In support of an Organization for Economic Cooperation and Development (OECD) Amphibian Metamorphosis Assay (AMA) Test Guideline for the detection of substances that interact with the hypothalamic-pituitary-thyroid axis, a document was developed that provides a standardized appro...
The Amphibian Metamorphosis Assay (AMA), developed for Xenopus laevis, is designed to identify chemicals that disrupt thyroid hormone (TH)-mediated biological processes. We adapted the AMA for use on an ecologically-relevant North American species, the Pacific tree frog (Pseudacris regilla), and applied molecular endpoints to evaluate the effects of the antibacterial agent, triclosan (TCS). Premetamorphic (Gosner stage 26-28) tadpoles were immersed for 21 days in solvent control, 1.5 ?g/L thyroxine (T(4)), 0.3, 3 and 30 ?g/L (nominal) TCS, or combined T(4)/TCS treatments. Exposure effects were scored by morphometric (developmental stage, wet weight, and body, snout-vent and hindlimb lengths) and molecular (mRNA abundance using quantitative real time polymerase chain reaction) criteria. T(4) treatment alone accelerated development concomitant with altered levels of TH receptors ? and ?, proliferating cell nuclear antigen, and gelatinase B mRNAs in the brain and tail. We observed TCS-induced perturbations in all of the molecular and morphological endpoints indicating that TCS exposure disrupts coordination of postembryonic tadpole development. Clear alterations in molecular endpoints were evident at day 2 whereas the earliest morphological effects appeared at day 4 and were most evident at day 21. Although TCS alone (3 and 30 ?g/L) was protective against tadpole mortality, this protection was lost in the presence of T(4). The Pacific tree frog is the most sensitive species examined to date displaying disruption of TH-mediated development by a common antimicrobial agent. PMID:23159728
Marlatt, Vicki L; Veldhoen, Nik; Lo, Bonnie P; Bakker, Dannika; Rehaume, Vicki; Vallée, Kurtis; Haberl, Maxine; Shang, Dayue; van Aggelen, Graham C; Skirrow, Rachel C; Elphick, James R; Helbing, Caren C
The U.S. Environmental Protection Agency (U.S. EPA) has included an amphibian metamorphosis assay (AMA) to detect thyroid active chemicals in Tier 1 testing of their endocrine screening program. To understand the variability, specificity, and reliability of the key endpoints of this assay, two exposure studies with Xenopus laevis tadpoles were conducted with two known thyroid-active compounds, namely, methimazole or L-thyroxine, for a total of 21 d. In addition, various increased-flow-rate treatments were included in the exposures to evaluate the effects of physical stress on metamorphic development. The endpoints examined in the exposures were wet weight, snout-vent length, hind-limb length, developmental stage, and thyroid and gonadal histopathology. As expected, the results indicated that both methimazole and L-thyroxine were thyroid active in the AMA, hind-limb length and thyroid histopathology being the most sensitive endpoints of thyroid activity. Tadpoles that were exposed to the various physical stressors in these experiments showed no signs of altered metamorphic development, and exposure to the thyroid-active compounds had no effect on the developing gonad of X. laevis. Taken together, these results support the use of the AMA as a Tier 1 endocrine screen for detection of potential thyroid pathway activity; however, the lack of a true negative response (no-effect) during the validation process prevents a full evaluation of this assay's specificity at this time. PMID:20821516
Coady, Katherine; Marino, Troy; Thomas, Johnson; Currie, Rebecca; Hancock, Gregg; Crofoot, Jackie; McNalley, Lindsay; McFadden, Lisa; Geter, David; Klecka, Gary
During amphibian metamorphosis, the larval tissues\\/organs rapidly degenerate to adapt from the aquatic to the terrestrial\\u000a life. At the cellular level, a large quantity of apoptosis occurs in a spatiotemporally-regulated fashion in different organs\\u000a to ensure timely removal of larval organs\\/tissues and the development of adult ones for the survival of the individuals. Thus,\\u000a amphibian metamorphosis provides us a good
Atsuko Ishizuya-Oka; Takashi Hasebe; Yun-Bo Shi
We examined the validity of an amphibian (Silurana tropicalis) metamorphosis assay (a 28-day semistatic test) under an individual-separated exposure system, where tadpoles were individually held in small glass beakers. We first conducted a comparative rearing experiment for 28 days between this exposure system and the traditional individual-grouped exposure system, both of which held 30 tadpoles (stages 49 and 50) in dechlorinated tap water (a control solution). The former system served to reduce interindividual variability in regard to three morphological measures (developmental stage, hind limb length, and total body length). Under this system, we tested thyroxine (T4, 1?g/L) and propylthiouracil (PTU, 75mg/L) for 28 days of exposure. The morphological data collected at 7-day intervals indicated that significant metamorphic acceleration and retardation were consistently induced in the tadpoles exposed to T4 and PTU, respectively. In addition, the thyroid glands of the tadpoles exposed to T4 and PTU clearly exhibited atrophy and hypertrophy accompanied with severe follicular cell hyperplasia, respectively. Our results are in agreement with the historical data generated from previous studies employing the traditional exposure system, thus indicating the validity of our alternative testing protocol. PMID:23067544
Saka, Masahiro; Tada, Noriko; Kamata, Yoichi
Amphibians are important vertebrates in toxicology often representing both aquatic and terrestrial forms within the life history of the same species. Of the thousands of species, only two have substantial genomics resources: the recently published genome of the Pipid, Xenopus (Silurana) tropicalis, and transcript information (and ongoing genome sequencing project) of Xenopus laevis. However, many more species representative of regional ecological niches and life strategies are used in toxicology worldwide. Since Xenopus species diverged from the most populous frog family, the Ranidae, ~200 million years ago, there are notable differences between them and the even more distant Caudates (salamanders) and Caecilians. These differences include genome size, gene composition, and extent of polyploidization. Application of toxicogenomics to amphibians requires the mobilization of resources and expertise to develop de novo sequence assemblies and analysis strategies for a broader range of amphibian species. The present mini-review will present the advances in toxicogenomics as pertains to amphibians with particular emphasis upon the development and use of genomic techniques (inclusive of transcriptomics, proteomics, and metabolomics) and the challenges inherent therein. PMID:22435070
Helbing, Caren C
2,4-Dichlorophenoxyacetic acid (2,4-D) was evaluated in both the Amphibian Metamorphosis Assay (AMA) and the Fish Short Term Reproduction Assay (FSTRA). In the AMA, tadpoles were exposed to mean measured 2,4-D concentrations of 0 (water control), 0.273, 3.24, 38.0 and 113 mg acid equivalents (ae)/L for either seven or 21 days. In the FSTRA, fathead minnows were exposed to mean measured 2,4-D concentrations of 0 (water control), 0.245, 3.14, 34.0, and 96.5 mg ae/L for 21 days. The respective concentrations of 2,4-D were not overtly toxic to either Xenopus laevis tadpoles or fathead minnows (Pimephales promelas). In the AMA, there were no signs of either advanced or delayed development, asynchronous development, or significant histopathological effects of the thyroid gland among 2,4-D exposed tadpoles evaluated on either day seven or day 21 of the exposure. Therefore, following the AMA decision logic, 2,4-D is considered "likely thyroid inactive" in the AMA with a No Observable Effect Concentration (NOEC) of 113 mg ae 2,4-D/L. In the FSTRA, there were no significant differences between control and 2,4-D exposed fish in regard to fertility, wet weight, length, gonado-somatic indices, tubercle scores, or blood plasma concentrations of vitellogenin. Furthermore, there were no treatment-related histopathologic changes in the testes or ovaries in any 2,4-D exposed group. The only significant effect was a decrease in fecundity among fish exposed to 96.5 mg ae 2,4-D/L. The cause of the reduced fecundity at the highest concentration of 2,4-D tested in the assay was most likely due to a generalized stress response in the fish, and not due to a specific endocrine mode of action of 2,4-D. Based on fish reproduction, the NOEC in the FSTRA was 34.0 mg ae 2,4-D/L. PMID:23357564
Coady, Katherine; Marino, Troy; Thomas, Johnson; Sosinski, Lindsay; Neal, Barbara; Hammond, Larry
This study examined the effects of freshwater petroleum contamination on amphibian reproduction. The primary objectives were to assess the potential environmental and physiological impacts of runoff petroleum products on amphibians, using the green tree frog (Hyla cinerea) as a target species and engine crankcase oil as a contaminant. Egg hatching success, tadpole growth, and successful metamorphosis were measured in four concentrations of oil. The effects of oil on food source was also studied. Hatching success was not measurably influenced by the presence of oil. Tadpole and alga growth were negatively associated with the presence of oil. No tadpoles from the high concentration of oil treatments successfully metamorphosed.
Mahaney, P.A. (Univ. of Georgia, Aiken, SC (United States). Dept. of Zoology)
Despite widespread concern about the role of environmental contaminants in global amphibian declines, and evidence that post-metamorphic life stages contribute disproportionately to amphibian population dynamics, most studies in amphibian ecotoxicology focus on larval life stages. Studies that focus solely on early life stages may miss important effects of contaminant exposure, such as latent effects that manifest some time after previous exposure. Moreover, it is often assumed that effects observed in amphibian larvae will persist to affect survival or reproduction later in life. We used terrestrial enclosures to determine whether exposure to mercury (Hg) through maternal transfer and/or larval diet had any adverse effects in post-metamorphic American toads (Bufo americanus). We found a 5% difference in size at metamorphosis that was attributed to maternal Hg exposure persisted for 1 year in the terrestrial environment, resulting in a 7% difference at the conclusion of the study. Although patterns of survival differed among treatments through time, we found no overall difference in survival after 1 year. We also found no evidence of emergent latent effects in the terrestrial toads that could be attributed to earlier exposure. Our results indicate that adverse effects of maternal Hg exposure that were observed in larval amphibians may persist to affect later terrestrial life stages but that no novel adverse effects developed when animals were raised in a semi-natural environment. Moreover, we found no evidence of persistent effects of dietary Hg exposure in larvae, highlighting a need for greater focus on maternal effects in amphibian ecotoxicology. Finally, we suggest an increase in the use of longitudinal studies to better understand contaminant impacts to amphibian populations via effects in both aquatic and terrestrial life stages. PMID:21850489
Todd, Brian D; Willson, John D; Bergeron, Christine M; Hopkins, William A
A need is recognized for the development and evaluation of bioassays for detection of thyroid system-disrupting compounds. The issue of testing for thyroid disruption can be addressed by exploiting amphibian metamorphosis as a biological model. In the present study, a test protocol for a Xenopus metamorphosis assay (XEMA) was developed and its interlaboratory transferability was evaluated in an informal ring
Robert Opitz; Thomas Braunbeck; Christian Bögi; Daniel B. Pickford; Gerrit Nentwig; Jörg Oehlmann; Osamu Tooi; Ilka Lutz; Werner Kloas
Questions in population ecology require the study of marked animals, and marks are assumed to be permanent and not overlooked by observers. I evaluated retention through metamorphosis of visual implant elastomer marks in larval salamanders and frogs and assessed error in observer identification of these marks. I found 1) individual marks were not retained in larval wood frogs (Rana sylvatica), whereas only small marks were likely to be retained in larval salamanders (Eurycea bislineata), and 2) observers did not always correctly identify marked animals. Evaluating the assumptions of marking protocols is important in the design phase of a study so that correct inference can be made about the population processes of interest. This guidance should be generally useful to the design of mark?recapture studies, with particular application to studies of larval amphibians.
Questions in population ecology require the study of marked animals, and marks are assumed to be permanent and not overlooked by observers. I evaluated retention through metamorphosis of visual implant elastomer marks in larval salamanders and frogs and assessed error in observer identification of these marks. I found 1) individual marks were not retained in larval wood frogs (Rana sylvatica), whereas only small marks were likely to be retained in larval salamanders (Eurycea bislineata), and 2) observers did not always correctly identify marked animals. Evaluating the assumptions of marking protocols is important in the design phase of a study so that correct inference can be made about the population processes of interest. This guidance should be generally useful to the design of mark-recapture studies, with particular application to studies of larval amphibians.
Grant, E. H. C.
Amphibians are vertebrates. Amphibians lay eggs to reproduce and undergo metamorphosis to go from offspring to adult. They are cold-blooded, meaning they rely on their surrounding environment and the sun to stay warm.
Olivia Worland (Purdue University;Biological Sciences)
Amphibian metamorphosis is a dynamic period of post-embryonic development which transforms the larval anuran into the juvenile. The body structure is remodeled through a variety of processes which may be perturbed by exposure to chemicals as well as other environmental stressors....
Calmodulin isolated and purified to homogeneity from young larvae is very similar to that obtained from adult Pleurodeles waltlii and these proteins are almost identical to previously described vertebrate calmodulins. During P. waltlii development, an increase in total individual calmodulin content is observed after the heart beating stage. In dorsal axial muscle, calmodulin level which is very high at the beginning of larval life (premetamorphosis) decreases strikingly in the first part of prometamorphosis. Such an evolution is observed in Ambystoma mexicanum too. Then, a significant increase occurs during metamorphosis. In contrast, calmodulin level in P. waltlii cardiac ventricular muscle increases continuously from hatching to the end of metamorphic climax. Thyroxine treatment which promotes precocious metamorphosis in P. waltlii and experimental metamorphosis in neotenic A. mexicanum, induces a rapid and significant increase in muscle calmodulin concentration. PMID:6537929
Weinman, J S; Gallien, C L; Rainteau, D P; Guyot, M; Weinman, S J; Demaille, J G
Amphibian larvae at contaminated sites may experience an alteration of metamorphic traits and survival compared to amphibians in uncontaminated conditions. Effects of chronic cadmium (Cd) exposure on the metamorphosis of American toads (Bufo americanus) and southern leopard frogs (Rana sphenocephala) were determined. The two species were reared separately from shortly after hatching through metamorphosis in outdoor mesocosms (1,325-L polyethylene cattle tanks) that simulated natural ponds and enhanced environmental realism relative to the laboratory. Both species exhibited a decrease in survival with increasing initial nominal aqueous Cd concentration. Cadmium treatment did not influence mass at metamorphosis for either species when survival was included as a covariate, but increased the age at metamorphosis for the American toads. The whole body Cd content of metamorphs increased with aqueous Cd treatment level for both species, and the American toads tended to possess more elevated residues. Cadmium quickly partitioned out of the water column and accumulated in and altered the abundance of the tadpoles' diet. Cadmium-contaminated sites may produce fewer metamorphs, and those that survive will metamorphose later and contain Cd. Interspecific differences in the response variables illustrate the importance of testing multiple species when assessing risk. PMID:16152972
James, Stacy M; Little, Edward E; Semlitsch, Raymond D
Managing areas designed for human recreation so that they are compatible with natural amphibian populations can reduce the negative impacts of habitat destruction. We examined the potential for amphibians to complete larval development in golf course ponds in the presence or absence of overwintered bullfrog tadpoles (Rana catesbeiana), which are frequently found in permanent, human-made ponds. We reared larval American toads (Bufo americanus), southern leopard frogs (R. sphenocephala), and spotted salamanders (Ambystoma maculatum) with 0 or 5 overwintered bullfrog tadpoles in field enclosures located in ponds on golf courses or in experimental wetlands at a reference site. Survival to metamorphosis of American toads, southern leopard frogs, and spotted salamanders was greater in ponds on golf courses than at reference sites. We attributed this increased survival to low abundance of insect predators in golf course ponds. The presence of overwintered bullfrogs, however, reduced the survival of American toads, southern leopard frogs, and spotted salamanders reared in golf course ponds, indicating that the suitability of the aquatic habitats for these species partly depended on the biotic community present. Our results suggest that ponds in human recreational areas should be managed by maintaining intermediate hydroperiods, which will reduce the presence of bullfrog tadpoles and predators, such as fish, and which may allow native amphibian assemblages to flourish. PMID:18254862
Boone, Michelle D; Semlitsch, Raymond D; Mosby, Cory
Although aquatic communities frequently are exposed to a number of pesticides, the effects of chemical mixtures are not well understood. In two separate studies, I examined how insecticide mixtures influenced the likelihood of unpredictable, nonadditive effects on American toad (Bufo americanus) and green frog (Rana clamitans) tadpoles reared in outdoor aquatic communities. I exposed tadpoles to single or multiple insecticides at approximately half the reported median lethal concentrations using insecticides that were either acetylcholinesterase inhibitors (carbaryl or malathion) or a sodium-channel disruptor (permethrin). I found that combinations of insecticides with the same mode of action were more likely to have nonadditive effects on amphibian metamorphosis compared with those having different modes of action. Additionally, in one study, a commercial formulation of permethrin led to near-complete elimination of American toads, suggesting that this formulation could have adverse effects on aquatic communities. Many community studies exploring the ecological effects of expected environmental concentrations of pesticides have suggested that indirect effects in the food web, rather than direct effects on individual physiology, have the largest effect on amphibians. The present study indicates that direct effects of pesticides may become particularly important when insecticides with the same mode of action are present in the environment. PMID:18260698
Boone, Michelle D
The estrogenic chemical bisphenol A (BPA) has multiple hormonal activities, but its effects on thyroid hormone (TH) action are not fully understood. TH is required for the metamorphosis of tadpoles into frogs, and thus tadpole tail regression, one of the most spectacular events in metamorphosis, can be used for studying the effect of BPA and related compounds (BPAs) on TH
Akihiko Kashiwagi; Kozo Utsumi; Keiko Kashiwagi; Shigeru Ohta; Kazumi Sugihara; Hideki Hanada; Shigeyuki Kitamurad
Selenium (Se) is an essential micronutrient with a narrow therapeutic concentration range. The relative toxicity of Se increases as it is biotransformed into organic compounds, primarily selenomethionine (SeMet), within the aquatic food chain. Effects of aquatic Se contamination are well quantified for many freshwater fish and aquatic bird species, but impacts on amphibians are not well known. This study investigated the responses of larval Cope's gray tree frogs (Hyla chrysoscelis) fed a diet enriched with one of two concentrations of SeMet (50.1 and 489.9 ?g Se g(-1) dw [low and high groups, respectively]) by way of a food-limited (ration) or ad libitum (ad lib) feeding regimen. The high dose caused 100 % mortality during the larval period independent of resource provision levels. Regardless of feeding regimen, the low dose decreased larval survival and successful metamorphosis relative to control treatments. The low dose also induced rear limb deformities in ?73 % of individuals initiating metamorphosis. Providing low-dose food by way of a rationed feeding regimen decreased observed toxicity, likely because of decreased dietary exposure to SeMet relative to the low ad lib treatment. Individuals from the low ration treatment had decreased wet mass at initiation and completion of metamorphic climax (Gosner stages 42 through 46) compared with those from the control ad lib treatment, indicating that resource limitation combined with Se exposure might negatively affect energy stores after metamorphosis. However, lipid content analyses of recently metamorphosed individuals did not reveal any influence of treatment or resource provision on energy stored as lipids. The mean tissue Se concentration of individuals that received the low dose and completed metamorphosis was significantly greater than that of control ad lib or ration individuals at the same developmental stage. This study demonstrates that larval exposure to dietary SeMet can decrease growth and survival and induce deformities in a developing amphibian. Furthermore, retention of Se body burdens through metamorphosis suggests that surviving individuals can transport Se accumulated from contaminated aquatic environments into terrestrial food webs. PMID:23229196
Lockard, Laura; Rowe, Christopher L; Heyes, Andrew
To investigate, at the molecular level, the remodeling of small intestine during amphibian metamorphosis, a subtractive hybridization approach was used to identify genes that are differentially regulated by thyroid hormone. A frog cDNA was isolated from Xenopus laevis and determined to be the gene encoding the intestinal fatty acid-binding protein (IFABP) based on its high sequence homology to the previously cloned mammalian IFABP gene. Northern blot analyses and in situ hybridization histochemistry also showed that, like the mammalian IFABP genes, frog IFABP gene expression is restricted to the intestinal epithelium. Xenopus embryos express detectable IFABP mRNA at stage 33/34, suggesting that intestinal epithelial cells differentiate well before feeding begins at stage 45. Moreover, during metamorphosis, levels of IFABP mRNA were gradually down-regulated over a period of about 20 days between stages 54 and 62, reaching a minimum at metamorphic climax, after which they were reelevated as the secondary epithelium forms. This reduction in IFABP gene expression could be reproduced in only 3 days by treating premetamorphic tadpoles with thyroid hormone. Our findings also show that this effect, while likely to be indirect, takes place before overt morphological changes are evident in primary epithelial cells. Thus, the down-regulation of IFABP mRNA is one of the early molecular events preceding epithelial cell death during intestinal remodeling. PMID:8293885
Shi, Y B; Hayes, W P
Metamorphosis in Xenopus laevis represents an elaborate process of post-embryonic development which is thyroid hormone (TH) dependent. The development of a functional thyroid axis and the responses of tissues to different TH concentrations are well defined in this species, provid...
Coal tar based pavement sealers are applied regularly to parking lots and contain significant levels of polycyclic aromatic\\u000a hydrocarbons (PAHs). Recently a connection between elevated levels of PAHs in streams and storm water runoff from parking\\u000a lots has been identified. We tested the hypothesis that coal tar based pavement sealers could alter the survival, growth,\\u000a and development of amphibians using
Pamela J. Bryer; Jan. N. Elliott; Emily J. Willingham
This is an activity where learners will compare the different metamorphosis stages of amphibians. By matching different life stages of different species, the learners can compare and contrast key characteristics and stages of the life cycle. Learners will match larval stages to adult stages and notice bodily changes in the growth process. This activity can be modified for a slightly more advanced topic.
Aquariums, Association O.
Adult organ-specific stem cells are essential for organ homeostasis and repair in adult vertebrates. The intestine is one of the best-studied organs in this regard. The intestinal epithelium undergoes constant self-renewal throughout adult life across vertebrates through the proliferation and subsequent differentiation of the adult stem cells. This self-renewal system is established late during development, around birth, in mammals when endogenous thyroid hormone (T3) levels are high. Amphibian metamorphosis resembles mammalian postembryonic development around birth and is totally dependent upon the presence of high levels of T3. During this process, the tadpole intestine, predominantly a monolayer of larval epithelial cells, undergoes drastic transformation. The larval epithelial cells undergo apoptosis and concurrently, adult epithelial stem/progenitor cells develop de novo, rapidly proliferate, and then differentiate to establish a trough-crest axis of the epithelial fold, resembling the crypt-villus axis in the adult mammalian intestine. We and others have studied the T3-dependent remodeling of the intestine in Xenopus laevis. Here we will highlight some of the recent findings on the origin of the adult intestinal stem cells. We will discuss observations suggesting that liganded T3 receptor (TR) regulates cell autonomous formation of adult intestinal progenitor cells and that T3 action in the connective tissue is important for the establishment of the stem cell niche. We will further review evidence suggesting similar T3-dependent formation of adult intestinal stem cells in other vertebrates.
Background Chronic exposure to excess arsenic in drinking water has been strongly associated with increased risks of multiple cancers, diabetes, heart disease, and reproductive and developmental problems in humans. We previously demonstrated that As, a potent endocrine disruptor at low, environmentally relevant levels, alters steroid signaling at the level of receptor-mediated gene regulation for all five steroid receptors. Objectives The goal of this study was to determine whether As can also disrupt gene regulation via the retinoic acid (RA) receptor (RAR) and/or the thyroid hormone (TH) receptor (TR) and whether these effects are similar to previously observed effects on steroid regulation. Methods and results Human embryonic NT2 or rat pituitary GH3 cells were treated with 0.01–5 ?M sodium arsenite for 24 hr, with or without RA or TH, respectively, to examine effects of As on receptor-mediated gene transcription. At low, noncytotoxic doses, As significantly altered RAR-dependent gene transcription of a transfected RAR response element–luciferase construct and the native RA-inducible cytochrome P450 CYP26A gene in NT2 cells. Likewise, low-dose As significantly altered expression of a transfected TR response element–luciferase construct and the endogenous TR-regulated type I deiodinase (DIO1) gene in a similar manner in GH3 cells. An amphibian ex vivo tail metamorphosis assay was used to examine whether endocrine disruption by low-dose As could have specific pathophysiologic consequences, because tail metamorphosis is tightly controlled by TH through TR. TH-dependent tail shrinkage was inhibited in a dose-dependent manner by 0.1– 4.0 ?M As. Conclusions As had similar effects on RAR- and TR-mediated gene regulation as those previously observed for the steroid receptors, suggesting a common mechanism or action. Arsenic also profoundly affected a TR-dependent developmental process in a model animal system at very low concentrations. Because RAR and TH are critical for both normal human development and adult function and their dysregulation is associated with many disease processes, disruption of these hormone receptor–dependent processes by As is also potentially relevant to human developmental problems and disease risk.
Davey, Jennifer C.; Nomikos, Athena P.; Wungjiranirun, Manida; Sherman, Jenna R.; Ingram, Liam; Batki, Cavus; Lariviere, Jean P.; Hamilton, Joshua W.
Metamorphosis in frogs has long fascinated laymen and scientists alike. This remarkable developmental transformation involves the simultaneous remodelling of almost every organ in the body, including the gut, associated with a switch in diet from filter feeder to predator, and the visual system, from laterally-directed monocular to forward-directed binocular vision. In the context of locomotion there is the complete loss of the tail, the main structure involved in generating thrust during swimming in larvae, and the gain of the limbs which produce rhythmic extension-flexion kicks during swimming and jumping. Here we review recent evidence from experiments utilizing novel in vitro isolated preparations of the Xenopus laevis spinal cord and brainstem which remain viable for several days and can generate motor rhythms similar to those that would normally drive locomotion in vivo. The results indicate that the developing limb circuitry is born from within the existing axial-based network, which acts like a functional scaffold. Initially the limb activity shares the same left-right alternation coordination and relatively high frequency as the tail swimming network. Only later, once the limbs are fully functional, does the limb network break free to produce left-right synchrony of limb motoneuron bursting and with a different, slower cadence than the tail-based system. During the initial formation of the limb networks nitric oxide-producing neurons appear in the spinal cord, but occupy regions other than those in which the new limb circuitry is developing. Now exogenous nitric oxide facilitates locomotor activity, in contrast to its inhibitory effects on swimming at earlier larval stages of development. PMID:17900702
Sillar, Keith T; Combes, Denis; Ramanathan, Sankari; Molinari, Micol; Simmers, John
Teleosts are the largest and most diverse group of vertebrates, and many species undergo morphological, physiological, and behavioral transitions, "metamorphoses," as they progress between morphologically divergent life stages. The larval metamorphosis that generally occurs as teleosts mature from larva to juvenile involves the loss of embryo-specific features, the development of new adult features, major remodeling of different organ systems, and changes in physical proportions and overall phenotype. Yet, in contrast to anuran amphibians, for example, teleost metamorphosis can entail morphological change that is either sudden and profound, or relatively gradual and subtle. Here, we review the definition of metamorphosis in teleosts, the diversity of teleost metamorphic strategies and the transitions they involve, and what is known of their underlying endocrine and genetic bases. We suggest that teleost metamorphosis offers an outstanding opportunity for integrating our understanding of endocrine mechanisms, cellular processes of morphogenesis and differentiation, and the evolution of diverse morphologies and life histories. PMID:23347518
McMenamin, Sarah K; Parichy, David M
In order to minimize risks to human and environmental health, chemical safety assessment programs are being reinforced with toxicity tests more specifically designed for detecting endocrine disrupters. This includes the necessity to detect thyroid-disrupting chemicals, which may operate through a variety of modes of action, and have potential to impair neurological development in humans, with resulting deficits of individual and social potential. Mindful of these concerns, the consensus favors in vivo models for both hazard characterization (testing) and hazard identification (screening) steps, in order to minimize false negatives. Owing to its obligate dependence on thyroid hormones, it has been proposed that amphibian metamorphosis be used as a generalized vertebrate model for thyroid function in screening batteries for detection of thyroid disrupters. However, it seems unlikely that such an assay would ever fully replace in vivo mammalian assays currently being validated for human health risk assessment: in its current form the amphibian metamorphosis screening assay would not provide capacity for reliably detecting other modes of endocrine-disrupting activity. Conversely, several candidate mammalian screening assays appear to offer robust capacity to detect a variety of modes of endocrine-disrupting activity, including thyroid activity. To assess whether omission of an amphibian metamorphosis assay from an in vivo screening battery would generate false negatives, the response of amphibian and mammalian assays to a variety known thyroid disrupters, as reported in peer-reviewed literature or government agency reports, was critically reviewed. Of the chemicals investigated from the literature selected (41), more had been tested in mammalian studies with thyroid-relevant endpoints (32) than in amphibian assays with appropriate windows of exposure and developmental endpoints (27). One chemical (methoxychlor) was reported to exhibit thyroid activity in an appropriate amphibian assay in the absence of corresponding activity in a suitable mammalian assay, whereas none of the chemicals surveyed were reported as thyroid active in mammalian assays but reported as negative in an appropriate amphibian assay. Given the need for one or more in vivo mammalian assays for screening chemicals for detecting (anti-)estrogenic/(anti-)androgenic activity and effects on steroidogenesis, inclusion of an in vivo amphibian assay specifically to detect thyroid disrupters would likely be as an addition to these mammalian assays. As there is little convincing evidence that an amphibian screening assay would detect significant numbers of thyroid-active chemicals not picked up by mammalian assays, the routine use of an amphibian metamorphosis assay at screening level could introduce unnecessary and unjustified redundancy into chemical safety assessment programs, when there is pressure to reduce animal use in toxicity testing. PMID:20684730
Pickford, Daniel B
Many modern amphibians have biphasic life cycles with aquatic larvae and terrestrial adults. The central questions are how and when this complicated ontogeny was established, and what is known about the lives of amphibians in the Paleozoic. Fossil evidence has accumulated that sheds light on the life histories of early amphibians, the origin of metamorphosis, and the transition to a fully terrestrial existence. The majority of early amphibians were aquatic or amphibious and underwent only gradual ontogenetic changes. Developmental plasticity played a major role in some taxa but was restricted to minor modification of ontogeny. In the Permo-Carboniferous dissorophoids, a condensation of crucial ontogenetic steps into a short phase (metamorphosis) is observed. It is likely that the origin of both metamorphosis and neoteny falls within these taxa. Fossil evidence also reveals the sequence of evolutionary changes: apparently, the ontogenetic change in feeding, not the transition to a terrestrial existence per se, made a drastic metamorphosis necessary.
Schoch, Rainer R.
Biologically active substances could reach the aquatic compartment when livestock wastes are considered for recycling. Recently, the standardized FETAX assay has been questioned, and some researchers have considered that the risk assessment performed on fish could not be protective enough to cover amphibians. In the present study a Xenopus laevis acute assay was developed in order to compare the sensitivity of larvae relative to fish or FETAX assays; veterinary medicines (ivermectin, oxytetracycline, tetracycline, sulfamethoxazole, and trimethoprim) and essential metals (zinc, copper, manganese, and selenium) that may be found in livestock wastes were used for the larvae exposure. Lethal (LC50) and sublethal effects were estimated. Available data in both, fish and FETAX studies, were in general more protective than values found out in the current study, but not in all cases. Moreover, the presence of nonlethal effects, caused by ivermectin, zinc, and copper, suggested that several physiological mechanisms could be affected. Thus, this kind of effects should be deeply investigated. The results obtained in the present study could expand the information about micropollutants from livestock wastes on amphibians.
Martini, Federica; Tarazona, Jose V.; Pablos, M. Victoria
The genetic and developmental bases for trait expression and variation in adults are largely unknown. One system in which genes and cell behaviors underlying adult traits can be elucidated is the larval-to-adult transformation of zebrafish, Danio rerio. Metamorphosis in this and many other teleost fishes resembles amphibian metamorphosis, as a variety of larval traits (e.g., fins, skin, digestive tract, sensory
David M. Parichy; Jessica M. Turner
The most asymmetrically shaped and behaviorally lateralized of all the vertebrates, the flatfishes are an endless source of fascination to all fortunate enough to study them. Although all vertebrates undergo left-right asymmetric internal organ placement during embryogenesis, flatfish are unusual in that they experience an additional period of postembryonic asymmetric remodeling during metamorphosis, and thus deviate from a bilaterally symmetrical body plan more than other vertebrates. As with amphibian metamorphosis, all the developmental programs of flatfish metamorphosis are ultimately under the control of thyroid hormone. At least one gene pathway involved in embryonic organ lateralization (nodal-lefty-pitx2) is re-expressed in the larval stage during flatfish metamorphosis. Aspects of modern flatfish ontogeny, such as the gradual translocation of one eye to the opposite side of the head and the appearance of key neurocranial elements during metamorphosis, seem to elegantly recapitulate flatfish phylogeny. This chapter highlights the current state of knowledge of the developmental biology of flatfish metamorphosis with emphases on the genetic, morphological, behavioral, and evolutionary origins of flatfish asymmetry. PMID:23347519
Schreiber, Alexander M
. Since thyroid hormones play a pivotal role in amphibian metamorphosis we used PCR to amplify DNA fragments corresponding\\u000a to a portion of the ligand-binding domain of the thyroid hormone receptor (TR) genes in several neotenic amphibians: the obligatory\\u000a neotenic members of the family Proteidea the mudpuppy Necturus maculosus and Proteus anguinus as well as two members of the facultative
Rachid Safi; Agnès Begue; Catherine Hänni; Dominique Stehelin; Jamshed R. Tata; Vincent Laudet
In response to the initial EDSTAC recommendations, research was conducted on the development of a Xenopus laevis based tail resorption assay for evaluating thyroid axis disruption. These experiments highlighted key limitations associated with relying on tail resorption as a measu...
Most studies in evolution are centered on how homologous genes, structures, and/or processes appeared and diverged. Although historical homology is well defined as a concept, in practice its establishment can be problematic, especially for some morphological traits or developmental processes. Metamorphosis in chordates is such an enigmatic character. Defined as a spectacular postembryonic larva-to-adult transition, it shows a wide morphological diversity between the different chordate lineages, suggesting that it might have appeared several times independently. In vertebrates, metamorphosis is triggered by binding of the thyroid hormones (THs) T(4) and T(3) to thyroid-hormone receptors (TRs). Here we show that a TH derivative, triiodothyroacetic acid (TRIAC), induces metamorphosis in the cephalochordate amphioxus. The amphioxus TR (amphiTR) mediates spontaneous and TRIAC-induced metamorphosis because it strongly binds to TRIAC, and a specific TR antagonist, NH3, inhibits both spontaneous and TRIAC-induced metamorphosis. Moreover, as in amphibians, amphiTR expression levels increase around metamorphosis and are enhanced by THs. Therefore, TH-regulated metamorphosis, mediated by TR, is an ancestral feature of all chordates. This conservation of a regulatory network supports the homology of metamorphosis in the chordate lineage. PMID:18514519
Paris, Mathilde; Escriva, Hector; Schubert, Michael; Brunet, Frédéric; Brtko, Julius; Ciesielski, Fabrice; Roecklin, Dominique; Vivat-Hannah, Valérie; Jamin, Emilien L; Cravedi, Jean-Pierre; Scanlan, Thomas S; Renaud, Jean-Paul; Holland, Nicholas D; Laudet, Vincent
In previous studies we demonstrated that indigenous amphibian tadpoles are suitable organisms for monitoring small bodies of water (e.g., creeks, ponds, and drainage ditches) using the alkaline single cell gel electrophoresis (SCG) or 'comet' assay. This approach involves detection, under alkaline conditions, of cell DNA fragments which on electrophoresis migrate from the nuclear core, resulting in a 'comet with tail' formation. However, although often plentiful, tadpoles are not present in all aquatic environments. Both larger bodies of water (e.g., lakes and rivers) and those impacted upon heavily by man (e.g., bodies of water near industrial sites, on landfills, and in urban areas) often do not support amphibian tadpole populations. An alternative approach to the collection of indigenous tadpoles is to place caged tadpoles at these sites for short term exposures to environmental contaminants. To determine the feasibility of such an approach, Rana clamitans (green frog) and Bufo americanus (American toad) tadpoles were housed in cages at 11 sites in southwestern Ontario (Canada). In a preliminary experiment, we found that tadpoles caged at a polluted reference site (Tallgrass Prairie Heritage Park in Windsor, Ontario) for either 7 or 14 days showed significant (P < 0.05) increases in DNA damage, relative to tadpoles caged in the laboratory in dechlorinated water. As a result we routinely used a 7 day exposure time. Significantly (P < 0.05) increased levels of DNA damage, relative to their controls, were observed in tadpoles caged at three sites along two creeks draining a large petrochemical installation south of Sarnia, Ontario; at two sites in the Tallgrass Prairie Heritage Park; and at a site along the Ecarte Channel which is part of the St. Clair River. The DNA damage levels of animals caged in Lake St. Clair, in the Trenton Channel of the Detroit River, at a landfill site, and in two creeks in the city of Windsor did not differ significantly (P > 0.05) from their controls. This study demonstrates that caged tadpoles are suitable for monitoring most bodies of fresh water, particularly those aquatic habitats mentioned above where indigenous tadpoles are not present. A combined approach of collecting indigenous tadpoles and using caged tadpoles should provide a sensitive system for aquatic genotoxicity monitoring. PMID:9651536
Ralph, S; Petras, M
Nonylphenol (NP) is an estrogenic endocrine disruptor in many aquatic species. In an effort to highlight the developmental toxicity of NP in amphibians, we examined the effects of NP on the embryonic survival, tadpole growth, melanophore development and metamorphosis of a native Korean amphibian species, Bombina orientalis (Anura). When treated to fertilized eggs, 1 ?M NP significantly decreased embryonic survival at 48 h post fertilization (p.f.), suggesting that 1 ?M NP can exert systemic toxicity in B. orientalis embryos. In the surviving embryos, there were no significant differences in malformation rates between NP-treated embryos and controls at 240 h p.f., suggesting no or low teratogenicity of NP in B. orientalis embryos. Below LC(50) NP significantly decreased body growth and development of melanophores at 0.1 ?M, suggesting that NP far below the LC(50) targets multiple developmental events in tadpoles of this frog species. In metamorphosis assay using the premetamorphic tadpoles (corresponding to Nieuwkoop Faber stage 53 in Xenopus laevis) exogenous 3,5,3'-triiodothyronine (T3)-induced tail resorption was significantly decreased by 1 ?M NP. However, NP (0.1 and 1 ?M)-only treatment did not affected total body T3 and T4 levels, suggesting that NP at tested concentrations inhibits thyroid hormones action but not the synthesis of hormones during metamorphosis. PMID:20870264
Park, Chan Jin; Kang, Han Seung; Gye, Myung Chan
In this activity, learners explore the concept of permeability to better understand why amphibians are extremely sensitive to pollution. Learners soak one regular hard-boiled egg and one peeled hard-boiled egg in dyed water and then record how the eggs' circumference and appearance change after 24 hours. Learners investigate how the peeled egg represents amphibian skin and how amphibians are affected by pollution.
Aquarium, Omaha'S H.
Metamorphosis of insects is controlled and regulated by effector hormones that are controlled by neurosecretory peptide hormones in the brain. Complete metamorphosis of an insect consists of an egg and the larvae emerges from the egg and usually molts 5 times, loses the cytoskeleton that it has out grown and produces a new one, and spins a cocoon and enters
Caleb R. Baker
Neotenic amphibians such as the axolotl (Ambystoma mexi- canum) are often unable to undergo metamorphosis under natural conditions. It is thought that neoteny represents a deviation from the standard course of amphibian ontogeny, affecting the thyroid axis at different levels from the central nervous system to peripheral organs. Thyroid hormone re- ceptors (TRs) that bind the thyroid hormone (TH) T3
RACHID SAFI; STEPHANIE BERTRAND; ORIANE MARCHAND; MARILYNE DUFFRAISSE; AMAURY DE LUZE; JEAN-MARC VANACKER; MARIE MARANINCHI; ALAIN MARGOTAT; BARBARA DEMENEIX; VINCENT LAUDET
Heterochrony is an important mechanism in the evolution of amphibians. Although studies have centered on the relationship between size and shape and the rates of development, ossification sequence heterochrony also may have been important. Rigorous, phylogenetic methods for assessing sequence heterochrony are relatively new, and a comprehensive study of the relative timing of ossification of skeletal elements has not been used to identify instances of sequence heterochrony across Amphibia. In this study, a new version of the program Parsimov-based genetic inference (PGi) was used to identify shifts in ossification sequences across all extant orders of amphibians, for all major structural units of the skeleton. PGi identified a number of heterochronic sequence shifts in all analyses, the most interesting of which seem to be tied to differences in metamorphic patterns among major clades. Early ossification of the vomer, premaxilla, and dentary is retained by Apateon caducus and members of Gymnophiona and Urodela, which lack the strongly biphasic development seen in anurans. In contrast, bones associated with the jaws and face were identified as shifting late in the ancestor of Anura. The bones that do not shift late, and thereby occupy the earliest positions in the anuran cranial sequence, are those in regions of the skull that undergo the least restructuring throughout anuran metamorphosis. Additionally, within Anura, bones of the hind limb and pelvic girdle were also identified as shifting early in the sequence of ossification, which may be a result of functional constraints imposed by the drastic metamorphosis of most anurans. PMID:24074280
Harrington, Sean M; Harrison, Luke B; Sheil, Christopher A
The Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC) recommended in its final report to EPA that an amphibian tail resorption assay be implemented as a Tier 1 screening assay......
