction in New Zealand, with the additional loss of associated functions such as pollination and seed dispersal, these predictions imply potentially serious adverse impacts of climate change for the conservation of biodiversity and ecosystem function. Our study also highlights the importance of long-term monitoring data for assessing and managing

  17. Species invasion history influences community evolution in a tri-trophic food web model.

    PubMed

    Mougi, Akihiko; Nishimura, Kinya

    2009-08-24

    Recent experimental studies have demonstrated the importance of invasion history for evolutionary formation of community. However, only few theoretical studies on community evolution have focused on such views. We used a tri-trophic food web model to analyze the coevolutionary effects of ecological invasions by a mutant and by a predator and/or resource species of a native consumer species community and found that ecological invasions can lead to various evolutionary histories. The invasion of a predator makes multiple evolutionary community histories possible, and the evolutionary history followed can determine both the invasion success of the predator into the native community and the fate of the community. A slight difference in the timing of an ecological invasion can lead to a greatly different fate. In addition, even greatly different community histories can converge as a result of environmental changes such as a predator trait shift or a productivity change. Furthermore, the changes to the evolutionary history may be irreversible. Our modeling results suggest that the timing of ecological invasion of a species into a focal community can largely change the evolutionary consequences of the community. Our approach based on adaptive dynamics will be a useful tool to understand the effect of invasion history on evolutionary formation of community.

  18. Predation of caterpillars on understory saplings in an Ozark forest

    USGS Publications Warehouse

    Lichtenberg, J.S.; Lichtenberg, D.A.

    2003-01-01

    Predators of caterpillars (Lepidoptera larvae) can indirectly enhance economic gains from plant resources by reducing herbivore damage to plants. For this study, we directly observed predation of caterpillars on understory trees in the Ozarks. Our objectives were to determine the relative importance of diurnal guilds of caterpillar predators, the time of day most diurnal predation events occur, and whether predators spend more time feeding in open or closed canopy areas. Once per month, June-September, we tethered caterpillars to understory saplings and recorded all predation events. Only invertebrate predators were observed feeding on caterpillars, and most predation events were attributed to ants and vespids (wasps, hornets and yellow jackets). Predation by vertebrate predators such as birds, small mammals, reptiles and amphibians was not observed. Most predation events took place at mid-day between 1200 and 1600 hrs. Predation pressure differed significantly over the four observation dates with peak ant predation in July and peak vespid predation in September. Canopy environment appeared to influence predation events as there was a trend towards higher vespid predation of caterpillars on open canopy as opposed to closed canopy saplings. Ants and vespids accounted for 90% of observed predation events; therefore they appear to be important predators of caterpillars during the summer months. Future studies at earlier sampling dates would be valuable in determining whether the relative importance of other diurnal guilds of caterpillar predators might be greater in the spring.

  19. Aquatic predation alters a terrestrial prey subsidy.

    PubMed

    Wesner, Jeff Scott

    2010-05-01

    Organisms with complex life histories (CLH) often cross habitat or ecosystem boundaries as they develop from larvae to adults, coupling energy flow between ecosystems as both prey (bottom-up) and consumers (top-down). Predation effects on one stage of this life cycle can therefore cascade across ecosystems, magnifying the impact of local predation. The majority of predation studies have assessed effects only on a local level, within the habitat of the predator. I used large outdoor stream mesocosms to test the hypothesis that predation in an aquatic habitat alters the magnitude and trophic structure of a prey assemblage in a terrestrial habitat. I also tested how a consumer in the terrestrial habitat (web-weaving spiders) responded to these changes in prey export. Two fish species were the predators (red shiner, Cyprinella lutrensis and orangethroat darter, Etheostoma spectabile) in an experiment with three treatments: both fish species monocultures plus a fishless control. Fish predation reduced aquatic insect emergence biomass by 50% compared to the fishless control and altered the trophic structure of the emergent community, reducing emerging insect predator biomass by 50%, but had no effect on other insect trophic groups. Spiders captured only insects that were unaffected by fish predation (mostly chironomids) and therefore did not respond numerically to overall changes in insect abundance or biomass. Patterns of insect emergence were largely driven by a strong negative relationship between fish and a predatory dragonfly (Pantala flavescens). The results of this experiment show that predation in one habitat can have strong effects on the biomass and trophic structure of subsidies entering adjacent habitats, resulting in contrasting predictions for the role of these subsidies in recipient food webs. In the absence of fish, aquatic habitats produced terrestrial insect communities with higher biomass (bottom-up potential) and a higher proportion of predators (top