The biological effects of thyroid hormone (T3) are mediated by the thyroid hormone receptor (TR). Amphibian metamorphosis is one of the most dramatic processes that are dependent on T3. T3 regulates a series of orchestrated developmental changes, which ultimately result in the conversion of an aquatic herbivorous tadpole to a terrestrial carnivorous frog. T3 is presumed to bind to TRs,
Bindu D PAUL; Yun-Bo SHI
Pesticide chemical contamination is one of the suspected contributors of the amphibian population decline. The herbicide atrazine is one of the major surface water contaminants in the U.S. A previous study has shown that atrazine at concentrations as low as 100 parts per billion (ppb) increased the time to metamorphosis in Xenopus laevis tadpoles. However, questions remain as to the
Jennifer L. Freeman; Nathan Beccue
Sclerotium-forming filamentous fungi are of great agricultural and biological interest because they can be viewed as models of simple metamorphosis. They differentiate by asexually producing sclerotia but the processes involved in sclerotial metamorphosis were poorly understood. In 1997, it was shown for the first time that the sclerotial differentiation state in Sclerotium rolfsii concurred with increasing levels of lipid peroxides. This finding prompted the development of a theory supporting that sclerotial metamorphosis is induced by oxidative stress. Growth factors that reduce or increase oxidative stress are expected to inhibit or promote sclerotium metamorphosis, respectively. This theory has been verified by a series of published data on the effect of certain hydroxyl radical scavengers on sclerotial metamorphosis, on the identification and quantification of certain endogenous antioxidants (such as ascorbic acid, ?-carotene) in relation to the fungal undifferentiated and differentiated states, and on their inhibiting effect on sclerotial metamorphosis as growth nutrients. In 2004-2005, we developed assays for the measurement of certain redox markers of oxidative stress, such as the thiol redox state, the small-sized fragmented DNA, and the superoxide radical. These new advances allowed us to initiate studies on the exact role of glutathione, hydrogen peroxide, and superoxide radical on sclerotial metamorphosis. The emerging data, combined with similar data from other better-studied fungi, allowed us to make some preliminary postulations on the ROS-dependent biochemical signal transduction pathways in sclerotiogenic filamentous fungi. PMID:21672779
Georgiou, Christos D; Patsoukis, Nikolaos; Papapostolou, Ioannis; Zervoudakis, George
Thyroid hormones (THs) are crucial for normal vertebrate development and are the one obligate morphogen that drives amphibian metamorphosis. However, contrary to other metamorphosing vertebrates, lampreys exhibit a sharp drop in serum TH early in metamorphosis, and anti-thyroid agents such as potassium perchlorate (KClO(4)) induce metamorphosis. The type 2 deiodinase (D2) enzyme is a key regulator of TH availability during amphibian metamorphosis. We set out to determine how D2 may be involved in the regulation of lamprey metamorphosis and thyroid homeostasis. We cloned a 1.8Kb Petromyzon marinus D2 cDNA that includes the entire protein coding region and a selenocysteine (Sec) codon. Northern blotting indicated that the lamprey D2 mRNA is the longest reported to date (>9Kb). Using real-time PCR, we showed that intestinal and hepatic D2 mRNA levels were elevated prior to and during the early stages of metamorphosis and then declined dramatically to low levels that were sustained for the remainder of metamorphosis. These data are consistent with previously reported changes in serum TH levels and deiodinase activity. Treatment of larvae with either TH or KClO(4) significantly affected D2 mRNA levels in the intestine and liver. These D2 mRNA levels during metamorphosis and in response to thyroid challenges suggest that D2 may function in the regulation of TH levels during lamprey metamorphosis and the maintenance of TH homeostasis. PMID:23295540
Stilborn, S Salina M; Manzon, Lori A; Schauenberg, Jennifer D; Manzon, Richard G
In response to the initial EDSTAC recommendations, research was conducted on the development of a Xenopus laevis based tail resorption assay for evaluating thyroid axis disruption. These experiments highlighted key limitations associated with reliance on tail resorption as a meas...
Amphibians are sensitive to a great variety of agrochemicals. Nitrate compounds are commonly applied as fertilizers, whereas perchlorate salts occur as by-products of the military industry and in some nitrate fertilizers. Both compounds are highly soluble and can easily diffuse between ground and surface water, thus potentially affecting amphibians. Nitrate reduces embryonic and larval survival and development, whereas perchlorate has a well-known goitrogenic effect and inhibits metamorphosis. We present the results of an experiment that assessed the combined effects of these two chemicals on the development and metamorphosis of southern leopard frogs (Rana sphenocephala) larvae. Individual frogs were exposed in a block design throughout their larval stages until they metamorphosed. Nitrate at 100 mg/l increased larval mortality and reduced the growth of developing tadpoles. Perchlorate at 15 mg/l was not lethal to larvae, but inhibited metamorphosis, resulting in high mortality during metamorphosis compared with control animals. At 30 mg/l of perchlorate, larvae experienced increased mortality. Together, the chemicals exhibited additive effects on developmental rate and survival. When nitrate and perchlorate occur simultaneously in the environment, they can have greater effects on an amphibian population than either chemical alone. PMID:17657452
Ortiz-Santaliestra, Manuel E; Sparling, Donald W
Although amphibian sex determination is genetic, it can be manipulated by exogenous hormone exposure during sexual differentiation. The timing of sexual differentiation varies among anuran amphibians such that species may or may not be a tadpole during this period, and therefore, may or may not be exposed to aquatic contaminants. Estrogenic contamination is present in amphibian habitats worldwide. We examined three species with varying somatic and ovarian developmental rates to assess their susceptibility to estrogenic contaminants. American toads (Bufo americanus), gray treefrogs (Hyla versicolor), and Southern leopard frogs (Ranasphenocephala) were exposed as larvae to 17-beta-estradiol (10(-7)M), three concentrations of a widespread herbicide (1, 3, 30 ppb atrazine), or a solvent control (ethanol). Somatic and ovarian developmental stages as well as time to metamorphosis were recorded. Toads and treefrogs were examined at three weeks and metamorphosis, while leopard frogs were examined at three, six, and nine weeks as well as at metamorphosis. Our results demonstrate that each species displays heterochronic somatic and ovarian development. Further, the more rapid of the two rates determines the susceptibility to estrogenic contaminants. These results suggests that amphibians with shorter larval periods, and therefore quicker somatic developmental rates (i.e. American toads, gray treefrogs), are more susceptible to somatic treatment effects (i.e. prolonged time to metamorphosis) due to estrogenic contaminants. Moreover, the results suggest that amphibians with relatively rapid ovarian development (i.e. Southern leopard frogs) are more susceptible to gonadal treatment effects caused by estrogenic contaminants. PMID:18420201
Storrs, Sara I; Semlitsch, Raymond D
Population declines of amphibian species in many parts of the world are associated with a lethal fungal pathogen, Batrachochytrium dendrobatidis. Using laboratory challenge assays, we describe the inhibition of B. dendrobatidis by members of eight genera of bacteria isolated from the skin of two amphibian species that exhibit parental care behavior\\u000a (Plethodon cinereus and Hemidactylium scutatum). We found that members
Reid N. Harris; Timothy Y. James; Antje Lauer; Mary Alice Simon; Amit Patel
Background Thyroid hormones (TH) induce gene expression programs that orchestrate amphibian metamorphosis. In contrast to anurans, many salamanders do not undergo metamorphosis in nature. However, they can be induced to undergo metamorphosis via exposure to thyroxine (T4). We induced metamorphosis in juvenile Mexican axolotls (Ambystoma mexicanum) using 5 and 50 nM T4, collected epidermal tissue from the head at four time points (Days 0, 2, 12, 28), and used microarray analysis to quantify mRNA abundances. Results Individuals reared in the higher T4 concentration initiated morphological and transcriptional changes earlier and completed metamorphosis by Day 28. In contrast, initiation of metamorphosis was delayed in the lower T4 concentration and none of the individuals completed metamorphosis by Day 28. We identified 402 genes that were statistically differentially expressed by ? two-fold between T4 treatments at one or more non-Day 0 sampling times. To complement this analysis, we used linear and quadratic regression to identify 542 and 709 genes that were differentially expressed by ? two-fold in the 5 and 50 nM T4 treatments, respectively. Conclusion We found that T4 concentration affected the timing of gene expression and the shape of temporal gene expression profiles. However, essentially all of the identified genes were similarly affected by 5 and 50 nM T4. We discuss genes and biological processes that appear to be common to salamander and anuran metamorphosis, and also highlight clear transcriptional differences. Our results show that gene expression in axolotls is diverse and precise, and that axolotls provide new insights about amphibian metamorphosis.
Page, Robert B; Voss, Stephen R; Samuels, Amy K; Smith, Jeramiah J; Putta, Srikrishna; Beachy, Christopher K
Pesticide chemical contamination is one of the suspected contributors of the amphibian population decline. The herbicide atrazine is one of the major surface water contaminants in the U.S. A previous study has shown that atrazine at concentrations as low as 100 parts per billion (ppb) increased the time to metamorphosis in Xenopus laevis tadpoles. However, questions remain as to the applicability of a study of a non-native species to a native organism. The possible effects of atrazine on developing Bufo americanus were explored. Atrazine at potentially (albeit high) environmental concentrations was found not to delay the metamorphosis of developing B. americanus tadpoles as observed in X. laevis. Several studies have indicated that atrazine affects thyroid hormones. Since thyroid hormones are critical in amphibian metamorphosis, B. americanus and X. laevis tadpoles were exposed to exogenous 3,5,3'-triiodothyronine (T3). X. laevis were found to be more responsive to the effects of exogenous T3 compared to B. americanus, indicating that X. laevis may be more sensitive to endocrine active chemicals than B. americanus. In X. laevis, nuclear heterogeneity has been associated with metamorphosis. Flow cytometric analysis of the nuclei of normal metamorphing B. americanus indicates a decrease in the amount of thyroid mediated chromatin alterations relative to the nuclei of metamorphing X. laevis. Indications are that the differential response to endocrine disruption is due to the differential role of chromatin associated gene expression during metamorphosis of B. americanus versus X. laevis. A second native species, Hyla versicolor, was observed to have the X. laevis nuclear pattern with respect to metamorphosis. As such, sensitivity to endocrine disruption is hypothesized not to be limited to laboratory non-native species. PMID:16213604
Freeman, Jennifer L; Beccue, Nathan; Rayburn, A Lane
We measured the energetic cost of metamorphosis in the fruitfly, Drosophila melanogaster. Metabolic rates decreased rapidly in the first 24h and remained low until shortly before eclosion, when the rates increased rapidly, thus creating a U-shaped metabolic curve. The primary fuel used during metamorphosis was lipid, which accounted for >80% of total metabolism. The total energy consumed during metamorphosis was
Allison B. Merkey; Carrie K. Wong; Deborah K. Hoshizaki; Allen G. Gibbs
The effects of variable hydroperiod (three levels) and initial density of amphibians (two levels) on survival, growth rate, and time to and mass at metamorphosis were studied for wood frogs (Rana sylvatica), Jefferson salamanders (Ambystoma jeffersonianum), and spotted salamanders (A. maculatum). Experiments were carried out in 260-1 mesocosms set up outdoors in a forest. These pond simulations were designed to
Christopher L. Rowe; William A. Dunson
Managing habitats for the benefit of native fauna is a priority for many government and private agencies. Often, these agencies view nonnative plants as a threat to wildlife habitat, and they seek to control or eradicate nonnative plant populations. However, little is known about how nonnative plant invasions impact native fauna, and it is unclear whether managing these plants actually improves habitat quality for resident animals. Here, we compared the impacts of native and nonnative wetland plants on three species of native larval amphibians; we also examined whether plant traits explain the observed impacts. Specifically, we measured plant litter quality (carbon : nitrogen : phosphorus ratios, and percentages of lignin and soluble phenolics) and biomass, along with a suite of environmental conditions known to affect larval amphibians (hydroperiod, temperature, dissolved oxygen, and pH). Hydroperiod and plant traits, notably soluble phenolics, litter C:N ratio, and litter N:P ratio, impacted the likelihood that animals metamorphosed, the number of animals that metamorphosed, and the length of larval period. As hydroperiod decreased, the likelihood that amphibians achieved metamorphosis and the percentage of tadpoles that successfully metamorphosed also decreased. Increases in soluble phenolics, litter N:P ratio, and litter C:N ratio decreased the likelihood that tadpoles achieved metamorphosis, decreased the percentage of tadpoles metamorphosing, decreased metamorph production (total metamorph biomass), and increased the length of larval period. Interestingly, we found no difference in metamorphosis rates and length of larval period between habitats dominated by native and nonnative plants. Our findings have important implications for habitat management. We suggest that to improve habitats for native fauna, managers should focus on assembling a plant community with desirable traits rather than focusing only on plant origin. PMID:22471085
Cohen, Jillian S; Maerz, John C; Blossey, Bernd
The evolutionary removal of the tadpole from the frog life history is a very successful strategy, particularly in the tropics. These direct developers form limbs and a frog-like head early in embryogenesis, and they have reduced or lost tadpole-specific structures, like gills, a long, coiled intestine, and tadpole teeth and jaws. Despite the apparently continuous development to the frog morphology, the direct developer, Eleutherodactylus coqui, undergoes a cryptic metamorphosis requiring thyroid hormone. As in Xenopus laevis, there is a stimulation by corticotrophin-releasing factor (CRF) and an upregulation of thyroid hormone receptor ? (thrb). In addition to changes in skin and muscle, thyroid hormone stimulates yolk utilization for froglet growth from a novel tissue, the nutritional endoderm. The activities of CRF and corticosterone (CORT) in metamorphosis may provide the basis for the multiple evolutionary origins of direct development in anuran amphibians. Potential roles for maternally supplied thyroid hormone and its receptor and for deiodinases in regulating tissue sensitivity to thyroid hormone should be the subjects of future investigations. PMID:23347522
Elinson, Richard P
Objective The biological effects of the herbicide atrazine on freshwater vertebrates are highly controversial. In an effort to resolve the controversy, we conducted a qualitative meta-analysis on the effects of ecologically relevant atrazine concentrations on amphibian and fish survival, behavior, metamorphic traits, infections, and immune, endocrine, and reproductive systems. Data sources We used published, peer-reviewed research and applied strict quality criteria for inclusion of studies in the meta-analysis. Data synthesis We found little evidence that atrazine consistently caused direct mortality of fish or amphibians, but we found evidence that it can have indirect and sublethal effects. The relationship between atrazine concentration and timing of amphibian metamorphosis was regularly nonmonotonic, indicating that atrazine can both accelerate and delay metamorphosis. Atrazine reduced size at or near metamorphosis in 15 of 17 studies and 14 of 14 species. Atrazine elevated amphibian and fish activity in 12 of 13 studies, reduced antipredator behaviors in 6 of 7 studies, and reduced olfactory abilities for fish but not for amphibians. Atrazine was associated with a reduction in 33 of 43 immune function end points and with an increase in 13 of 16 infection end points. Atrazine altered at least one aspect of gonadal morphology in 7 of 10 studies and consistently affected gonadal function, altering spermatogenesis in 2 of 2 studies and sex hormone concentrations in 6 of 7 studies. Atrazine did not affect vitellogenin in 5 studies and increased aromatase in only 1 of 6 studies. Effects of atrazine on fish and amphibian reproductive success, sex ratios, gene frequencies, populations, and communities remain uncertain. Conclusions Although there is much left to learn about the effects of atrazine, we identified several consistent effects of atrazine that must be weighed against any of its benefits and the costs and benefits of alternatives to atrazine use.
Rohr, Jason R.; McCoy, Krista A.
The aim of the present work is the assessment of teratogenic effects of three triazole-derived fungicides (Triadimefon, FON, Tebuconazole, TEBU, Cyproconazole, CYPRO) on rat and Xenopus laevis embryos cultured in vitro. Rat embryos, exposed to FON 31.25-250?M, CYPRO 31.25-62.5?M and to TEBU 62.5-250?M, showed specific malformations (fusions) at the level of the first and second branchial arches, with a concentration-dependent increase of severity of malformative pictures. After immunostaining, the ectomesenchyme has been identified as the target tissue. X. laevis larvae showed, at the same concentrations, specific malformations at the level of cartilaginous element derived from the first and second branchial arch ectomesenchyme. This work indicates the three tested triazoles as teratogenic both in rodents and in amphibian, inducing ectomesenchymal abnormalities, and suggests, at least for this class of molecules, the X. laevis method as adequate alternative model for teratogenic screening. PMID:21601633
Di Renzo, Francesca; Bacchetta, Renato; Bizzo, Andrea; Giavini, Erminio; Menegola, Elena
This resource on the Amphibians of Washington State has recently been placed online. Created by Brad Moon at the University of Washington at Seattle's Burke Museum of Natural History and Culture (Herpetology Section), the Website features northwestern amphibians. The Website is organized by Order, Family, and Species, with details provided for some species, including a color photograph, written description, and information on Distribution, Habitat, Cool Biology Facts, and Conservation status. Other information accessible via links includes distribution maps, identification keys, phylogenetic information, and online bibliographies. For students and researchers seeking basic information and natural history facts on Washington's amphibians, this resource is a nice reference.
Exceptionally preserved fossils from the Wenlock Series (Silurian) of Herefordshire, UK, provide unique evidence of metamorphosis from free-swimming cyprid larva to attached juvenile in a Palaeozoic barnacle. The larva had large brush-like anterior limbs. The juvenile shows the head transformed into a stalk and the development of the primordial condition of five mineralized plates within the carapace. The discovery of a cyprid larva indicates that crown group cirripedes had evolved by the Silurian.
Briggs, Derek E.G; Sutton, Mark D; Siveter, David J; Siveter, Derek J
Because amphibians have both aquatic and terrestrial life stages they can serve in a unique way among vertebrates as sources of information for bioassessments of both wetlands and surrounding habitats. Although there are many data gaps in our knowledge about the habitat requirements and ecology of many amphibian species, it is apparent that community composition, presence and frequency of abnormalities, various mensural characteristics (e.g. snout vent length divided by body weight) and laboratory diagnostics (e.g. cholinesterase activity, blood chemistry) can be used in developing metrics for an index of biotic integrity. In addition, potential metrics can be derived from the various life stages that most amphibians experience such as egg clusters; embryonic development and hatching rates; tadpole growth, development, and survival; progress and success of metamorphosis; and breeding behavior and presence of adults. It is important, however, to focus on regional biodiversity and species assemblages of amphibians in the development of metrics rather than to strive for broadscale application of common metrics. This report discusses the procedures of developing an index of biotic integrity based on amphibians, explains potential pitfalls in using amphibians in bioassessments, and demonstrates where more research is needed to enhance the use of amphibians in evaluating wetland conditions.
Sparling, D.W.; Richter, K.O.; Calhoun, A.; Micacchion, M.
Despite ecologists increasingly recognizing pathogens as playing significant roles in community dynamics, few experimental studies have quantified patterns of disease impacts on natural systems. Amphibians are experiencing population declines, and a fungal pathogen ( Batrachochytrium dendrobatidis; Chytridiomycota) is a suspected causal agent in many declines. We studied the effects of a pathogenic fungus on community interactions between the gray treefrog, Hyla chrysoscelis, and eastern newts, Notophthalmus viridescens. Recent studies have characterized chytridiomycosis as an emerging infectious disease, whose suspected rapid range expansion and widespread occurrence pose a significant risk for amphibian populations worldwide. We reared larvae in outdoor polyethylene experimental tanks and tested the effects of initial larval density, predator presence, and fungal exposure on Hyla recruitment and predator-prey interactions between Hyla and Notophthalmus. Newts reduced treefrog survival, and high intraspecific density decreased metamorphic body mass independent of B. dendrobatidis. The presence of fungi reduced treefrog body mass at metamorphosis by 34%, but had no significant main effect on survival or larval period length. B. dendrobatidis differentially affected larval development in the presence of predators; Hyla developed slower when reared with the pathogen, but only when newts were present. This significant predator-by-pathogen interaction suggests that the impact of chytridiomycosis on larval amphibians may be exacerbated in complex communities. Our data suggest that B. dendrobatidis effects on host life history may be complex and indirect. Direct measurements of the community-level effects of pathogens offer an important opportunity to understand a significant threat to global biodiversity-declining amphibian populations. PMID:15235903
Parris, Matthew J; Beaudoin, Joseph G
Many studies have assessed the impact of different pollutants on amphibians across a variety of experimental venues (laboratory, mesocosm, and enclosure conditions). Past reviews, using vote-counting methods, have described pollution as one of the major threats faced by amphibians. However, vote-counting methods lack strong statistical power, do not permit one to determine the magnitudes of effects, and do not compare responses among predefined groups. To address these challenges, we conducted a meta-analysis of experimental studies that measured the effects of different chemical pollutants (nitrogenous and phosphorous compounds, pesticides, road deicers, heavy metals, and other wastewater contaminants) at environmentally relevant concentrations on amphibian survival, mass, time to hatching, time to metamorphosis, and frequency of abnormalities. The overall effect size of pollutant exposure was a medium decrease in amphibian survival and mass and a large increase in abnormality frequency. This translates to a 14.3% decrease in survival, a 7.5% decrease in mass, and a 535% increase in abnormality frequency across all studies. In contrast, we found no overall effect of pollutants on time to hatching and time to metamorphosis. We also found that effect sizes differed among experimental venues and among types of pollutants, but we only detected weak differences among amphibian families. These results suggest that variation in sensitivity to contaminants is generally independent of phylogeny. Some publication bias (i.e., selective reporting) was detected, but only for mass and the interaction effect size among stressors. We conclude that the overall impact of pollution on amphibians is moderately to largely negative. This implies that pollutants at environmentally relevant concentrations pose an important threat to amphibians and may play a role in their present global decline. PMID:22957147
Egea-Serrano, Andrés; Relyea, Rick A; Tejedo, Miguel; Torralva, Mar
|Introducing students to the process of scientific inquiry is a major goal of high school and college labs. Environmental toxins are of great concern and public interest. Modifications of a vertebrate developmental toxicity assay using the frog Xenopus laevis can support student-initiated toxicology experiments that are relevant to humans. Teams…
Sauterer, Roger; Rayburn, James R.
Progress towards Development of an Amphibian-Based Thyroid Screening Assay Using Xenopus laevis. Organismal and Thyroidal Responses to the Model Compounds 6Propylthiouracil, Methimazole, and Thyroxine
In response to the initial Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC) recommendations, re- search was conducted on the development of a Xenopus laevis based tail resorption assay for evaluating thyroid axis disruption. This research highlighted key limitations associated with relying on tail resorption as a measure of anti\\/thyroid activity. The most critical limitation being that tail tissues of
Sigmund J. Degitz; Gary W. Holcombe; Kevin M. Flynn; Patricia A. Kosian; Joseph J. Korte; Joseph E. Tietge
Many causes have been proposed to explain the global decline of amphibian populations. These include acid precipitation, UV-b radiation, epidemic diseases, deformities, habitat disruption, etc. Amphibians are noted for their bi-phasic life histories, supposedly limited abilities to disperse, and permeable skins, yet amphibians also exhibit enormous variation in life histories and can maintain large populations. How do these intrinsic factors
David M. Green
Many, but not all, amphibian populations have been declining on all six continents on which they live. Although habitat destruction, direct application of toxicants, and introduction of predators\\/competitors are obvious causes of amphibian declines, many amphibians are dying of infectious diseases in relatively pristine habitats on several continents. In this paper, we review the patterns of these disease outbreaks and
Cynthia Carey; Nicholas Cohen; Louise Rollins-Smith
The current model amphibian, Xenopus laevis, develops rapidly in water to a tadpole which metamorphoses into a frog. Many amphibians deviate from the X. laevis developmental pattern. Among other adaptations, their embryos develop in foam nests on land or in pouches on their mother’s back or on a leaf guarded by a parent. The diversity of developmental patterns includes multinucleated oogenesis, lack of RNA localization, huge non-pigmented eggs, and asynchronous, irregular early cleavages. Variations in patterns of gastrulation highlight the modularity of this critical developmental period. Many species have eliminated the larva or tadpole and directly develop to the adult. The wealth of developmental diversity among amphibians coupled with the wealth of mechanistic information from X. laevis permit comparisons that provide deeper insights into developmental processes.
Elinson, Richard P.; del Pino, Eugenia M.
Patuxent Wildlife Research Center (US Geological Servey) provides these companion sites on amphibians in conjunction with the US Environmental Protection Agency, The National Park Service, SUNY Syracuse, and Pennsylvania State University. Building off the parent site, Power Analysis of Monitoring Programs (discussed in the February 4, 1998 Scout Report for Science & Engineering), the Searchable Database of Amphibian Counts "is designed for use by anyone planning a wildlife monitoring program for amphibians." The Searchable database (searchable by Taxon) provides user access to amphibian count references. Though designed for amphibian research, both sites offer a clear, stepwise approach to survey methodology and can be helpful to graduate students and researchers planning wildlife monitoring programs.
Contaminants have been associated with population declines of several amphibian species in California (USA). Pesticides from the Central Valley of California are transported by winds into the Sierra Nevada Mountains and precipitate into wet meadows where amphibians breed. The present study examined the chronic toxicity of two of the insecticides most commonly used in the Central Valley and found in the mountains, chlorpyrifos and endosulfan, to larval Pacific treefrogs (Pseudacris regilla) and foothill yellow-legged frogs (Rana boylii) and discusses the implications of this toxicity to declining amphibian populations. Larvae were exposed to the pesticides from Gosner stages 25 to 26 through metamorphosis. The estimated median lethal concentration (LC50) for chlorpyrifos was 365 ??g/L in P. regilla and 66.5 ??g/L for R. boylii. Time to metamorphosis increased with concentration of chlorpyrifos in both species, and cholinesterase activity declined with exposure concentration in metamorphs of both species at Gosner stages 42 to 46. For endosulfan, the estimated LC50 was 15.6 ??g/L for P. regilla and 0.55 ??g/L for R. boylii. All R. boylii exposed to concentrations of greater than 0.8 ??g/L died before they entered metamorphosis. Pseudacris regilla remains relatively abundant and is broadly distributed throughout California. In contrast, R. boylii is among the species experiencing severe population declines. The present study adds to the increasing evidence that pesticides are very harmful to amphibians living in areas that are miles from sources of pesticide application. ?? 2009 SETAC.
Sparling, D. W.; Fellers, G. M.
|Rainforest reptiles and amphibians are a vibrantly colored, multimedia art experience. To complete the entire project one may need to dedicate many class periods to production, yet in each aspect of the project a new and important skill, concept, or element is being taught or reinforced. This project incorporates the study of warm and cool color…
The effects of aquatic deposition of coal combustion residues (CCRs) on amphibian life histories have been the focus of many recent studies. In summer 2005, we raised larval Southern Leopard Frogs, Rana sphenocephala, on either sand or CCR substrate (approximately 1 cm deep within plastic bins) and documented effects of sediment type on oral disc condition, as well as time to, mass at, and total body length at key developmental stages, including metamorphosis (Gosner stages (GS) 37, 42, and 46). We found no significant difference in mortality between the two treatments and mortality was relatively low (eight of 48 in the control group and four of 48 in the CCR group). Ninety percent of exposed tadpoles displayed oral disc abnormalities, while no control individuals displayed abnormalities. Tadpoles raised on CCR-contaminated sediment had decreased developmental rates and weighed significantly less at all developmental stages, on average, when compared to controls. The CCR treatment group was also significantly shorter In length than controls at the completion of metamorphosis (GS 46). Collectively, these findings are the most severe sub-lethal effects noted for any amphibian exposed to CCRs to date. More research is needed to understand how these long term effects may contribute to the dynamics of local amphibian populations.
Peterson, J.D.; Peterson, V.A.; Mendonca, M.T. [Auburn University, Auburn, AL (United States). Dept. for Biological Science
The thyroid hormone-disrupting activity of tetrabromobisphenol A (TBBPA), a flame retardant, and related compounds was examined. TBBPA, tetrachlorobisphenol A (TCBPA), tetramethylbisphenol A (TMBPA) and 3,3'-dimethylbisphenol A (DMBPA) markedly inhibited the binding of triiodothyronine (T3; 1 x 10(-10) M) to thyroid hormone receptor in the concentration range of 1 x 10(-7)-1 x 10(-4) M, while bisphenol A and 2,2-diphenylpropane were inactive. TBBPA, TCBPA, TMBPA and DMBPA did not exhibit thyroid hormonal activity in a thyroid hormone-responsive reporter assay using a Chinese hamster ovary cell line (CHO-K1) transfected with thyroid hormone receptor alpha1 or beta1, but TBBPA and TCBPA showed significant anti-thyroid hormone effects on the activity of T3 (1 x 10(-8) M) in the concentration range of 3 x 10(-6) - 5 x 10(-5) M. The thyroid hormone-disrupting activity of TBBPA was also examined in terms of the effect on amphibian metamorphosis stimulated by thyroid hormone. TBBPA in the concentration range of 1 x 10(-8) to 1 x 10(-6) M showed suppressive action on T3 (5 x 10(-8) M)-enhancement of Rana rugosa tadpole tail shortening. These facts suggest that TBBPA, TCBPA, TMBPA and DMBPA can act as thyroid hormone-disrupting agents. PMID:15680168
Kitamura, Shigeyuki; Kato, Teruhisa; Iida, Mitsuru; Jinno, Norimasa; Suzuki, Tomoharu; Ohta, Shigeru; Fujimoto, Nariaki; Hanada, Hideki; Kashiwagi, Keiko; Kashiwagi, Akihiko
Biofilms of the bacterium Pseudoalteromonas induce metamorphosis of acroporid coral larvae. The bacterial metabolite tetrabromopyrrole (TBP), isolated from an extract of Pseudoalteromonas sp. associated with the crustose coralline alga (CCA) Neogoniolithon fosliei, induced coral larval metamorphosis (100%) with little or no attachment (0–2%). To better understand the molecular events and mechanisms underpinning the induction of Acropora millepora larval metamorphosis, including cell proliferation, apoptosis, differentiation, migration, adhesion and biomineralisation, two novel coral gene expression assays were implemented. These involved the use of reverse-transcriptase quantitative PCR (RT-qPCR) and employed 47 genes of interest (GOI), selected based on putative roles in the processes of settlement and metamorphosis. Substantial differences in transcriptomic responses of GOI were detected following incubation of A. millepora larvae with a threshold concentration and 10-fold elevated concentration of TBP-containing extracts of Pseudoalteromonas sp. The notable and relatively abrupt changes of the larval body structure during metamorphosis correlated, at the molecular level, with significant differences (p<0.05) in gene expression profiles of 24 GOI, 12 hours post exposure. Fourteen of those GOI also presented differences in expression (p<0.05) following exposure to the threshold concentration of bacterial TBP-containing extract. The specificity of the bacterial TBP-containing extract to induce the metamorphic stage in A. millepora larvae without attachment, using a robust, low cost, accurate, ecologically relevant and highly reproducible RT-qPCR assay, allowed partially decoupling of the transcriptomic processes of attachment and metamorphosis. The bacterial TBP-containing extract provided a unique opportunity to monitor the regulation of genes exclusively involved in the process of metamorphosis, contrasting previous gene expression studies that utilized cues, such as crustose coralline algae, biofilms or with GLW-amide neuropeptides that stimulate the entire onset of larval metamorphosis and attachment.
Siboni, Nachshon; Abrego, David; Seneca, Francois; Motti, Cherie A.; Andreakis, Nikos; Tebben, Jan; Blackall, Linda L.; Harder, Tilmann
Lens regeneration among vertebrates is basically restricted to some amphibians. The most notable cases are the ones that occur in premetamorphic frogs and in adult newts. Frogs and newts regenerate their lens in very different ways. In frogs the lens is regenerated by transdifferentiation of the cornea and is limited only to a time before metamorphosis. On the other hand, regeneration in newts is mediated by transdifferentiation of the pigment epithelial cells of the dorsal iris and is possible in adult animals as well. Thus, the study of both systems could provide important information about the process. Molecular tools have been developed in frogs and recently also in newts. Thus, the process has been studied at the molecular and cellular levels. A synthesis describing both systems was long due. In this review we describe the process in both Xenopus and the newt. The known molecular mechanisms are described and compared.
Henry, Jonathan J.; Tsonis, Panagiotis A.
In most sessile marine invertebrates, metamorphosis is dependent on environmental cues. Here we report that heat stress is capable of inducing metamorphosis in the hydroid Hydractinia echinata. The onset of heat-induced metamorphosis is correlated with the appearance of heat-shock proteins. Larvae treated with the metamorphosis-inducing agents Cs+ or NH4+ also synthesize heat-shock proteins. In heat-shocked larvae, the internal NH4+-concentration increases.
Michael Kroiher; Michael Walther; Stefan Berking
Stormwater ponds have become common features of modern development and often represent significant amounts of open space in urbanized areas. Although stormwater ponds may provide habitat for wildlife, factors responsible for producing variation in wildlife use of ponds have received limited attention. To investigate the role of variation in species tolerances of pollutants in structuring pond-breeding amphibian assemblages, we exposed species tolerant (Bufo americanus) and not tolerant (Rana sylvatica) of urbanization to pond sediments in laboratory microcosms. Pond microcosms had elevated sediment metal levels and chloride water concentrations. Among R. sylvatica embryos, exposure to pond sediments resulted in 100% mortality. In contrast, B. americanus embryos and larvae experienced only sublethal effects (i.e., reduced size at metamorphosis) due to pond sediment exposure. Our results suggest variation in pollutant tolerance among early developmental stages of amphibians may act in concert with terrestrial habitat availability to structure amphibian assemblages associated with stormwater ponds. PMID:18023947
Snodgrass, Joel W; Casey, Ryan E; Joseph, Debra; Simon, Judith A
Sampled shrews at 9.3 ha plots from logs manually removed and control plots in loblolly pine forests of the Southeastern Coastal Plain. Capture rates of Cryptotis parva were lower at plots from which deadwood was removed whereas capture rates of Blarina cavolinensis and Sorex longirostris did not differ between control and removal plots. Cryptotis may have been most sensitive to removal plots due to low population density, hence poor ability to move into areas of low reproduction. (Second Abstract, p. 37)Presentation of evidence that juvenile amphibians including Ambystomatid salamanders may disperse hundreds of meter from their natal wetlands within the weeks to months following metamorphosis. Data indicates Ambystoma trigrinum metamorphs can take at least six months to disperse and en route use non-polar lipid reserves garnished as larvae. Report suggests a land management regime that allows for both juvenile amphibian dispersal and also the consumptive use of the surrounding landscape.
McCay, T.S.; Forschler, B.T.; Komoroski, M.J.; Ford, W.M.
Amphibian metamorphosis is accompanied by extensive intestinal remodeling. This process, mediated by thyroid hormone (TH) and its nuclear receptors, affects every cell type. Gut remodeling in Xenopus laevis involves epithelial and mesenchymal proliferation, smooth muscle thickening, neuronal aggregation, formation of intestinal folds, and shortening of its length by 75%. Transgenic tadpoles expressing a dominant negative TH receptor (TRDN) controlled by epilthelial-, fibroblast-, and muscle-specific gene promoters were studied. TRDN expression in the epithelium caused abnormal development of virtually all cell types, with froglet guts displaying reduced intestinal folds, thin muscle and mesenchyme, absence of neurons, and reduced cell proliferation. TRDN expression in fibroblasts caused abnormal epithelia and mesenchyme development, and expression in muscle produced fewer enteric neurons and a reduced inter-muscular space. Gut shortening was inhibited only when TRDN was expressed in fibroblasts. Gut remodeling results from both cell-autonomous and cell-cell interactions.
Schreiber, Alexander M.; Mukhi, Sandeep; Brown, Donald D.
Image morphing has been extensively studied in computer graphics and it can be summarized as follows: given two input images, morphing algorithms produce a sequence of inbetween images which transforms the source image into the target image in a visually pleasant way. In this paper, we propose an algorithm, based on recent advances from texture-from-sample ideas, which synthesizes a metamorphosis
Leandro Tonietto; Marcelo Walter
To utilize the advantages offered by the large identified nerve cells of the marine mollusc Aplysia californica for cellular biological studies of development, we have devised simple techniques for growing this species in the laboratory in large number with a generation time as short as nineteen weeks. We have used the cultured animals to study the life cycle from fertilized egg to reproductive adult. The major developmental and behavioral changes occur at metamorphosis, when the larvae settle on the seaweed Laurencia pacifica and the locomotor and feeding behaviors are transformed into their adult forms. We have examined the timetable for the abandonment of larval behaviors and the emergence of adult ones and found that the transition from swimming to crawling occurs first and marks the onset of metamorphosis. The change from ciliary feeding to radular feeding occurs later and signals the end of metamorphosis. Other adult behaviors, such as the reflex responses and fixed-action patterns of the mantle organs, appear after metamorphosis.
Kriegstein, Arnold R.; Castellucci, Vincent; Kandel, Eric R.
|Notes that Kafka's "The Metamorphosis" is not only a masterpiece of modern literature but also a work that exemplifies many ideas of structural family therapy. Examines how Kafka's novella embodies concepts such as parentified children, enmeshment, intergenerational boundaries, coalitions and triangles, structural dysfunction, and structural…
The marine invertebrate Bugula neritina has a biphasic life cycle that consists of a swimming larval stage and a sessile juvenile and adult stage. The attachment of larvae to the substratum and their subsequent metamorphosis have crucial ecological consequences. Despite many studies on this species, little is known about the molecular mechanism of these processes. Here, we report a comparative study of swimming larvae and metamorphosing individuals at 4 and 24 h postattachment using label-free quantitative proteomics. We identified more than 1100 proteins at each stage, 61 of which were differentially expressed. Specifically, proteins involved in energy metabolism and structural molecules were generally down-regulated, whereas proteins involved in transcription and translation, the extracellular matrix, and calcification were strongly up-regulated during metamorphosis. Many tightly regulated novel proteins were also identified. Subsequent analysis of the temporal and spatial expressions of some of the proteins and an assay of their functions indicated that they may have key roles in metamorphosis of B. neritina. These findings not only provide molecular evidence with which to elucidate the substantial changes in morphology and physiology that occur during larval attachment and metamorphosis but also identify potential targets for antifouling treatment. PMID:21090758
Zhang, Huoming; Wong, Yue Him; Wang, Hao; Chen, Zhangfan; Arellano, Shawn M; Ravasi, Timothy; Qian, Pei-Yuan
Hydroides elegans is a common marine fouling organism in most tropical and subtropical waters. The life cycle of H. elegans includes a planktonic larval stage in which swimming larvae normally take 5 days to attain competency to settle. Larval metamorphosis marks the beginning of its benthic life; however, the endogenous molecular mechanisms that regulate metamorphosis remain largely unknown. In this study, a PCR-based suppressive subtractive hybridization (SSH) library was constructed to screen the genes expressed in competent larvae but not in precompetent larvae. Among the transcripts isolated from the library, 21 significantly matched sequences in the GenBank. Many of these isolated transcripts have putative roles in the reactive oxygen species (ROS) signal transduction pathway or in response to ROS stress. A putative novel p38 mitogen-activated protein kinase (MAPK), which was also isolated with SSH screen, was then cloned and characterized. The MAPK inhibitors assay showed that both p38 MAPK inhibitors SB202190 and SB203580 effectively inhibited the biofilm-induced metamorphosis of H. elegans. A cell stressors assay showed that H(2)O(2) effectively induced larval metamorphosis of H. elegans, but the inductivity of H(2)O(2) was also inhibited by both SB inhibitors. The catalase assay showed that the catalase could effetely inhibit H. elegans larvae from responding to inductive biofilm. These results showed that the p38 MAPK-dependent pathway plays critical role in controlling larval metamorphosis of the marine polychaete H. elegans, and the reactive oxygen radicals produced by biofilm could be the cue inducing larval metamorphosis. PMID:20535771
Wang, Hao; Qian, Pei-Yuan
Abstract—Larval Xenopus laevis were exposed to one of four concentrations of atrazine (0, 1, 10, or 25 mg\\/L, 11 replicate tanks per treatment, 60?65 larvae per replicate) dissolved in an artificial pond water (frog embryo teratogenesis assay-Xenopus[FETAX]) medium,beginning,48 h after hatching,until the completion,of metamorphosis.,Separate groups of larvae (six replicate tanks per treatment, 60?65 larvae per replicate) were exposed to estradiol
James A. Carr; Angie Gentles; Ernest E. Smith; Wanda L. Goleman; Lina J. Urquidi; Kerry Thuett; Ronald J. Kendall; John P. Giesy; Tim S. Gross; Keith R. Solomon; Glen Van Der Kraak
Selenium (Se) and vanadium (V) are contaminants commonly found in aquatic systems affected by wastes derived from fossil fuels. To examine their effects on a widely distributed species of amphibian, we exposed gray tree frogs (Hyla versicolor) to Se (as SeO?) or V (as NaVO?) in their diet from the early larval period to metamorphosis. Concentrations of Se in Se-enriched food were 1.0 (Se control), 7.5 (Se low), and 32.7 (Se high) ?g/g dw. Concentrations of V in V-enriched food were 3.0 (V control), 132.1 (V low), and 485.7 (V high) ?g/g dw. Although we observed bioaccumulation of both metals throughout the larval period, no effects on growth, survival, metabolic rate, or lipid content were observed. Se concentrations in tissues did not vary among life stages, neither in Se low nor Se high treatments, such that maximum accumulation had occurred by the mid-larval period. In addition, there was no evidence of depuration of Se in either the Se low or the Se high treatments during metamorphosis. A strikingly different pattern of accumulation and depuration occurred in V-exposed individuals. In treatments V low and V high, maximum body burdens occurred in "premetamorphs" (i.e., animals with developed forelimbs but in which tail resorption had not begun), whereas body burdens in animals having completed metamorphosis were much lower and similar to those in larvae. These results suggest that compared with Se-exposed animals, V-exposed animals were able to depurate a substantial amount of accumulated V during the metamorphic period. In an ecologic context, it appears that amphibians exposed to Se during the larval period may serve as a vector of the metal to terrestrial predators, yet potential transfer of accumulated V to predators would largely be restricted to the aquatic habitat. PMID:20878520
Rowe, Christopher L; Heyes, Andrew; Hilton, Jessica
Metamorphosis or morphing is the process of continuously transforming one object into another, and is popular in computer animation, industrial design, and growth simulation. In this paper, a novel metamorphosis approach is presented for computing continuous shape transformation between polyhedral objects. Metamorphosis can be achieved by decomposing two objects into sets of individual convex sub- objects respectively and constructing the mapping relationship of subsets, this method can solve the metamorphosis problem of two non-homotopic objects (including concave objects and holey objects). The results of object metamorphosis are also discussed in this paper. The experiments show that this method can generate natural, high quality metamorphosis results with simple computation. This method can also be used in font composition and interpolation between two keyframes in 2D and 3D computer animation automatically.
Li, Hua; Liu, Wen-Yu; Zhu, Yaoting; Zhu, Guang-Xi
Stalked and acorn barnacles (Cirripedia Thoracica) have a complex life cycle that includes a free-swimming nauplius larva, a cypris larva and a permanently attached sessile juvenile and adult barnacle. The barnacle cyprid is among the most highly specialized of marine invertebrate larvae and its settlement biology has been intensively studied. By contrast, surprisingly few papers have dealt with the critical series of metamorphic events from cementation of the cyprid to the substratum until the appearance of a suspension feeding juvenile. This metamorphosis is both ontogenetically complex and critical to the survival of the barnacle. Here we use video microscopy to present a timeline and description of morphological events from settled cyprid to juvenile barnacle in the model species Balanus amphitrite, representing an important step towards both a broader understanding of the settlement ecology of this species and a platform for studying the factors that control its metamorphosis. Metamorphosis in B. amphitrite involves a complex sequence of events: cementation, epidermis separation from the cypris cuticle, degeneration of cypris musculature, rotation of the thorax inside the mantle cavity, building of the juvenile musculature, contraction of antennular muscles, raising of the body, shedding of the cypris cuticle, shell plate and basis formation and, possibly, a further moult to become a suspension feeding barnacle. We compare these events with developmental information from other barnacle species and discuss them in the framework of barnacle settlement ecology. PMID:22666355
Maruzzo, Diego; Aldred, Nick; Clare, Anthony S; Høeg, Jens T
The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), is a globally emerging pathogen that has caused widespread amphibian population declines, extirpations, and extinctions. However, Bd does not occur in all apparently suitable amphibian populations, even within regions where it is widespread, and it is often unclear why Bd occurs in some habitats but not others. In this study, we rigorously surveyed the amphibian and invertebrate biodiversity of 29 ponds in Missouri, screened resident amphibian larvae (Rana (Lithobates) sp.) for Bd infection, and characterized the aquatic physiochemical environment of each pond (temperature pH, conductivity, nitrogen, phosphorus, and chlorophyll-a). Our goal was to generate hypotheses toward answering the question, “Why does Bd not occur in all apparently suitable habitats?” Bd occurred in assayed amphibians in 11 of the 29 ponds in our study area (38% of ponds). We found no significant relationship between any single biotic or abiotic variable and presence of Bd. However, multivariate analyses (nonmetric multidimensional scaling and permutational tests of dispersion) revealed that ponds in which Bd occurred were a restricted subset of all ponds in terms of amphibian community structure, macroinvertebrate community structure, and pond physiochemistry. In other words, Bd ponds from 6 different conservation areas were more similar to each other than would be expected based on chance. The results of a structural equation model suggest that patterns in the occurrence of Bd among ponds are primarily attributable to variation in macroinvertebrate community structure. When combined with recent results showing that Bd can infect invertebrates as well as amphibians, we suggest that additional research should focus on the role played by non-amphibian biota in determining the presence, prevalence, and pathogenicity of Bd in amphibian populations.
Strauss, Alex; Smith, Kevin G.
Growing concern over worldwide amphibian declines warrants serious examination. Amphibians are important to the proper functioning of ecosystems and provide many direct benefits to humans in the form of pest and disease control, pharmaceutical compounds, and even food. Amphibians have permeable skin and rely on both aquatic and terrestrial ecosystems during different seasons and stages of their lives. Their association with these ecosystems renders them likely to serve as sensitive indicators of environmental change. While much research on amphibian declines has centered on mysterious causes, or on causes that directly affect humans (global warming, chemical pollution, ultraviolet-B radiation), most declines are the result of habitat loss and habitat alteration. Improving our ability to characterize, model, and monitor the interactions between environmental variables and amphibian habitats is key to addressing amphibian conservation. In 2000, the U.S. Geological Survey (USGS) initiated the Amphibian Research and Monitoring Initiative (ARMI) to address issues surrounding amphibian declines.
Amphibians have long been utilized in scientific research and in education. Historically, investigators have accumu- lated a wealth of information on the natural history and biology of amphibians, and this body of information is con- tinually expanding as researchers describe new species and study the behaviors of these animals. Amphibians evolved as models for a variety of developmental and physiological
Dorcas P. O'Rourke
A series of recent papers have impli- cated pathogens and parasites in amphibian population declines. Here, we review evidence on the link between infectious disease and amphibian population declines. We conclude that available data provide the clearest link for the fungal disease amphibian chytridiomycosis, although other pathogens are also implicated. We suggest additional experimental and observa- tional data that need
Peter Daszak; Andrew A. Cunningham; Alex D. Hyatt
Reports of malformed amphibians and global amphibian declines have led to public concern, particularly because amphibians are thought to be indicator species of overall envi- ronmental health. The topic also draws scientific attention because there is no obvious, simple answer to the question of what is causing amphi- bian declines? Complex interactions of several anthropogenic factors are probably at work,
James P. Collins; Andrew Storfer
Microorganisms have been reported to induce settlement and metamorphosis in a wide range of marine invertebrate species. However, the primary cue reported for metamorphosis of coral larvae is calcareous coralline algae (CCA). Herein we report the community structure of developing coral reef biofilms and the potential role they play in triggering the metamorphosis of a scleractinian coral. Two-week-old biofilms induced metamorphosis in less than 10% of larvae, whereas metamorphosis increased significantly on older biofilms, with a maximum of 41% occurring on 8-week-old microbial films. There was a significant influence of depth in 4- and 8-week biofilms, with greater levels of metamorphosis occurring in response to shallow-water communities. Importantly, larvae were found to settle and metamorphose in response to microbial biofilms lacking CCA from both shallow and deep treatments, indicating that microorganisms not associated with CCA may play a significant role in coral metamorphosis. A polyphasic approach consisting of scanning electron microscopy, fluorescence in situ hybridization (FISH), and denaturing gradient gel electrophoresis (DGGE) revealed that coral reef biofilms were comprised of complex bacterial and microalgal communities which were distinct at each depth and time. Principal-component analysis of FISH data showed that the Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Cytophaga-Flavobacterium of Bacteroidetes had the largest influence on overall community composition. A low abundance of Archaea was detected in almost all biofilms, providing the first report of Archaea associated with coral reef biofilms. No differences in the relative densities of each subdivision of Proteobacteria were observed between slides that induced larval metamorphosis and those that did not. Comparative cluster analysis of bacterial DGGE patterns also revealed that there were clear age and depth distinctions in biofilm community structure; however, no difference was detected in banding profiles between biofilms which induced larval metamorphosis and those where no metamorphosis occurred. This investigation demonstrates that complex microbial communities can induce coral metamorphosis in the absence of CCA.
Webster, Nicole S.; Smith, Luke D.; Heyward, Andrew J.; Watts, Joy E. M.; Webb, Richard I.; Blackall, Linda L.; Negri, Andrew P.
Thyroid hormones (THs), and more precisely the 3,3',5-triiodo-l-thyronine (T(3)) acetic derivative 3,3',5-triiodothyroacetic acid (TRIAC), have been shown to activate metamorphosis in amphioxus. However, it remains unknown whether TRIAC is endogenously synthesized in amphioxus and more generally whether an active TH metabolism is regulating metamorphosis. Here we show that amphioxus naturally produces TRIAC from its precursors T(3) and l-thyroxine (T(4)), supporting its possible role as the active TH in amphioxus larvae. In addition, we show that blocking TH production inhibits metamorphosis and that this effect is compensated by exogenous T(3), suggesting that a peak of TH production is important for advancement of proper metamorphosis. Moreover, several amphioxus genes encoding proteins previously proposed to be involved in the TH signaling pathway display expression profiles correlated with metamorphosis. In particular, thyroid hormone receptor (TR) and deiodinases gene expressions are either up- or down-regulated during metamorphosis and by TH treatments. Overall, these results suggest that an active TH metabolism controls metamorphosis in amphioxus, and that endogenous TH production and metabolism as well as TH-regulated metamorphosis are ancestral in the chordate lineage. PMID:21558188
Paris, Mathilde; Hillenweck, Anne; Bertrand, Stéphanie; Delous, Georges; Escriva, Hector; Zalko, Daniel; Cravedi, Jean-Pierre; Laudet, Vincent
During the period of approximately 1570--1790 the first metamorphosis of science transformed the operational foundations of science, that were largely the heritage from the time of Aristotle, into its modern form. These new foundations consisted of the use of (1) Physical Experiments and the use of (2) Mathematical Models, involving differential equations. This metamorphosis was largely due to Brahe, Kepler,
E. Atlee Jackson; Santa Fe
We analyze the spatial and energy dependence of the local density of states in a SNS junction. We model our system as a one-dimensional tight-binding chain which we solve exactly by numerical diagonalization. We calculate the dependence of the Andreev bound states on position, phase difference, gate voltage, and coupling with the superconducting leads. Our results confirm the physics predicted by certain analytical approximations, but reveal a much richer set of phenomena beyond the grasp of these approximations, such as the metamorphosis of the discrete states of the normal link (the normal bound states) into Andreev bound states as the leads become superconducting.
The use of amphibians in classrooms and research labora- tories has increased, along with a corresponding increase in the amount of information about these animals on the In- ternet. This review is intended to aid both novices and ex- perts in the search of such information. The bibliography of Internet resources is organized by discipline and includes general and selected
Michael W. Nolan; Stephen A. Smith
Amphibians are thought to be unable to disperse over ocean barriers because they do not tolerate the osmotic stress of salt water. Their distribution patterns have therefore generally been explained by vicari- ance biogeography. Here, we present compelling evidence for overseas dispersal of frogs in the Indian Ocean region based on the discovery of two endemic species on Mayotte. This
Miguel Vences; D. Rodriguez Vieites; Frank Glaw; Henner Brinkmann; Joachim Kosuch; Michael Veith; Axel Meyer
Ranaviruses are capable of infecting amphibians from at least 14 families and over 70 individual species. Ranaviruses infect multiple cell types, often culminating in organ necrosis and massive hemorrhaging. Subclinical infections have been documented, although their role in ranavirus persistence and emergence remains unclear. Water is an effective transmission medium for ranaviruses, and survival outside the host may be for significant duration. In aquatic communities, amphibians, reptiles and fish may serve as reservoirs. Controlled studies have shown that susceptibility to ranavirus infection and disease varies among amphibian species and developmental stages, and likely is impacted by host-pathogen coevolution, as well as, exogenous environmental factors. Field studies have demonstrated that the likelihood of epizootics is increased in areas of cattle grazing, where aquatic vegetation is sparse and water quality is poor. Translocation of infected amphibians through commercial trade (e.g., food, fish bait, pet industry) contributes to the spread of ranaviruses. Such introductions may be of particular concern, as several studies report that ranaviruses isolated from ranaculture, aquaculture, and bait facilities have greater virulence (i.e., ability to cause disease) than wild-type isolates. Future investigations should focus on the genetic basis for pathogen virulence and host susceptibility, ecological and anthropogenic mechanisms contributing to emergence, and vaccine development for use in captive populations and species reintroduction programs.
Miller, Debra; Gray, Matthew; Storfer, Andrew
In many respects, amphibian spatial dynamics resemble classical metapopulation models, where subpopulations in breeding ponds blink in and out of existance and where extinction and colonization rates are functions of pond spatial arrangement. This "ponds-as-patches" view of amphi...
For many years, ecological research on amphibians and reptiles has lagged behind that of other vertebrates such as fishes, birds, and mammals, despite the known importance of these animals in their environments. The lack of study has been particularly acute in the he area of ecotoxicology where the number of published scientific papers is a fraction of that found for the other vertebrate classes. Recently, scientists have become aware of severe crises among amphibian populations, including unexplained and sudden extinctions, worldwide declines, and hideous malformations. In many of these instances, contaminants have been listed as probable contributors. Data on the effects of contaminants on reptiles are so depauperate that even the most elementary interpretations are difficult. This state-of-the-science review and synthesis of amphibian and reptile ecotoxicology demonstrates the inter-relationships among distribution, ecology, physiology, and contaminant exposure, and interprets these topics as they pertain to comparative toxicity, population declines, malformations, and risk assessment . In this way, the book identifies and serves as a basis for the most pressing research needs in the coming years. The editors have invited 27 other internationally respected experts to examine the state of existing data in specific areas, interpret it in light of current problems, and identify research gaps and needs. Through its emphasis on recent research, extensive reviews and synthesis, Ecotoxicology of Amphibians and Reptiles will remain a definitive reference work well into the new century.
Rather than being a static, species specific trait, reproductive behavior in female amphibians is variable within an individual during the breeding season when females are capable of reproductive activity. Changes in receptivity coincide with changes in circulating estrogen. Estrogen is highest at the point when females are ready to choose a male and lay eggs. At this time female receptivity
Walter Wilczynski; Kathleen S. Lynch
Between the first and the second postnatal week, the development of rodent Purkinje cells is characterized by several profound transitions. Purkinje cells acquire their typical dendritic “espalier” tree morphology and form distal spines. During the first postnatal week, they are multi-innervated by climbing fibers and numerous collateral branches sprout from their axons, whereas from the second postnatal week, the regression of climbing fiber multi-innervation begins, and Purkinje cells become innervated by parallel fibers and inhibitory molecular layer interneurons. Furthermore, their periods of developmental cell death and ability to regenerate their axon stop and their axons become myelinated. Thus a Purkinje cell during the first postnatal week looks and functions differently from a Purkinje cell during the second postnatal week. These fundamental changes occur in parallel with a peak of circulating thyroid hormone in the mouse. All these features suggest to some extent an interesting analogy with amphibian metamorphosis.
Dusart, Isabelle; Flamant, Frederic
This article present a review of species numbers, biogeographic patterns and evolutionary trends of amphibians in freshwater.\\u000a Although most amphibians live in freshwater in at least their larval phase, many species have evolved different degrees of\\u000a independence from water including direct terrestrial development and viviparity. Of a total of 5,828 amphibian species considered\\u000a here, 4,117 are aquatic in that they
Miguel Vences; Jörn Köhler
This article present a review of species numbers, biogeographic patterns and evolutionary trends of amphibians in freshwater.\\u000a Although most amphibians live in freshwater in at least their larval phase, many species have evolved different degrees of\\u000a independence from water including direct terrestrial development and viviparity. Of a total of 5,828 amphibian species considered\\u000a here, 4,117 are aquatic in that they
Miguel Vences; Jörn Köhler
Abstract. Most research to assess amphibian,declines has focused on local-scale projects on one or a few species. The Amphibian Research and Monitoring Initiative (ARMI) is a national program,in the United States mandated,by congressional directive and implemented,by the U.S. Department of the Interior (specifically the U.S. Geological Survey, USGS). Program goals are to monitor changes in populations of amphibians,across U.S. Department
Erin Muths; Robin E. Jung; Larissa L. Bailey; Michael J. Adams; P. Stephen Corn; C. Kenneth Dodd; G Ary M. Fellers; Walter J. Sadinski; Cecil R. Schwalbe; Susan C. Walls; Robert N. Fisher; Alisa L. Gallant; William A. Battaglin; D. Earl Green
Despite the influence that amphibians have on the flow of energy and nutrients in ecological systems, the role that amphibians play in transporting contaminants through food webs has received very little attention. This study was undertaken to investigate bioaccumulation of trace elements in amphibians relative to other small aquatic organisms in a contaminated wetland. We collected bullfrog larvae (Rana catesbeiana)
Jason M. Unrine; William A. Hopkins; Christopher S. Romanek; Brian P. Jackson
Rather than being a static, species specific trait, reproductive behavior in female amphibians is variable within an individual during the breeding season when females are capable of reproductive activity. Changes in receptivity coincide with changes in circulating estrogen. Estrogen is highest at the point when females are ready to choose a male and lay eggs. At this time female receptivity (her probability of responding to a male vocal signal) is highest and her selectivity among conspecific calls (measured by her probability of responding to a degraded or otherwise usually unattractive male signal) is lowest. These changes occur even though females retain the ability to discriminate different acoustic characteristics of various conspecific calls. After releasing her eggs, female amphibians quickly become less receptive and more choosy in terms of their responses to male sexual advertisement signals. Male vocal signals stimulate both behavior and estrogen changes in amphibian females making mating more probable. The changes in female reproductive behavior are the same as those generally accepted as indicative of a change in female sexual arousal leading to copulation. They are situationally triggered, gated by interactions with males, and decline with the consummation of sexual reproduction with a chosen male. The changes can be triggered by either internal physiological state or by the presence of stimuli presented by males, and the same stimuli change both behavior and physiological (endocrine) state in such a way as to make acceptance of a male more likely. Thus amphibian females demonstrate many of the same general characteristics of changing female sexual state that in mammals indicate sexual arousal.
Wilczynski, Walter; Lynch, Kathleen S.
Amphibians with biphasic life histories occupy aquatic and terrestrial habitats at different times in their lives, leading to a double jeopardy of contaminant risk in both habitats. The present study examines individual and interactive effects of mercury exposure to terrestrial adults and aquatic larvae on fitness-related traits of American toads, Bufo americanus. Eggs from reference mothers or contaminated mothers were allowed to hatch and larvae were fed diets of either no added Hg or 2.5 or 10 µg/g total Hg (dry wt). Both dietary and maternal Hg had adverse effects on developing larvae, but there was no interaction between these factors. Dietary Hg had a marginal effect of decreased survival with increasing Hg in the diet. Animals from Hg-exposed mothers weighed 14% less than those from reference mothers, and size at metamorphosis was directly correlated with hopping performance. Animals from Hg-exposed mothers also took longer to complete metamorphosis and had 2.5 times the prevalence of spinal malformations compared with those from reference mothers. Results of the present study demonstrate that amphibians do indeed face a double jeopardy of contaminant exposure stemming from terrestrial and aquatic environments, because both exposure pathways adversely affected developing offspring. The present study also demonstrates that all possible routes of exposure over an organism's life history must be examined to provide a comprehensive picture of the ecological consequences of habitat contamination. PMID:21755529
Todd, Brian D; Bergeron, Christine M; Hepner, Mark J; Hopkins, William A
A feasibility study was initiated to investigate the ability of algorithms developed for medical sonogram image analysis, to be trained for extraction of cartographic information from synthetic aperture radar imagery. BioComputer Research Inc. has applied proprietary `junctive image metamorphosis' algorithms to cancer cell recognition and identification in ultrasound prostate images. These algorithms have been shown to support automatic radar image feature detection and identification. Training set images were used to develop determinants for representative point, line and area features, which were used on test images to identify and localize the features of interest. The software is computationally conservative; operating on a PC platform in real time. The algorithms are robust; having applicability to be trained for feature recognition on any digital imagery, not just those formed from reflected energy, such as sonograms and radar images. Applications include land mass characterization, feature identification, target recognition, and change detection.
Krueger, Peter G.; Gouge, Sally B.; Gouge, Jim O.
The midgut of the tobacco hornworm (Manduca sexta) is a highly aerobic tissue that is destroyed and replaced by a pupal epithelium at metamorphosis. To determine how oxidative phosphorylation is altered during the programmed death of the larval cells, top-down control analysis was performed on mitochondria isolated from the midguts of larvae before and after the commitment to pupation. Oxygen consumption and protonmotive force (measured as membrane potential in the presence of nigericin) were monitored to determine the kinetic responses of the substrate oxidation system, proton leak, and phosphorylation system to changes in the membrane potential. Mitochondria from precommitment larvae have higher respiration rates than those from postcommitment larvae. State 4 respiration is controlled by the proton leak and the substrate oxidation system. In state 3, the substrate oxidation system exerted 90% of the control over respiration, and this high level of control did not change with development. Elasticity analysis, however, revealed that, after commitment, the activity of the substrate oxidation system falls. This decline may be due, in part, to a loss of cytochrome c from the mitochondria. There are no differences in the kinetics of the phosphorylation system, indicating that neither the F(1)F(0) ATP synthase nor the adenine nucleotide translocase is affected in the early stages of metamorphosis. An increase in proton conductance was observed in mitochondria isolated from postcommitment larvae, indicating that membrane area, lipid composition, or proton-conducting proteins may be altered during the early stages of the programmed cell death of the larval epithelium. PMID:15072964
Chamberlin, M E
Amphibian populations are declining globally at an alarming rate. Pesticides are among a number of proposed causes for these declines. Although a sizable database examining effects of pesticides on amphibians exists, the vast majority of these studies focus on toxicological effects (lethality, external malformations, etc.) at relatively high doses (parts per million). Very few studies focus on effects such as endocrine disruption at low concentrations. Further, most studies examine exposures to single chemicals only. The present study examined nine pesticides (four herbicides, two fungicides, and three insecticides) used on cornfields in the midwestern United States. Effects of each pesticide alone (0.1 ppb) or in combination were examined. In addition, we also examined atrazine and S-metolachlor combined (0.1 or 10 ppb each) and the commercial formulation Bicep II Magnum, which contains both of these herbicides. These two pesticides were examined in combination because they are persistent throughout the year in the wild. We examined larval growth and development, sex differentiation, and immune function in leopard frogs (Rana pipiens). In a follow-up study, we also examined the effects of the nine-compound mixture on plasma corticosterone levels in male African clawed frogs (Xenopus laevis). Although some of the pesticides individually inhibited larval growth and development, the pesticide mixtures had much greater effects. Larval growth and development were retarded, but most significantly, pesticide mixtures negated or reversed the typically positive correlation between time to metamorphosis and size at metamorphosis observed in controls: exposed larvae that took longer to metamorphose were smaller than their counterparts that metamorphosed earlier. The nine-pesticide mixture also induced damage to the thymus, resulting in immunosuppression and contraction of flavobacterial meningitis. The study in X. laevis revealed that these adverse effects may be due to an increase in plasma levels of the stress hormone corticosterone. Although it cannot be determined whether all the pesticides in the mixture contribute to these adverse effects or whether some pesticides are effectors, some are enhancers, and some are neutral, the present study revealed that estimating ecological risk and the impact of pesticides on amphibians using studies that examine only single pesticides at high concentrations may lead to gross underestimations of the role of pesticides in amphibian declines.
Hayes, Tyrone B.; Case, Paola; Chui, Sarah; Chung, Duc; Haeffele, Cathryn; Haston, Kelly; Lee, Melissa; Mai, Vien Phoung; Marjuoa, Youssra; Parker, John; Tsui, Mable
The external metamorphosis of the sea lamprey was divided into four stages, based primarily on the condition of the mouth: mouth reduced, mouth fused, mouth enclosed, and mouth elongated. During metamorphosis, the eye enlarged greatly, the snout and mouth region changed from a fleshy hood enclosing a sieve apparatus to a large sucking disc, the nasopore membrane and the branchial area shrank, the branchiopores changed in shape, the general color changed from dark brown and yellow to an intense blue-black dorsally and white ventrally, and the total length increased. Metamorphosis began in early to mid-July and did not take place after August. The duration of external metamorphosis was about 3 months for lampreys transforming under natural conditions. The mean lengths of metamorphosing lampreys from tributaries of lakes Superior and Michigan were 145 and 136 mm, respectively.
Manion, Patrick J.; Stauffer, Thomas M.
Background Earlier studies from this laboratory reported that light and its spectra influence reproduction in the Indian skipper frog Rana cyanophlyctis through both ocular and extra ocular photoreception. During the course of our ongoing studies on chromotactic behaviour of the tadpoles, we noticed that tadpoles held in red light metamorphosed earlier than those held in white or other colours of light. The focus of the present study therefore was to examine the effect of red light on metamorphosis of the tadpoles. Results Tadpoles, both intact and blind (optectomised), held in red light metamorphosed earlier than those held in white light. Addition of melatonin to aquarium water (5 micrograms/litre) prevented the red light-induced acceleration of metamorphosis both in intact and blinded tadpoles. Conclusion Both ocular and extra-ocular perception of light is involved in red light-induced precocious metamorphosis. Melatonin inhibits the red light-induced acceleration of metamorphosis. The mechanism by which red light accelerates metamorphosis is not yet known. Melatonin counteracts red-light induced acceleration of metamorphosis in this tadpole.
Joshi, Bhaskar N; Mohinuddin, Khaja
Current pesticide risk assessment does not specifically consider amphibians. Amphibians in the aquatic environment (aquatic life stages or postmetamorphic aquatic amphibians) and terrestrial living juvenile or adult amphibians are assumed to be covered by the risk assessment for aquatic invertebrates and fish, or mammals and birds, respectively. This procedure has been evaluated as being sufficiently protective regarding the acute risk posed by a number of pesticides to aquatic amphibian life stages (eggs, larvae). However, it is unknown whether the exposure and sensitivity of terrestrial living amphibians are comparable to mammalian and avian exposure and sensitivity. We reviewed the literature on dermal pesticide absorption and toxicity studies for terrestrial life stages of amphibians, focusing on the dermal exposure pathway, that is, through treated soil or direct overspray. In vitro studies demonstrated that cutaneous absorption of chemicals is significant and that chemical percutaneous passage, P (cm/h), is higher in amphibians than in mammals. In vivo, the rapid and substantial uptake of the herbicide atrazine from treated soil by toads (Bufo americanus) has been described. Severe toxic effects on various amphibian species have been reported for field-relevant application rates of different pesticides. In general, exposure and toxicity studies for terrestrial amphibian life stages are scarce, and the reported data indicate the need for further research, especially in light of the global amphibian decline. PMID:21898550
Brühl, Carsten A; Pieper, Silvia; Weber, Brigitte
Amphibians developing in wetlands embedded within or near agricultural lands may frequently encounter chemical mixtures. The objectives of our study were to determine the effects that post-application concentrations of an insecticide (carbaryl) and an herbicide (atrazine) have on body mass, development, and survival of two anuran species (southern leopard frog, Rana sphenocephala; American toad, Bufo americanus) and two caudate species (spotted salamander, Ambystoma maculatum; small-mouthed salamander, A. texanum) reared in outdoor cattle tank mesocosms. In one experiment, we manipulated tadpole density (low or high), carbaryl exposure (0, 3.5, 7.0 mg/L), and atrazine exposure (0 or 200 ??g/L) to test for effects on development, mass, and survival of larvae. In a second experiment, we manipulated pond hydroperiod (constant or drying), carbaryl exposure (0 or 5 mg/L), and atrazine exposure (0 or 200 ??g/L) to test for effects on mass, time, and survival to metamorphosis. Salamanders were virtually eliminated in carbaryl treatments, indicating that at realistic levels, this insecticide could cause population declines for salamanders in contaminated habitats. Carbaryl also had negative effects on toad survival. Exposure to atrazine had negative effects on body size, development, and time to metamorphosis in anuran species, which were associated with reduced chlorophyll levels. Both chemicals interacted significantly with density or hydroperiod, indicating that the environmental conditions could influence the impact of a contaminant. A significant atrazine-by-carbaryl interaction resulted in smaller and less developed spotted salamander larvae than in control ponds. Atrazine exposure, however, appeared to moderate negative effects of carbaryl for spotted salamanders. Our research suggests that important changes in the community's food web result from chemical exposure, which influence the susceptibility of amphibian species to contaminants.
Boone, M. D.; James, S. M.
Amphibian populations are often imbedded in agricultural landscapes. Therefore the potential for contamination of their habitat is considerable. Our study examined the effects of an insecticide (carbaryl, a neurotoxin), on larval amphibian communities experiencing natural stresses of competition for resources, predation, and pond drying. In a set of experimental ponds, tadpoles of three anuran species (southern leopard frog [Rana sphenocephala], plains leopard frog [R. blairi], and the Woodhouse's toad [Bufo woodhousii]) were added to 1000-L ponds containing leaf litter, plankton, two newts (Notophthalmus viridescens), and four overwintered green frog (R. clamitans) tadpoles. We manipulated the overall tadpole density (low or high), pond hydroperiod (constant or drying), and chemical exposure (0, 3.5, 5.0, or 7.0 mg/L carbaryl) of the ponds. We measured mass, time, and survival to metamorphosis to determine treatment effects. Carbaryl positively affected Woodhouse's toad survival, although it had a negligible effect on both leopard frog species. Tadpole density interacted with the chemical treatment: Proportionately more Woodhouse's toads survived to metamorphosis in high-density environments than in low-density or control environments. Greater survival may be an indirect effect of increased algal food resources from carbaryl exposure. Most newts lost mass over the course of the experiment, although ponds with drying hydroperiods and high anuran density were the least favorable environments. Overwintered green frogs exposed to carbaryl had longer larval periods on average than did green frogs in control ponds. Our study demonstrated that even sublethal, short-lived contaminants can alter natural communities in ways that cannot be predicted from simple, one-factor studies.
Boone, M. D.; Semlitsch, R. D.
Population losses and extinctions of species are occurring at unprecedented rates, as exemplified by declines and extinctions of amphibians worldwide. However, studies of amphibian population declines generally do not address the complexity of the phenomenon or its implications for ecological communities, focusing instead on single factors affecting particular amphibian species. We argue that the causes for amphibian population declines are complex; may differ among species, populations, and life stages within a population; and are context dependent with multiple stressors interacting to drive declines. Because amphibians are key components of communities, we emphasize the importance of investigating amphibian declines at the community level. Selection pressures over evolutionary time have molded amphibian life history characteristics, such that they may remain static even in the face of strong, recent human-induced selection pressures. PMID:21449968
Blaustein, Andrew R; Han, Barbara A; Relyea, Rick A; Johnson, Pieter T J; Buck, Julia C; Gervasi, Stephanie S; Kats, Lee B
This addresses the USEPA's need for a cost effective, non-mammalian screening assay for thyroid axis disrupting chemicals; a multi-endpoint strategy combining molecular and in vivo protocols in an amphibian model is being applied at MED Duluth....
Numerous species of amphibians are frequently utilized as animal models in biomedical research. Despite their rela- tively common occurrence as laboratory animals, the regu- latory guidelines that institutional animal care and use committees (IACUCs) must employ provide little in the way of written standards for ectothermic animals. Yet, as vertebrates, laboratory amphibians are covered by the Na- tional Research Council
Leanne C. Alworth; Stephen B. Harvey
Although invasive plants can have transformative effects on native plant communities, studies of the consequences of plant invasion for native fauna are generally restricted to primary consumers. Here we investigate whether an invasive shrub, Lonicera maackii, impacts native amphibians and evaluate evidence for the role of invasive plant-induced alteration of forest understory microclimate as a mechanism driving amphibian responses to
James I. Watling; Caleb R. Hickman; John L. Orrock
1. Urban ecosystems are expanding throughout the world, and urban ecology is attracting increasing research interest. Some authors have questioned the value of existing ecological theories for understanding the processes and consequences of urbanization. 2. In order to assess the applicability of metacommunity theory to urban systems, I evaluated three assumptions that underlie the theory - the effect of patch area, the effect of patch isolation, and species-environment relations - using data on assemblages of pond-breeding amphibians in the Greater Melbourne area of Australia. I also assessed the relative impact of habitat fragmentation, habitat isolation, and changes to habitat quality on these assemblages. 3. Poisson regression modelling provided support for an important increase in species richness with patch area (pond size) and a decrease in species richness with increasing patch isolation, as measured by surrounding road cover. Holding all other variables constant, species richness was predicted to be 2.8-5.5 times higher at the largest pond than at the smallest, while the most isolated pond was predicted to have 12-19% of the species richness of the least isolated pond. Thus, the data were consistent with the first two assumptions of metacommunity theory evaluated. 4. The quality of habitat at a pond was also important, with a predicted 44-56% decrease in the number of species detected at ponds with a surrounding vertical wall compared with those with a gently sloping bank. This demonstrates that environmental differences between habitat patches were also influencing amphibian assemblages, providing support for the species-sorting and/or mass-effect perspectives of metacommunity theory. 5. Without management intervention, urbanization may lead to a reduction in the number of amphibian species persisting in urban ponds, particularly where increasing isolation of ponds by roads and associated infrastructure reduces the probability of re-colonization following local extinction. Journal of Animal Ecology (2006) 75, 757-764 doi: 10.1111/j.1365-2656.2006.01096.x. PMID:16689958
Parris, Kirsten M
Mesoderm induction in the amphibian embryo can be studied by exposing animal region explants (destined to become ectoderm) to appropriate stimuli and assaying the appearance of mesodermal products like alpha -actin messenger RNA. Transforming growth factor beta 2 (TGF-beta 2), but not TGF-beta 1, was active in alpha -actin induction, while addition of fibroblast growth factor had a small synergistic
Frederic Rosa; Anita B. Roberts; David Danielpour; Linda L. Dart; Michael B. Sporn; Igor B. Dawid
The research presented here describes the development of in vivo and in vitro assay systems to test chemicals for their ability to alter the HPT-axis. This data derived from this research will be used to support development of diagnostic indicators for use with amphibian whole o...
Amphibian declines and extinctions are critical concerns of biologists around the world. The estimated current rate of amphibian extinction is known, but how it compares to the background amphibian extinction rate from the fossil record has not been well studied. I compared current amphibian extinction rates with their reported background extinction rates using standard and fuzzy arithmetic. These calculations suggest
Malcolm L. McCallum
Background Female sperm storage has evolved independently multiple times among vertebrates to control reproduction in response to the environment. In internally fertilising amphibians, female salamanders store sperm in cloacal spermathecae, whereas among anurans sperm storage in oviducts is known only in tailed frogs. Facilitated through extensive field sampling following historical observations we tested for sperm storing structures in the female urogenital tract of fossorial, tropical caecilian amphibians. Findings In the oviparous Ichthyophis cf. kohtaoensis, aggregated sperm were present in a distinct region of the posterior oviduct but not in the cloaca in six out of seven vitellogenic females prior to oviposition. Spermatozoa were found most abundantly between the mucosal folds. In relation to the reproductive status decreased amounts of sperm were present in gravid females compared to pre-ovulatory females. Sperm were absent in females past oviposition. Conclusions Our findings indicate short-term oviductal sperm storage in the oviparous Ichthyophis cf. kohtaoensis. We assume that in female caecilians exhibiting high levels of parental investment sperm storage has evolved in order to optimally coordinate reproductive events and to increase fitness.
The regulatory guanine nucleotide binding protein (G protein) activators cholera toxin and the GTP analog 5-guanylyl imidophosphate, the second messenger diacylglycerol, and certain diamino acids all facilitate (amplify) the settlement and metamorphic responses of planktonic larvae of Haliotis rufescens (marine mollusc) to morphogenetic chemical stimuli. In contrast, the G protein-inhibiting analog guanosine 5?-O-[?-thio]diphosphate inhibits facilitation by L-?,?-diaminopropionic acid but does not block facilitation by diacylglycerol. Diacylglycerol, cholera toxin, and the guanine nucleotide analogs alone neither induce the settlement and metamorphosis of the larvae nor do they inhibit induction of metamorphosis by ?-aminobutyric acid. These results thus establish the existence of separate regulatory and inductive pathways controlling larval metamorphosis in response to two classes of exogenous chemical signals from the environment. The regulatory pathway, operating independently through a G protein-diacylglycerol cascade apparently controlled by facilitating diamino acids in the water column, can amplify the larval responsiveness to inducers of metamorphosis. This mechanism may have adaptive significance in the recognition and selection of favorable habitats for metamorphosis of the larvae. Similar regulatory pathways, based on exogenous control of a G protein-diacylglycerol cascade, may govern responsiveness to stimuli in other sensory and developmental systems.
Baxter, Gregory; Morse, Daniel E.
We review here the scientific significance of the use of amphibians for research in gravitational biology. Since amphibian eggs are quite large, yet develop rapidly and externally, it is easy to observe their development. Consequently amphibians were the first vertebrates to have their early developmental processes investigated in space. Though several deviations from normal embryonic development occur when amphibians are raised in microgravity, their developmental program is robust enough to return the organisms to an ostensibly normal morphology by the time they hatch. Evolutionally, amphibians were the first vertebrate animal to come out of the water and onto land. Subsequently they diversified and have adaptively radiated to various habitats. They now inhabit aquatic, terrestrial, arboreal and fossorial niches. This diversity can be used to help study the biological effects of gravity at the organismal level, where macroscopic phenomena are associated with gravitational loading. By choosing different amphibian models and using a comparative approach one can effectively identify the action of gravity on biological systems, and the adaptation that vertebrates have made to this loading. Advances in cellular and molecular biology provide powerful tools for the study in many fields, including gravitational biology, and amphibians have proven to be good models for studies at those levels as well. The low metabolic rates of amphibians make them convenient organisms to work with (compared to birds and mammals) in the difficult and confined spaces on orbiting research platforms. We include here a review of what is known about and the potential for further behavioral and physiological researches in space using amphibians. PMID:12721528
Yamashita, Masamichi; Naitoh, Tomio; Wassersug, Richard J
Many captive amphibians have high serum or plasma cholesterol and concomittant lesions such as corneal lipidosis and xanthomas. The underlying cause of this disorder is unknown, but it is likely that a diet high in cholesterol plays a role. The metabolism of lipids in healthy amphibians remains poorly documented, which makes it challenging to interpret the findings in affected specimens. Affected amphibians should be maintained on a low-cholesterol diet and fed sparingly, and their captive environment modified to provide an optimal temperature gradient for thermoregulation. PMID:12616838
This site, from The Amphibian Research and Monitoring Initiative (ARMI), is a compilation of current and historic records of amphibian occurrences. The atlas is organized taxonomically. There are separate sections for frogs and toads, and salamanders and newts. The location of each species is mapped separately. The ARMI Atlas is meant to be an educational tool for people wanting to learn or teach others about amphibians. It can also serve as a reference for habitat managers and researchers, identifying areas where more research is needed, as well as providing information about research that has previously been done.