  20. Does sex-selective predation stabilize or destabilize predator-prey dynamics?

    PubMed

    Boukal, David S; Berec, Ludek; Krivan, Vlastimil

    2008-07-16

    Little is known about the impact of prey sexual dimorphism on predator-prey dynamics and the impact of sex-selective harvesting and trophy hunting on long-term stability of exploited populations. We review the quantitative evidence for sex-selective predation and study its long-term consequences using several simple predator-prey models. These models can be also interpreted in terms of feedback between harvesting effort and population size of the harvested species under open-access exploitation. Among the 81 predator-prey pairs found in the literature, male bias in predation is 2.3 times as common as female bias. We show that long-term effects of sex-selective predation depend on the interplay of predation bias and prey mating system. Predation on the 'less limiting' prey sex can yield a stable predator-prey equilibrium, while predation on the other sex usually destabilizes the dynamics and promotes population collapses. For prey mating systems that we consider, males are less limiting except for polyandry and polyandrogyny, and male-biased predation alone on such prey can stabilize otherwise unstable dynamics. On the contrary, our results suggest that female-biased predation on polygynous, polygynandrous or monogamous prey requires other stabilizing mechanisms to persist. Our modelling results suggest that the observed skew towards male-biased predation might reflect, in addition to sexual selection, the evolutionary history of predator-prey interactions. More focus on these phenomena can yield additional and interesting insights as to which mechanisms maintain the persistence of predator-prey pairs over ecological and evolutionary timescales. Our results can also have implications for long-term sustainability of harvesting and trophy hunting of sexually dimorphic species.

  1. Nest Predation Deviates from Nest Predator Abundance in an Ecologically Trapped Bird.

    PubMed

    Hollander, Franck A; Van Dyck, Hans; San Martin, Gilles; Titeux, Nicolas

    2015-01-01

    In human-modified environments, ecological traps may result from a preference for low-quality habitat where survival or reproductive success is lower than in high-quality habitat. It has often been shown that low reproductive success for birds in preferred habitat types was due to higher nest predator abundance. However, between-habitat differences in nest predation may only weakly correlate with differences in nest predator abundance. An ecological trap is at work in a farmland bird (Lanius collurio) that recently expanded its breeding habitat into open areas in plantation forests. This passerine bird shows a strong preference for forest habitat, but it has a higher nest success in farmland. We tested whether higher abundance of nest predators in the preferred habitat or, alternatively, a decoupling of nest predator abundance and nest predation explained this observed pattern of maladaptive habitat selection. More than 90% of brood failures were attributed to nest predation. Nest predator abundance was more than 50% higher in farmland, but nest predation was 17% higher in forest. Differences between nest predation on actual shrike nests and on artificial nests suggested that parent shrikes may facilitate nest disclosure for predators in forest more than they do in farmland. The level of caution by parent shrikes when visiting their nest during a simulated nest predator intrusion was the same in the two habitats, but nest concealment was considerably lower in forest, which contributes to explaining the higher nest predation in this habitat. We conclude that a decoupling of nest predator abundance and nest predation may create ecological traps in human-modified environments.

  2. Does Sex-Selective Predation Stabilize or Destabilize Predator-Prey Dynamics?

    PubMed Central

    Boukal, David S.; Berec, Luděk; Křivan, Vlastimil

    2008-01-01

    Background Little is known about the impact of prey sexual dimorphism on predator-prey dynamics and the impact of sex-selective harvesting and trophy hunting on long-term stability of exploited populations. Methodology and Principal Findings We review the quantitative evidence for sex-selective predation and study its long-term consequences using several simple predator-prey models. These models can be also interpreted in terms of feedback between harvesting effort and population size of the harvested species under open-access exploitation. Among the 81 predator-prey pairs found in the literature, male bias in predation is 2.3 times as common as female bias. We show that long-term effects of sex-selective predation depend on the interplay of predation bias and prey mating system. Predation on the ‘less limiting’ prey sex can yield a stable predator-prey equilibrium, while predation on the other sex usually destabilizes the dynamics and promotes population collapses. For prey mating systems that we consider, males are less limiting except for polyandry and polyandrogyny, and male-biased predation alone on such prey can stabilize otherwise unstable dynamics. On the contrary, our results suggest that female-biased predation on polygynous, polygynandrous or monogamous prey requires other stabilizing mechanisms to persist. Conclusions and Significance Our modelling results suggest that the observed skew towards male-biased predation might reflect, in addition to sexual selection, the evolutionary history of predator-prey interactions. More focus on these phenomena can yield additional and interesting insights as to which mechanisms maintain the persistence of predator-prey pairs over ecological and evolutionary timescales. Our results can also have implications for long-term sustainability of harvesting and trophy hunting of sexually dimorphic species. PMID:18628951