Cortisol, the main glucocorticoid in fish, increases during flatfish metamorphosis and peaks before the surge of thyroxine. A large body of evidence indicates the essential role of thyroxine in flatfish metamorphosis, whereas information on cortisol is limited. We administered cortisol to spotted halibut Verasper variegatus larvae in order to examine the effect on pigmentation during metamorphosis. Administration of 10?g cortisol
Toshiyuki Yamada; Hayato Donai; Masanori Okauchi; Masatomo Tagawa; Kazuo Araki
The direct developing anuran, Eleutherodactylus coqui, lacks a tadpole, hatching as a tiny frog. We investigated the role of the metamorphic trigger, thyroid hormone (TH), in this unusual ontogeny. Expression patterns of the thyroid hormone receptors, TR? and TR?, were similar to those of indirect developers. TR? mRNA levels increased dramatically around the time of thyroid maturation, when remodeling events reminiscent of metamorphosis occur. Treatment with the goitrogen methimazole inhibited this remodeling, which was reinitiated on cotreatment with TH. Despite their radically altered ontogeny, direct developers still undergo a TH-dependent metamorphosis, which occurs before hatching. We propose a new model for the evolution of anuran direct development.
Callery, Elizabeth M.; Elinson, Richard P.
The direct developing anuran, Eleutherodactylus coqui, lacks a tadpole, hatching as a tiny frog. We investigated the role of the metamorphic trigger, thyroid hormone (TH), in this unusual ontogeny. Expression patterns of the thyroid hormone receptors, TRalpha and TRbeta, were similar to those of indirect developers. TRbeta mRNA levels increased dramatically around the time of thyroid maturation, when remodeling events reminiscent of metamorphosis occur. Treatment with the goitrogen methimazole inhibited this remodeling, which was reinitiated on cotreatment with TH. Despite their radically altered ontogeny, direct developers still undergo a TH-dependent metamorphosis, which occurs before hatching. We propose a new model for the evolution of anuran direct development. PMID:10706622
Callery, E M; Elinson, R P
To determine whether the remodeling of the well-organized intestinal epithelium during amphibian metamorphosis is regionally regulated along the anteroposterior axis of the intestine, we raised a polyclonal antibody against the Xenopus laevis intestinal fatty acid-binding protein (IFABP), which is known to be specifically expressed in intestinal absorptive cells, and examined immunohistochemically the differentiation, proliferation, and apoptosis of the epithelial cells throughout X. laevis small intestine. During pre- and prometamorphosis, IFABP-immunoreactive (ir) epithelial cells were localized only in the anterior half of the larval intestine. At the beginning of metamorphic climax, apoptotic cells detected by nick end-labeling (TUNEL) suddenly increased in number in the entire larval epithelium, concurrently with the appearance of adult epithelial primordia. Subsequently, the adult primordia in the anterior part of the intestine developed more rapidly by active cell proliferation than those in the posterior part, and replaced the larval epithelial cells earlier than those in the posterior part. IFABP-ir cells in the adult epithelium were first detectable at the tips of newly formed folds in the proximal part of the intestine. Thereafter, IFABP expression gradually progressed both in the anteroposterior direction and in the crest-trough direction of the folds. These results suggest that developmental processes of the adult epithelium in the X. laevis intestine are regionally regulated along the anteroposterior axis of the intestine, which is maintained throughout metamorphosis, and along the trough-crest axis of the epithelial folds, which is newly established during metamorphosis. Furthermore, the regional differences in IFABP expression along the anteroposterior axis of the intestine were reproduced in organ cultures in vitro. In addition, IFABP expression was first down-regulated and then reactivated in vitro when the anterior part, but not the posterior part, of the larval intestine was treated with thyroid hormone (TH) for extended periods. Therefore, it seems that, in addition to TH, an endogenous factor(s) localized in the intestine itself with an anteroposterior gradient participates in the development of the adult epithelium during amphibian metamorphosis. PMID:9405104
Ishizuya-Oka, A; Ueda, S; Damjanovski, S; Li, Q; Liang, V C; Shi, Y B
The 74 native species of reptiles and amphibians of South Florida (Lake Okeechobee southward) are listed. Their distributions among six major habitats, xeric, mesic, alternohygric, hygric, halohygric, and edificarian-ruderal are noted, with reference to t...
J. P. Crowder
We explored the relationship between amphibian declines and climate variations in Colorado (U.S.A.), Puerto Rico, Costa Rica-Panama, and Queensland (Australia) through two sources of data: output from the National Center for Environmental Prediction \\
Michael A. Alexander; Jon K. Eischeid
A growing number of substances released into the environment disrupt normal endocrine mechanisms in a wide range of vertebrates. Little is known about the effects and identities of endocrine-disrupting chemicals (EDCs) that target thyroid hormone (TH) action, particularly at the cellular level. Frog tadpole metamorphosis depends completely on TH, which has led to the suggestion of a metamorphosis-based assay for screening potential EDCs. A major mechanism of TH action is the alteration of gene expression via hormone-bound nuclear receptors. To assess the gene expression profiles in the frog model, we designed a novel multispecies frog cDNA microarray. Recently, the preemergent herbicide acetochlor was shown to accelerate 3,5,3 -triiodothyronine (T3)-induced forelimb emergence and increase mRNA expression of thyroid hormone ss receptors in ranid tadpoles. Here we show that T3-induced metamorphosis of Xenopus laevis, a species commonly used in the laboratory, is accelerated upon acute exposure to an environmentally relevant level of acetochlor. The morphologic changes observed are preceded by alterations in gene expression profiles detected in the tadpole tail, and the nature of these profiles suggest a novel mechanism of action for acetochlor.
Crump, Doug; Werry, Kate; Veldhoen, Nik; Van Aggelen, Graham; Helbing, Caren C
Recent studies have shown that amphibians and reptiles are good indicators of environmental health. They live in terrestrial and aquatic environments and are often the first animals to be affected by environmental change. This publication provides baseline information about amphibians and reptiles that are present on the Pajarito Plateau. Ten years of data collection and observations by researchers at Los Alamos National Laboratory, the University of New Mexico, the New Mexico Department of Game and Fish, and hobbyists are represented.
Teralene S. Foxx; Timothy K. Haarmann; David C. Keller
Competent larvae are induced to undergo metamorphosis by sand from a sand dollar bed or an aqueous extract of the sand. Gel permeation chromatography and high-performance liquid chromatography of the extract yielded a 980-dalton peptide that will induce metamorphosis between 10(-6) and 10(-5) molar. Extracts of whole adults and gonads were also able to induce metamorphosis, and adults can condition substrates to induce metamorphosis. Therefore, the initiation of metamorphosis in Dendraster excentricus is controlled by a pheromone released by adult sand dollars. PMID:17813263
Burke, R D
Poisons are common in nature, where they often serve the organism in chemical defense. Such poisons either are produced de novo or are sequestered from dietary sources or symbiotic organisms. Among vertebrates, amphibians are notable for the wide range of noxious agents that are contained in granular skin glands. These compounds include amines, peptides, proteins, steroids, and both water-soluble and lipid-soluble alkaloids. With the exception of the alkaloids, most seem to be produced de novo by the amphibian. The skin of amphibians contains many structural classes of alkaloids previously unknown in nature. These include the batrachotoxins, which have recently been discovered to also occur in skin and feathers of a bird, the histrionicotoxins, the gephyrotoxins, the decahydroquinolines, the pumiliotoxins and homopumiliotoxins, epibatidine, and the samandarines. Some amphibian skin alkaloids are clearly sequestered from the diet, which consists mainly of small arthropods. These include pyrrolizidine and indolizidine alkaloids from ants, tricyclic coccinellines from beetles, and pyrrolizidine oximes, presumably from millipedes. The sources of other alkaloids in amphibian skin, including the batrachotoxins, the decahydroquinolines, the histrionicotoxins, the pumiliotoxins, and epibatidine, are unknown. While it is possible that these are produced de novo or by symbiotic microorganisms, it appears more likely that they are sequestered by the amphibians from as yet unknown dietary sources. PMID:7816854
Daly, J W
Currently no comparative studies exist on helminth and leech community structure among sympatric anuran tadpoles and salamander larvae. During June-August 2007-2009, we examined 50 bullfrog tadpoles, Rana catesbeiana , 50 barred tiger salamander larvae, Ambystoma mavortium , and 3 species of snails from Nevens Pond, Keith County, Nebraska for helminth and leech infections. The helminth and leech compound community of this larval amphibian assemblage consisted of at least 7 species, 4 in bullfrog tadpoles and 4 in barred tiger salamander larvae. Bullfrog tadpoles were infected with 2 species of nematodes ( Gyrinicola batrachiensis and Spiroxys sp.) and 2 types of metacercariae ( Telorchis sp. and echinostomatids), whereas barred tiger salamander larva were infected with 1 species of leech ( Placobdella picta ), 2 species of adult trematodes ( Telorchis corti and Halipegus sp.), and 1 species of an unidentified metacercaria. The component community of bullfrog tadpoles was dominated by helminths acquired through active penetration, or incidentally ingested through respiratory currents, or both, whereas the component community of larval salamanders was dominated by helminths acquired through ingestion of intermediate hosts (?² ?=? 3,455.00, P < 0.00001). Differences in amphibian larval developmental time (2-3 yr for bullfrog tadpoles versus 2-5 mo for salamander larvae), the ephemeral nature of intermediate hosts in Nevens Pond, and the ability of bullfrog tadpole to eliminate echinostome infections had significant effects on mean helminth species richness among amphibian species and years (t ?=? 12.31, P < 0.0001; t ?=? 2.09, P ?=? 0.04). Differences in herbivorous and carnivorous diet and time to metamorphosis among bullfrog tadpoles and barred tiger salamander larvae were important factors in structuring helminth communities among the larval stages of these 2 sympatric amphibian species, whereas size was important in structuring helminth and leech communities in larval salamanders, but not in bullfrog tadpoles. PMID:22059380
Rhoden, Heather R; Bolek, Matthew G
The mechanical oscillation of the heart is fundamental during insect metamorphosis, but it is unclear how morphological changes affect its mechanical dynamics. Here, the micromechanical heartbeat with the monarch chrysalis (Danaus plexippus) during metamorphosis is compared with the structural changes observed through in vivo magnetic resonance imaging (MRI). We employ a novel ultra-sensitive detection approach, optical beam deflection, in order to measure the microscale motions of the pupae during the course of metamorphosis. We observed very distinct mechanical contractions occurring at regular intervals, which we ascribe to the mechanical function of the heart organ. Motion was observed to occur in approximately 15?min bursts of activity with frequencies in the 0.4–1.0?Hz range separated by periods of quiescence during the first 83 per cent of development. In the final stages, the beating was found to be uninterrupted until the adult monarch butterfly emerged. Distinct stages of development were characterized by changes in frequency, amplitude, mechanical quality factor and de/repolarization times of the mechanical pulsing. The MRI revealed that the heart organ remains functionally intact throughout metamorphosis but undergoes morphological changes that are reflected in the mechanical oscillation.
Pelling, Andrew E; Wilkinson, Paul R; Stringer, Richard; Gimzewski, James K
Mealworm beetles have been used in numerous experiments as bioindicators. The aim of our experiment was to study the elemental composition in three larvae, pupae and first and second generation adult stages during their life cycle. We selected 180 larvae from a genetically similar population and put them in three groups, in two boxes (60 larvae in each box). Larvae were fed with mashed potato made of the same quality and quantity of potato powder. Then, we selected 10 individuals from each stage to the elemental analysis, using the ICP-OES method. The following elements were analysed in the studied stages: Ca, Cu, Fe, K, Mg, Mn, Na, P, S, Sr and Zn. The results of principal component analysis demonstrated that based on elemental composition, different stages were separated with each other, but in the cases of the three larvae stages, high overlap was found. The results of the GLM ANOVA showed significant differences between the different stages of metamorphosis-based elemental composition. Our results show that the calcium and magnesium were found in a relatively high concentration, while the iron and zinc may be essential elements during the metamorphosis. Our results also show that in insect, the concentration of sodium was higher than in the pupa which may cause by hemolymph. We also demonstrated that the metamorphosis has an effect on the concentration of elements. Our study shows that in the different stages of insects, there are significant changes in the elemental composition of different stages of insects during their metamorphosis. PMID:23695727
Simon, Edina; Baranyai, Edina; Braun, Mihály; Fábián, István; Tóthmérész, Béla
Metamorphosis is a most dramatic example of hormonally regulated genetic reprogramming during postembryonic development. The initiation and sustenance of the process are under the control of ecdysteroids in invertebrates and thyroid hormone, 3,3?,5-triiodothyronine, in oviparous vertebrates. Their actions are inhibited or potentiated by other endogenous or exogenous hormones — juvenile hormone in invertebrates and prolactin and glucocorticoids in vertebrates. The
Jamshed R Tata
The mechanical oscillation of the heart is fundamental during insect metamorphosis, but it is unclear how morphological changes affect its mechanical dynamics. Here, the micromechanical heartbeat with the monarch chrysalis (Danaus plexippus) during metamorphosis is compared with the structural changes observed through in vivo magnetic resonance imaging (MRI). We employ a novel ultra-sensitive detection approach, optical beam deflection, in order to measure the microscale motions of the pupae during the course of metamorphosis. We observed very distinct mechanical contractions occurring at regular intervals, which we ascribe to the mechanical function of the heart organ. Motion was observed to occur in approximately 15 min bursts of activity with frequencies in the 0.4-1.0 Hz range separated by periods of quiescence during the first 83 per cent of development. In the final stages, the beating was found to be uninterrupted until the adult monarch butterfly emerged. Distinct stages of development were characterized by changes in frequency, amplitude, mechanical quality factor and de/repolarization times of the mechanical pulsing. The MRI revealed that the heart organ remains functionally intact throughout metamorphosis but undergoes morphological changes that are reflected in the mechanical oscillation. PMID:18682363
Pelling, Andrew E; Wilkinson, Paul R; Stringer, Richard; Gimzewski, James K
Ocean acidification may negatively impact the early life stages of some marine invertebrates including corals. Although reduced growth of juvenile corals in acidified seawater has been reported, coral larvae have been reported to demonstrate some level of tolerance to reduced pH. We hypothesize that the observed tolerance of coral larvae to low pH may be partly explained by reduced metabolic rates in acidified seawater because both calcifying and non-calcifying marine invertebrates could show metabolic depression under reduced pH in order to enhance their survival. In this study, after 3-d and 7-d exposure to three different pH levels (8.0, 7.6, and 7.3), we found that the oxygen consumption of Acropora digitifera larvae tended to be suppressed with reduced pH, although a statistically significant difference was not observed between pH conditions. Larval metamorphosis was also observed, confirming that successful recruitment is impaired when metamorphosis is disrupted, despite larval survival. Results also showed that the metamorphosis rate significantly decreased under acidified seawater conditions after both short (2 h) and long (7 d) term exposure. These results imply that acidified seawater impacts larval physiology, suggesting that suppressed metabolism and metamorphosis may alter the dispersal potential of larvae and subsequently reduce the resilience of coral communities in the near future as the ocean pH decreases.
Nakamura, Masako; Ohki, Shun; Suzuki, Atsushi; Sakai, Kazuhiko
Ocean acidification may negatively impact the early life stages of some marine invertebrates including corals. Although reduced growth of juvenile corals in acidified seawater has been reported, coral larvae have been reported to demonstrate some level of tolerance to reduced pH. We hypothesize that the observed tolerance of coral larvae to low pH may be partly explained by reduced metabolic rates in acidified seawater because both calcifying and non-calcifying marine invertebrates could show metabolic depression under reduced pH in order to enhance their survival. In this study, after 3-d and 7-d exposure to three different pH levels (8.0, 7.6, and 7.3), we found that the oxygen consumption of Acropora digitifera larvae tended to be suppressed with reduced pH, although a statistically significant difference was not observed between pH conditions. Larval metamorphosis was also observed, confirming that successful recruitment is impaired when metamorphosis is disrupted, despite larval survival. Results also showed that the metamorphosis rate significantly decreased under acidified seawater conditions after both short (2 h) and long (7 d) term exposure. These results imply that acidified seawater impacts larval physiology, suggesting that suppressed metabolism and metamorphosis may alter the dispersal potential of larvae and subsequently reduce the resilience of coral communities in the near future as the ocean pH decreases. PMID:21264208
Nakamura, Masako; Ohki, Shun; Suzuki, Atsushi; Sakai, Kazuhiko
We conducted an intensive inventory of Harris Neck National Wildlife Refuge in coastal Georgia to determine the feasibility of establishing an amphibian monitoring program at this location. Thirteen semi-aquatic amphibian species were identified at 21 locations. Amphibian species richness at Harris Neck was similar to that of nearby barrier islands. The amphibian fauna of Harris Neck has long been affected by human-induced landscape changes, including the inadvertent introduction of tadpoles from distant fish hatcheries and the creation of artificial impoundments. Land-use history provides important information necessary to understand current amphibian distribution, especially when census data are used to establish a baseline from which to monitor future status and trends.
Dodd, Jr. , C. K.; Barichivich, W. J.
Monitoring the occurrence of specific amphibian species in ponds is one component of the US Geological Survey's Amphibian Monitoring and Research Initiative. Two collaborative studies were conducted in Olympic National Park and southeastern region of Oregon. The number of ponds...
Title: Engineering a future for amphibians under climate change ... climates in the 21st century pose serious threats for biological systems and practical actions ... into local or regional management plans, programs and activities for amphibians.
Since the appearance of of Reptiles and amphibians of the Cimarron National Grassland, Mortoll County, Kansas (Collins and Collins, 1991), new information has accumulated on the diversity, distribution and biology of amphibians, reptiles, and turtles nati...
J. T. Collins S. L. Collins T. W. Taggart
Amphibian species have inexplicably declined or disappeared in many regions of the world, and in some instances, serious malformations have been observed. In the United States, amphibian declines frequently have occurred even in protected areas. Causes fo...
C. K. Dodd
The widespread emergence of human and wildlife diseases has challenged ecologists to understand how large-scale agents of environmental change affect host–pathogen interactions. Accelerated eutrophication of aquatic ecosystems owing to nitrogen and phosphorus enrichment is a pervasive form of environmental change that has been implicated in the emergence of diseases through direct and indirect pathways. We provide experimental evidence linking eutrophication and disease in a multihost parasite system. The trematode parasite Ribeiroia ondatrae sequentially infects birds, snails, and amphibian larvae, frequently causing severe limb deformities and mortality. Eutrophication has been implicated in the emergence of this parasite, but definitive evidence, as well as a mechanistic understanding, have been lacking until now. We show that the effects of eutrophication cascade through the parasite life cycle to promote algal production, the density of snail hosts, and, ultimately, the intensity of infection in amphibians. Infection also negatively affected the survival of developing amphibians. Mechanistically, eutrophication promoted amphibian disease through two distinctive pathways: by increasing the density of infected snail hosts and by enhancing per-snail production of infectious parasites. Given forecasted increases in global eutrophication, amphibian extinctions, and similarities between Ribeiroia and important human and wildlife pathogens, our results have broad epidemiological and ecological significance.
Johnson, Pieter T. J.; Chase, Jonathan M.; Dosch, Katherine L.; Hartson, Richard B.; Gross, Jackson A.; Larson, Don J.; Sutherland, Daniel R.; Carpenter, Stephen R.
The role of facilities and associated services for amphibians has recently undergone diversification. Amphibians tradi- tionally used as research models adjust well to captivity and thrive with established husbandry techniques. However, it is now necessary to maintain hundreds of novel amphibian species in captive breeding, conservation research, and bio- medical research programs. These diverse species have a very wide range
Robert K. Browne; R. Andrew Odum; Timothy Herman; Kevin Zippel
Estimating the distribution of amphibians in terrestrial habitats surrounding wetlands is essential for determining how much habitat is required to maintain viable amphibian populations and how much habitat may be allocated to other land use practices. We apply univariate kernel estimation in a new manner to determine the distribution of amphibians during the non-breeding season. We summarized data from 13
Tracy A. G. Rittenhouse; Raymond D. Semlitsch
Amphibians have declined dramatically in many areas of the world. These declines seem to have worsened over the past 25 years and amphibians are now more threatened than either mammals or birds, though comparisons with other taxa are confounded by a shortage of reliable data. Research into amphibian declines has focused on: (1) documentation at the landscape or population level;
Trevor J. C. Beebee; Richard A. Griffiths
The first global assessment of amphibians provides new context to the well-publicised phenomenon of amphibian declines. Amphibians are more threatened, and are declining more rapidly, than either birds or mammals. Although many declines are due to habitat loss and over- utilization, other, unidentified processes threaten 48% of rapidly declining species, and are driving species most quickly to extinction. Declines are
Simon N. Stuart; Janice S. Chanson; Neil A. Cox; Bruce E. Young; Ana S. L. Rodrigues; Debra L. Fischman; Robert W. Waller
The loss of global amphibian biodiversity has been well documented in recent years. The greatest information from Latin America came from countries such as Costa Rica, Panama, Ecuador, and Puerto Rico. The five papers in this special section illustrate the critical status of Latin American amphibians and further demonstrate certain commonalities of amphibian population declines within the region. These studies
Karen R. Lips; Patricia A. Burrowes; Joseph R. Mendelson; Gabriela Parra-Olea
From 1999 to 2006, we sampled >1200 amphibians for the fungal pathogen Batrachochytnum dendrobatidis (Bd) at 30 sites in the southeastern USA. Using histological techniques or PCR assays, we detected chytrid infection in 10 species of aquatic-breeding amphibians in 6 states. The prevalence of chytrid infection was 17.8% for samples of postmetamorphic amphibians examined using skin swab-PCR assays (n = 202 samples from 12 species at 4 sites). In this subset of samples, anurans had a much higher prevalence of infection than caudates (39.2% vs. 5.5%, respectively). Mean prevalence in ranid frogs was 40.7 %. The only infected salamanders were Notophthalmus viridescens at 3 sites. We found infected amphibians from late winter through late spring and in 1 autumn sample. Although we encountered moribund or dead amphibians at 9 sites, most mortality events were not attributed to Bd. Chytridiomycosis was established as the probable cause of illness or death in fewer than 10 individuals. Our observations suggest a pattern of widespread and subclinical infections. However, because most of the sites in our study were visited only once, we cannot dismiss the possibility that chytridiomycosis is adversely affecting some populations. Furthermore, although there is no evidence of chytrid-associated declines in our region, the presence of this pathogen is cause for concern given global climate change and other stressors. Although presence-absence surveys may still be needed for some taxa, such as bufonids, we recommend that future researchers focus on potential population-level effects at sites where Bd is now known to occur. ?? Inter-Research 2008.
Rothermel, B. B.; Walls, S. C.; Mitchell, J. C.; Dodd, Jr. , C. K.; Irwin, L. K.; Green, D. E.; Vazquez, V. M.; Petranka, J. W.; Stevenson, D. J.
Created in June, 1997 and funded by the US Geological Survey and Environmental Protection Agency, this site is a response to the discovery of numerous deformed amphibians (mostly frogs) in areas as widespread as Minnesota, California, and Florida. Malformations include extra or missing limbs, missing eyes, and split limbs. The site is intended to serve as a central repository for data on the type and relative frequency of such malformations throughout the US. Researchers hope to use the site to help discover the cause(s) of these deformities. The site contains a map of where malformations have been reported, background on the occurrence and possible causes of defects, numerous images of malformed amphibians, a searchable bibliography, instructions on how to report the discovery of a malformed amphibian, and links to eight related web sites. NARCAM's site also contains a toll-free number for citizen reports.
Center., Northern P.
Amphibians possess the ability to vomit in response to a variety of stimuli that provoke emesis in mammals. Pharmacological studies have establish that the ejection of gastric contents and the basic mechanism for vomiting have been phylogenetically conserved among these tetrapods. As part of on-going comparative studies on emesis in vertebrates, we previously documented that some postmetamorphic anurans and salamander larvae experience motion-induced emesis when exposed to the provocative stimulus of parabolic aircraft flight. However, more recent experiments suggest that there are strict conditions for inducing emesis in amphibians exposed to parabolic flight and that amphibians are not as sensitive to this stimulus as mammals. Further studies on emesis in lower vertebrates may help us understand the processes that cause emesis in abnormal gravitational regimes
Naitoh, T.; Yamashita, M.; Izumi-Kurotani, A.; Takabatake, I.; Wassersug, R. J.
Thyroid hormone (TH) is essential for proper development in vertebrates. TH deficiency during gestation and early postnatal development produces severe neurological, skeletal, metabolism and growth abnormalities. It is therefore important to consider environmental chemicals that may interfere with TH signaling. Exposure to environmental contaminants that disrupt TH action may underlie the increasing incidence of human developmental disorders worldwide. One contaminant
Rachel A. Heimeier; Yun-Bo Shi
A newly discovered infectious disease of amphibians, chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis, is implicated in population declines and possible extinctions throughout the world. The purpose of our study was to examine the effects of B. dendrobatidis on the mountain yellow-legged frog (Rana muscosa) in the Sierra Nevada of California (USA). We (1) quantified the prevalence and incidence of B. dendrobatidis through repeat surveys of several hundred R. muscosa populations in the southern Sierra Nevada; (2) described the population-level effects of B. dendrobatidis on R. muscosa population abundance; and (3) compared the mortality rates of infected and uninfected R. muscosa individuals from pre- through post-metamorphosis using both laboratory and field experiments. Mouthpart inspections conducted in 144 and 132 R. muscosa populations in 2003 and 2004, respectively, indicated that 19% of R. muscosa populations in both years showed indications of chytridiomycosis. Sixteen percent of populations that were uninfected in 2003 became infected by 2004. Rana muscosa population sizes were reduced by an average of 88% following B. dendrobatidis outbreaks at six sites, but at seven B. dendrobatidis-negative sites, R. muscosa population sizes increased by an average of 45% over the same time period. In the laboratory, all infected R. muscosa developed fatal chytridiomycosis after metamorphosis, while all uninfected individuals remained healthy. In the field experiment in which R. muscosa tadpoles were caged at infected and uninfected sites, 96% of the individuals that metamorphosed at infected sites died vs. 5% at the uninfected sites. These studies indicate that chytridiomycosis causes high mortality in post-metamorphic R. muscosa, that this emerging disease is the proximate cause of numerous observed R. muscosa population declines, and that the disease threatens this species with extirpation at numerous sites in California's Sierra Nevada. PMID:16922318
Rachowicz, Lara J; Knapp, Roland A; Morgan, Jess A T; Stice, Mary J; Vredenburg, Vance T; Parker, John M; Briggs, Cheryl J
Hydractinia echinata and Aurelia aurita produce motile larvae which undergo metamorphosis to sessile polyps when induced by external cues. The polyps are found at restricted sites, A. aurita predominantly on rocks close to the shore, H. echinata on shells inhabited by hermit crabs. It has been argued that the differential distribution of the polyps in their natural environment largely reflects the distribution of the natural metamorphosis-inducing cues. In the case of H. echinata, bacteria of the genus Alteromonas were argued to meet these conditions. We found that almost all substrates collected in the littoral to induce metamorphosis in H. echinata, and several bacterial strains isolated from the sea, including the common E. coli, induce metamorphosis efficiently. In A. aurita metamorphosis may be induced by the water-air interface, whereby metamorphosis precedes (final) settlement.
Kroiher, M.; Berking, S.
In insects juvenile hormone (JH) regulates both metamorphosis and reproduction. This lecture focuses on our current understanding of JH action at the molecular level in both of these processes based primarily on studies in the tobacco hornworm Manduca sexta, the flour beetle Tribolium castaneum, the mosquito Aedes aegypti, and the fruit fly Drosophila melanogaster. The roles of the JH receptor complex and the transcription factors that it regulates during larval molting and metamorphosis are summarized. Also highlighted are the intriguing interactions of the JH and insulin signaling pathways in both imaginal disc development and vitellogenesis. Critical actions of JH and its receptor in the timing of maturation of the adult optic lobe and of female receptivity in Drosophila are also discussed. PMID:22728566
Riddiford, Lynn M
Known primarily for creating beautiful images of butterflies and flowers, Maria Sibylla Merian (German, 1647-1717) has remained largely unappreciated for her seminal contribution to early modern natural history. Merian was indeed a talented artist, but she clearly thought of herself as a naturalist, and employed both text and images to depict lepidopteran metamorphosis and behavior with unprecedented accuracy and detail. Merian documented larvae and adult insects feeding not only on plants, but also on other animals, and she depicted other creatures preying on insects. An image of battling spiders and ants and the accompanying text in her 1705 Metamorphosis insectorum surinamensium illuminated the world of tropical arthropods in a way that was groundbreaking, and set the stage for a new way to envision nature. PMID:21126767
Amphibian species have experienced population declines and extinctions worldwide that are unprecedented in recent history. Many of these recent declines have been linked to a pathogenic skin fungus, Batrachochytrium dendrobatidis, or to iridoviruses of the genus Ranavirus. One of the first lines of defense against pathogens that enter by way of the skin are antimicrobial peptides synthesized and stored in
Louise A. Rollins-Smith
The life cycle of the sea lamprey, Petromyzon marinus, includes two metamorphoses. At the end of a period spent as a blind larva, buried in the mud of streams, a first metamorphosis prepares it to migrate downstream to the sea or a lake for its growth phase. Then, following a second metamorphosis, it migrates upstream as a sexually mature adult to spawn and die. The downstream migrants have a visual system based upon rhodopsin and vitamin A1, whereas that of the upstream migrants is based upon porphyropsin and vitamin A2. The livers contain vitamin A1 at all stages. The sea lamprey therefore exhibits a metamorphosis of visual systems, like those observed earlier among amphibia. The presence of porphyropsin in this member of the most primitive living group of vertebrates, as in fishes and amphibia, supports the notion that porphyropsin may have been the primitive vertebrate visual pigment. Its association with fresh water existence throughout this range of organisms also is consistent with the view that the vertebrate stock originated in fresh water. The observation that in the life cycle of the lamprey rhodopsin precedes porphyropsin is not at variance with the idea that porphyropsin is the more primitive pigment, since this change is part of the second metamorphosis, marking the return to the original environment. The observation that in lampreys, fishes, and amphibia, porphyropsin maintains the same general association with fresh water, and rhodopsin with marine and terrestrial habit, suggests that a single genetic mechanism may govern this association throughout this wide span of organisms.
Introduces an online zoology course that was offered primarily to upper elementary and middle school teachers in which teachers were expected to take action to help the local amphibian population. (Author/YDS)
Murphy, Tony P.
Literature has much to offer the psychotherapist. This paper has discussed some lessons for the psychotherapist contained in Franz Kafka's short story, The Metamorphosis. The therapist, like the therapist-reader of this story, can empathize with Gregor's monstrous change but still must hold him personally accountable. At the same time, the therapist-reader becomes increasingly impressed with the malignant nature of the Samsa household, and its role in generating Gregor's capacity for self-deception. The story also instructs about the paradox of catastrophe: Gregor is treated no less respectfully after his metamorphosis than he was before it. The therapist is thereby reminded of the centrality of feelings in human affairs. The constriction of Gregor's space does not cut him off from human feeling; rather, Gregor's inability to access, know, and take responsibility for his own feelings, especially his destructive ones, results in his constrictedness and detachment. In thinking about the story as dream, or in imagining a patient's account of a reality situation as if it were a dream, unseen mental process and content become more apparent. The disgusting, loathsome arrangements that people make with each other can evoke, be it in the therapist-reader or the therapist, reactions of aversion or hate. Such arrangements become more understandable when the importance, sometimes the necessity, of human attachment is appreciated. And finally, Kafka's The Metamorphosis alerts us to a sometimes but powerful preference and countertransference pitfall: we don't want to be bugged. PMID:9742316
Gans, J S
The reorganization of cranial cartilages during tadpole metamorphosis is a set of complex processes. The fates of larval cartilage-forming cells (chondrocytes) and sources of adult chondrocytes are largely unknown. Individual larval cranial cartilages may either degenerate or remodel, while many adult cartilages appear to form de novo during metamorphosis. Determining the extent to which adult chondrocytes/cartilages are derived from larval chondrocytes during metamorphosis requires new techniques in chondrocyte lineage tracing. We have developed two transgenic systems to label cartilage cells throughout the body with fluorescent proteins. One system strongly labels early tadpole cartilages only. The other system inducibly labels forming cartilages at any developmental stage. We examined cartilages of the skull (viscero- and neurocranium), and identified larval cartilages that either resorb or remodel into adult cartilages. Our data show that the adult otic capsules, tecti anterius and posterius, hyale, and portions of Meckel’s cartilage are derived from larval chondrocytes. Our data also suggest that most adult cartilages form de novo, though we cannot rule out the potential for extreme larval chondrocyte proliferation or de- and re-differentiation, which could dilute our fluorescent protein signal. The transgenic lineage tracing strategies developed here are the first examples of inducible, skeleton-specific, lineage tracing in Xenopus.
Kerney, Ryan R.; Brittain, Alison L.; Hall, Brian K.; Buchholz, Daniel R.
In insects, initiation of metamorphosis requires a surge in the production of the steroid hormone 20-hydroxyecdysone from the prothoracic gland, the primary endocrine organ of juvenile larvae. Here, we show that blocking TGF?/Activin signaling, specifically in the Drosophila prothoracic gland, results in developmental arrest prior to metamorphosis. The terminal, giant third instar larval phenotype results from a failure to induce the large rise in ecdysteroid titer that triggers metamorphosis. We further demonstrate that activin signaling regulates competence of the prothoracic gland to receive PTTH and insulin signals, and that these two pathways act at the mRNA and post-transcriptional levels, respectively, to control ecdysone biosynthetic enzyme expression. This dual regulatory circuitry may provide a cross-check mechanism to ensure that both developmental and nutritional inputs are synchronized before initiating the final genetic program leading to reproductive adult development. As steroid hormone production in C. elegans and mammals is also influenced by TGF?/Activin signaling, this family of secreted factors may play a general role in regulating developmental transitions across phyla.
Gibbens, Ying Y.; Warren, James T.; Gilbert, Lawrence I.; O'Connor, Michael B.
Aromatase is a steroidogenic enzyme that catalyzes the conversion of androgens to estrogens in vertebrates. Modulation of this enzyme's activity by xenobiotic exposure has been shown to adversely affect gonad differentiation in a number of diverse species. We hypothesized that exposure to the aromatase inhibitor, fadrozole, during the larval development of the tropical clawed frog, Xenopus tropicalis, would result in masculinization of the developing female gonad. Tadpoles were exposed to fadrozole at nominal concentrations from 1 to 64 microg/L in a flow-through system from < 24 h post-fertilization (Nieuwkoop Faber (NF) stage 15-20) to metamorphosis (NF stage 66). At metamorphosis, morphologically examined gonads indicated complete masculinization of all tadpoles at concentrations of 16 microg/L and above and a significant bias in sex ratio towards males at concentrations of 1 microg/L and above. No effects on time to metamorphosis, body mass, or body length were observed. A random subsample of frogs was raised to reproductive maturity (39 weeks post-fertilization) in control water. All frogs exposed as tadpoles to 16 microg/L fadrozole or greater possessed testes at sexual maturity. Intersexed gonads characterized by the presence of both testicular and ovarian tissue were observed in 12% of frogs in the 4 microg/L treatment. No differences in estradiol, testosterone, or vitellogenin plasma concentrations were observed in exposed males or females compared to controls. Females in the 4 microg/L treatment possessed a significantly greater percentage of pre-vitellogenic oocytes than controls and were significantly smaller in body mass. No differences in sperm counts were observed in exposed males compared to controls. Results from this study demonstrate that larval exposure to an aromatase inhibitor can result in the complete masculinization of female gonads. These masculinized females are phenotypically indistinguishable from normal males at adulthood. Lower levels of aromatase inhibition resulted in intersexed gonads and possible female reproductive impairment at adulthood. These results indicate that exposure of amphibians to xenobiotics capable of inhibiting aromatase would result in adverse reproductive consequences. PMID:18804292
Olmstead, Allen W; Kosian, Patricia A; Korte, Joseph J; Holcombe, Gary W; Woodis, Kacie K; Degitz, Sigmund J
Size variance among similarly aged individuals within populations is a pattern common to many organisms that is a result of interactions between intrinsic and extrinsic traits of individuals. While genetic and maternal effects, as well as physiological and behavioral traits have been shown to contribute to size variation in animal populations, teasing apart the influence of such factors on individual growth rates remain a challenge. Furthermore, tracing the effects of these interactions across life stages and in shaping adult phenotypes also requires further exploration. In this study we investigated the relationship between genetics, hatching patterns, behaviors, neuroendocrine stress axis activity and variance in growth and metamorphosis among same-aged larval amphibians. Through parallel experiments we found that in the absence of conspecific interactions, hatch time and to a lesser extent egg clutch identity (i.e. genetics and maternal effects) influenced the propensity for growth and development in individual tadpoles and determined metamorphic traits. Within experimental groups we found that variance in growth rates was associated with size-dependent foraging behaviors and responses to food restriction. We also found an inverse relationship between glucocorticoid (GC) hormone levels and body mass and developmental stage among group-reared tadpoles, which suggests that GC expression plays a role in regulating differing within-population growth trajectories in response to density-dependent conditions. Taken together these findings suggest that factors that influence hatching conditions can have long-term effects on growth and development. These results also raise compelling questions regarding the extent to which maternal and genetic factors influence physiological and behavioral profiles in amphibians.
Warne, Robin W.; Kardon, Adam; Crespi, Erica J.
Size variance among similarly aged individuals within populations is a pattern common to many organisms that is a result of interactions between intrinsic and extrinsic traits of individuals. While genetic and maternal effects, as well as physiological and behavioral traits have been shown to contribute to size variation in animal populations, teasing apart the influence of such factors on individual growth rates remain a challenge. Furthermore, tracing the effects of these interactions across life stages and in shaping adult phenotypes also requires further exploration. In this study we investigated the relationship between genetics, hatching patterns, behaviors, neuroendocrine stress axis activity and variance in growth and metamorphosis among same-aged larval amphibians. Through parallel experiments we found that in the absence of conspecific interactions, hatch time and to a lesser extent egg clutch identity (i.e. genetics and maternal effects) influenced the propensity for growth and development in individual tadpoles and determined metamorphic traits. Within experimental groups we found that variance in growth rates was associated with size-dependent foraging behaviors and responses to food restriction. We also found an inverse relationship between glucocorticoid (GC) hormone levels and body mass and developmental stage among group-reared tadpoles, which suggests that GC expression plays a role in regulating differing within-population growth trajectories in response to density-dependent conditions. Taken together these findings suggest that factors that influence hatching conditions can have long-term effects on growth and development. These results also raise compelling questions regarding the extent to which maternal and genetic factors influence physiological and behavioral profiles in amphibians. PMID:24143188
Warne, Robin W; Kardon, Adam; Crespi, Erica J
Presently available data on anatomical, electrophysiological, and behavioral aspects of the Mauthner cell in amphibians are reviewed. Urodelian Mauthner cells appear morphologically distinct from those in anurans with respect to their abundant somatic dendrites, axon cap structures, lack of nodes of Ranvier, and size of axon collaterals. The presence of Mauthner cells does not seem to correlate with the presence
Global declines of amphibians are well documented, yet effects of these dramatic losses on ecosystem structure and function are poorly understood. As part of a larger collaborative project, we compared two upland Panamanian streams. Both streams are biologically and geologically similar; however, one stream (Fortuna) has recently experienced almost complete extirpation of stream-dwelling frogs, while the other (Cope) still has
S. Connelly; C. M. Pringle; R. J. Bixby; M. R. Whiles; K. R. Lips; R. Brenes; J. C. Colon-Gaud; S. Kilham; M. Hunte-Brown
|Describes a method for in vitro culturing of cells from amphibian early embryos. Such cells can be used to demonstrate such properties of eukaryote cells as cell motility, adhesion, differentiation, and cell sorting into tissues. The technique may be extended to investigate other factors. (Author/JN)|
We present evidence that the most commonly found deformities in wild-caught amphibians, those featuring missing limbs and missing limb segments, may be the result of selective predation. Here we report that predatory dragonfly nymphs can severely injure and even fully amputate developing hind limbs of anuran tadpoles. Developmental responses of the injured\\/ amputated tadpole limbs range from complete regeneration to
Bioacoustic signals appear to be so essential to the social communication of anuran amphibians that other sensory modalities have been largely ignored. We studied the abilities of Leiopelma hamiltoni, a species evolutionarily basal to most living anurans, to communicate by means of chemosignals. We collected frogs in the field, held them in captivity for 72 h, and then tested their
Bruce Waldman; Phillip J. Bishop
Population declines have previously been reported for at least 31 amphibian species in Brazil, in the families Leptodactylidae (19), Hylidae (7), Centrolenidae (2), Dendrobatidae (2), and Bufonidae (1). In five Brazilian museum collections, we found no entries of new records dating back to at least 15 yr ago for 13 of these species. We suggest that these taxa be studied
Paula Cabral Eterovick; Ana Carolina Oliveira de Queiroz Carnaval; Diva Maria Borges-Nojosa; Debora Leite Silvano; Magno Vicente Segalla; Ivan Sazima
Although worldwide distributions of many amphibians and reptiles are declining, a handful of species are spreading rapidly throughout tropical regions of the world. The species that have the greatest effect tend to be generalist feeders, have high reproductive rates, attain large population sizes, and often due to their behavior and or small size, are easily transported or are difficult to
WILLIAM C. PITT; DANIEL S. VICE; MIKE E. PITZLER
In this activity, learners will discover how the thin layers of amphibians' skin allow water and other chemicals to pass through it. Learners will also discover how different body coverings affect permeability. Learn why and how this affects their body, and what you can do to protect them in the wild. Thin skin is in, dirty environments are not!