  3. Nest Predation Deviates from Nest Predator Abundance in an Ecologically Trapped Bird

    PubMed Central

    Hollander, Franck A.; Van Dyck, Hans; San Martin, Gilles; Titeux, Nicolas

    2015-01-01

    In human-modified environments, ecological traps may result from a preference for low-quality habitat where survival or reproductive success is lower than in high-quality habitat. It has often been shown that low reproductive success for birds in preferred habitat types was due to higher nest predator abundance. However, between-habitat differences in nest predation may only weakly correlate with differences in nest predator abundance. An ecological trap is at work in a farmland bird (Lanius collurio) that recently expanded its breeding habitat into open areas in plantation forests. This passerine bird shows a strong preference for forest habitat, but it has a higher nest success in farmland. We tested whether higher abundance of nest predators in the preferred habitat or, alternatively, a decoupling of nest predator abundance and nest predation explained this observed pattern of maladaptive habitat selection. More than 90% of brood failures were attributed to nest predation. Nest predator abundance was more than 50% higher in farmland, but nest predation was 17% higher in forest. Differences between nest predation on actual shrike nests and on artificial nests suggested that parent shrikes may facilitate nest disclosure for predators in forest more than they do in farmland. The level of caution by parent shrikes when visiting their nest during a simulated nest predator intrusion was the same in the two habitats, but nest concealment was considerably lower in forest, which contributes to explaining the higher nest predation in this habitat. We conclude that a decoupling of nest predator abundance and nest predation may create ecological traps in human-modified environments. PMID:26624619

  4. Responses of tadpoles to hybrid predator odours: strong maternal signatures and the potential risk/response mismatch

    PubMed Central

    Chivers, Douglas P.; Mathiron, Anthony; Sloychuk, Janelle R.; Ferrari, Maud C. O.

    2015-01-01

    Previous studies have established that when a prey animal knows the identity of a particular predator, it can use this knowledge to make an ‘educated guess' about similar novel predators. Such generalization of predator recognition may be particularly beneficial when prey are exposed to introduced and invasive species of predators or hybrids. Here, we examined generalization of predator recognition for woodfrog tadpoles exposed to novel trout predators. Tadpoles conditioned to recognize tiger trout, a hybrid derived from brown trout and brook trout, showed generalization of recognition of several unknown trout odours. Interestingly, the tadpoles showed stronger responses to odours of brown trout than brook trout. In a second experiment, we found that tadpoles trained to recognize brown trout showed stronger responses to tiger trout than those tadpoles trained to recognize brook trout. Given that tiger trout always have a brown trout mother and a brook trout father, these results suggest a strong maternal signature in trout odours. Tadpoles that were trained to recognize both brown trout and brook trout showed stronger response to novel tiger trout than those trained to recognize only brown trout or only brook trout. This is consistent with a peak shift in recognition, whereby cues that are intermediate between two known cues evoke stronger responses than either known cue. Given that our woodfrog tadpoles have no evolutionary or individual experience with trout, they have no way of knowing whether or not brook trout, brown trout or tiger trout are more dangerous. The differential intensity of responses that we observed to hybrid trout cues and each of the parental species indicates that there is a likely mismatch between risk and anti-predator response intensity. Future work needs to address the critical role of prey naivety on responses to invasive and introduced hybrid predators. PMID:26041358