Aquariums, Association O.
Research to date has indicated that a range of environmental variables such as disease, parasitism, predation, competition, environmental contamination, solar ultraviolet radiation, climate change, or habitat alteration may be responsible for declining amphibian populations and the appearance of deformed organisms, yet in many cases no definitive environmental variable stands out as a causal factor. Multiple Stressors are often present in the habitat, and interactions among these can magnify injury to biota. This raises the possibility that the additive or synergistic impact of these Stressors may be the underlying cause of amphibian declines. Effective management for the restoration of amphibian populations requires the identification of causal factors contributing to their declines. A systematic approach to determine causality is especially important because initial impressions may be misleading or ambiguous. In addition, the evaluation of amphibian populations requires consideration of a broader spatial scale than commonly used in regulatory monitoring. We describe a systematic three-tiered approach to determine causality in amphibian declines and deformities. Tier 1 includes an evaluation of historic databases and extant data and would involve a desktop synopsis of the status of various stressors as well as site visits. Tier 2 studies are iterative, hypothesis driven studies beginning with general tests and continuing with analyses of increasing complexity as certain stressors are identified for further investigation. Tier 3 applies information developed in Tier 2 as predictive indicators of habitats and species at risk over broad landscape scales and provides decision support for the adaptive management of amphibian recovery. This comprehensive, tiered program could provide a mechanistic approach to identifying and addressing specific stressors responsible for amphibian declines across various landscapes.
Little, E. E.; Bridges, C. M.; Linder, G.; Boone, M.
Settlement and metamorphosis are induced by environmental cues in many marine invertebrates. These signals emanate from biotic or abiotic material indicating the presence of a suitable habitat. In Cnidarians, pelagic larvae undergo metamorphosis to a sessile polyp. Environmental signals reactivate the morphogenetically inactive larvae and internal mechanisms are turned onto coordinate the development of the polyp. In recent years developmental
The ability of marine invertebrate larvae to delay their metamorphosis in the absence of adequate environmental cues has been reported for numerous sedentary and sessile species. In the present study, the effect of various substrata and the presence of conspecific adults on the metamorphosis of a mobile species, the crab Chasmagnathus granulata, was evaluated. The duration of the megalopa stage
P. Gebauer; I. Walter; K. Anger
Newly hatched larval plaice were grown to metamorphosis using an artificial diet. The overall survival rate to metamorphosis was of the order of 20%. This compares with a survival rate of 38% in control larvae fed Artemia in a similar tank system. The pre...
J. W. Adron A. Blair C. B. Cowey
During the first 15 to 20 min of metamorphosis the larval arms are retracted and resorbed into the aboral surface of the juvenile. Arms excised from metamorphosing larvae will undergo a sequence of contraction and histolysis that is identical to that occurring in intact larvae. Prior to and during metamorphosis, epidermal cells contain bundles of 5 to 7-nm microfilaments in
Robert D. Burke
The induction of metamorphosis in mature larvae by selected chemical compounds and natural substrata was investigated in two species of sea urchins from the Sea of Japan, Strongylocentrotus intermedius and Scaphechinus mirabilis. Glutamine in crystalline form was added directly to water containing mature larvae, and this compound, at a final concentration of 10 µg ml-1, was an inducer of metamorphosis
T. Kh. Naidenko
BACKGROUND: While the larval-juvenile transition (metamorphosis) in the spionid polychaete Pseudopolydora vexillosa involves gradual morphological changes and does not require substantial development of juvenile organs, the opposite occurs in the barnacle Balanus amphitrite. We hypothesized that the proteome changes during metamorphosis in the spionids are less drastic than that in the barnacles. To test this, proteomes of pre-competent larvae, competent
Flora SY Mok; Vengatesen Thiyagarajan; Pei-Yuan Qian
Processes involved in both metamorphosis and settlement of young sole were studied at the population, cohort and individual level in order to evaluate their role in survival and recruitment regulation. Metamorphosis can be defined as a phase of variable duration (10 days on average) at the end of which the larval period of pelagic dissemination is completed. Size at the
Rachid AMARA; Françoise LAGARDERE; Yves DESAUNAY; Jocelyne MARCHAND
Chemical and biological cues associated with substrata in the environment were considered to be the primary stimuli initiating larval settlement and metamorphosis in many marine mollusks. In present study, various settlement and metamorphosis inducers at both the laboratory and scale-up experiments were investigated to determine their effects in inducing settlement and metamorphosis on the abalone Haliotis diversicolor supertexta. In lab
Haifang Li; Wei Lin; Guang Zhang; Zhonghua Cai; Guopin Cai; Yaqing Chang; Kezhi Xing
Recruitment of crabs to nursery habitat requires settlement of the megalopal stage on suitable substratum followed by metamorphosis into the first juvenile stage. Reducing the time to metamorphosis may result in higher recruitment and survival. Previous work has shown that metamorphosis of the Asian shore crab is accelerated by cues from three different sources: (a) water-soluble exudate produced by conspecific
Julie A. Anderson; Charles E. Epifanio
A pilot on-line course on amphibians was offered free to 20 educators around the United States in 1999. This course, called Helping Your Local Amphibians (HYLA), was the first of its kind on-line course for educators dealing with amphibian issues. It also used these animals as a focus to teach about the environment. The course lasted 9 weeks with some additional time for continued discussions and used various aspects of Internet technology (including a virtual conference center), media, and traditional paper-based products to complete the learning process. Five teachers were selected to attend a national amphibian summit hosted by the Center for Global Environmental Education, Hamline University, St. Paul, MN. The course was aimed primarily at upper elementary and middle school teachers, but participants included formal and nonformal educators. For the most part, educators expressed satisfaction with the course and the content, as well as the structure of the web site. For 80% of the group, this was their first Internet-based course. In addition, as part of the course, the educators were expected to take some action with their primary audiences to help local amphibian populations. This mainly took the form of surveys or habitat clean-ups. The development of the course was underwritten by grants from the National Fish and Wildlife Foundation, U.S. Fish and Wildlife Service, the Best Buy Children's Foundation, and Hamline University.
Murphy, Tony P.
Background The nemertean pilidium is one of the most notable planktotrophic larval types among marine invertebrates. The juvenile forms inside the larva from a series of isolated rudiments, called the imaginal discs. The development culminates in catastrophic metamorphosis, in which the larval body is consumed by the juvenile worm. Although the pilidium was first described in 1847, and is commonly found among marine plankton, there is not a single complete description of its development. The few published studies of pilidial development are based on observations of typically unidentified larvae opportunistically collected from plankton at various developmental stages. Results The development of Micrura alaskensis, a common Northwest Pacific coast intertidal nemertean, is described from fertilization to metamorphosis. A staging scheme is proposed based on characteristic developmental milestones. Three pairs of imaginal discs develop as invaginations of larval epidermis. The cephalic discs invaginate from the larval epidermis above the ciliated band, while the cerebral organ discs and the trunk discs invaginate below the ciliated band. All paired imaginal disc invaginations are closely associated with different portions of the larval ciliated band. In addition, two unpaired rudiments contribute to the juvenile - the proboscis rudiment and the dorsal rudiment, which do not develop as invaginations. A pair of thick-walled esophageal pouches previously thought to represent nephridial rudiments give rise to the juvenile foregut. Branched rudiments of protonephridia, and their efferent ducts are also described. Larval and juvenile serotonergic nervous systems are briefly described. Development of the juvenile is completed by 5-8 weeks at 11-15 degrees C. During the rapid metamorphosis the juvenile emerges from and devours the larva. Conclusions This study is the first description of pilidial development from fertilization to metamorphosis in a single species. It is illustrated with photomicrographs of live larvae, diagrams, confocal images, and videos. The findings are discussed in the context of previously published accounts of pilidial development, with which they disagree on several accounts. The results described here indicate a different number, origin and fate of various juvenile rudiments. The proposed staging scheme will be useful in subsequent studies of pilidial development.
The US Geological Survey's Patuxent Wildlife Research Center hosts this nice page on the North American Amphibian Monitoring Program. At the site, users will find an overview and history of the program, as well as regional program updates, educational information, and links to related sites. The heart of the site is the Monitoring Programs section, however, as it provides in-depth content on the surveys, including Calling Surveys, Terrestrial Salamander Monitoring, Aquatic Surveys, Atlassing, and Western Surveys. This easy-to-navigate site has much to offer, whether for volunteers interested in participating in surveys, researchers searching for in-depth sampling methodology, or anyone interested in learning more about the distribution and abundance of amphibians in North America.
Amphibians have been widely used to investigate the synthesis of biologically active steroids in the brain and the regulation of neurosteroid production by neurotransmitters and neuropeptides. The aim of the present review is to summarize the current knowledge regarding the neuroanatomical distribution and biochemical activity of steroidogenic enzymes in the brain of anurans and urodeles. The data accumulated over the past two decades demonstrate that discrete populations of neurons and/or glial cells in the frog and newt brains express the major steroidogenic enzymes and are able to synthesize de novo a number of neurosteroids from cholesterol/pregnenolone. Since neurosteroidogenesis has been conserved during evolution from amphibians to mammals, it appears that neurosteroids must play important physiological functions in the central nervous system of vertebrates.
Vaudry, Hubert; Do Rego, Jean-Luc; Burel, Delphine; Luu-The, Van; Pelletier, Georges; Vaudry, David; Tsutsui, Kazuyoshi
Estimating the distribution of amphibians in terrestrial habitats surrounding wetlands is essential for determining how much\\u000a habitat is required to maintain viable amphibian populations and how much habitat may be allocated to other land use practices.\\u000a We apply univariate kernel estimation in a new manner to determine the distribution of amphibians during the non-breeding\\u000a season. We summarized data from 13
Tracy A. G. Rittenhouse; Raymond D. Semlitsch
This Issue focuses on a research article by Blaustein and Johnson (2003) that was published in Frontiers in Ecology and the Environment. The article discusses amphibian deformities, which may be related to a global decline in amphibians. By working with this paper and additional figures, students come to appreciate the complexity of biodiversity loss. Specifically, they gain an understanding of why scientists disagree about causes of amphibian limb deformities and why the search for a single factor is likely too simple.
The New Mexico Department of Game and Fish compiled this extensive list of reptiles and amphibians for New Mexico and Arizona. Organized alphabetically by common name (with scientific name in parenthesis), each hyperlinked name connects the viewer to further details (taxonomy, status, life history, distribution, habitat information, food habits, environmental associations, management practices, and references) via the Biota Information System Of New Mexico (BISON). Researchers will appreciate the extent and clarity of information in this database.
Ranaviruses infect fish, amphibians, and reptiles. The present study was conducted to compare the persistence of amphibian and reptilian ranaviruses in a pond habitat. The 4 viruses used in this study included 2 amphibian ranaviruses, Frog virus 3 (FV3, the type species of the genus Ranavirus) and an isolate from a frog, and 2 ranaviruses of reptilian origin (from a tortoise and from a gecko). A sandwich germ-carrier technique was used to study the persistence of these viruses in sterile and unsterile pond water (PW) and soil obtained from the bank of a pond. For each virus, virus-loaded carriers were placed in each of the 3 substrates, incubated at 4 and 20°C, and titrated at regular intervals. Serial data were analyzed using a linear regression model to calculate T-90 values (time required for 90% reduction in the virus titer). Resistance of the viruses to drying was also studied. All 4 viruses were resistant to drying. At 20°C, T-90 values of the viruses were 22 to 31 d in sterile PW and 22 to 34 d in unsterile PW. Inactivation of all 4 viruses in soil at this temperature appeared to be non-linear. T-90 values at 4°C were 102 to 182 d in sterile PW, 58 to 72 d in unsterile PW, and 30 to 48 d in soil. Viral persistence was highest in the sterile PW, followed by the unsterile PW, and was lowest in soil. There were no significant differences in the survival times between the amphibian and reptilian viruses. The results of the present study suggest that ranaviruses can survive for long periods of time in pond habitats at low temperatures. PMID:22535867
Nazir, J; Spengler, M; Marschang, R E
1.A culture medium has been developed for amphibian sympathetic nervous tissue but it is suggested that the ionic values should be adjusted to correspond to the concentrations of salts in the plasma of particular species.2.The morphology, monoamine fluorescence, growth and differentiation of sympathetic ganglia of the frog, Limnodynastes dumerili, have been studied in culture.3.Two types of neuron could be distinguished
C. E. Hill; G. Burnstock
Bent's Old Fort National Historic Site sits along the Arkansas River in the semi-desert prairie of southeastern Colorado. The USGS provided assistance in designing surveys to assess the variety of herpetofauna (amphibians and reptiles) resident at this site. This brochure is the results of those efforts and provides visitors with information on what frogs, toads, snakes and salamanders might be seen and heard at Bent's Old Fort.
Although the effects of contaminants on amphibians have been studied for decades, relatively little is known about these effects compared to the more intensively studied mammals. and birds. Science has advanced its understanding of the complexities linked to declining amphibian populations; however, there are many remaining questions whose answers would directly benefit amphibians and adaptive management plans ministering to them. In an effort to answer those questions and focus on ecological risk assessment of amphibians, scientists, researchers, and resource management professionals from diverse fields participated in a Society of Environmental Toxicology and Chemistry (SETAC)-Johnson Foundation Wingspread conference with three goals: characterize a process that would bring a range of interdisciplinary technical and management tools to the tasks of causal analysis; demonstrate the current state of available technical tools to assess amphibian populations exposed to various environmental stressors; and focus on identifying research that would likely benefit sustainable populations through adaptive management programs. A result of the Wingspread conference, Amphibian Decline examines the ecotoxicology and stressors of amphibians in an attempt to address issues related to declining amphibian populations and the role that various stressors might have in those losses. It identifies gaps in current data, interprets information into an existing framework, and points toward critical areas for future research. Through the combined efforts of research and resource management communities, recommendations can be developed to change current policies and management actions to address the problem of amphibian decline.
One of the most dramatic examples of programmed cell death occurs during Drosophila metamorphosis, when most of the larval tissues are destroyed in a process termed histolysis. Much of our understanding of this process comes from analyses of salivary gland and midgut cell death. In contrast, relatively little is known about the degradation of the larval musculature. Here, we analyze the programmed destruction of the abdominal dorsal exterior oblique muscle (DEOM) which occurs during the first 24h of metamorphosis. We find that ecdysone signaling through Ecdysone receptor isoform B1 is required cell autonomously for the muscle death. Furthermore, we show that the orphan nuclear receptor FTZ-F1, opposed by another nuclear receptor, HR39, plays a critical role in the timing of DEOM histolysis. Finally, we show that unlike the histolysis of salivary gland and midgut, abdominal muscle death occurs by apoptosis, and does not require autophagy. Thus, there is no set rule as to the role of autophagy and apoptosis during Drosophila histolysis. PMID:24051228
Zirin, Jonathan; Cheng, Daojun; Dhanyasi, Nagaraju; Cho, Julio; Dura, Jean-Maurice; Vijayraghavan, Krishnaswamy; Perrimon, Norbert
Calcific metamorphosis (CM) is seen commonly in the dental pulp after traumatic tooth injuries and is recognized clinically as early as 3 months after injury. Calcific metamorphosis is characterized by deposition of hard tissue within the root canal space and yellow discoloration of the clinical crown. Opinion differs among practitioners as to whether to treat these cases upon early detection of CM or to observe them until symptoms or radiographic signs of pulpal necrosis are detected. In this review, the clinical, radiographic, and histopathologic appearance of CM is described; a review of the literature is presented to address these issues in an attempt to establish a sound rationale for treatment. Approximately 3.8% to 24% of traumatized teeth develop varying degrees of CM. Studies indicate that of these, approximately 1% to 16% will develop pulpal necrosis. Most of the literature does not support endodontic intervention unless periradicular pathosis is detected or the involved tooth becomes symptomatic. It may be advisable to manage cases demonstrating CM through observation and periodic examination. PMID:11491624
Amir, F A; Gutmann, J L; Witherspoon, D E
A large number of factors are known to affect amphibian population viability, but most authors agree that the principal causes of amphibian declines are habitat loss, alteration, and fragmentation. We provide a global assessment of land use dynamics in the context of amphibian distributions. We accomplished this by compiling global maps of amphibian species richness and recent rates of change in land cover, land use, and human population growth. The amphibian map was developed using a combination of published literature and digital databases. We used an ecoregion framework to help interpret species distributions across environmental, rather than political, boundaries. We mapped rates of land cover and use change with statistics from the World Resources Institute, refined with a global digital dataset on land cover derived from satellite data. Temporal maps of human population were developed from the World Resources Institute database and other published sources. Our resultant map of amphibian species richness illustrates that amphibians are distributed in an uneven pattern around the globe, preferring terrestrial and freshwater habitats in ecoregions that are warm and moist. Spatiotemporal patterns of human population show that, prior to the 20th century, population growth and spread was slower, most extensive in the temperate ecoregions, and largely exclusive of major regions of high amphibian richness. Since the beginning of the 20th century, human population growth has been exponential and has occurred largely in the subtropical and tropical ecoregions favored by amphibians. Population growth has been accompanied by broad-scale changes in land cover and land use, typically in support of agriculture. We merged information on land cover, land use, and human population growth to generate a composite map showing the rates at which humans have been changing the world. When compared with the map of amphibian species richness, we found that many of the regions of the earth supporting the richest assemblages of amphibians are currently undergoing the highest rates of landscape modification. ?? 2007 by the American Society of Ichthyologists and Herpetologists.
Gallant, A. L.; Klaver, R. W.; Casper, G. S.; Lannoo, M. J.
Background While the larval-juvenile transition (metamorphosis) in the spionid polychaete Pseudopolydora vexillosa involves gradual morphological changes and does not require substantial development of juvenile organs, the opposite occurs in the barnacle Balanus amphitrite. We hypothesized that the proteome changes during metamorphosis in the spionids are less drastic than that in the barnacles. To test this, proteomes of pre-competent larvae, competent larvae (ready to metamorphose), and juveniles of P. vexillosa were compared using 2-dimensional gel electrophoresis (2-DE), and they were then compared to those of the barnacle. Results Unlike the significant changes found during barnacle metamorphosis, proteomes of competent P. vexillosa larvae were more similar to those of their juveniles. Pre-competent larvae had significantly fewer protein spots (384 spots), while both competent larvae and juveniles expressed about 660 protein spots each. Proteins up-regulated during competence identified by MALDI-TOF/TOF analysis included a molecular chaperon (calreticulin), a signal transduction regulator (tyrosin activation protein), and a tissue-remodeling enzyme (metallopeptidase). Conclusions This was the first time to study the protein expression patterns during the metamorphosis of a marine polychaete and to compare the proteomes of marine invertebrates that have different levels of morphological changes during metamorphosis. The findings provide promising initial steps towards the development of a proteome database for marine invertebrate metamorphosis, thus deciphering the possible mechanisms underlying larval metamorphosis in non-model marine organisms.
We assessed the extinction risks of Malagasy amphibians by evaluating their distribution, occur- rence in protected areas, population trends, habitat quality, and prevalence in commercial trade. We estimated and mapped the distribution of each of the 220 described Malagasy species and applied, for the first time, the IUCN Red List categories and criteria to all species described at the time
FRANCO ANDREONE; JOHN E. CADLE; NEIL COX; FRANK GLAW; RONALD A. NUSSBAUM; CHRISTOPHER J. RAXWORTHY; SIMON N. STUART; DENIS VALLAN; MIGUEL VENCES
The vegetation in and around the basins of ephemeral wetlands can greatly affect light environments for aquatic species such as amphibians. We used hemispherical photographs to quantify the light environment in terms of the global site factor (GSF), the proportion of available solar radiation that actually strikes the wetland. We compared GSF to the distribution and performance of two amphibian
M. A. Halverson; D. K. Skelly; J. M. Kiesecker; L. K. Freidenburg
Numerous springs are scattered throughout the eastern Mojave Desert, most of which are concentrated near the bases of mountain ranges. Spring-fed wetlands in this region comprise nearly all the available habitat for amphibians. We surveyed 128 springs for amphibians and habitat t...
Amphibians, a class of vertebrates consisting of frogs and toads, salamanders, and caecilians, are excellent organisms for middle school science students to study because of their ecological significance. Because they exchange oxygen and carbon dioxide through their skin, amphibians absorb any chemicals or substances present in their immediate…
Talley, Brooke L.
CARBONIFEROUS amphibians are very rare as fossils and almost all major finds of British specimens were made in the nineteenth century. Nevertheless, knowledge of Carboniferous tetrapods, both amphibians and reptiles, has expanded considerably in recent years1,2. All are from Europe or North America and most are from horizons equivalent to or later than the British Coal Measures (Westphalian and Stephanian,
S. M. Andrews
A number of amphibian species historically inhabited sparsely distributed wetlands in the Mojave Desert, USA, habitats that have been dramatically altered or eliminated as a result of human activities. The population status and distribution of amphibians were investigated in a 20...
SUMMARY 1. Agricultural practices such as cattle farming may have direct or indirect negative effects on larval amphibians by decreasing water quality through deposition of nitrogenous waste, causing eutrophication, and grazing shoreline vegetation that contributes to detrital cover and food. 2. We sampled amphibian larvae on the Cumberland Plateau, Tennessee, U.S.A., twice per week, water quality twice per month and
A. C HANDLER; M ATTHEW; J. G RAY; E LIZABETH C. B URTON; DEBRA L. M ILLER
Amphibians are highly adapted for life in wetland habitats. They form a major component of wetland faunas, and being both prey and predator, they are important in ecosystem functioning. Wetlands provide aquatic habitats that amphibians require for breeding, development, foraging, hibernation and refuge, and they form an interface with essential adjacent upland habitat. The size and type of wetlands as
S. J. Hecnar
There is compelling evidence that amphibians in western North America and elsewhere have suffered significant declines over the last 10-15 years. The loss of amphibians is particularly significant because it is occurring on a world-wide basis, including o...
G. M. Fellers K. L. Freel
Habitat loss, climate change, over-exploitation, disease and other factors have been hypothesised in the global decline of amphibian biodiversity. However, the relative importance of and synergies among different drivers are still poorly understood. We present the largest global analysis of roughly 45% of known amphibians (2,583 species) to quantify the influences of life history, climate, human density and habitat loss
Navjot S. Sodhi; David Bickford; Arvin C. Diesmos; Tien Ming Lee; Lian Pin Koh; Barry W. Brook; Cagan H. Sekercioglu; Corey J. A. Bradshaw
Human alteration of the environment has arguably propelled the Earth into its sixth mass extinction event and amphibians, the most threatened of all vertebrate taxa, are at the forefront. Many of the worldwide amphibian declines have been caused by the chytrid fungus, Batrachochytrium dendrobatidis (Bd), and two contrasting hypotheses have been proposed to explain these declines. Positive correlations between global
Jason R. Rohr; Thomas R. Raffel; John M. Romansic; Hamish McCallum; Peter J. Hudson
ABSTRACT A recently described chytrid fungus, genus Batrachochytrium, killed free-living and captive amphibians in Australia, Central America and the USA. There is epidemiological, pathological, and experimental evidence that some amphibian populations suddenly declined due to mass mortalities caused by chytridiomycosis. These were notably high altitude, stream dwelling rainforest anurans in protected areas of Queensland and Panama. Chytrid fungi caused a
Lee Berger; Rick Speare; Alex Hyatt
Recent concern over the possibility of a global decline in amphibians prompted this assessment of the West Indian species. At the species level, the West Indian amphibian fauna (156 species, all frogs and toads) has not undergone a general decline, and no species is known to be extinct. However, one Puerto Rican species (Eleutherodactylus karlschmidti) has not been seen in
S. Blair Hedges
Breeding phenology of amphibians in inextricably linked to weather, and change in the timing of breeding resulting from climate change may have consequences for the fitness of individuals and may affect persistence of amphibian populations. Amphibians in some north temperate locations have been observed to breed earlier in recent years in response to warmer spring temperatures, but this is not a universal phenomenon. In mountain populations, phenology is influenced by snow deposition as much as temperature. A trend towards earlier breeding, associated with increasing El Niño frequency, may be occurring in the Cascade Mountains in Oregon, but only at lower elevations. There is no evidence for changes in the dates of breeding activity by amphibians in the Rocky Mountains. Too few amphibian species have been studied, and those for which data exist have been studied for too brief a span of years to allow general conclusions about the effects of climate change. However, regardless of whether climate change has contributed to current amphibian declines, changes in temperature and the extent and duration of snow cover predicted for the next century will have increasingly severe consequences for the persistence of some species. Additional observations from amphibian populations, and spatial and temporal modeling of climate variables are needed to generate predictions of past and future breeding phenology, and the effects on amphibian population dynamics.
As part of an overall 'biodiversity crisis', many amphibian populations are in decline throughout the world. Numerous factors have contributed to these declines, including habitat destruction, pathogens, increasing ultraviolet (UV) radiation, introduced non-native species and contaminants. In this paper we review the contribution of increasing UV radiation and environmental contamination to the global decline of amphibian populations. Both UV radiation
Andrew R. Blaustein; John M. Romansic; Joseph M. Kiesecker; Audrey C. Hatch
|Amphibians, a class of vertebrates consisting of frogs and toads, salamanders, and caecilians, are excellent organisms for middle school science students to study because of their ecological significance. Because they exchange oxygen and carbon dioxide through their skin, amphibians absorb any chemicals or substances present in their immediate…
Talley, Brooke L.
Culexterritans Walker (Diptera: Culicidae) acquires bloodmeals from amphibian hosts. Females overwinter as inseminated adults and exit diapause in New Jersey when spring peepers (Pseudacris crucifer) are calling. We tested the hypothesis that Cx. territans uses amphibian vocal- izations as a long-distance attractant. Two thirds of females oriented toward sound across all exper- iments. Females allowed to orient toward or away
Kristen Bartlett-Healy; Wayne Crans; Randy Gaugler
Many amphibian species, in widely scattered locations, currently show population declines and/or reductions in range, but other amphibian species show no such declines. There is no known single cause for these declines. Differential sensitivity to UVB radiation among species might be one contributing factor. We have focused on amphibian eggs, potentially the most UVB-sensitive stage, and compared their resistance to UVB components of sunlight with their levels of photolyase, typically the most important enzyme for repair of the major UV photoproducts in DNA, cyclobutane pyrimidine dimers. Photolyase varied 100-fold among eggs/oocytes of 10 species. Among three species-Hyla regilla, Rana cascadae, and Bufo boreas-for which resistance of eggs to solar UVB irradiance in their natural locations was measured, hatching success correlated strongly with photolyase. Two additional species, Rana aurora and Ambystoma gracile, now show similar correlations. Among the low-egg-photolyase species, R. cascadae and B. boreas are showing declines, and the status of A. gracile is not known. Of the two high-photolyase species, populations of H. regilla remain robust, but populations of R. aurora are showing declines. To determine whether levels of photolyase or other repair activities are affected by solar exposures during amphibian development, we have initiated an extended study of H. regilla and R. cascadae, and of Xenopus laevis, laboratory-reared specimens of which previously showed very low photolyase levels. Hyla regilla and R. cascadae tadpoles are being reared to maturity in laboratories supplemented with modest levels of UV light or light filtered to remove UVB wavelengths. Young X. laevis females are being reared indoors and outdoors. Initial observations reveal severe effects of both UVA and UVB light on H. regilla and R. cascadae tadpoles and metamorphs, including developmental abnormalities and high mortalities. Assays of photolyase levels in the skins of young animals roughly parallel previous egg/oocyte photolyase measurements for all three species. PMID:8806225
Hays, J B; Blaustein, A R; Kiesecker, J M; Hoffman, P D; Pandelova, I; Coyle, D; Richardson, T
In vertebrates, the macular end organs of the inner ear are gravity sensing organs. They consist of a neuroepithelium overlaid by a mass of little otoconia or by a single large otolith. These crystallites provide essential informations for orientation and equilibrium. They are mosaic biominerals composed of proteic and inorganic phases. In amphibian adults, the mineral phase is calcium carbonate in the form of calcite or aragonite. The calcitic otoconia with a rhomboedric shape are observed in the utricle of Pleurodeles waltl (urodele amphibian). The aragonitic otoconia with a prismatic or a fusiform shape are observed in the saccule and lagena of Pleurodeles, and in the three gravity-sensing regions of Xenopus laevis (anuran amphibian). The aragonitic biocrystallites are in different proportions depending on the inner ear regions. During the development, in Pleurodeles larvae, we observed that saccular otoconia changed from calcitic to aragonitic form. In Xenopus tadpoles, we observed peculiar otoconia with a rhomboedric-like morphology or a tripartite morphology. We called the latter crystallites cauliflower-like otoconia according to the aspect. We reported our observations performed after two space missions, the experiment Torcol which flew on the French Soyuz taxi flight Perseus to MIR (launch: February 20, 1999; landing: August 28, 1999), and the experiment Aquarius-Xenopus which flew on the French Soyuz taxi flight Andromède to ISS (launch: October 21, 2001; landing: October 31, 2001). After a long journey in space, both calcitic and aragonitic otoconia were altered in Pleurodeles adults. After a short space mission, otoconia with rhomboedric, fusiform or cauliflower-like aspects were observed in Xenopus tadpoles. In these tadpoles, otoconia with rhomboedric aspect were never mixed with the other otoconia types, whereas fusiform otoconia were never alone. Cauliflower-shaped otoconia were alone or associated with fusiform otoconia. The study needs further investigations.
Membre, H.; Horn, E.; Dournon, C.
Recent advances in immersion lithography have created the need for a small field microstepper to carry out the early learning necessary for next generation device application. Combined with fluid immersion, multiple-beam lithography can provide an opportunity to explore lithographic imaging at oblique propagation angles and extreme NA imaging. Using the phase preserving properties of Smith Talbot interferometry, the Amphibian XIS immersion lithography microstepper has been created for research and development applications directed toward sub-90nm patterning. The system has been designed for use at ArF and KrF excimer laser wavelengths, based on a fused silica or sapphire prism lens with numerical aperture values up to 1.60. Combined with a chromeless phase grating mask, two and four beam imaging is made possible for feature resolution to 35nm. The approach is combined with X-Y staging to provide immersion imaging on a microstepper platform for substrates ranging up to 300mm. The Amphibian system consists of single or dual wavelength sources (193nm and 248nm), a 2mm exposure field size, stage accuracy better than 1 um, polarization control over a full range from linear polarization to unpolarized illumination, full control of exposure dose and demodulation (to synthesize defocus), and the ability to image both line patterns as well as contact features. A fluid control system allows use of water or alternative fluids, with the ability to change fluids rapidly between wafers. The Amphibian system is fully enclosed in a HEPA and amine controlled environment for use in fab or research environments.
Smith, Bruce W.; Bourov, Anatoly; Fan, Yongfa; Cropanese, Frank; Hammond, Peter
The main component of classical contraceptives, 17?-ethinylestradiol (EE2), has high estrogenic activity even at environmentally relevant concentrations. Although estrogenic endocrine disrupting compounds are assumed to contribute to the worldwide decline of amphibian populations by adverse effects on sexual differentiation, evidence for EE2 affecting amphibian mating behaviour is lacking. In this study, we demonstrate that EE2 exposure at five different concentrations (0.296 ng/L, 2.96 ng/L, 29.64 ng/L, 2.96 µg/L and 296.4 µg/L) can disrupt the mating behavior of adult male Xenopus laevis. EE2 exposure at all concentrations lowered male sexual arousal, indicated by decreased proportions of advertisement calls and increased proportions of the call type rasping, which characterizes a sexually unaroused state of a male. Additionally, EE2 at all tested concentrations affected temporal and spectral parameters of the advertisement calls, respectively. The classical and highly sensitive biomarker vitellogenin, on the other hand, was only induced at concentrations equal or higher than 2.96 µg/L. If kept under control conditions after a 96 h EE2 exposure (2.96 µg/L), alterations of male advertisement calls vanish gradually within 6 weeks and result in a lower sexual attractiveness of EE2 exposed males toward females as demonstrated by female choice experiments. These findings indicate that exposure to environmentally relevant EE2 concentrations can directly disrupt male mate calling behavior of X. laevis and can indirectly affect the mating behavior of females. The results suggest the possibility that EE2 exposure could reduce the reproductive success of EE2 exposed animals and these effects might contribute to the global problem of amphibian decline. PMID:22355410
Hoffmann, Frauke; Kloas, Werner
\\u000a The herbicide glyphosate, sold under a variety of commercial names including Roundup\\u000a ®\\u000a and Vision\\u000a ®\\u000a , has long been viewed as an environmentally friendly herbicide. In the 1990s, however, after nearly 20 years of use, the\\u000a first tests were conducted on the herbicide’s effects on amphibians in Australia. The researchers found that the herbicide\\u000a was moderately toxic to Australian
Rick A. Relyea
Overseas dispersals are often invoked when Southern Hemisphere terrestrial and freshwater organism phylogenies do not fit the sequence or timing of Gondwana fragmentation. We used dispersal-vicariance analyses and molecular timetrees to show that two species-rich frog groups, Microhylidae and Natatanura, display congruent patterns of spatial and temporal diversification among Gondwanan plates in the Late Cretaceous, long after the presumed major tectonic break-up events. Because amphibians are notoriously salt-intolerant, these analogies are best explained by simultaneous vicariance, rather than by oceanic dispersal. Hence our results imply Late Cretaceous connections between most adjacent Gondwanan landmasses, an essential concept for biogeographic and palaeomap reconstructions. PMID:17183706
Van Bocxlaer, Ines; Roelants, Kim; Biju, S D; Nagaraju, J; Bossuyt, Franky
The tiger salamander lives in shallow water with bright light in the aquatic phase, and in dim tunnels or caves in the terrestrial phase. In the aquatic phase, there are five types of photoreceptors--two types of rods and three types of cones. Our previous studies showed that the green rods and blue-sensitive cones contain the same visual pigment and have the same absorbance spectra; however, the green rods have a larger photon-catch area and thus have higher light sensitivity than the blue-sensitive cones. Here we show that after metamorphosis, the terrestrial salamander looses the blue-sensitive cones, while the density of the green rods increases. Moreover, the size of the green rod outer segments is increased in the terrestrial phase, compared to that in the aquatic phase. This switch from the blue-sensitive cones to the green rods may represent an adaptation to the dim light environment of the terrestrial phase. PMID:18331398
Chen, Ying; Znoiko, Sergey; DeGrip, Willem J; Crouch, Rosalie K; Ma, Jian-xing
Three-dimensional metamorphosis is a powerful technique to produce a 3D shape transformation between two or more existing models. In this paper, we propose a novel 3D morphing technique that avoids creating a merged embedding that contains the faces, edges, and vertices of two given embeddings. This novel 3D morphing technique dynamically adds or removes vertices to gradually transform the connectivity of 3D polyhedrons from a source model into a target model and simultaneously creates the intermediate shapes. In addition, a priority control function provides the animators with control of arising or dissolving of input models' features in a morphing sequence. This is a useful tool to control a morphing sequence more easily and flexibly. Several examples of aesthetically pleasing morphs are demonstrated using the proposed method. PMID:15631124
Lin, Chao-Hung; Lee, Tong-Yee
The application of image morphing to computer animation and computer graphics is experiencing broad growth. It has proven to be a powerful visual effect tool in film and television, depicting the fluid transformation of one digital image into another. In this paper, the authors present a new method for image morphing based on field morphing and mesh warping. Our method makes use of the feature specification method of field morphing which is simple and expressive and the warp generation approach of mesh warping which is straightforward and fast. Some measures are taken to make the proposed method work; experimental results show that the proposed method facilitates the input of features and calculates quickly with a steady metamorphosis effect.
Wu, Hao; Zhang, Rong; Feng, Niu
The tiger salamander lives in shallow water with bright light in the aquatic phase, and in dim tunnels or caves in the terrestrial phase. In the aquatic phase, there are five types of photoreceptors—two types of rods and three types of cones. Our previous studies showed that the green rods and blue-sensitive cones contain the same visual pigment and have the same absorbance spectra; however, the green rods have a larger photon-catch area and thus have higher light sensitivity than the blue-sensitive cones. Here we show that after metamorphosis, the terrestrial salamander looses the blue-sensitive cones, while the density of the green rods increases. Moreover, the size of the green rod outer segments is increased in the terrestrial phase, compared to that in the aquatic phase. This switch from the blue-sensitive cones to the green rods may represent an adaptation to the dim light environment of the terrestrial phase.
Chen, Ying; Znoiko, Sergey; DeGrip, Willem J.; Crouch, Rosalie K.; Ma, Jian-xing
Some causative agents of amphibian declines act synergistically to impact individual amphibians and their populations. In particular, pathogenic water molds (aquatic oomycetes) interact with environmental stressors and increase mortality in amphibian embryos. We documented colonization of eggs of three amphibian species, the wood frog (Rana sylvatica), the green frog (Rana clamitans), and the spotted salamander (Ambystoma maculatum), by water molds
Nancy E. Karraker; Gregory R. Ruthig
The widely accepted paradigm that epoxidized methyl farnesoates (“juvenile hormones,” JHs) are the principle sesquiterpenoid hormones regulating insect metamorphosis was assessed in Drosophila melanogaster. GC-MS analysis showed that methyl farnesoate, rather than methyl epoxyfarnesoate (= JH III), ...
The amphibian decline and extinction crisis demands urgent action to prevent further large numbers of species extinctions. Lists of priority species for conservation, based on a combination of species’ threat status and unique contribution to phylogenetic diversity, are one tool for the direction and catalyzation of conservation action. We describe the construction of a near-complete species-level phylogeny of 5713 amphibian species, which we use to create a list of evolutionarily distinct and globally endangered species (EDGE list) for the entire class Amphibia. We present sensitivity analyses to test the robustness of our priority list to uncertainty in species’ phylogenetic position and threat status. We find that both sources of uncertainty have only minor impacts on our ‘top 100‘ list of priority species, indicating the robustness of the approach. By contrast, our analyses suggest that a large number of Data Deficient species are likely to be high priorities for conservation action from the perspective of their contribution to the evolutionary history.