  5. Responses of tadpoles to hybrid predator odours: strong maternal signatures and the potential risk/response mismatch.

    PubMed

    Chivers, Douglas P; Mathiron, Anthony; Sloychuk, Janelle R; Ferrari, Maud C O

    2015-06-22

    Previous studies have established that when a prey animal knows the identity of a particular predator, it can use this knowledge to make an 'educated guess' about similar novel predators. Such generalization of predator recognition may be particularly beneficial when prey are exposed to introduced and invasive species of predators or hybrids. Here, we examined generalization of predator recognition for woodfrog tadpoles exposed to novel trout predators. Tadpoles conditioned to recognize tiger trout, a hybrid derived from brown trout and brook trout, showed generalization of recognition of several unknown trout odours. Interestingly, the tadpoles showed stronger responses to odours of brown trout than brook trout. In a second experiment, we found that tadpoles trained to recognize brown trout showed stronger responses to tiger trout than those tadpoles trained to recognize brook trout. Given that tiger trout always have a brown trout mother and a brook trout father, these results suggest a strong maternal signature in trout odours. Tadpoles that were trained to recognize both brown trout and brook trout showed stronger response to novel tiger trout than those trained to recognize only brown trout or only brook trout. This is consistent with a peak shift in recognition, whereby cues that are intermediate between two known cues evoke stronger responses than either known cue. Given that our woodfrog tadpoles have no evolutionary or individual experience with trout, they have no way of knowing whether or not brook trout, brown trout or tiger trout are more dangerous. The differential intensity of responses that we observed to hybrid trout cues and each of the parental species indicates that there is a likely mismatch between risk and anti-predator response intensity. Future work needs to address the critical role of prey naivety on responses to invasive and introduced hybrid predators.

  6. Predator harvesting in stage dependent predation models: insights from a threshold management policy.

    PubMed

    Costa, Michel Iskin da Silveira

    2008-11-01

    Stage dependent predation may give rise to the hydra effect--the increase of predator density at equilibrium as its mortality rate is raised. Management strategies that adjust predator harvest rates or quotas based on responses of populations to past changes in capture rates may eventually lead to a catastrophic collapse of predator species. A proposed threshold management policy avoids the hydra effect and its subsequent danger of predator extinction. Suggestions to extend the application of threshold policies in areas such as intermediate disturbance hypothesis, density-trait mediated interactions and non-optimal anti-predatory behavior are put forward.

  7. Does predation contribute to tree diversity?

    Treesearch

    Brian Beckage; James S. Clark

    2005-01-01

    Seed and seedling predation may differentially affect competitively superior tree species to increase the relative recruitment success of poor competitors and contribute to the coexistence of tree species. We examined the effect of seed and seedling predation on the seedling recruitment of three tree species, Acer rubrum (red maple), ...

  8. Pinpointing Predation Events: A different molecular approach.

    USDA-ARS?s Scientific Manuscript database

    A glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, protien marking system has been developed as a diagnostic tool for quantifying predation rates via gut content analysis. A field study was conducted to quantify predation rates on each of the GWSS lifestages. Specifically, two GWSS nymp...

  9. Modeling predator habitat to enhance reintroduction planning

    Treesearch

    Shiloh M. Halsey; William J. Zielinski; Robert M. Scheller

    2015-01-01

    Context The success of species reintroduction often depends on predation risk and spatial estimates of predator habitat. The fisher (Pekania pennanti) is a species of conservation concern and populations in the western United States have declined substantially in the last century. Reintroduction plans are underway, but the ability...

  10. Predator population depending on lemming cycles

    NASA Astrophysics Data System (ADS)

    Anashkina, Ekaterina I.; Chichigina, Olga A.; Valenti, Davide; Kargovsky, Aleksey V.; Spagnolo, Bernardo

    2016-07-01

    In this paper, a Langevin equation for predator population with multiplicative correlated noise is analyzed. The noise source, which is a nonnegative random pulse noise with regulated periodicity, corresponds to the prey population cycling. The increase of periodicity of noise affects the average predator density at the stationary state.

  11. Spatiotemporal dynamics of the epidemic transmission in a predator-prey system.

    PubMed

    Su, Min; Hui, Cang; Zhang, Yanyu; Li, Zizhen

    2008-11-01

    Epidemic transmission is one of the critical density-dependent mechanisms that affect species viability and dynamics. In a predator-prey system, epidemic transmission can strongly affect the success probability of hunting, especially for social animals. Predators, therefore, will suffer from the positive density-dependence, i.e., Allee effect, due to epidemic transmission in the population. The rate of species contacting the epidemic, especially for those endangered or invasive, has largely increased due to the habitat destruction caused by anthropogenic disturbance. Using ordinary differential equations and cellular automata, we here explored the epidemic transmission in a predator-prey system. Results show that a moderate Allee effect will destabilize the dynamics, but it is not true for the extreme Allee effect (weak or strong). The predator-prey dynamics amazingly stabilize by the extreme Allee effect. Predators suffer the most from the epidemic disease at moderate transmission probability. Counter-intuitively, habitat destruction will benefit the control of the epidemic disease. The demographic stochasticity dramatically influences the spatial distribution of the system. The spatial distribution changes from oil-bubble-like (due to local interaction) to aggregated spatially scattered points (due to local interaction and demographic stochasticity). It indicates the possibility of using human disturbance in habitat as a potential epidemic-control method in conservation.