Isaac, Nick J. B.; Redding, David W.; Meredith, Helen M.; Safi, Kamran
The amphibian decline and extinction crisis demands urgent action to prevent further large numbers of species extinctions. Lists of priority species for conservation, based on a combination of species' threat status and unique contribution to phylogenetic diversity, are one tool for the direction and catalyzation of conservation action. We describe the construction of a near-complete species-level phylogeny of 5713 amphibian species, which we use to create a list of evolutionarily distinct and globally endangered species (EDGE list) for the entire class Amphibia. We present sensitivity analyses to test the robustness of our priority list to uncertainty in species' phylogenetic position and threat status. We find that both sources of uncertainty have only minor impacts on our 'top 100' list of priority species, indicating the robustness of the approach. By contrast, our analyses suggest that a large number of Data Deficient species are likely to be high priorities for conservation action from the perspective of their contribution to the evolutionary history. PMID:22952807
Isaac, Nick J B; Redding, David W; Meredith, Helen M; Safi, Kamran
Larval metamorphosis inducers of the sea cucumber Apostichopus japonicus were screened from physiologically active compounds. Doliolaria larvae completed their metamorphosis to juveniles in 120 h\\u000a when treated with 5–10 ?M of dopamine and l-DOPA, and 50 ?M of l-adrenaline and l-noradrenaline. Doliolaria larvae had to be exposed to dopamine or l-DOPA for at least 24 h. D1-like dopamine receptor antagonists SKF87566 and LE300 (10 ?M)
Hiroshi Matsuura; Ikuko Yazaki; Tatsufumi Okino
Marine invertebrates commonly have a biphasic life cycle in which the metamorphic transition from a pelagic larva to a benthic post-larva is mediated by the nitric oxide signalling pathway. Nitric oxide (NO) is synthesised by nitric oxide synthase (NOS), which is a client protein of the molecular chaperon heat shock protein 90 (HSP90). It is notable, then, that both NO and HSP90 have been implicated in regulating metamorphosis in marine invertebrates as diverse as urochordates, echinoderms, molluscs, annelids, and crustaceans. Specifically, the suppression of NOS activity by the application of either NOS- or HSP90-inhibiting pharmacological agents has been shown consistently to induce the initiation of metamorphosis, leading to the hypothesis that a negative regulatory role of NO is widely conserved in biphasic life cycles. Further, the induction of metamorphosis by heat-shock has been demonstrated for multiple species. Here, we investigate the regulatory role of NO in induction of metamorphosis of the solitary tropical ascidian, Herdmania momus. By coupling pharmacological treatments with analysis of HmNOS and HmHSP90 gene expression, we present compelling evidence of a positive regulatory role for NO in metamorphosis of this species, in contrast to all existing ascidian data that supports the hypothesis of NO as a conserved negative regulator of metamorphosis. The exposure of competent H. momus larvae to a NOS inhibitor or an NO donor results in an up-regulation of NOS and HSP90 genes. Heat shock of competent larvae induces metamorphosis in a temperature dependent manner, up to a thermal tolerance that approaches 35°C. Both larval/post-larval survival and the appearance of abnormal morphologies in H. momus post-larvae reflect the magnitude of up-regulation of the HSP90 gene in response to heat-shock. The demonstrated role of NO as a positive metamorphic regulator in H. momus suggests the existence of inter-specific adaptations of NO regulation in ascidian metamorphosis.
Ueda, Nobuo; Degnan, Sandie M.
Larvae of the marine cheilostomatid bryozoan Bugula neritina (L.) were prevented from settling for 1, 4 and 8?h by mechanical agitation, following which settlement and metamorphosis\\u000a success were examined. Settlement rates were significantly affected by swimming time, which decreased from 100% after 2?h\\u000a to 93.7? 4.3% after 8?h. Similarly, metamorphosis to the feeding ancestrula was significantly impaired following a swimming
E. Hunter; K. Shimizu; N. Fusetani
Fish larval development, not least the spectacular process of flatfish metamorphosis, appears to be under complex endocrine\\u000a control, many aspects of which are still not fully elucidated. In order to obtain data on the functional development of two\\u000a major endocrine glands, the pituitary and the thyroid, during flatfish metamorphosis, histology, immunohistochemistry and\\u000a in situ hybridization techniques were applied on larvae
Ingibjörg Eir Einarsdóttir; Nadia Silva; Deborah M. Power; Heiddis Smáradóttir; Björn Thrandur Björnsson
Larval sea lampreys Petromyzon marinus in seven lampricide-treated streams were studied to assess the effects of density and abiotic factors on growth, length at metamorphosis, and age at metamorphosis. Support for density-dependent growth was not found in these streams. A linear relationship between total length and age was found for all populations. The daily growth of larvae in lampricide-treated streams
Ronald W. Griffiths; F. W. H. Beamish; B. J. Morrison; L. A. Barker
Recent experiments suggest that timing of metamorphosis is fixed during development in some anurans, insects, and freshwater\\u000a invertebrates. Yet, these experiments do not exclude a growth rate optimization model for the timing of metamorphosis. I manipulated\\u000a food resources available to larvae of squirrel treefrogs (Hyla squirella) to determine if there is a loss of plasticity in duration of larval period
Christopher W. Beck
Mechanisms by which attainment of specific body sizes trigger developmental transitions to adulthood (e.g. puberty or metamorphosis) are incompletely understood. In Drosophila, metamorphosis is triggered by ecdysone synthesis from the prothoracic gland (PG), whereas growth rate is increased by insulin/insulin growth factor signalling (IIS). Transgene-induced activation of PI3K, the major effector of IIS, within the PG advances the onset of metamorphosis via precocious ecdysone synthesis, raising the possibility that IIS triggers metamorphosis via PI3K activation in the PG. Here we show that blocking the protein kinase A (PKA) pathway in the insulin producing cells (IPCs) increases IIS. This increased IIS increases larval growth rate and also advances the onset of metamorphosis, which is accompanied by precocious ecdysone synthesis and increased transcription of at least one ecdysone biosynthetic gene. Our observations suggest that IIS is regulated by PKA pathway activity in the IPCs. In addition, taken together with previous findings, our observations are consistent with the possibility that, in Drosophila, attainment of a specific body size triggers metamorphosis via the IIS–mediated activation of PI3K and hence ecdysone synthesis in the PG.
Walkiewicz, Magdalena A.; Stern, Michael
This peer-reviewed article from BioScience journal is about the effects of UV radiation on amphibian population. The hypothesis that increasing ultraviolet-B (UVB) radiation is a causal factor in the decline of amphibian populations has received considerable attention in the scientific and public media. To evaluate the validity of this hypothesis, it is necessary to examine the natural environmental factors and biological traits of amphibians that protect them from UVB radiation. A careful reading of the literature reveals that most published studies on the effects of ambient UVB radiation on amphibian embryos have found no increased mortality. Those few reports that show harmful effects employ experimental methods that do not place enough importance on the natural abiotic and biotic factors that provide UVB protection. In the laboratory, amphibian embryos are resistant to doses of UVB radiation far higher than those they would normally receive from ambient sunlight. The jelly surrounding amphibian eggs absorbs UVB radiation, as revealed by spectral measurements of absorbance; after UVB exposure, embryos with their jelly capsules removed show significantly higher mortality than those with the jelly intact. In light of this and other factors mitigating UVB absorption, the hypothesis that ambient UVB radiation causes amphibian mortality and population declines is without support.
LAWRENCE E. LICHT (;)
The potential for nitrate to affect amphibian survival was evaluated by examining the areas in North America where concentrations of nitrate in water occur above amphibian toxicity thresholds. Nitrogen pollution from anthropogenic sources enters bodies of water through agricultural runoff or percolation associated with nitrogen fertilization, livestock, precipitation, and effluents from industrial and human wastes. Environmental concentrations of nitrate in watersheds throughout North America range from < 1 to > 100 mg/L. Of the 8,545 water quality samples collected from states and provinces bordering the Great Lakes, 19.8% contained nitrate concentrations exceeding those which can cause sublethal effects in amphibians. In the laboratory lethal and sublethal effects in amphibians are detected at nitrate concentrations between 2.5 and 100 mg/L. Furthermore, amphibian prey such as insects and predators of amphibians such as fish are also sensitive to these elevated levels of nitrate. From this we conclude that nitrate concentrations in some watersheds in North America are high enough to cause death and developmental anomalies in amphibians and impact other animals in aquatic ecosystems. In some situations, the use of vegetated buffer strips adjacent to water courses can reduce nitrogen contamination of surface waters. Ultimately, there is a need to reduce runoff, sewage effluent discharge, and the use of fertilizers, and to establish and enforce water quality guidelines for nitrate for the protection of aquatic organisms. PMID:10504145
Rouse, J D; Bishop, C A; Struger, J
The potential for nitrate to affect amphibian survival was evaluated by examining the areas in North America where concentrations of nitrate in water occur above amphibian toxicity thresholds. Nitrogen pollution from anthropogenic sources enters bodies of water through agricultural runoff or percolation associated with nitrogen fertilization, livestock, precipitation, and effluents from industrial and human wastes. Environmental concentrations of nitrate in watersheds throughout North America range from < 1 to > 100 mg/L. Of the 8,545 water quality samples collected from states and provinces bordering the Great Lakes, 19.8% contained nitrate concentrations exceeding those which can cause sublethal effects in amphibians. In the laboratory lethal and sublethal effects in amphibians are detected at nitrate concentrations between 2.5 and 100 mg/L. Furthermore, amphibian prey such as insects and predators of amphibians such as fish are also sensitive to these elevated levels of nitrate. From this we conclude that nitrate concentrations in some watersheds in North America are high enough to cause death and developmental anomalies in amphibians and impact other animals in aquatic ecosystems. In some situations, the use of vegetated buffer strips adjacent to water courses can reduce nitrogen contamination of surface waters. Ultimately, there is a need to reduce runoff, sewage effluent discharge, and the use of fertilizers, and to establish and enforce water quality guidelines for nitrate for the protection of aquatic organisms. Images Figure 1 Figure 2
Rouse, J D; Bishop, C A; Struger, J
The role of facilities and associated services for amphibians has recently undergone diversification. Amphibians traditionally used as research models adjust well to captivity and thrive with established husbandry techniques. However, it is now necessary to maintain hundreds of novel amphibian species in captive breeding, conservation research, and biomedical research programs. These diverse species have a very wide range of husbandry requirements, and in many cases the ultimate survival of threatened species will depend on captive populations. Two critical factors have emerged in the maintenance of amphibians, stringent quarantine and high-quality water. Because exotic diseases such as chytridiomycosis have devastated both natural and captive populations of amphibians, facilities must provide stringent quarantine. The provision of high-quality water is also essential to maintain amphibian health and condition due to the intimate physiological relationship of amphibians to their aquatic environment. Fortunately, novel technologies backed by recent advances in the scientific knowledge of amphibian biology and disease management are available to overcome these challenges. For example, automation can increase the reliability of quarantine and maintain water quality, with a corresponding decrease in handling and the associated disease-transfer risk. It is essential to build facilities with appropriate nontoxic waterproof materials and to provide quarantined amphibian rooms for each population. Other spaces and services include live feed rooms, quarantine stations, isolation rooms, laboratory space, technical support systems, reliable energy and water supplies, high-quality feed, and security. Good husbandry techniques must include reliable and species-specific management by trained staff members who receive support from the administration. It is possible to improve husbandry techniques for many species by sharing knowledge through common information systems. Overall, good facility design corresponds to the efficient use of space, personnel, energy, materials, and other resources. PMID:17592183
Browne, Robert K; Odum, R Andrew; Herman, Timothy; Zippel, Kevin
This study examined the gross morphology and ultrastructure of the olfactory organ of larvae, neotenic adults, and terrestrial adults of the Coastal Giant Salamander (Dicamptodon tenebrosus). The olfactory organ of all aquatic animals (larvae and neotenes) is similar in structure, forming a tube extending from the external naris to the choana. A nonsensory vestibule leads into the main olfactory cavity. The epithelium of the main olfactory cavity is thrown into a series of transverse valleys and ridges, with at least six dorsal and nine ventral valleys lined with olfactory epithelium, and separated by ridges of respiratory epithelium. The ridges enlarge with growth, forming large flaps extending into the lumen in neotenes. The vomeronasal organ is a diverticulum off the ventrolateral side of the main olfactory cavity. In terrestrial animals, by contrast, the vestibule has been lost. The main olfactory cavity has become much broader and dorsoventrally compressed. The prominent transverse ridges are lost, although small diagonal ridges of respiratory epithelium are found in the lateral region of the ventral olfactory epithelium. The posterior and posteromedial wall of the main olfactory cavity is composed of respiratory epithelium, in contrast to the olfactory epithelium found here in aquatic forms. The vomeronasal organ remains similar to that in large larvae, but is now connected to the mouth by a groove that extends back through the choana onto the palate. Bowman's glands are present in the main olfactory cavity at all stages, but are most abundant and best developed in terrestrial adults. They are lacking in the lateral olfactory epithelium of the main olfactory cavity. At the ultrastructural level, in aquatic animals receptor cells of the main olfactory cavity can have cilia, short microvilli, a mix of the two, or long microvilli. Supporting cells are of two types: secretory supporting cells with small, electron-dense secretory granules, and ciliated supporting cells. Receptor cells of the vomeronasal organ are exclusively microvillar, but supporting cells are secretory or ciliated, as in the main olfactory cavity. After metamorphosis two distinct types of sensory epithelium occur in the main olfactory cavity. The predominant epithelium, covering most of the roof and the medial part of the floor, is characterized by supporting cells with large, electron-lucent vesicles. The epithelium on the lateral floor of the main olfactory cavity, by contrast, resembles that of aquatic animals. Both types have both microvillar and ciliated receptor cells. No important changes are noted in cell types of the vomeronasal organ after metamorphosis. A literature survey suggests that some features of the metamorphic changes described here are characteristic of all salamanders, while others appear unique to D. tenebrosus. PMID:16121394
Stuelpnagel, Jeremy T; Reiss, John O
Sound source perception refers to the auditory system’s ability to parse incoming sensory information into coherent representations of distinct sound sources in the environment. Such abilities are no doubt key to successful communication in many taxa, but we know little about their function in animal communication systems. For anuran amphibians (frogs and toads), social and reproductive behaviors depend on a listener’s ability to hear and identify sound signals amid high levels of background noise in acoustically cluttered environments. Recent neuroethological studies are revealing how frogs parse these complex acoustic scenes to identify individual calls in noisy breeding choruses. Current evidence highlights some interesting similarities and differences in how the auditory systems of frogs and other vertebrates (most notably birds and mammals) perform auditory scene analysis.
Bee, Mark A
The exchange of isotopic water, 2H2O and H2(18)O has been studied in amphibian eggs. The experiments were carried out with ovarian and body cavity eggs of Rana temporaria and unfertilized eggs of Ambystoma mexicanum. The cytoplasmic diffusion coefficient for H2(18)O was found to be 4.6 x 10(-6) cm2/s, somewhat higher than that for 2H2O, 3.4 x 10(-6) cm2/s. The total change in reduced weight, delta RW, during the isotope experiments was compared with the total amount of water in the egg cell, m. The ratio delta RW/m was significantly higher than would be expected from calculations using ordinary water density values. The results are discussed in terms of different phases of structured cell water. PMID:317089
Mild, K H; Løvtrup, S; Forslind, E
Taxonomic, distributional, and ecological information on the reptiles and amphibians of the Savannah River Plant (SRP) is provided. The purpose of such a presentation is to give a professional biologist an initial familiarity with herpetology on the SRP, ...
J. W. Gibbons K. K. Patterson
Summary Amphibian epithelia have been used as models for studying the effects of psychotropic drugs on membrane transport. Several of these agents added to the internal or to the external media, at concentrations greater than 10?3
A. Grosso; R. C. Sousa
There has been a great deal of recent attention on the suspected increase in amphibian deformities. However, most reports of amphibian deformities have been anecdotal, and no experiments in the field under natural conditions have been performed to investigate this phenomenon. Under laboratory conditions, a variety of agents can induce deformities in amphibians. We investigated one of these agents, UV-B radiation, in field experiments, as a cause for amphibian deformities. We monitored hatching success and development in long-toed salamanders under UV-B shields and in regimes that allowed UV-B radiation. Embryos under UV-B shields had a significantly higher hatching rate and fewer deformities, and developed more quickly than those exposed to UV-B. Deformities may contribute directly to embryo mortality, and they may affect an individual's subsequent survival after hatching.
Blaustein, A. R.; Kiesecker, J. M.; Chivers, D. P.; Anthony, R. G.
During frog metamorphosis, the vestibular sensory system remains unchanged, while spinal motor networks undergo a massive restructuring associated with the transition from the larval to adult biomechanical system. We investigated in Xenopus laevis the impact of a pre- (tadpole stage) or post-metamorphosis (juvenile stage) unilateral labyrinthectomy (UL) on young adult swimming performance and underlying spinal locomotor circuitry. The acute disruptive effects on locomotion were similar in both tadpoles and juvenile frogs. However, animals that had metamorphosed with a preceding UL expressed restored swimming behavior at the juvenile stage, whereas animals lesioned after metamorphosis never recovered. Whilst kinematic and electrophysiological analyses of the propulsive system showed no significant differences in either juvenile group, a 3D biomechanical simulation suggested that an asymmetry in the dynamic control of posture during swimming could account for the behavioral restoration observed in animals that had been labyrinthectomized before metamorphosis. This hypothesis was subsequently supported by in vivo electromyography during free swimming and in vitro recordings from isolated brainstem/spinal cord preparations. Specifically, animals lesioned prior to metamorphosis at the larval stage exhibited an asymmetrical propulsion/posture coupling as a post-metamorphic young adult. This developmental alteration was accompanied by an ipsilesional decrease in propriospinal coordination that is normally established in strict left-right symmetry during metamorphosis in order to synchronize dorsal trunk muscle contractions with bilateral hindlimb extensions in the swimming adult. Our data thus suggest that a disequilibrium in descending vestibulospinal information during Xenopus metamorphosis leads to an altered assembly of adult spinal locomotor circuitry. This in turn enables an adaptive compensation for the dynamic postural asymmetry induced by the vestibular imbalance and the restoration of functionally-effective behavior.
Beyeler, Anna; Rao, Guillaume; Ladepeche, Laurent; Jacques, Andre; Simmers, John; Le Ray, Didier
The rarity of spontaneous cancer in amphibians, and the difficulty of inducing cancer in these lower vertebrates, suggest that they possess an effective system for resistance to the development of cancer. The first part of this narrative presents evidence for cancer resistance in amphibians, and then a variety of studies designed to help understand the physiological basis for this resistance are reviewed. Here, our emphasis is on evidence with regard to the role that apoptosis might play. PMID:23971703
Ruben, Laurens N; Johnson, Rachel O; Clothier, Richard H; Balls, Michael
Landscape-level variables operating at multiple spatial scales likely influence wetland amphibian assemblages but have not\\u000a been investigated in detail. We examined the significance of habitat loss and fragmentation, as well as selected within-wetland\\u000a conditions, affecting amphibian assemblages in twenty-one glacial marshes. Wetlands were located within urban and agricultural\\u000a regions of central and southwestern Minnesota, USA and were distributed across two
Richard M. Lehtinen; Susan M. Galatowitsch; John R. Tester
We studied the pattern of amphibian distributions within 19 wetlands of the Puget Sound Basin in King County, Washington State\\u000a from 1988 through 1991. Amphibian richness was compared to wetland size, vegetation classes, presence of bullfrog and fish\\u000a predators, hydrologic characteristics of water flow, fluctuation, and permanence, and land use. Low velocity flow and low\\u000a fluctuation were correlated with high
Klaus O. Richter; Amanda L. Azous
The processes that lead to the formation of Planetary Nebula (PN), through the short intermediate stage of pre-PN, are complex and poorly known. The biggest challenge in the study of PN formation is understanding the origin of the remarkable morphological and kinematical differences between the circumstellar envelopes (CSEs) around Asymptotic Giant Branch (AGB) stars, which result from the star mass-loss process during the AGB, and their more evolved counterparts, PPNe and PNe. While AGB CSEs expand isotropically at low velocity (about 5-15 km/s), most PPNe and PNe have clear departures from sphericity and show fast (>100 km/s) bipolar or multipolar outflows. This spectacular metamorphosis is believed to be governed by the interaction between fast, collimated post-AGB winds (or jets), and the slow AGB CSE. In this presentation, I will review these late stages of the evolution of solar type stars and will describe some common observational techniques used to characterize the different nebular components in these objects.
Sanchez Contreras, C.
Habitat loss and disease are main drivers of global amphibian declines, yet the interaction between them remains largely unexplored. Here we show that paradoxically, habitat loss is negatively associated with occurrence, prevalence, and infection intensity of the chytrid fungus Batrachochytrium dendrobatidis (Bd) in amphibian populations in the tropics. At a large spatial scale, increased habitat loss predicted lower disease risk in amphibian populations across Costa Rica and eastern Australia, even after jointly considering the effect of potential biotic and abiotic correlates. Lower host-species richness and suboptimal microclimates for Bd in disturbed habitats are potential mechanisms underlying this pattern. Furthermore, we found that anthropogenic deforestation practices biased to lowlands and natural vegetation remaining in inaccessible highlands explain increased Bd occurrence at higher elevations. At a smaller spatial scale, holding constant elevation, latitude, and macroclimate, we also found a negative relationship between habitat loss, and both Bd prevalence and infection intensity in frog populations in two landscapes of the Brazilian Atlantic Forest. Our results indicate that amphibians will be disproportionately affected by emerging diseases in pristine environments, and that, paradoxically, disturbed habitats may act as shelters from disease, but only for the very few species that can tolerate deforestation. Thus, tropical amphibian faunas are threatened both by destruction of natural habitats as well as increased disease in pristine forests. To curb further extinctions and develop effective mitigation and restoration programs we must look to interactions between habitat loss and disease, the two main factors at the root of global amphibian declines. PMID:21628560
Becker, C Guilherme; Zamudio, Kelly R
Installation and maintenance of stormwater ponds to detain and treat runoff from impervious surfaces is a common method of stormwater control in developed areas. That these ponds capture pollutants, however, is of concern for wildlife species that use the ponds, particularly pond-breeding amphibians. To assess the relative contribution of stormwater ponds to the persistence of amphibian populations in suburban landscapes, we compared amphibian use of stormwater ponds and other available wetlands in suburban and forested watersheds. We surveyed three suburban and three primarily forested first-order watersheds to identify all potential wetlands that might serve as breeding sites for pond-breeding amphibians. We performed call, egg-mass, and larval surveys to measure breeding effort at each wetland in spring and summer 2007 and 2008. In suburban watersheds most (89%) of the wetlands that had breeding activity were either stormwater ponds or otherwise artificial. This pattern was also evident in the forested watersheds, where amphibians were primarily found breeding in wetlands created by past human activity. Late-stage larvae were found only in anthropogenic wetlands in all study areas because the remaining natural wetlands did not hold water long enough for larvae to complete development. Our results suggest that in urban and suburban landscapes with naturally low densities of wetlands, wetlands created by current or historic land uses may be as important to amphibian conservation as natural wetlands or pools and that management strategies directed at urban and suburban landscapes should recognize and incorporate human-created wetlands. PMID:19681986
Brand, Adrianne B; Snodgrass, Joel W
Over recent decades, amphibians have experienced population declines, extirpations and species-level extinctions at an alarming rate. Numerous potential etiologies for amphibian declines have been postulated including climate and habitat degradation. Other potential anthropogenic causes including overexploitation and the frequent introductions of invasive predatory species have also been blamed for amphibian declines. Still other underlying factors may include infectious diseases caused by the chytrid fungus Batrachochytrium dendrobatidis, pathogenic viruses (Ranavirus), and other agents. It is nearly certain that more than one etiology is to blame for the majority of the global amphibian declines, and that these causal factors include some combination of climatological or physical habitat destabilization and infectious disease, most notably chytridiomycosis. Scientific research efforts are aimed at elucidating these etiologies on local, regional, and global scales that we might better understand and counteract the driving forces behind amphibian declines. Conservation efforts as outlined in the Amphibian Conservation Action Plan of 2005 are also being made to curtail losses and prevent further extinctions wherever possible.
Densmore, Christine L.
It has long been known that metamorphosis of ascidian larvae is induced by exposure to adult tunic extract or larval-conditioned seawater. However, such a natural 'inducer' has not been identified, probably due to its very low concentration in organisms. Here we have succeeded in isolating the same metamorphosis-inducing substance from the larvae, the larval-conditioned seawater, and the adult tunic of the ascidian Halocynthia roretzi. Structural analysis revealed that this substance was identical to lumichrome. Lumichrome was active toward H. roretzi larvae, but inactive toward another ascidian larvae, suggesting that lumichrome is species-specific. Riboflavin (vitamin B2), from which lumichrome might be derived from, was found to be inactive in induction of larval metamorphosis. In addition, it was demonstrated that lumichrome is localized predominantly in the basal region of the adhesive organ and the posterior part of the larval trunk. Thus, we propose that lumichrome functions as a natural inducer for larval metamorphosis in H. roretzi. This is the first natural metamorphosis-inducing substance to be identified in ascidians. PMID:10491124
Tsukamoto, S; Kato, H; Hirota, H; Fusetani, N
Coral larvae appear to sense appropriate environments for settlement and start metamorphosis by converting external cues into internal signals, although little is known about these molecular mechanisms. A family of neuropeptides, GLWamides, are thought to be such internal signals, acting hormonally to induce metamorphosis in some hydrozoan species. Here we report that one member of the GLWamide peptide family, Hym-248,
K. Iwao; T. Fujisawa; M. Hatta
Accurate forecasts of the number of larval sea lamprey (Petromyzon marinus) within a stream that will enter into metamorphosis are critical to currently used methods for allocating lampricide treatments among streams in the Great Lakes basin. To improve our ability to predict metamorphosis we used a mark-recapture technique, involving the marking of individual larval lamprey with sequentially coded wire tags,
Andrew J. Treble; Michael L. Jones; Todd B. Steeves
Serotonin-immunoreactive neurons in the brain of Tenebrio molitor L. have been demonstrated and mapped throughout metamorphosis. Most serotonin-immunoreactive brain neurons persist throughout metamorphosis; their fate can be followed during development because of their characteristic cell body locations and arborization patterns. The detailed morphology of the persisting neurons, however, changes during metamorphosis, probably to accommodate architectural changes of the different brain
Developmental plasticity is increasingly recognized as important for ecological and evolutionary processes. However, few studies consider the potential for delayed effects of early environments. Here, we show that tadpoles hatching from clutches exposed to water mold (Saprolegnia) have 20% decreased mass at metamorphosis, despite no further exposure subsequent to hatching. The effects were consistent across four populations that have previously been shown to vary in their resistance to infection during embryonic development. Contrary to expectations, time to hatching or metamorphosis was not affected, suggesting that the results do not reflect an evolved escape strategy from infected waters triggered by embryonic conditions. Instead, decreased mass at metamorphosis may arise from carry-over effects of impaired embryo development. Such strong links across developmental stages have potential consequences for the evolution of plasticity and the responses of populations to emergent infections. PMID:19189128
Uller, Tobias; Sagvik, Jörgen; Olsson, Mats
Human-induced habitat loss and degradation are major threats to wetland species as reflected in the fact that wetlands have declined by more than 50% in Europe and North America during the last century. Both current and historic land-use patterns are likely to be significant determinants of wetland species' distributions; however their relative importance is often unknown. We studied the importance of local (study pond) and landscape (current and 18th-century landscape) characteristics in explaining the occurrence and species richness of amphibians (Rana arvalis, Bufo bufo, and Triturus vulgaris) on the Swedish island of Gotland, where more than 40% of wetlands have been lost since the 18th century. Current local habitat characteristics were the strongest determinants of occurrence for all study species. Additionally, species occurrence was related to current and historic landscape characteristics, which generally explained equal amounts of the variation in species-occurrence data. The proportions of both current and historic arable land were negative determinants of amphibian occurrence and species richness, indicating that agricultural land use may have an overall negative impact on amphibians, and that amphibians may occur less frequently in areas with a long agricultural history. Likewise, historic forest area was positively related to B. bufo occurrence and species richness, whereas current forests had no significant effects, suggesting that there may be a lag in the response of amphibians to agriculture-mediated habitat loss. Our results suggest that historic land-use patterns may influence current amphibian populations and that inclusion of historic land-use information could be a valuable tool in future studies on amphibian-habitat relations. PMID:18213970
Piha, Henna; Luoto, Miska; Merilä, Juha
Amphibians globally are in decline, yet there is still a tremendous amount of unrecognized diversity, calling for an acceleration of taxonomic exploration. This process will be greatly facilitated by a DNA barcoding system; however, the mitochondrial population structure of many amphibian species presents numerous challenges to such a standardized, single locus, approach. Here we analyse intra- and interspecific patterns of mitochondrial variation in two distantly related groups of amphibians, mantellid frogs and salamanders, to determine the promise of DNA barcoding with cytochrome oxidase subunit I (cox1) sequences in this taxon. High intraspecific cox1 divergences of 7–14% were observed (18% in one case) within the whole set of amphibian sequences analysed. These high values are not caused by particularly high substitution rates of this gene but by generally deep mitochondrial divergences within and among amphibian species. Despite these high divergences, cox1 sequences were able to correctly identify species including disparate geographic variants. The main problems with cox1 barcoding of amphibians are (i) the high variability of priming sites that hinder the application of universal primers to all species and (ii) the observed distinct overlap of intraspecific and interspecific divergence values, which implies difficulties in the definition of threshold values to identify candidate species. Common discordances between geographical signatures of mitochondrial and nuclear markers in amphibians indicate that a single-locus approach can be problematic when high accuracy of DNA barcoding is required. We suggest that a number of mitochondrial and nuclear genes may be used as DNA barcoding markers to complement cox1.
Vences, Miguel; Thomas, Meike; Bonett, Ronald M; Vieites, David R
Mammalian Nrf2-Keap1 and the homologous Drosophila CncC-dKeap1 protein complexes regulate both transcriptional responses to xenobiotic compounds as well as native cellular and developmental processes. The relationships between the functions of these proteins in xenobiotic responses and in development were unknown. We investigated the genes regulated by CncC and dKeap1 during development and the signal transduction pathways that modulate their functions. CncC and dKeap1 were enriched within the nuclei in many tissues, in contrast to the reported cytoplasmic localization of Keap1 and Nrf2 in cultured mammalian cells. CncC and dKeap1 occupied ecdysone-regulated early puffs on polytene chromosomes. Depletion of either CncC or dKeap1 in salivary glands selectively reduced early puff gene transcription. CncC and dKeap1 depletion in the prothoracic gland as well as cncCK6/K6 and dKeap1EY5/EY5 loss of function mutations in embryos reduced ecdysone-biosynthetic gene transcription. In contrast, dKeap1 depletion and the dKeap1EY5/EY5 loss of function mutation enhanced xenobiotic response gene transcription in larvae and embryos, respectively. Depletion of CncC or dKeap1 in the prothoracic gland delayed pupation by decreasing larval ecdysteroid levels. CncC depletion suppressed the premature pupation and developmental arrest caused by constitutive Ras signaling in the prothoracic gland; conversely, constitutive Ras signaling altered the loci occupied by CncC on polytene chromosomes and activated transcription of genes at these loci. The effects of CncC and dKeap1 on both ecdysone-biosynthetic and ecdysone-regulated gene transcription, and the roles of CncC in Ras signaling in the prothoracic gland, establish the functions of these proteins in the neuroendocrine axis that coordinates insect metamorphosis.
Deng, Huai; Kerppola, Tom K.
The role of the pineal complex in lamprey metamorphosis was investigated by examining the influence of pinealectomy and continuous light and darkness on the initiation of this event in anadromous sea lampreys, Petromyzon marinus L. Larval lampreys, which on the basis of a condition factor were considered likely to enter metamorphosis in July, were separated in May of 1979 and 1980 into the following groups: (1) intact controls, (2) sham-operated controls, (3) pinealectomized individuals, (4) those exposed to continuous light, and (5) those exposed to continuous light or dark. The importance of the pineal complex to metamorphosis was supported by morphological evidence that, in all presumably pinealectomized individuals that entered metamorphosis, the complex had apparently not been removed during the surgical procedure. The ways in which the pineal complex may be involved in lamprey metamorphosis are discussed.
Cole, W.C.; Youson, J.H.
Insect molting and metamorphosis are intricately governed by two hormones, ecdysteroids and juvenile hormones (JHs). JHs prevent precocious metamorphosis and allow the larva to undergo multiple rounds of molting until it attains the proper size for metamorphosis. In the silkworm, Bombyx mori, several “moltinism” mutations have been identified that exhibit variations in the number of larval molts; however, none of them have been characterized molecularly. Here we report the identification and characterization of the gene responsible for the dimolting (mod) mutant that undergoes precocious metamorphosis with fewer larval–larval molts. We show that the mod mutation results in complete loss of JHs in the larval hemolymph and that the mutant phenotype can be rescued by topical application of a JH analog. We performed positional cloning of mod and found a null mutation in the cytochrome P450 gene CYP15C1 in the mod allele. We also demonstrated that CYP15C1 is specifically expressed in the corpus allatum, an endocrine organ that synthesizes and secretes JHs. Furthermore, a biochemical experiment showed that CYP15C1 epoxidizes farnesoic acid to JH acid in a highly stereospecific manner. Precocious metamorphosis of mod larvae was rescued when the wild-type allele of CYP15C1 was expressed in transgenic mod larvae using the GAL4/UAS system. Our data therefore reveal that CYP15C1 is the gene responsible for the mod mutation and is essential for JH biosynthesis. Remarkably, precocious larval–pupal transition in mod larvae does not occur in the first or second instar, suggesting that authentic epoxidized JHs are not essential in very young larvae of B. mori. Our identification of a JH–deficient mutant in this model insect will lead to a greater understanding of the molecular basis of the hormonal control of development and metamorphosis.
Daimon, Takaaki; Kozaki, Toshinori; Niwa, Ryusuke; Kobayashi, Isao; Furuta, Kenjiro; Namiki, Toshiki; Uchino, Keiro; Banno, Yutaka; Katsuma, Susumu; Tamura, Toshiki; Mita, Kazuei; Sezutsu, Hideki; Nakayama, Masayoshi; Itoyama, Kyo; Shimada, Toru; Shinoda, Tetsuro
Background Drosophila melanogaster undergoes a complete metamorphosis, during which time the larval male and female forms transition into sexually dimorphic, reproductive adult forms. To understand this complex morphogenetic process at a molecular-genetic level, whole genome microarray analyses were performed. Results The temporal gene expression patterns during metamorphosis were determined for all predicted genes, in both somatic and germline tissues of males and females separately. Temporal changes in transcript abundance for genes of known functions were found to correlate with known developmental processes that occur during metamorphosis. We find that large numbers of genes are sex-differentially expressed in both male and female germline tissues, and relatively few are sex-differentially expressed in somatic tissues. The majority of genes with somatic, sex-differential expression were found to be expressed in a stage-specific manner, suggesting that they mediate discrete developmental events. The Sex-lethal paralog, CG3056, displays somatic, male-biased expression at several time points in metamorphosis. Gene expression downstream of the somatic, sex determination genes transformer and doublesex (dsx) was examined in two-day old pupae, which allowed for the identification of genes regulated as a consequence of the sex determination hierarchy. These include the homeotic gene abdominal A, which is more highly expressed in females as compared to males, as a consequence of dsx. For most genes regulated downstream of dsx during pupal development, the mode of regulation is distinct from that observed for the well-studied direct targets of DSX, Yolk protein 1 and 2. Conclusion The data and analyses presented here provide a comprehensive assessment of gene expression during metamorphosis in each sex, in both somatic and germline tissues. Many of the genes that underlie critical developmental processes during metamorphosis, including sex-specific processes, have been identified. These results provide a framework for further functional studies on the regulation of sex-specific development.
Lebo, Matthew S; Sanders, Laura E; Sun, Fengzhu; Arbeitman, Michelle N
Toads (Rhinella arenarum) received training with a novel incentive procedure involving access to solutions of different NaCl concentrations. In Experiment 1, instrumental behavior and weight variation data confirmed that such solutions yield incentive values ranging from appetitive (deionized water, DW, leading to weight gain), to neutral (300 mM slightly hypertonic solution, leading to no net weight gain or loss), and aversive (800 mM highly hypertonic solution leading to weight loss). In Experiment 2, a downshift from DW to a 300 mM solution or an upshift from a 300 mM solution to DW led to a gradual adjustment in instrumental behavior. In Experiment 3, extinction was similar after acquisition with access to only DW or with a random mixture of DW and 300 mM. In Experiment 4, a downshift from DW to 225, 212, or 200 mM solutions led again to gradual adjustments. These findings add to a growing body of comparative evidence suggesting that amphibians adjust to incentive shifts on the basis of habit formation and reorganization.
Muzio, Ruben N.; Pistone Creydt, Virginia; Iurman, Mariana; Rinaldi, Mauro A.; Sirani, Bruno; Papini, Mauricio R.
1. A culture medium has been developed for amphibian sympathetic nervous tissue but it is suggested that the ionic values should be adjusted to correspond to the concentrations of salts in the plasma of particular species. 2. The morphology, monoamine fluorescence, growth and differentiation of sympathetic ganglia of the frog, Limnodynastes dumerili, have been studied in culture. 3. Two types of neuron could be distinguished largely according to size, namely small, 18 X 20 mum and large, 38 X 42 mum. The possibility that these represent one type at different stages in development or represent functionally distinct neurons is discussed. 4. The sympathetic neurons are extremely sensitive to nerve growth factor (NGF) which caused an increase in the size of the cell bodies, the number of nerve fibres regenerating, the rate of axonal growth and synthesis of catecholamines. 5. Various other cell types appearing in the cultures have been described, including chromaffin, satellite, Schwann, multipolar and epithelial cells as well as fibroblasts, melanocytes and macrophages. The epithelial cells show slow contractions and changes in shape. PMID:171072
Hill, C E; Burnstock, G
Global declines of amphibians are well documented, yet effects of these dramatic losses on ecosystem structure and function are poorly understood. As part of a larger collaborative project, we compared two upland Panamanian streams. Both streams are biologically and geologically similar; however, one stream (Fortuna) has recently experienced almost complete extirpation of stream-dwelling frogs, while the other (Cope) still has intact populations. We experimentally excluded tadpoles from localized areas in each stream. We then compared chlorophyll a, algal community composition, ash-free dry mass (AFDM), inorganic matter, and insect assemblages in control and exclusion areas. Additionally, we sampled the natural substrate of both streams monthly for chlorophyll a, algal community composition, AFDM, and inorganic matter. At Cope, chlorophyll a, AFDM, and inorganic matter were greater in areas where tadpoles were excluded than in their presence. Numbers of dominant algal species (e.g., Nupela praecipua and Eunotia siolii) were greater in the exclusion versus control treatments. Monthly sampling of natural substrate indicated higher chlorophyll a and AFDM at Cope compared to Fortuna. Our data suggest that stream-dwelling anuran larvae have significant impacts on algal communities. These results also have implications for predicting the relevance of short-term experimental manipulations to long-term, whole-stream processes.
Connelly, S.; Pringle, C. M.; Bixby, R. J.; Whiles, M. R.; Lips, K. R.; Brenes, R.; Colon-Gaud, J. C.; Kilham, S.; Hunte-Brown, M.
Conspecific foot mucus, excessive [K+] and gamma-aminobutyric acid (GABA) showed different metamorphosis-inductive effect on the veliger of Haliotis discus hannai. The inductive effect of excessive [K+] and GABA was developmental stage-dependent and dose-dependent, while that of conspecific foot mucus was only developmental stage-dependent. At 20°C the veliger larvae became competent within 4 days after fertilization. H. discus hannai larvae showed gregarious settlement pattern on the conspecific foot mucus under the conditions of either presence or absence of KCl or GABA. The present studies showed that the effect of conspecific foot mucus on abalone larvae metamorphosis could be dose-independent.