  12. Coexistence of predator and prey in intraguild predation systems with ontogenetic niche shifts.

    PubMed

    Hin, Vincent; Schellekens, Tim; Persson, Lennart; de Roos, André M

    2011-12-01

    In basic intraguild predation (IGP) systems, predators and prey also compete for a shared resource. Theory predicts that persistence of these systems is possible when intraguild prey is superior in competition and productivity is not too high. IGP often results from ontogenetic niche shifts, in which the diet of intraguild predators changes as a result of growth in body size (life-history omnivory). As a juvenile, a life-history omnivore competes with the species that becomes its prey later in life. Competition can hence limit growth of young predators, while adult predators can suppress consumers and therewith neutralize negative effects of competition. We formulate and analyze a stage-structured model that captures both basic IGP and life-history omnivory. The model predicts increasing coexistence of predators and consumers when resource use of stage-structured predators becomes more stage specific. This coexistence depends on adult predators requiring consumer biomass for reproduction and is less likely when consumers outcompete juvenile predators, in contrast to basic IGP. Therefore, coexistence occurs when predation structures the community and competition is negligible. Consequently, equilibrium patterns over productivity resemble those of three-species food chains. Life-history omnivory thus provides a mechanism that allows intraguild predators and prey to coexist over a wide range of resource productivity.

  13. The Behavioral Type of a Top Predator Drives the Short-Term Dynamic of Intraguild Predation.

    PubMed

    Michalko, Radek; Pekár, Stano

    2017-03-01

    Variation in behavior among individual top predators (i.e., the behavioral type) can strongly shape pest suppression in intraguild predation (IGP). However, the effect of a top predator's behavioral type-namely, foraging aggressiveness (number of killed divided by prey time) and prey choosiness (preference degree for certain prey type)-on the dynamic of IGP may interact with the relative abundances of top predator, mesopredator, and pest. We investigated the influence of the top predator's behavioral type on the dynamic of IGP in a three-species system with a top predator spider, a mesopredator spider, and a psyllid pest using a simulation model. The model parameters were estimated from laboratory experiments and field observations. The top predator's behavioral type altered the food-web dynamics in a context-dependent manner. The system with an aggressive/nonchoosy top predator, without prey preferences between pest and mesopredator, suppressed the pest more when the top predator to mesopredator abundance ratio was high. In contrast, the system with a timid/choosy top predator that preferred the pest to the mesopredator was more effective when the ratio was low. Our results show that the behavioral types and abundances of interacting species need to be considered together when studying food-web dynamics, because they evidently interact. To improve biocontrol efficiency of predators, research on the alteration of their behavioral types is needed.

  14. Bifurcation analysis of a predator-prey model with predators using hawk and dove tactics.

    PubMed

    Auger, Pierre; Kooi, Bob W; Bravo de la Parra, Rafael; Poggiale, Jean-Christophe

    2006-02-07

    Most classical prey-predator models do not take into account the behavioural structure of the population. Usually, the predator and the prey populations are assumed to be homogeneous, i.e. all individuals behave in the same way. In this work, we shall take into account different tactics that predators can use for exploiting a common self-reproducing resource, the prey population. Predators fight together in order to keep or to have access to captured prey individuals. Individual predators can use two behavioural tactics when they encounter to dispute a prey, the classical hawk and dove tactics. We assume two different time scales. The fast time scale corresponds to the inter-specific searching and handling for the prey by the predators and the intra-specific fighting between the predators. The slow time scale corresponds to the (logistic) growth of the prey population and mortality of the predator. We take advantage of the two time scales to reduce the dimension of the model and to obtain an aggregated model that describes the dynamics of the total predator and prey densities at the slow time scale. We present the bifurcation analysis of the model and the effects of the different predator tactics on persistence and stability of the prey-predator community are discussed.

  15. Invasive Candidiasis.

    PubMed

    McCarty, Todd P; Pappas, Peter G

    2016-03-01

    Invasive candidiasis is a collective term that refers to a group of infectious syndromes caused by a variety of species of Candida, 5 of which cause most cases. Candidemia is the most commonly recognized syndrome associated with invasive candidiasis. Certain conditions may influence the likelihood for one species versus another in a specific clinical scenario, and this can have important implications for selection of antifungal therapy and the duration of treatment. Molecular diagnostic technology plays an ever-increasing role as an adjunct to traditional culture-based diagnostics, offering significant potential toward improvement in patient care.

  16. Do predators influence the behaviour of bats?

    PubMed

    Lima, Steven L; O'Keefe, Joy M

    2013-08-01

    Many aspects of animal behaviour are affected by real-time changes in the risk of predation. This conclusion holds for virtually all taxa and ecological systems studied, but does it hold for bats? Bats are poorly represented in the literature on anti-predator behaviour, which may reflect a lack of nocturnal predators specialized on bats. If bats actually experience a world with minimal anti-predator concerns, then they will provide a unique contrast within the realm of vertebrate ecology. Alternatively, such predator-driven behaviour in bats may not yet be fully understood, given the difficulties in working with these highly mobile and nocturnal animals. We provide a wide-ranging exploration of these issues in bat behaviour. We first cover the basic predator-prey information available on bats, both on potential predators and the ways in which bats might perceive predators and respond to attacks. We then cover work relevant to key aspects of bat behaviour, such as choice of daytime roosts, the nature of sleep and torpor, evening roost departures, moonlight avoidance, landscape-related movement patterns, and habitat selection. Overall, the evidence in favour of a strong influence of predators on bat behaviour is equivocal, with the picture clouded by contradictory results and a lack of information on potential predators and the perception of risk by bats. It seems clear that day-active bats run a considerable risk of being killed by diurnal raptors, which are able to capture bats with relative ease. Thus, bats taking advantage of a pulse of insects just prior to sunset are likely taking risks to gain much-needed energy. Further, the choice of daytime roosts by bats is probably strongly influenced by roost safety. Few studies, however, have directly addressed either of these topics. As a group, insectivorous temperate-zone bats show no clear tendency to avoid apparently risky situations, such as activity on moonlit nights. However, some observations are consistent

  17. A multiple phenotype predator-prey model with mutation

    NASA Astrophysics Data System (ADS)

    Abernethy, Gavin M.; Mullan, Rory; Glass, David H.; McCartney, Mark

    2017-01-01

    An existing multiple phenotype predator-prey model is expanded to include mutation amongst the predator phenotypes. Two unimodal maps are used for the underlying dynamics of the prey. A predation strategy is also defined which differs for each of the predators in the model. Results show that the introduction of predator mutation enhances predator survival both in terms of the number of phenotypes and total population for a range of values of the predation rate. In general, the dominant predator phenotype is the one which is most focused on the prey phenotype with the largest population.

  18. The relationship between direct predation and antipredator responses: a test with multiple predators and multiple prey.

    PubMed

    Creel, Scott; Dröge, Egil; M'soka, Jassiel; Smit, Daan; Becker, Matt; Christianson, Dave; Schuette, Paul

    2017-08-01

    Most species adjust their behavior to reduce the likelihood of predation. Many experiments have shown that antipredator responses carry energetic costs that can affect growth, survival, and reproduction, so that the total cost of predation depends on a trade-off between direct predation and risk effects. Despite these patterns, few field studies have examined the relationship between direct predation and the strength of antipredator responses, particularly for complete guilds of predators and prey. We used scan sampling in 344 observation periods over a four-year field study to examine behavioral responses to the immediate presence of predators for a complete antelope guild (dominated by wildebeest, zebra, and oribi) in Liuwa Plains National Park, Zambia, testing for differences in response to all large carnivores in the ecosystem (lions, spotted hyenas, cheetahs, and African wild dogs). We quantified the proportion that each prey species contributed to the kills made by each predator (516 total kills), used distance sampling on systematic line transects to determine the abundance of each prey species, and combined these data to quantify the per-capita risk of direct predation for each predator-prey pair. On average, antelopes increased their vigilance by a factor of 2.4 when predators were present. Vigilance varied strongly among prey species, but weakly in response to different predators. Increased vigilance was correlated with reduced foraging in a similar manner for all prey species. The strength of antipredator response was not detectably related to patterns of direct predation (n = 15 predator-prey combinations with sufficient data). This lack of correlation has implications for our understanding of the role of risk effects as part of the limiting effect of predators on prey. © 2017 by the Ecological Society of America.