Yang, Yu; Wu, Bao-Ling
Background The metamorphosis of Drosophila melanogaster is accompanied by elimination of obsolete neurons via programmed cell death (PCD). Metamorphosis is regulated by ecdysteroids,\\u000a including 20-hydroxyecdysone (20E), but the roles and modes of action of hormones in regulating neuronal PCD are incompletely\\u000a understood.\\u000a \\u000a \\u000a \\u000a \\u000a Results We used targeted expression of GFP to track the fate of a larval motoneuron, RP2, in ventral ganglia. RP2s
Settlement and metamorphosis of pediveliger larvae of Mytilus coruscus in response to natural biofilms was investigated in the laboratory. Pediveliger larvae settled and metamorphosed in response to biofilms and post-larval settlement and metamorphosis increased with biofilm age. The activity of the biofilm was positively correlated with biofilm age, dry weight, bacterial density and diatom density, but had no apparent relationship with chlorophyll a concentration. The change in bacterial community composition corresponding to biofilm age may explain differences in the age-dependent inducing activities of biofilms, which in turn may play an important role in larval settlement in this species. PMID:22435742
Wang, Chong; Bao, Wei-Yang; Gu, Zhong-Qi; Li, Yi-Feng; Liang, Xiao; Ling, Yun; Cai, Sheng-Li; Shen, He-Ding; Yang, Jin-Long
Background/Question/Methods Dermal exposure presents a potentially significant but understudied route for pesticide uptake in terrestrial amphibians. Historically, evaluation of pesticide risk to both amphibians and reptiles has been achieved by comparing ingestion and inhalat...
...false Hull type rotorcraft: Water-based and amphibian. 29...AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Strength Requirements Water Loads Â§ 29.519 Hull type rotorcraft: Water-based and amphibian....
...false Hull type rotorcraft: Water-based and amphibian. 29...AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Strength Requirements Water Loads Â§ 29.519 Hull type rotorcraft: Water-based and amphibian....
The primary goal of this project was to determine the distribution, abundance and habitat associations of the amphibian and reptile species on Craig Mountain (CM), Idaho. This study is important because little was known about the amphibian and reptile spe...
R. L. Llewellyn C. R. Peterson
Amphibian declines have been documented worldwide; however the vast majority are species associated with aquatic habitats. Information on the status and trends of terrestrial amphibians is almost entirely lacking. Here we use data collected across a 12-yr period (sampling from 1984-86 and from 1993-95) to address the question of whether evidence exists for declines among terrestrial amphibians in northwestern California forests. The majority of amphibians, both species and relative numbers, in these forests are direct-developing salamanders of the family Plethodontidae. We examined amphibian richness and evenness, and the relative abundances of the four most common species of plethodontid salamanders. We examined evidence of differences between years in two ecological provinces (coastal and interior) and across young, mature, and late seral forests and with reference to a moisture gradient from xeric to hydric within late seral forests. We found evidence of declines in species richness across years on late seral mesic stands and in the coastal ecological province, but these differences appeared to be caused by differences in the detection of rarer species, rather than evidence of an overall pattern. We also found differences among specific years in numbers of individuals of the most abundant species, Ensatina eschscholtzii, but these differences also failed to reflect a consistent pattern of declines between the two decadal sample periods. Results showing differences in richness, evenness, and relative abundances along both the seral and moisture continua were consistent with previous research. Overall, we found no compelling evidence of a downward trend in terrestrial plethodontid salamanders. We believe that continued monitoring of terrestrial salamander populations is important to understanding mechanisms of population declines in amphibian species. Copyright 2007 Society for the Study of Amphibians and Reptiles.
Welsh, Jr. , H. H.; Fellers, G. M.; Lind, A. J.
CONCLUSIONS--Although there are no published studies that demonstrate beyond all doubt that contaminants are involved in long term population declines of amphibians, there is ample evidence and reason to encourage active research and concern about effects. Many contaminants are lethal to amphibians at environmentally realistic concentrations. Acute mortality from these compounds may be difficult to detect because investigators would have to be present shortly after exposures. Chronic mortality may be masked by metapopulation phenomena so that areas that serve as population sinks may be repeatedly recolonized and difficult to identify. Metapopulation dynamics also make it more difficult to define discrete populations. Contaminants also have many sublethal effects on behavior, energetics, malformations, and diverse effects on physiological pathways which, by themselves might not lead to overt death but could alter reproduction or interact with other factors to result in gradual declines in populations. Scientific understanding of these interactions, and of the ecotoxicology of amphibians in general is far behind what is known about birds, fish, and mammals, and research is desperately needed in this area. Some specific suggestions for critically needed research include: (1) Determination of lethal concentrations of common contaminants - pesticides, PAHs, metals--under environmentally realistic conditions of light, temperature, and water chemistry. (2) Better understanding of the effects of long term (weeks, months), low- concentration exposure of persistent pesticides and stable contaminants on amphibians. (3) Development and refinement of bioindicators in amphibians to use in monitoring and screening for potential effects of contaminants in declining amphibian populations. (4) Further studies on the interaction between contaminants and disease agents including immunosuppression in amphibians. (5) Additional research on the interaction between ultraviolet radiation - both UV-A and UV-B--and a broader range of contaminants. (6) Development of models to assess risk in amphibians as related to landscape factors and especially in the aquatic-terrestrial interface. (7) Population survival requires that organisms survive through their entire life cycle; to date, there have been no studies that have examined the responses of amphibians to contaminants in all phases (egg, embryo, larvae and adult) of their life cycles.
Sparling, D. W.
Establishing the relationships among modern amphibians (lissamphibians) and their ancient relatives is necessary for our understanding of early tetrapod evolution. However, the phylogeny is still intractable because of the highly specialized anatomy and poor fossil record of lissamphibians. Paleobiologists are still not sure whether lissamphibians are monophyletic or polyphyletic, and which ancient group (temnospondyls or lepospondyls) is most closely related to them. In an attempt to address these problems, eight mitochondrial genomes of living amphibians were determined and compared with previously published amphibian sequences. A comprehensive molecular phylogenetic analysis of nucleotide sequences yields a highly resolved tree congruent with the traditional hypotheses (Batrachia). By using a molecular clock-independent approach for inferring dating information from molecular phylogenies, we present here the first molecular timescale for lissamphibian evolution, which suggests that lissamphibians first emerged about 330 million years ago. By observing the fit between molecular and fossil times, we suggest that the temnospondyl-origin hypothesis for lissamphibians is more credible than other hypotheses. Moreover, under this timescale, the potential geographic origins of the main living amphibian groups are discussed: (i) advanced frogs (neobatrachians) may possess an Africa-India origin; (ii) salamanders may have originated in east Asia; (iii) the tropic forest of the Triassic Pangaea may be the place of origin for the ancient caecilians. An accurate phylogeny with divergence times can be also helpful to direct the search for "missing" fossils, and can benefit comparative studies of amphibian evolution. PMID:16012106
Zhang, Peng; Zhou, Hui; Chen, Yue-Qin; Liu, Yi-Fei; Qu, Liang-Hu
We monitored 11 populations of eight species of Eleutherodactylus in Puerto Rico from 1989 through 2001. We determined relative abundance of active frogs along transects established in the Caribbean National Forest (El Yunque), Carite Forest, San Lorenzo, and in the vicinity of San Juan. Three species (Eleutherodactylus karlschmidti, E. jasperi, and E. eneidae) are presumed to be extinct and eight populations of six different species of endemic Eleutherodactylus are significantly declining at elevations above 400 m. Of the many suspected causes of amphibian declines around the world, we focused on climate change and disease. Temperature and precipitation data from 1970a??2000 were analyzed to determine the general pattern of oscillations and deviations that could be correlated with amphibian declines. We examined a total of 106 tissues taken from museum specimens collected from 1961a??1978 and from live frogs in 2000. We found chytrid fungi in two species collected at El Yunque as early as 1976, this is the first report of chytrid fungus in the Caribbean. Analysis of weather data indicates a significant warming trend and an association between years with extended periods of drought and the decline of amphibians in Puerto Rico. The 1970's and 1990's, which represent the periods of amphibian extirpations and declines, were significantly drier than average. We suggest a possible synergistic interaction between drought and the pathological effect of the chytrid fungus on amphibian populations.
Burrowes, P. A.; Joglar, R. L.; Green, David E.
Cathelicidins comprise a family of antimicrobial peptides (AMPs) sharing a highly conserved cathelin domain, and play a central role in the innate defense against infection in most of vertebrates. But so far it has not yet been found in amphibians although a large number of other groups of AMPs have been identified. In the current work, the first amphibian cathelicidin (cathelicidin-AL) has been characterized from the frog skin of Amolops loloensis. Cathelicidin-AL (RRSRRGRGGGRRGGSGGRGGRGGGGRSGAGSSIAGVGSRGGGGGRHYA) is a cationic peptide containing 48 amino acid residues (aa) with 12 basic aa and no acidic aa. The chemical synthesized peptide efficiently killed bacteria and some fungal species including clinically isolated drug-resistance microorganisms. The cDNA encoding cathelicidin-AL precursor was cloned from the skin cDNA library of A. loloensis. As other cathelicidins, the precursor of cathelicidin-AL also contains highly conserved anionic cathelin domain of cysteine proteinase inhibitor followed by the AMP fragment at C-terminus. Phylogenetic analysis revealed that as connecting link, the amphibian cathelicidin predates reptilia but postdates fish cathelicidin. The peptide purification combined with gene cloning results confirms the presence of cathelicidin in amphibians and filled the evolutionary gap of cathelicidin in vertebrate, considering amphibians' special niche as the animals bridging the evolutionary land-water gap. PMID:22009138
Hao, Xue; Yang, Hailong; Wei, Ling; Yang, Shilong; Zhu, Wenjuan; Ma, Dongying; Yu, Haining; Lai, Ren
There is significant variation among and within amphibian species with respect to reports of population decline; declining species are often found in environments that are physiograpically similar to environments where the same species is thriving. Because variability exists among organisms in their sensitivity to environmental stressors, it is important to determine the degree of this variation when undertaking conservation efforts. We conducted both lethal (time-to-death) and sublethal (activity change) assays to determine the degree of variation in the sensitivity of tadpoles to a pesticide, carbaryl, at three hierarchical levels: among ranid species, among several populations of a single ranid species (Rana sphenocephala), and within populations of R. sphenocephala. We observed significant variation in time to death among the nine ranid species and among the 10 R. sphenocephala populations we tested. Four out of eight R. sphenocephala populations exhibited significantly different times to death among families. The magnitude of the activity change in response to exposure to sublethal carbaryl levels was significantly different among species and within R. sphenocephala populations. Chemical contamination, at lethal or sublethal levels, can alter natural regulatory processes such as juvenile recruitment in amphibian populations and should be considered a contributing cause of declines in amphibian populations.
Bridges, C. M.; Semlitsch, R. D.
The blood meals of field-collected female Culex territans (Diptera: Culicidae) were concurrently assayed for the presence of trypanosomes and for vertebrate host identification. We amplified vertebrate DNA in 42 of 119 females and made positive identification to the host species level in 29 of those samples. Of the 119 field-collected Cx. territans females, 24 were infected with trypanosomes. Phylogenetic analysis placed the trypanosomes in the amphibian portion of the aquatic clade of the Trypanosomatidae. These trypanosomes were isolated from Cx. territans females that had fed on the frog species Rana clamitans, R. catesbeiana, R. virgatipes, and Rana spp. Results support a potential new lineage of dipteran-transmitted amphibian trypanosomes may occur within the aquatic clade. The frequency in which female Cx. territans acquire trypanosomes, through diverse feeding habits, indicates a new relationship between amphibian trypanosomes and mosquitoes that has not been examined previously. Combining Trypanosoma species, invertebrate, and vertebrate hosts to existing phylogenies can elucidate trypanosome and host relationships. PMID:18850768
Bartlett-Healy, Kristen; Crans, Wayne; Gaugler, Randy
Populations of amphibians and reptiles are experiencing new or increasing threats to their survival. Many of these threats are directly attributable to human activity and resource development.This presents the increasing need for worldwide amphibian and reptile assessments and effective, standardized monitoring protocols. Adaptive management techniques can assist managers in identifying and mitigating threats to amphibian and reptile populations. In 1996,
Javier Icochea; Eliana Quispitupac; Alfredo Portilla; Elias Ponce
...Importation of live amphibians or their eggs. 16.14 Section 16.14 Wildlife...Importation of live amphibians or their eggs. Upon the filing of a written declaration...all species of live amphibians or their eggs may be imported, transported,...
...Importation of live amphibians or their eggs. 16.14 Section 16.14 Wildlife...Importation of live amphibians or their eggs. Upon the filing of a written declaration...all species of live amphibians or their eggs may be imported, transported,...
The middle Pleistocene site of Atapuerca (Spain) has many archaeological, palaeontological and human remains in stratigraphic position. Amphibian remains are abundant and easily identifiable in many levels of the site. We have investigated the taphonomy of the amphibian remains, with the question to be answered being their source. Did the amphibians live and die inside the cave, as occurs naturally
Ana Cristina Pinto Llona; Peter J Andrews
One hypothesis for amphibian declines is that increased dryness attributed to global climate change exposes amphibians to greater biotic threat and, consequently, greater mortality. But, little is known about behavioral responses of terrestrial amphibians to dry conditions alone or in combination with biotic threats. We used field observations and laboratory experiments to test the response of efts (terrestrial juveniles) of
Jason R. Rohr; Dale M. Madison
Temporin A and structurally related peptides produced in amphibian dermal granular glands and in wasp venom were tested for growth inhibition of Batrachochytrium dendrobatidis, a pathogen associated with global amphibian declines. Two natural amphibian temporins, a wasp temporin, and six synthetic analogs effectively inhibited growth. Differences in potency due to amino acid substitution suggest that ability to penetrate membranes and
Louise A. Rollins-Smith; Cynthia Carey; J. Michael Conlon; Laura K. Reinert; Jennifer K. Doersam; Tomas Bergman; Jerzy Silberring; Hilkka Lankinen; David Wade
Amphibians can be important consumers in both aquatic and terrestrial habitats and may represent an impor- tant energetic link between the two, particularly in the tropics, where amphibian species richness and abun- dance are high. In the past 20 years, amphibian populations have declined dramatically around the world; numbers have decreased catastrophically in protected upland sites throughout the neotropics, usually
Matt R. Whiles; Karen R. Lips; Cathy M. Pringle; Susan S. Kilham; Rebecca J. Bixby; Roberto Brenes; Scott Connelly; Jose Checo Colon-Gaud; Meshagae Hunte-Brown; Alexander D. Huryn; Chad Montgomery; Scot Peterson
Declines of amphibian populations have been well documented in the US, Canada, and Central America, but little is known regarding the status of amphibian populations in Mexico. In 2000, we surveyed 43 transects from 3 upland regions in Guerrero and Oaxaca, Mexico. We found 161 adult amphibians belonging to 39 species, representing only 19–48% of the anuran fauna known from
Karen R. Lips; Joseph R. Mendelson III; Antonio Muñoz-Alonso; Luis Canseco-Márquez; Daniel G. Mulcahy
Amphibians and reptiles were surveyed at Berara, a forest on the Sahamalaza Peninsula, NW Madagascar. Visual methods and pitfalls were used, leading to the discovery of 12 amphibian and 30 reptile species. The herpetofaunal community appeared as a mosaic of dry forest species and species from the more humid Sambirano Domain. The comparatively low amphibian diversity may be correlated with
Franco Andreone; Miguel Vences; Jasmin Emile Randrianirina
Juvenile dispersal is important for the persistence of . amphibian populations. Previous studies have observed nonrandom orientation in juvenile amphibians emigrating from breeding ponds; however, the environmental cues associ- ated with these movements are not well understood. We examined the emigration behavior of recently metamorphosed ju- veniles of three pond-breeding amphibian species from three woodland ponds. We found that juvenile
Leroy J. Walston; Stephen J. Mullin
Eastern equine encephalitis virus (EEEV) is endemic throughout most of the eastern United States. Although it is transmitted year round in Florida, transmission elsewhere is seasonal. The mechanism that enables EEEV to overwinter in seasonal foci remains obscure. In previous field studies, early season EEEV activity was detected in mosquito species that feed primarily upon ectothermic hosts, suggesting that reptiles and amphibians might represent overwintering reservoir hosts for EEEV. To determine if this might be possible, two commonly fed upon amphibian and reptile species were evaluated as hosts for the North American subtype I strain of EEEV. Neither amphibian species was a competent host. However, circulating viremias were detected in both reptile species examined. Hibernating infected garter snakes remained viremic after exiting hibernation. These data suggest that snakes may represent an overwintering host for North American EEEV. PMID:21896798
White, Gregory; Ottendorfer, Christy; Graham, Sean; Unnasch, Thomas R
The extent of research conducted on the effects of contaminants on reptiles and amphibians has been scant compared to that of other vertebrate classes including fishes, birds and mammals. In a review of literature from 1972 until 1998 we found that only about 2.7% of the papers published on ecotoxicology in vertebrates concerned amphibians and 1.4% for reptiles. Most studies on amphibian ecotoxicology were on metals, pesticides, and acid deposition. For reptiles the greatest frequency of papers included metals, organochlorines, and others. In proportion to the taxonomic importance, far more papers were written on turtles than on other reptile orders. Most of the papers dealt with residues and very few dealt with effects of contaminant exposure.
Sparling, D.W.; Bishop, C.A.; Linder, G.
The barnacle, Balanus amphitrite, is one of the primary model organisms for rocky-shore ecology studies and biofouling research. This barnacle species has a complex life cycle during which the swimming nauplius molts six times and transforms into a cyprid stage. Cyprids must attach to a surface to metamorphose into a juvenile barnacle. To clarify the overall profile of protein expression during larval development and metamorphosis, 2-DE was used to compare the proteome of the nauplius, the swimming cyprid, the attached cyprid, and the metamorphosed cyprid. The proteome of the swimming cyprid was distinctly different from that of other life stages and had about 400 spots. The proteomes of the attached and metamorphosed cyprids were similar with respect to major proteins but had significantly lower numbers of spots compared to that of swimming larval stages. Obviously, synthesis of most proteins from swimming cyprids was switched off after attachment and metamorphosis. Our advanced MS analysis (MALDI-TOF/TOF MS/MS) allowed us to identify the proteins that were differentially and abundantly expressed in the swimming cyprid. These proteins included signal transduction proteins (adenylate cyclase and calmodulin) and juvenile hormone binding proteins. In summary, for the first time, we have analyzed the global protein expression pattern of fouling marine invertebrate larvae during metamorphosis. Our study provides new insights into the mechanisms of barnacle larval metamorphosis and also provides a foundation for exploring novel targets for antifouling treatments. PMID:18654988
Thiyagarajan, Vengatesen; Qian, Pei-Yuan
Predation risk can cause organisms to alter the timing of life history switch points. Theory suggests that increased risk in an early life stage should select for switching earlier and smaller, while increased risk in the subsequent stage should select for switching later and larger. This framework has frequently been applied to metamorphosis in amphib- ians, with mixed results. Few
James R. Vonesh; Karen M. Warkentin
The attachment and metamorphic responses of veliger larvae of the abalone, Haliotis diversicolor (Reeve) to potassium chloride (KCl), gamma-aminobutyric acid (GABA) and natural cues were determined. Attachment and metamorphosis of H. diversicolor were two distinctly different responses. Attachment was characterized by larval contact with a substratum followed by crawling with the larval foot firmly attached to the surface of the
Patrick J Bryan; Pei-Yuan Qian
A set of motor neurons and interneurons in the thoracic nervous system of the meal beetle Tenebrio molitor L. is described that persist during metamorphosis. The motor neurons under discussion innervate the thoracic ventral longitudinal muscles and were identified by retrograde transport of intramuscularly injected horseradish peroxidase. Persisting motor neurons exhibit a complex repetitive pattern that changes only slightly during
During metamorphosis, the larval thoracic legs of the hawk moth Manduca sexta are replaced by a new set of adult legs. The larval leg motoneurons persist to innervate new adult muscles, and the motor terminals remain within the developing adult legs. Here we describe the fate of the larval leg muscles and the origin of new muscles within the adult
C. Consoulas; M. Anezaki; R. B. Levine
Serum thyroid hormone (TH) concentrations in anuran larvae rise rapidly during metamorphosis. Such a rise in an adult anuran would inevitably trigger a negative feedback response resulting in decreased synthesis and secretion of thyroid-stimulating hormone (TSH) by the pituitary....
In this paper, we propose a new image metamorphosis algorithm which uses elastic body splines to generate warp functions for interpolating scattered data points. The spline is based on a partial differential equation proposed by Navier that describes the equilibrium displacement of an elastic body subjected to forces. The spline maps can be expressed as the linear combination of an
Hassanien Aboul-Ella; Masayuki Nakajima
The polychaete Hydroides elegans (Serpulidae, Lophotrochozoa) is a problematic marine fouling organism in most tropical and subtropical coastal environment. Competent larvae of H. elegans undergo the transition from the swimming larval stage to the sessile juvenile stage with substantial morphological, physiological, and behavior changes. This transition is often referred to as larval settlement and metamorphosis. In this study, we examined the possible involvement of calmodulin (CaM) - a multifunctional calcium metabolism regulator, in the larval settlement and metamorphosis of H. elegans. A full-length CaM cDNA was successfully cloned from H. elegans (He-CaM) and it contained an open reading frame of 450 bp, encoding 149 amino acid residues. It was highly expressed in 12h post-metamorphic juveniles, and remained high in adults. In situ hybridization conducted in competent larvae and juveniles revealed that He-CaM gene was continuously expressed in the putative growth zones, branchial rudiments, and collar region, suggesting that He-CaM might be involved in tissue differentiation and development. Our subsequent bioassay revealed that the CaM inhibitor W7 could effectively inhibit larval settlement and metamorphosis, and cause some morphological defects of unsettled larvae. In conclusion, our results revealed that CaM has important functions in the larval settlement and metamorphosis of H. elegans. PMID:22507549
Chen, Zhang-Fan; Wang, Hao; Qian, Pei-Yuan
The potency of flagellated cells of Halisarca dujardini (Halisarcida, Demospongiae) larvae from the White Sea (Arctic) was investigated experimentally during metamorphosis. Two types of experiments were conducted. First, larvae were maintained in Ca2+ free seawater (CFSW) until the internal cells were released outside through the opening of the posterior pole. These larvae that only composed of flagellated cells (epithelial larvae) were then returned to sea water (SW) to observe their metamorphosis. The posterior aperture closed before they settled on a substratum and started a metamorphosis similar to intact larvae. Secondly, epithelial larvae were, first, further treated in CFSW and then mechanically dissociated. Separated cells or groups of cells were returned to SW, where they constituted large friable conglomerates. After 12-17 h in SW, flagellated cells showed the first steps of dedifferentiation, and regional differentiation was noticeable within conglomerates after approximately 24-36 h. External cells differentiated into pinacocytes while internal cells kept their flagella and became united in a layer. Within 48-72 h, internal cells of the conglomerates formed spherical or ovoid clusters with an internal cavity bearing flagella. These clusters further fused together in a rhagon containing one or two large choanocyte chambers. The sequence of cellular processes in epithelial larvae and in flagellated cell conglomerates was similar. Previous observations indicating the totipotentiality of larval flagellated cells during normal metamorphosis of H. dujardini are thus confirmed. PMID:17427973
Ereskovsky, Alexander V; Konjukov, Paul; Willenz, Philippe
The tobacco hornworm Manduca sexta, like many holometabolous insects, makes two versions of its thoracic legs. The simple legs of the larva are formed during embryogenesis, but then are transformed into the more complex adult legs at metamorphosis. To elucidate the molecular patterning mechanism underlying this biphasic development, we examined the expression patterns of five genes known to be involved
Kohtaro Tanaka; James W. Truman
Most marine sessile organisms have a planktonic larval phase in their life cycles, and then larvae settle and metamorphose into their adult forms. The selection of settlement sites is a critical event for these organisms because settlement on unsuitable places affects their survivorship severely. Ascidians live gregariously, and conspecific chemical cues are thought to play an important role in gregarious settlement of larvae. The extracts of conspecific adults or larvae have been claimed to contain "natural metamorphosis inducers." Little is known, however, about their chemical properties. To discover natural signal substances for larval metamorphosis in ascidians, we surveyed the metamorphosis-inducing activity of the medium conditioned by ascidian larvae, and succeeded in isolating a metamorphosis-inducing substance from the conditioned medium of Halocycthia roretzi larvae and found that it was identical to lumichrome. We have also isolated more than 40 active metabolites, which may mimic lumichrome, from marine sponges. On the contrary, marine sessile organisms cause serious problems by settling on fishing nets, hulls of ships, and cooling systems of power plants. Organotin compounds have been widely used for the control of these organisms, but they are known to be toxic to marine biota. Therefore, nontoxic antifouling substances are urgently needed. Marine sessile organisms possess chemical defense systems using their secondary metabolites, which might be potential by nontoxic antifouling agents. We have attempted to obtain antibarnacle substances from marine sponges and isolated 26 antifoulants. PMID:10434799
A wealth of information has suggested the involvement of protein kinase C (PKC) in metamorphosis of Hydractinia echinata and in pattern formation of Hydra magnipapillata. We have identified a Ca2+- and phospholipid-dependent kinase activity in extracts of both species. The enzyme was characterized as being similar to mammalian PKC by ion exchange chromatography. Gel filtration experiments revealed a molecular weight
Thomas Schneider; Thomas Leitz
Ecologists use stable isotopes to infer diets and trophic levels of animals in food webs, yet some assumptions underlying these inferences have not been thoroughly tested. We used laboratory-reared colonies of Solenopsis invicta Buren (Formicidae: Solenopsidini) to test the effects of metamorphosis,...
An alloantiserum produced against Xenopus MHC class I antigens has been used to distinguish different erythrocyte populations at metamorphosis. By analysis using a fluorescence-activated cell sorter (FACS) analyzer, tadpole (stage 55) and adult erythrocytes have distinct volume differences and tadpole cells have no MHC antigens on the cell surface. Both tadpole and adult erythrocytes express a "mature erythrocyte" antigen marker, recognized by its monoclonal antibody (F1F6). During metamorphosis, immature erythrocytes, at various stages of differentiation, which express adult levels of cell-surface MHC antigens by 12 days after tail resorption, are found in the bloodstream. These immature cells are biosynthetically active, produce adult hemoglobin, and mature by 60 days after the completion of metamorphosis. Percoll gradient-density fractionation has shown that all of the cells in the new erythrocyte series express adult levels of MHC antigens but there is only a gradual increase in the amount of "mature erythrocyte" antigen. Tadpole erythrocytes, which are biosynthetically active during larval stages, produce small amounts of surface MHC antigens before the metamorphic climax and then become metabolically inactive. They are completely cleared from the circulation by 60 days after metamorphosis. Erythrocytes from tadpoles arrested in their development for long periods of time express intermediate levels of MHC antigens, suggesting a "leaky" expression of these molecules in the tadpole cells. The most abundant erythrocyte cell-surface proteins from tadpoles and adults, as judged by two-dimensional gel electrophoresis, are very different. PMID:3384174
Flajnik, M F; Du Pasquier, L
Disease, pollution, and loss of habitat are killing off hundreds of species of amphibians. One of the biggest threats right now is an aquatic fungus called chytrid that infects the skin of these historically tough, resilient creatures. While a few species seem to be resistant to the fungus, chytrid is usually fatal to most others. Biologist Vance Vredenburg is using a National Science Foundation (NSF) grant to study the disease. An important part of his research is communicating with scientists who are dealing with this crisis on every continent where amphibians live.
1. Glutaurine (gamma-L-glutamyl-taurine) isolated from bovine parathyroid and later synthetized retards the metamorphosis of Rana arvalis. 2. From day 13 of treatment glutaurine moderates the metamorphosis inhibiting effect of antibiotics acting at the transcription and translation level. PMID:94855
Feurer, L; Cserhalmi, M; Csaba, G
Metamorphosis is a substantial morphological transition between 2 multicellular phases in an organism's life cycle, often marking the passage from a prereproductive to a reproductive life stage. It generally involves major physiological changes and a shift in habitat and feeding mode, and can be subdivided into an extended phase of substantial morphological change and/or remodeling, and a shorter-term phase (for example, marine invertebrate "settlement," insect "adult eclosion," mushroom fruiting body emergence) where the actual habitat shift occurs. Disparate metamorphic taxa differ substantially with respect to when the habitat shift occurs relative to the timing of the major events of morphogenetic change. I will present comparative evidence across a broad taxonomic scope suggesting that longer-term processes (morphogenetic changes) are generally hormonally regulated, whereas nitric oxide (NO) repressive signaling often controls the habitat shift itself. Furthermore, new evidence from echinoids (sea urchins, sand dollars) indicates a direct connection between hormonal and NO signaling during metamorphosis. I incorporate 2 hypotheses for the evolution of metamorphosis-one involving heterochrony, the other involving phenotypic integration and evolutionarily stable configurations (ESCs)-into a network model for metamorphosis in echinoderms (sea urchins, starfish, and their kin). Early indications are that this core regulatory network can be acted upon by natural selection to suit the diverse ecological needs of disparate metamorphic organisms, resulting in evolutionary expansions and contractions in the core network. I briefly speculate on the ways that exposure to xenobiotic pollutants and other compounds might influence successful settlement of juveniles in the wild. Indeed, environmentally regulated life history transitions-such as settlement, metamorphosis, and reproductive maturation-may be developmental periods that are especially sensitive to such pollutants. PMID:21672781
We provide an initial checklist of the herpetofauna of Baramita, a lowland rainforest site in the Northwest Region of Guyana. Twenty-five amphibian and 28 reptile species were collected during two separate dry-season visits. New country records for two species of snakes are documented, contributing to the knowledge on the incompletely known herpetofauna of Guyana.
Reynolds, R. P.; MacCulloch, R. D.
Glyphosate usage is increasing worldwide and the application schemes of this herbicide are currently changing. Amphibians migrating through arable fields may be harmed by Glyphosate applied to field crops. We investigated the population-based temporal coincidence of four amphibian species with Glyphosate from 2006 to 2008. Depending on a) age- and species-specific main migration periods, b) crop species, c) Glyphosate application mode for crops, and d) the presumed DT50 value (12 days or 47 days) of Glyphosate, we calculated up to 100% coincidence with Glyphosate. The amphibians regularly co-occur with pre-sowing/pre-emerging Glyphosate applications to maize in spring and with stubble management prior to crop sowing in late summer and autumn. Siccation treatment in summer coincides only with early pond-leaving juveniles. We suggest in-depth investigations of both acute and long-term effects of Glyphosate applications on amphibian populations not only focussed on exposure during aquatic periods but also terrestrial life stages. PMID:24018602
Berger, Gert; Graef, Frieder; Pfeffer, Holger
A major cause of amphibian declines worldwide is habitat destruction or alteration. Public green spaces, such as golf courses and parks, could serve as safe havens to curb the effects of habitat loss if managed in ways to bolster local amphibian communities. We reared larval Blanchard's cricket frogs (Acris blanchardi) and green frogs (Rana clamitans) in golf course ponds with and without 1 m terrestrial buffer zones, and released marked cricket frog metamorphs at the golf course ponds they were reared in. Larval survival of both species was affected by the presence of a buffer zone, with increased survival for cricket frogs and decreased survival for green frogs when reared in ponds with buffer zones. No marked cricket frog juveniles were recovered at any golf course pond in the following year, suggesting that most animals died or migrated. In a separate study, we released cricket frogs in a terrestrial pen and allowed them to choose between mown and unmown grass. Cricket frogs had a greater probability of using unmown versus mown grass. Our results suggest that incorporating buffer zones around ponds can offer suitable habitat for some amphibian species and can improve the quality of the aquatic environment for some sensitive local amphibians.
Puglis, Holly J.; Boone, Michelle D.
The recent discovery of a pathogenic fungus (Batrachochytrium dendrobatidis) associated with declines of frogs in the American and Australian tropics, suggests that at least the proximate cause, may be known for many previously unexplained amphibian declines. We have monitored boreal toads in Colorado since 1991 at four sites using capture–recapture of adults and counts of egg masses to examine the
Erin Muths; Paul Stephen Corn; Allan P. Pessier; D. Earl Green
Previous studies have shown that pesticides from the Central Valley of CA enter the Sierra Nevada ecosystem through aerial deposition in snow and rain, and that surface concentrations of certain pesticides are within an order of magnitude of the 96hr LC50 of amphibians. Pseudacris regilla hatchlings...
A major cause of amphibian declines worldwide is habitat destruction or alteration. Public green spaces, such as golf courses and parks, could serve as safe havens to curb the effects of habitat loss if managed in ways to bolster local amphibian communities. We reared larval Blanchard's cricket frogs (Acris blanchardi) and green frogs (Rana clamitans) in golf course ponds with and without 1 m terrestrial buffer zones, and released marked cricket frog metamorphs at the golf course ponds they were reared in. Larval survival of both species was affected by the presence of a buffer zone, with increased survival for cricket frogs and decreased survival for green frogs when reared in ponds with buffer zones. No marked cricket frog juveniles were recovered at any golf course pond in the following year, suggesting that most animals died or migrated. In a separate study, we released cricket frogs in a terrestrial pen and allowed them to choose between mown and unmown grass. Cricket frogs had a greater probability of using unmown versus mown grass. Our results suggest that incorporating buffer zones around ponds can offer suitable habitat for some amphibian species and can improve the quality of the aquatic environment for some sensitive local amphibians. PMID:22761833
Puglis, Holly J; Boone, Michelle D
A review of the 1982 world literature was conducted on the effects of pollution on freshwater fish and amphibians. This review contained 378 references and included papers on water quality such as dissolved gases and pH; chemical pollutants such as insecticides, herbicides, pesti...
|Reptiles and amphibians are a diverse and interesting group of organisms. The four activities described in this article take students' curiosity into the realm of scientific understanding. The activities involve the concepts of species identification; animal adaptations, communication, and habitat; and conservation. (Contains 1 table and 2…
Tomasek, Terry; Matthews, Catherine E.
Ultraviolet Radiation Dose and Amphibian Distributions in National Parks. Diamond, S. A., Detenbeck, N. E., USEPA, Duluth, MN, USA, Bradford, D. F., USEPA, Las Vegas, NV, USA, Trenham, P. C., University of California, Davis, CA., USA, Adams, M. J., Corn, P. S., Hossack, B., USGS,...
This review focuses on research into the hormonal control of behaviors in amphibians that was conducted prior to the 21st century. Most advances in this field come from studies of a limited number of species and investigations into the hormonal mechanisms that regulate reproductive behaviors in male frogs and salamanders. From this earlier research, we highlight five main generalizations or
Frank L. Moore; Sunny K. Boyd; Darcy B. Kelley
This report provides the basis for discussion and subsequent articulation of a national plan for the Amphibian Research and Monitoring Initiative (ARMI). The authors were members of a task force formed from within the U.S. Geological Survey (USGS) that in...
P. S. Corn M. J. Adams W. A. Battaglin A. L. Gallant D. L. James
? Abstract Declines and losses of amphibian populations are a global problem with complex local causes. These may include ultraviolet radiation, predation, habi- tat modification, environmental acidity and toxicants, diseases, changes in climate or weather patterns, and interactions among these factors. Understanding the extent of the problem and its nature requires an understanding of how local factors affect the dynamics
Ross A. Alford; Stephen J. Richards
Global declines of amphibian populations are a source of great concern. Several pathogens that can infect the skin have been implicated in the declines. The pathogen most frequently associated with recent die-offs is a chytrid fungus, Batrachochytrium dendrobatidis. A second fungus, Basidiobolus ranarum, was isolated from declining populations of Wyoming toads. A third pathogen, Aeromonas hydrophila, is an opportunistic bacterium
Louise A. Rollins-Smith; Jennifer K. Doersam; Joyce E. Longcore; Sharon K. Taylor; Jessica C. Shamblin; Cynthia Carey; Michael A. Zasloff
The recent discovery of a pathogenic fungus (Batrachochytrium dendrobatidis) associated with declines of frogs in the American and Australian tropics, suggests that at least the proximate cause, may be known for many previously unexplained amphibian declines. We have monitored boreal toads in Colorado since 1991 at four sites using capture-recapture of adults and counts of egg masses to examine the
Erin Muths; Paul Stephen Corn; Allan P. Pessier; D. Earl Green
The pathogen Batrachochytrium dendrobatidis (Bd), which causes the skin disease chytridiomycosis, is one of the few highly virulent fungi in vertebrates and has been implicated in worldwide amphibian declines. However, the mechanism by which Bd causes death has not been determined. We show that Bd infection is associated with pathophysiological changes that lead to mortality in green tree frogs (Litoria
Jamie Voyles; Sam Young; Lee Berger; Craig Campbell; W. F. Voyles; Anuwat Dinudom; David Cook; Rebecca Webb; R. A. Alford; L. F. Skerratt; Rick Speare
Serious threats to the health and sustainability of global amphibian populations have been well documented over the last few decades. Encroachment upon and destruction of primary habitat is the most critical threat, but some species have disappeared while their habitat remains. Additional stressor...
While the hypothalamo–pituitary–adrenocortical (HPA) response to stress appears to be conserved in vertebrates, the manner in which it is activated and its actions vary. We examine two trends in the stress biology literature that have been addressed in amphibian and reptilian species: (1) variable interactions among stress, corticosterone, and reproduction and (2) adrenocortical modulation. In the first topic we examine
Ignacio T. Moore; Tim S. Jessop
The current biodiversity crisis encompasses a sixth mass extinction event affecting the entire class of amphibians. The infectious disease chytridiomycosis is considered one of the major drivers of global amphibian population decline and extinction and is thought to be caused by a single species of aquatic fungus, Batrachochytrium dendrobatidis. However, several amphibian population declines remain unexplained, among them a steep decrease in fire salamander populations (Salamandra salamandra) that has brought this species to the edge of local extinction. Here we isolated and characterized a unique chytrid fungus, Batrachochytrium salamandrivorans sp. nov., from this salamander population. This chytrid causes erosive skin disease and rapid mortality in experimentally infected fire salamanders and was present in skin lesions of salamanders found dead during the decline event. Together with the closely related B. dendrobatidis, this taxon forms a well-supported chytridiomycete clade, adapted to vertebrate hosts and highly pathogenic to amphibians. However, the lower thermal growth preference of B. salamandrivorans, compared with B. dendrobatidis, and resistance of midwife toads (Alytes obstetricans) to experimental infection with B. salamandrivorans suggest differential niche occupation of the two chytrid fungi.
Martel, An; Spitzen-van der Sluijs, Annemarieke; Blooi, Mark; Bert, Wim; Ducatelle, Richard; Fisher, Matthew C.; Woeltjes, Antonius; Bosman, Wilbert; Chiers, Koen; Bossuyt, Franky; Pasmans, Frank
|Discusses using amphibians and reptiles as an excellent resource for students to observe and gain an understanding of the process of science. These animals are easy to maintain in the classroom and play important roles in ecosystems as the prey for many birds and mammals and as the predators of various organisms. (SAH)|
Greene, Janice Schnake; Greene, Brian D.
Hox genes encode transcription factors that play a key role in specifying the body plan in metazoans and are therefore essential in explaining patterns of evolutionary diversity. As an ancient tetrapod group with diverse limb types, amphibians are important for understanding the origin and diversification of limbs in land vertebrates. We conducted a PCR survey in two species of each
An Mannaert; Kim Roelants; Franky Bossuyt; Luc Leyns
Given their physiological requirements, limited dispersal abilities, and hydrologically sensitive habitats, amphibians are likely to be highly sensitive to future climatic changes. We used three approaches to map areas in the western hemisphere where amphibians are particularly likely to be affected by climate change. First, we used bioclimatic models to project potential climate-driven shifts in the distribution of 413 amphibian species based on 20 climate simulations for 2071–2100. We summarized these projections to produce estimates of species turnover. Second, we mapped the distribution of 1099 species with restricted geographic ranges. Finally, using the 20 future climate-change simulations, we mapped areas that were consistently projected to receive less seasonal precipitation in the coming century and thus were likely to have altered microclimates and local hydrologies. Species turnover was projected to be highest in the Andes Mountains and parts of Central America and Mexico, where, on average, turnover rates exceeded 60% under the lower of two emissions scenarios. Many of the restricted-range species not included in our range-shift analyses were concentrated in parts of the Andes and Central America and in Brazil's Atlantic Forest. Much of Central America, southwestern North America, and parts of South America were consistently projected to experience decreased precipitation by the end of the century. Combining the results of the three analyses highlighted several areas in which amphibians are likely to be significantly affected by climate change for multiple reasons. Portions of southern Central America were simultaneously projected to experience high species turnover, have many additional restricted-range species, and were consistently projected to receive less precipitation. Together, our three analyses form one potential assessment of the geographic vulnerability of amphibians to climate change and as such provide broad-scale guidance for directing conservation efforts.
Lawler, Joshua J.; Shafer, Sarah L.; Bancroft, Betsy A.; Blaustein, Andrew R.
Amphibian population declines have been documented worldwide and environmental contaminants are believed to contribute to some declines. Maternal transfer of bioaccumulated contaminants to offspring may be an important and overlooked mechanism of impaired reproductive success that affects amphibian populations. Mercury (Hg) is of particular concern due to its ubiquity in the environment, known toxicity to other wildlife, and complex relationships with other elements, such as selenium (Se). The objectives of the present study were to describe the relationships between total Hg (THg), methlymercury (MMHg), and Se in three amphibian species (Plethodon cinereus, Eurycea bislineata cirrigera, and Bufo americanus) along a Hg-polluted river and floodplain, and to determine if B. americanus maternally transfers Hg and Se to its eggs in a tissue residue-dependent manner. Total Hg and MMHg concentrations in all species spanned two orders of magnitude between the reference and contaminated areas, while Se concentrations were generally low in all species at both sites. Strong positive relationships between THg and MMHg in tissues of all species were observed throughout. Both Hg and Se were maternally transferred from females to eggs in B. americanus, but the percentage of the females' Hg body burden transferred to eggs was low compared with Se. In addition, Hg concentrations appeared to positively influence the amount of Se transferred from female to eggs. The present study is the first to confirm a correlation between Hg concentrations in female carcass and eggs in amphibians and among the first to describe co-transference of Se and Hg in an anamniotic vertebrate. The results suggest future work is needed to determine whether maternal transfer of Hg has transgenerational implications for amphibian progeny. PMID:20821530
Bergeron, Christine M; Bodinof, Catherine M; Unrine, Jason M; Hopkins, William A
As part of the National Park Service Inventory and Monitoring Program in the Mojave Network, we conducted an inventory of amphibians and reptiles at Death Valley National Park in 2002-04. Objectives for this inventory were to: 1) Inventory and document the occurrence of reptile and amphibian species occurring at DEVA, primarily within priority sampling areas, with the goal of documenting at least 90% of the species present; 2) document (through collection or museum specimen and literature review) one voucher specimen for each species identified; 3) provide a GIS-referenced list of sensitive species that are federally or state listed, rare, or worthy of special consideration that occur within priority sampling locations; 4) describe park-wide distribution of federally- or state-listed, rare, or special concern species; 5) enter all species data into the National Park Service NPSpecies database; and 6) provide all deliverables as outlined in the Mojave Network Biological Inventory Study Plan. Methods included daytime and nighttime visual encounter surveys, road driving, and pitfall trapping. Survey effort was concentrated in predetermined priority sampling areas, as well as in areas with a high potential for detecting undocumented species. We recorded 37 species during our surveys, including two species new to the park. During literature review and museum specimen database searches, we recorded three additional species from DEVA, elevating the documented species list to 40 (four amphibians and 36 reptiles). Based on our surveys, as well as literature and museum specimen review, we estimate an overall inventory completeness of 92% for Death Valley and an inventory completeness of 73% for amphibians and 95% for reptiles. Key Words: Amphibians, reptiles, Death Valley National Park, Inyo County, San Bernardino County, Esmeralda County, Nye County, California, Nevada, Mojave Desert, Great Basin Desert, inventory, NPSpecies.
Persons, Trevor B.; Nowak, Erika M.
Examination was made of the involvement of macrophage phagocytosis in programmed cell death of tail and body muscle of the\\u000a frog, Xenopus laevis, during metamorphosis by electron microscopy and immunohistochemical analysis. Electron microscopic observation revealed\\u000a that macrophages were often found to be present in body and tail muscles at the most active stage of metamorphosis and to\\u000a actively phagocytose apoptotic
A. Nishikawa; Eiko Murata; Masumi Akita; Katsuji Kaneko; Osamu Moriya; Mitsuko Tomita; Hideo Hayashi
The crustose coralline alga Lithothamnium pseudosorum induces high rates of settlement and metamorphosis of larvae of the coral-eating crown-of-thorns starfish (Acanthaster planci). In cases where crustose coralline algae (CCA) induce metamorphosis of marine invertebrate larvae it is normally assumed that the inductive molecules are produced by the alga, but an alternative is that they originate from bacteria on the plant
C. R. Johnson; D. C. Sutton
The swimming larvae of the chordate ascidians possess a dorsal hollowed central nervous system (CNS), which is homologous to that of vertebrates. Despite the homology, the ascidian CNS consists of a countable number of cells. The simple nervous system of ascidians provides an excellent experimental system to study the developmental mechanisms of the chordate nervous system. The neural fate of the cells consisting of the ascidian CNS is determined in both autonomous and non-autonomous fashion during the cleavage stage. The ascidian neural plate performs the morphogenetic movement of neural tube closure that resembles that in vertebrate neural tube formation. Following neurulation, the CNS is separated into five distinct regions, whose homology with the regions of vertebrate CNS has been discussed. Following their larval stage, ascidians undergo a metamorphosis and become sessile adults. The metamorphosis is completed quickly, and therefore the metamorphosis of ascidians is a good experimental system to observe the reorganization of the CNS during metamorphosis. A recent study has shown that the major parts of the larval CNS remain after the metamorphosis to form the adult CNS. In contrast to such a conserved manner of CNS reorganization, most larval neurons disappear during metamorphosis. The larval glial cells in the CNS are the major source for the formation of the adult CNS, and some of the glial cells produce adult neurons. PMID:22524611
Sasakura, Yasunori; Mita, Kaoru; Ogura, Yosuke; Horie, Takeo
Considerable progress has been made in understanding the responses of amphibians to climate change, with successful research carried out on climate change-associated shifts in amphibian phenology, elevational distributions and amphibian-parasite interactions. We review and synthesize the literature on this topic, emphasizing acutely lethal, sublethal, indirect and positive effects of climate change on amphibians, and major research gaps. For instance, evidence is lacking on poleward shifts in amphibian distributions and on changes in body sizes and morphologies of amphibians in response to climate change. We have limited information on amphibian thermal tolerances, thermal preferences, dehydration breaths, opportunity costs of water conserving behaviors and actual temperature and moisture ranges amphibians experience. Even when much of this information is available, there remains little evidence that climate change is acutely lethal to amphibians. This suggests that if climate change is contributing to declines, it might be through effects that are not acutely lethal, indirect, or both, but evidence in support of this suggestion is necessary. In fact, evidence that climate change is directly contributing to amphibian declines is weak, partly because researchers have not often ruled out alternative hypotheses, such as chytrid fungus or climate-fungus interactions. Consequently, we recommend that amphibian-climate research shift from primarily inductive, correlational approach as to studies that evaluate alternative hypotheses for declines. This additional rigor will require interdisciplinary collaborations, estimates of costs and benefits of climate change to amphibian fitness and populations, and the integration of correlative field studies, experiments on 'model' amphibian species, and mathematical and functional, physiological models. PMID:23731811
Li, Yiming; Cohen, Jeremy M; Rohr, Jason R
gamma-Aminobutyric acid (a simple amino acid and potent neurotransmitter in human brain and other tissues of higher animals) and certain of its congeners rapidly and synchronously induce planktonic larvae of the red abalone, Haliotis rufescens, to settle and commence behavioral and developmental metamorphosis. These naturally occurring inducers of algal origin apparently are responsible, in part, for the substrate-specific recruitment, induction of settling, and the onset of metamorphosis of abalone and other planktonic larvae upon specific algae which provide naturally favorable habitats for the young of these species in coastal waters. These observations provide a convenient experimental model for further analysis of the basic molecular mechanisms by which environmental and endogenous factors control the recruitment and development of planktonic larvae. Halogenated organic pesticides significantly interfere with larval settling, as quantified in a new bioassay based upon these findings. PMID:17758015
Morse, D E; Hooker, N; Duncan, H; Jensen, L
The problem of insect metamorphosis has inspired naturalists for centuries. One question that often arises is why some insects, such as butterflies and bees, undergo a fairly radical metamorphosis while others, such as crickets and lice, do not. Even before the concept of homology emerged scientists speculated which stage found in more direct-developing insects would correspond with the pupal stage of metamorphosing insects. William Harvey (1651) considered the pupal stage to be a continuation of embryonic events, calling it a "second egg." Since then variations of this idea have emerged over the centuries of scientific research and have been supported by a wide variety of methods and rationales. This review will follow those ideas and the ideas that emerged in opposition to them to the present state of the field. PMID:21672785
Erezyilmaz, Deniz F
During anticipatory development in lecithotrophic larvae that delay metamorphosis, the growth and differentiation of features of the adult action system continue to develop at a slow pace even though they do not become functional. After metamorphosis occurs, the larger size and advanced development of these components may allow juveniles to initially grow at a faster rate than they normally would. Anticipatory development has been demonstrated in archeogastropods, some solitary ascidians and a hydrozoan. In the gastropod Haliotis and the hydrozoan Phialidium anticipatory development increases the initial growth rate of juveniles. In Haliotis and ascidians all of the larvae of a given female that live long enough exhibit anticipatory development. In Phialidium, the ability of a given female to produce larvae that can exhibit anticipatory development is a maternal polymorphic character. In Haliotis and solitary ascidians that exhibit anticipatory development, it appears to be a slower version of the rapid developmental changes that occur in parts of the adult action system at metamorphosis. In Phialidium, developmental changes in relative sizes of the different presumptive regions of the polyp are slowly altered prior to and independently of metamorphosis. Anticipatory development is not linked to the decrease in the size or nutrient reserves of older larvae but to the length of their larval period. From an evolutionary perspective, the mechanisms that operate during anticipatory development are probably of adaptive significance for lecithotrophic larvae of species that spend variable amounts of time in the water column because of a patchy distribution of appropriate settlement cues. The developmental mechanisms that underlie anticipatory development may have been used during the transition from lecithotrophy to planktotrophy. PMID:23016974
This study investigates the effects of thyroxine (T4), triiodothyronine (T3) and thiourea (TU) on the metamorphosis of tarpon Megalops cryprinoides leptocephali. TU is an anti-thyroid hormone drug that inhibits the production of T4 and T3 in the thyroid tissue. Fully grown tarpons leptocephali were collected at the river mouth and, in the laboratory, were immediately treated with 100 ppb T4,
Jen-Chieh Shiao; Pung-Pung Hwang
An increase in the concentration of K@in defined sea water medium is dem onstrated to induce settlement and metamorphosis in larvae ofthe marine gastropod mollusc, Haliotis rufrscens. A decrease in external K@ ion concentration can inhibit the larval response to -y-aminobutyric acid (GABA), a stereochemically specific inducer ofmetamorphosis ofH. rufescens. Stimulation ofthe metamorphic response by GABA or by increasedK@may dependon
ANDREA J. BALOUN; DANIEL E. MORSE
Abalone Haliotis diversicolor supertexta is an important economic mollusk. The settlement and metamorphosis are two critical stages during its development period,\\u000a which has direct influence on abalone survival and production. The influence of reactive oxygen species (hydrogen peroxide)\\u000a on abalone embryo and juvenile development were examined in this study. Larvae of Haliotis diversicolor supertexta were induced to settlement and metamorphose
Xiangjing Zhang; Zhihui Yang; Zhonghua Cai
Metamorphosis induction and postlarval growth of the red abalone (Haliotis rufescens) were evaluated in a commercial farm of Baja California, Mexico. This hatchery settles larvae with gamma-aminobutyric acid (GABA, 1-mM final concentration) and culture postlarvae in 250-L tanks placed in a four-story structure inside a building with artificial illumination. Eight tanks (four at the top and four at the bottom
RICARDO SEARCY-BERNAL; ESTEBAN PÉREZ-SÁNCHEZ; CASANDRA ANGUIANO-BELTRÁN; ROBERTO FLORES-AGUILAR
Conspecific foot mucus, excessive [K+] and gamma-aminobutyric acid (GABA) showed different metamorphosis-inductive effect on the veliger ofHaliotis discus hannai. The inductive effect of excessive [K+] and GABA was developmental stage-dependent and dose-dependent, while that of conspecific foot mucus was only developmental\\u000a stage-dependent. At 20°C the veliger larvae became competent within 4 days after fertilization.H. discus hannai larvae showed gregarious settlement
Yu Yang; Bao-Ling Wu
Since its initial invasion in the late 1980s, the Asian shore crab Hemigrapsus sanguineus has spread over 650 km along the Atlantic Coast of the United States. Larvae of this species can live in the water column\\u000a for over 3 weeks, which provides ample time for transport to new locations. Previous research on the settlement and metamorphosis\\u000a of H. sanguineus showed that
Mia K. Steinberg; Lisa S. Krimsky; Charles E. Epifanio
Batches of hundreds of freshly collected megalopae of the shore crab Carcinus maenas (L.) showed persistent circatidal rhythms of moulting to the juvenile crab stage when maintained in constant laboratory conditions.\\u000a Peaks of moulting occurred around expected times of high tides, with few megalopae moulting at other times. In larvae collected\\u000a offshore, the highest tidally-timed peak of metamorphosis occurred during
C. Zeng; E. Naylor; P. Abello
Developmental plasticity is increasingly recognized as important for ecological and evolutionary processes. However, few studies\\u000a consider the potential for delayed effects of early environments. Here, we show that tadpoles hatching from clutches exposed\\u000a to water mold (Saprolegnia) have 20% decreased mass at metamorphosis, despite no further exposure subsequent to hatching. The effects were consistent across four populations that have previously
Tobias Uller; Jörgen Sagvik; Mats Olsson
Bullfrog tadpoles at metamorphic stages V, X and XVIII were immersed in 25 nM triiodothyronine (T3) to assess whether the 4–5 fold increase in fast axonal transport (FAxT) previously observed during this span of spontaneous\\u000a metamorphosis (1) could be mimicked by precocious application of thyroid hormone. The trend initially observed was for T3 to stimulate [35S]methionine incorporation into lumbar DRG
H. Z. Tang; R. Hammerschlag
The newt is an indispensable model animal, of particular utility for regeneration studies. Recently, a high-throughput transgenic protocol was established for the Japanese common newt, Cynops pyrrhogaster. For studies of regeneration, metamorphosed animals may be favorable; however, for this species, there is no efficient protocol for maintaining juveniles after metamorphosis in the laboratory. In these animals, survival drops drastically after metamorphosis as their foraging behaviour changes to adapt to a terrestrial habitat, making feeding in the laboratory with live or moving foods more difficult. To elevate the efficiency of laboratory rearing of this species, we examined metamorphosis inhibition (Ml) protocols to bypass the period (four months to two years after hatching) in which the animal feeds exclusively on moving foods. We found that approximately 30% of animals survived after 2-year Ml, and that the survivors continuously grew, only with static food while maintaining their larval form and foraging behaviour in 0.02% thiourea (TU) aqueous solution, then metamorphosed when returned to a standard rearing solution even after 2-year-MI. The morphology and foraging behavior (feeding on static foods in water) of these metamorphosed newts resembled that of normally developed adult newts. Furthermore, they were able to fully regenerate amputated limbs, suggesting regenerative capacity is preserved in these animals. Thus, controlling metamorphosis with TU allows newts to be reared with the same static food under aqueous conditions, providing an alternative rearing protocol that offers the advantage of bypassing the critical period and obtaining animals that have grown sufficiently for use in regeneration studies. PMID:22559962
Chiba, Chikafumi; Yamada, Shouta; Tanaka, Hibiki; Inae-Chiba, Maiko; Miura, Tomoya; Casco-Robles, Martin Miguel; Yoshikawa, Taro; Inami, Wataru; Mizuno, Aki; Islam, Md Rafiqul; Han, Wenje; Yasumuro, Hirofumi; Matsumoto, Mikiko; Takayanagi, Miyako
In the non-feeding larva of the marine gastropod, Haliotis rufescens, gut morphogenesis is initiated at metamorphosis. Intestine-specific chymotrypsin gene expression begins in amoebocytes located in the dorsoposterior region of the undifferentiated digestive gland prior to metamorphosis, 5 d post-fertilization. Transcript accumulates steadily in these cells over the next 6 d while the amoebocytes migrate slowly dorsally. Induction of metamorphosis dramatically
Bernard M. Degnan; Jay C. Groppe; Daniel E. Morse
Coral planulae settle, then metamorphose and form polyps. This study examined the morphological process of metamorphosis from planulae into primary polyps in the scleractinian corals Acropora nobilis and Acropora microphthalma, using the cnidarian neuropeptide Hym-248 . These two species release eggs that do not contain Symbiodinium. The mode of acquisition of freshly isolated Symbiodinium (zooxanthellae) (FIZ) by the non-symbiotic polyp was also examined. Non-Hym-248 treated swimming Acropora planulae did not develop blastopore, mesenteries or coelenteron until the induction of metamorphosis 16 days after fertilization. The oral pore was formed by invagination of the epidermal layer after formation of the coelenteron in metamorphosing polyps. At 3 days after settlement and metamorphosis, primary polyps exposed to FIZ established symbioses with the Symbiodinium. Two-four days after exposure to FIZ, the distribution of Symbiodinium was limited to the gastrodermis of the pharynx and basal part of the polyps. Eight-ten days after exposure to FIZ, Symbiodinium were present in gastrodermal cells throughout the polyps.
Hirose, M.; Yamamoto, H.; Nonaka, M.
Abalone Haliotis diversicolor supertexta is an important economic mollusk. The settlement and metamorphosis are two critical stages during its development period, which has direct influence on abalone survival and production. The influence of reactive oxygen species (hydrogen peroxide) on abalone embryo and juvenile development were examined in this study. Larvae of Haliotis diversicolor supertexta were induced to settlement and metamorphose by exposure to seawater supplemented with hydrogen peroxide. They had the best performance at 800 ?mol/L. The concentration of 1 000 ?mol/L or higher was toxic to the larvae, as the larvae could settle down only at benthic diatom plates without complete metamorphosis. In addition, H2O2 adding time was critical to the larval performance. 24h after two-day post-fertilization was proved to be the optimal adding time. In this paper, two action mechanisms of hydrogen peroxide are discussed: (1) hydrogen peroxide has direct toxicity to ciliated cells, thus cause apoptosis; (2) hydrogen peroxide, as a product from catecholamines’ autoxidation process in vivo, can reverse this process to produce neuro-transmitters to induce abalone metamorphosis.
Zhang, Xiangjing; Yang, Zhihui; Cai, Zhonghua
Cidaroids, one of the two major sister clades of sea urchins, first appeared during the lower Permian (ca. 270 mya) and are considered to represent the primitive form of all living echinoids. This study of Cidaris blakei, a deep-sea cidaroid urchin with planktotrophic larvae, provides a description of development from fertilization through early juvenile stages and is the first report of a deep-sea urchin reared through metamorphosis. C. blakei resembles other cidaroids in its lack of a cohesive hyaline layer, the absence of an amniotic invagination for juvenile rudiment formation, and the presence of spines with a single morphotype at metamorphosis. C. blakei differed from other cidaroids in the presence of an apical tuft, the extent of fenestration of postoral skeletal rods, the shape of juvenile spines, and an extended (14-day) lecithotrophic stage prior to development of a complete gut. The development of C. blakei, 120 days from fertilization to metamorphosis, was protracted relative to that of shallow-water cidaroids. Preliminary work on temperature tolerances suggests that C. blakei larvae would be unable to survive the warmer temperatures higher in the water column and are therefore unable to vertically migrate. PMID:22589401
Bennett, Kathleen C; Young, Craig M; Emlet, Richard B
Thyroid hormone (T3) is essential for normal development and organ function throughout vertebrates. Its effects are mainly mediated through transcriptional regulation by T3 receptor (TR). The identification and characterization of the immediate early, direct target genes are thus of critical importance in understanding the molecular pathways induced by T3. Unfortunately, this has been hampered by the difficulty to study gene regulation by T3 in uterus-enclosed mammalian embryos. Here we used Xenopus metamorphosis as a model for vertebrate postembryonic development to identify direct T3 response genes in vivo. We took advantage of the ability to easily induce metamorphosis with physiological levels of T3 and to carry out microarray analysis in Xenopus laevis and genome-wide sequence analysis in Xenopus tropicalis. This allowed us to identify 188 up-regulated and 249 down-regulated genes by T3 in the absence of new protein synthesis in whole animals. We further provide evidence to show that these genes contain functional TREs that are bound by TR in tadpoles and that their promoters are regulated by TR in vivo. More importantly, gene ontology analysis showed that the direct up-regulated genes are enriched in categories important for transcriptional regulation and protein degradation-dependent signaling processes but not DNA replication. Our findings thus revealed the existence of interesting pathways induced by T3 at the earliest step of metamorphosis.
Das, Biswajit; Heimeier, Rachel A.; Buchholz, Daniel R.; Shi, Yun-Bo
Background In the adult males of helminthomorph millipedes, one or two pairs of legs in the anterior part of the trunk are strongly modified into sexual appendages (gonopods) used for sperm transfer during the copula. Gonopods differentiate in an advanced phase of post-embryonic development, in most cases as replacement for the walking legs of the seventh trunk ring, as these first regress to tiny primordia, to eventually develop into gonopods at a subsequent stadium. These extremely localized but dramatic changes have been described as a non-systemic metamorphosis. In the present study we describe morphological and anatomical changes of trunk ring VII associated with non-systemic metamorphosis in four helminthomorph species. Results As documented here for the first time by means of traditional histology methods and new techniques based on confocal laser scanning microscopy, the external modifications caused by non-systemic metamorphosis are associated to a huge rearrangement of internal anatomy, mostly due to the development of gonopod apodemes and extrinsic muscles. Conclusions Internal changes in the seventh trunk ring, locally leading to the dorsal displacement of the ventral nerve cord and the digestive tract, are modulated in a taxon-specific manner, and are very conspicuous in the blaniulids Nopoiulus kochii and Blaniulus guttulatus, with likely major functional consequences.
Established in 1958, the Society for the Study of Amphibians and Reptiles (SSAR) "is the largest international herpetological society, and is recognized worldwide for having the most diverse program of publications, meetings, and other activities." The SSAR website contains resources for professional and amateur herpetologists alike. The site provides information about SSAR officers and editors, committees, membership, annual meetings, publications, grants, and awards. The site also contains guidelines for submitting to the _Journal of Herpetology_ and the _Herpetological Review_. Notably, members of the SSAR community provide a free (pre-submission) Manuscript Review Service for herpetologists "whose first language is not English, but who are striving to publish their findings in peer reviewed English language journals." Site visitors interested in reptile and amphibian conservation should be sure to check out the SSAE Conservation Committee page.
The deposition of chemical pollutants into roadside wetlands from runoff is a current environmental concern. In northern latitudes, a major pollutant in runoff water is salt (NaCl), used as de-icing agents. In this study, 26 roadside ponds were surveyed for amphibian species richness and chloride concentration. Acute toxicity tests (LC(50)) were performed on five locally common amphibian species using a range of environmentally significant NaCl concentrations. Field surveys indicated that spotted salamanders (Ambystoma maculatum) and wood frogs (Rana sylvatica) did not occupy high chloride ponds. American toads (Bufo americanus) showed no pond preference based on chloride concentration. Acute toxicity tests showed spotted salamanders and wood frogs were most sensitive to chloride, and American toads were the least. Spring peepers (Pseudacris crucifer) and green frogs (Rana clamitans) showed intermediate sensitivities. We concluded that chloride concentrations in ponds due to application of de-icing salts, influenced community structure by excluding salt intolerant species. PMID:18684543
Collins, Sara J; Russell, Ronald W
The aims of the study were to determine the heavy metal content in the tissues of Hypsiboas faber from a coal mining area and to compare the DNA damage in the blood cells of these animals with that of animals living in an unpolluted area. The heavy metal content was detected according to the technique of Particle-Induced X-ray Emission (PIXE) and the DNA damage was assessed by the Comet assay. Our results reveal that the specimens of H. faber collected from the coal mining area exhibited elements of order Fe>Cu>Al>Zn>Rb>Mn>Br, independently of the organ. The values of Comet assay parameters (DNA damage index and DNA damage frequency) were significantly higher in specimens collected from the coal mining area than in the reference animals. Our study concludes that the coal mining residues are genotoxic to amphibians and may have adverse effects on soil, water, vegetation and wild animals. PMID:23619523
Zocche, Jairo José; Damiani, Adriani Paganini; Hainzenreder, Giana; Mendonça, Rodrigo Ávila; Peres, Poliana Bernardo; Santos, Carla Eliete Iochims Dos; Debastiani, Rafaela; Dias, Johnny Ferraz; Andrade, Vanessa Moraes de
Amphibians and reptiles will be adversely affected by projected rapid changes in climate in the next decades. Here, we review\\u000a the known and potential impacts of climate change on the Southeast Asian amphibians and reptiles and make mitigation recommendations\\u000a for both research and policy. Current amphibian and reptile distributions and ecologies mirror climate patterns, and we expect\\u000a that adaptation to
David Bickford; Sam D. Howard; Daniel J. J. Ng; Jennifer A. Sheridan
We compared species richness and relative abundance of stream-associated amphibians in late-seral redwood forests with those in mid-seral, second-growth forests to examine the continued (as opposed to immediate) effects of timber harvest on amphibian populations. Lacking pre-harvest data on amphibian abundances for streams in the second-growth stands, we assumed that nearby tributaries transecting late-seral stands with similar topography and flora
Donald T. Ashton; Sharyn B. Marks; Hartwell H. Welsh
Ambient ultraviolet-b (UV-B) radiation (280-320 nm) has increased at north-temperate latitudes in the last two decades. UV-B can be detrimental to amphibians, and amphibians have shown declines in some areas during this same period. We documented the distribution of amphibians and salmonids in 42 remote, subalpine and alpine ponds in Olympic National Park, Washington, United States. We inferred relative exposure
Michael J. Adams; Daniel E. Schindler; Bruce R. Bury
To test whether gravity is required for normal amphibian development, Xenopus laevis females were induced to ovulate aboard the orbiting Space Shuttle. Eggs were fertilized in vitro, and although early embryonic stages showed some abnormalities, the embryos were able to regulate and produce nearly normal larvae. These results demonstrate that a vertebrate can ovulate in the virtual absence of gravity and that the eggs can develop to a free-living stage. PMID:7892210
Souza, K A; Black, S D; Wassersug, R J
Summary Measurements of acetylcholine-induced single-channel conductance and null potentials at the amphibian motor end-plate in solutions containing Na, K, Li and Cs ions (Gage & Van Helden, 1979;J. Physiol. (London) (in press) were analyzed in terms of three models. Two of these models, the “neutral” site channel model and the “charged” site channel model were developed to cater for three
Peter H. Barry; Peter W. Gage; Dirk F. Van Helden
Abstract—Several species of anuran amphibians,have undergone,drastic population declines in the western United States over the last 10 to 15 years. In California, the most severe declines are in the Sierra Mountains east of the Central Valley and downwind of the intensely agricultural San Joaquin Valley. In contrast, coastal and more northern populations across from the less agrarian Sacramento Valley are
DONALD W. S PARLING; ARY M. FELLERS; L AURA L. MCCONNELL
New temnospondyl material is described on the basis of cranial and postcranial remains from the Gai-As Formation of the Huab Basin, Namibia. An Early Permian age is indicated by U\\/Pb SHRIMP dating of zircons from fallout tuff beds occurring immediately above the temnospondy1 remains. This material represents the oldest known amphibian with stereospondylous vertebrae and has implications for temnospondy1 evolution,
A. A. Warren; B. S. Rubidge; I. G. Stanistreet; H. Stollhofen; A. Wanke; E. M. Latimer; C. A. Marsicano; R. J. Damiani
Steroid hormones influence neuronal structure and function throughout the animal kingdom, via highly conserved receptor proteins. Insights into steroid effects on neurons and behavior have come from a range of vertebrate species including reptiles, amphibians, fish, birds, rodents and primates. In many instances, steroid hormones regulate the volume of particular regions of the nervous system by affecting both the number
Background The phoronid larva, which is called the actinotrocha, is one of the most remarkable planktotrophic larval types among marine invertebrates. Actinotrochs live in plankton for relatively long periods and undergo catastrophic metamorphosis, in which some parts of the larval body are consumed by the juvenile. The development and organization of the muscular system has never been described in detail for actinotrochs and for other stages in the phoronid life cycle. Results In Phoronopsis harmeri, muscular elements of the preoral lobe and the collar originate in the mid-gastrula stage from mesodermal cells, which have immigrated from the anterior wall of the archenteron. Muscles of the trunk originate from posterior mesoderm together with the trunk coelom. The organization of the muscular system in phoronid larvae of different species is very complex and consists of 14 groups of muscles. The telotroch constrictor, which holds the telotroch in the larval body during metamorphosis, is described for the first time. This unusual muscle is formed by apical myofilaments of the epidermal cells. Most larval muscles are formed by cells with cross-striated organization of myofibrils. During metamorphosis, most elements of the larval muscular system degenerate, but some of them remain and are integrated into the juvenile musculature. Conclusion Early steps of phoronid myogenesis reflect the peculiarities of the actinotroch larva: the muscle of the preoral lobe is the first muscle to appear, and it is important for food capture. The larval muscular system is organized in differently in different phoronid larvae, but always exhibits a complexity that probably results from the long pelagic life, planktotrophy, and catastrophic metamorphosis. Degeneration of the larval muscular system during phoronid metamorphosis occurs in two ways, i.e., by complete or by incomplete destruction of larval muscular elements. The organization and remodeling of the muscular system in phoronids exhibits the combination of protostome-like and deuterostome-like features. This combination, which has also been found in the organization of some other systems in phoronids, can be regarded as an important characteristic and one that probably reflects the basal position of phoronids within the Lophotrochozoa.
1.?Altered global climates in the 21st century pose serious threats for biological systems and practical actions are needed to mount a response for species at risk. 2.?We identify management actions from across the world and from diverse disciplines that are applicable to minimizing loss of amphibian biodiversity under climate change. Actions were grouped under three thematic areas of intervention: (i) installation of microclimate and microhabitat refuges; (ii) enhancement and restoration of breeding sites; and (iii) manipulation of hydroperiod or water levels at breeding sites. 3.?Synthesis and applications. There are currently few meaningful management actions that will tangibly impact the pervasive threat of climate change on amphibians. A host of potentially useful but poorly tested actions could be incorporated into local or regional management plans, programmes and activities for amphibians. Examples include: installation of irrigation sprayers to manipulate water potentials at breeding sites; retention or supplementation of natural and artificial shelters (e.g. logs, cover boards) to reduce desiccation and thermal stress; manipulation of canopy cover over ponds to reduce water temperature; and, creation of hydrologoically diverse wetland habitats capable of supporting larval development under variable rainfall regimes. We encourage researchers and managers to design, test and scale up new initiatives to respond to this emerging crisis.
Shoo, L. P.; Olson, D. H.; Mcmenamin, S. K.; Murray, K. A.; Van Sluys, M.; Donnelly, M. A.; Stratford, D.; Terhivuo, J.; Merino-Viteri, A.; Herbert, S. M.; Bishop, P. J.; Corn, P. S.; Dovey, L.; Griffiths, R. A.; Lowe, K.; Mahony, M.; Mccallum, H.; Shuker, J. D.; Simpkins, C.; Skerratt, L. F.; Williams, S. E.; Hero, J. -M.
The emerging infectious disease chytridiomycosis is thought to have contributed to many of the recent alarming declines in amphibian populations. Mortalities associated with these declines have often occurred during cooler seasons and at high elevations, suggesting that environmental temperature may be an important factor in disease emergence. We found that thermal environment affects the progress of the disease, and that housing frogs Litoria chloris at an environmental temperature of 37 degrees C for less than 16 h can clear them of the chytrid pathogen Batrachochytrium dendrobatidis. Our experiment demonstrated that elevated body temperatures similar to those experienced in behavioral fever and during normal thermoregulation can clear frogs of chytrid infection; therefore, variation in thermoregulatory opportunities and behaviors are likely to contribute to the differences in disease incidence observed among host species, populations, and regions. Although further refinement of the technique is needed to encompass various host species, appropriately applied thermal manipulations of amphibians and their enclosures may prove to be a safe and effective way of eliminating the fungal pathogen from captive amphibian populations and: preventing accidental spread of the pathogen when animals are translocated or released from captivity. PMID:12887256
Woodhams, Douglas C; Alford, Ross A; Marantelli, Gerry
The origin and divergence of the three living orders of amphibians (Anura, Caudata, Gymnophiona) and their main lineages are one of the most hotly debated topics in vertebrate evolution. Here, we present a robust molecular phylogeny based on the nuclear RAG1 gene as well as results from a variety of alternative independent molecular clock calibrations. Our analyses suggest that the origin and early divergence of the three living amphibian orders dates back to the Palaeozoic or early Mesozoic, before the breakup of Pangaea, and soon after the divergence from lobe-finned fishes. The resulting new biogeographic scenario, age estimate, and the inferred rapid divergence of the three lissamphibian orders may account for the lack of fossils that represent plausible ancestors or immediate sister taxa of all three orders and the heretofore paradoxical distribution of some amphibian fossil taxa. Furthermore, the ancient and rapid radiation of the three lissamphibian orders likely explains why branch lengths connecting their early nodes are particularly short, thus rendering phylogenetic inference of implicated relationships especially difficult. PMID:15795855
San Mauro, Diego; Vences, Miguel; Alcobendas, Marina; Zardoya, Rafael; Meyer, Axel
Amphibians epitomize the modern biodiversity crisis, and attract great attention from the scientific community since a complex puzzle of factors has influence on their disappearance. However, these factors are multiple and spatially variable, and declining in each locality is due to a particular combination of causes. This study shows a suitable statistical procedure to determine threats to amphibian species in medium size administrative areas. For our study case, ten biological and ecological variables feasible to affect the survival of 15 amphibian species were categorized and reduced through Principal Component Analysis. The principal components extracted were related to ecological plasticity, reproductive potential, and specificity of breeding habitats. Finally, the factor scores of species were joined in a presence-absence matrix that gives us information to identify where and why conservation management are requires. In summary, this methodology provides the necessary information to maximize benefits of conservation measures in small areas by identifying which ecological factors need management efforts and where should we focus them on.
García-Muñoz, Enrique; Ceacero, Francisco; Carretero, Miguel A.; Pedrajas-Pulido, Luis; Parra, Gema; Guerrero, Francisco
B chromosomes are known from 26 species of salamanders and frogs, equivalent to about 2% of amphibian species that have been karyotyped. In most cases, the structure of amphibian B chromosomes has not been extensively investigated. The exceptions are the B chromosomes of Hochstetter's frog, Leiopelma hochstetteri, from New Zealand, and the Coastal Giant salamander, Dicamptodon tenebrosus, from North America. Dicamptodon tenebrosus carries from 0 to 10 non-heterochromatic, telocentric B chromosomes per individual, averaging 0 to 3.4 B chromosomes per individual in populations throughout its extensive range. The B chromosomes of L. hochstetteri occur in frequencies averaging from 0 to 11.4 per individual in different populations, with a known maximum of 15 B chromosomes. Amphibian B chromosomes vary in size, heterochromatin, occurrence and frequency. They are commensurate in size and structure with the rest of the A set of chromosomes of the same species in which they occur. The B chromosomes are at least partly composed of repetitive DNA sequences which exist in numerous copies throughout the autosomes, in conformity to an hypothesis of intraspecific B chromosome origins. PMID:15292597
Green, D M
Many of the recent global amphibian mass mortalities, declines and extinctions have been attributed to the emerging infectious disease chytridiomycosis. There have been mass mortalities due to ranaviral disease but no major declines or extinctions. Controlling the transmission and spread of disease is of utmost importance, especially where there is the potential for human involvement. We have reviewed current hygiene guidelines for working with wild frogs, identified potential flaws and recommended those most suitable and effective for the field environment. Our within-site hygiene measures aim to reduce the risk of transmission among individuals. These measures encompass the capture, handling and holding of amphibians, skin disinfection before and after invasive procedures, marking frogs, sealing open wounds and treatment of accessory equipment. Our between-site hygiene measures aim to mitigate the risk of pathogen spread among populations. We have designed a risk calculator to help simplify and standardise the decision-making process for determining the level of risk and appropriate risk mitigation strategies to reduce the risk of increasing pathogen spread above background levels. Calculation of an overall risk score for pathogen spread takes into account the prior activity of field workers, the proposed activity, remoteness of the site, presence of known pathogens and the consequences of increased pathogen spread for amphibians in a given area. PMID:21268979
Phillott, A D; Speare, R; Hines, H B; Skerratt, L F; Meyer, E; McDonald, K R; Cashins, S D; Mendez, D; Berger, L
More than ten bradykinin-related peptides and their cDNAs have been identified from amphibians, but their genes are unknown. In present study, four cDNAs encoding one, two, four and six copies of bradykinin-related peptides were cloned from the frog (Odorrana grahami) skin cDNA library, respectively. Three bradykinin-related peptides (bradykinin, Thr6-bradykinin, Leu5Thr6-bradykinin) were deduced from these four cDNA sequences. Based on the cDNA sequence, the gene sequence encoding an amphibian bradykinin-related peptide from O. grahami was determined. It is composed of 7481 base pairs including two exons and two introns. The first exon codes signal peptide and the second exon codes acidic spacer peptide and Thr6-bradykinin. The promoter region of the bradykinin gene contains several putative recognition sites for nuclear factors, such as SRY, GATA-1, LYF-1, DeltaE, CDXA, NKX-2.5, MIF1 and S8. The current work may facilitate to understand the regulation and possible functions of amphibian skin bradykinin-related peptides. PMID:20025925
Chen, Manda; Che, Qiaolin; Wang, Xu; Li, Jianxu; Yang, Hailong; Li, Dongsheng; Zhang, Keyun; Lai, Ren
Iridoviruses infect invertebrates (primarily insects and crustaceans) and ectothermic vertebrates (fish, amphibians, and reptiles). Identical, or nearly identical viruses, have been isolated from different animals within the same taxonomic class, indicating that infection by a given virus is not limited to a single species. Although inter-class infections have been documented following experimental infection with vertebrate iridoviruses, it is not clear whether such infections occur in nature. Here we report the isolation of apparently identical iridoviruses from wild sympatric fish (the threespine stickleback, Gasterostelus aculeatus) and amphibians (the red-legged frog, Rana aurora). Viruses isolated from sticklebacks (stickleback virus, SBV) and from a red-legged frog tadpole (tadpole virus 2, TV2) replicated in fathead minnow (FHM) cells and synthesized proteins which co-migrated with those of frog virus 3 (FV3). Following restriction endonuclease digestion of viral DNA with Hind III and Xba I, gel analysis showed that the profiles of SBV and TV2 were identical to each other and distinct from FV3. Using oligonucleotide primers specific for a highly conserved region of the iridovirus major capsid protein, an not, vert, ~500 nucleotide DNA fragment was amplified from SBV and TV2. Sequence analysis showed that within this 500 nucleotide region SBV and TV2 were identical to each other and to FV3. Taken together these results provide the first evidence that iridoviruses naturally infect animals belonging to different taxonomic classes, and strengthen the suggestion that fish may serve as a reservoir for amphibian viruses or vice versa.
Mao, J.; Green, D. E.; Fellers, G.; Chinchar, V. G.
Amphibians stand at the forefront of a global biodiversity crisis. More than one-third of amphibian species are globally threatened, and over 120 species have likely suffered global extinction since 1980. Most alarmingly, many rapid declines and extinctions are occurring in pristine sites lacking obvious adverse effects of human activities. The causes of these “enigmatic” declines remain highly contested. Still, lack of long-term data on amphibian populations severely limits our understanding of the distribution of amphibian declines, and therefore the ultimate causes of these declines. Here, we identify a systematic community-wide decline in populations of terrestrial amphibians at La Selva Biological Station, a protected old-growth lowland rainforest in lower Central America. We use data collected over 35 years to show that population density of all species of terrestrial amphibians has declined by ?75% since 1970, and we show identical trends for all species of common reptiles. The trends we identify are neither consistent with recent emergence of chytridiomycosis nor the climate-linked epidemic hypothesis, two leading putative causes of enigmatic amphibian declines. Instead, our data suggest that declines are due to climate-driven reductions in the quantity of standing leaf litter, a critical microhabitat for amphibians and reptiles in this assemblage. Our results raise further concerns about the global persistence of amphibian populations by identifying widespread declines in species and habitats that are not currently recognized as susceptible to such risks.
Whitfield, Steven M.; Bell, Kristen E.; Philippi, Thomas; Sasa, Mahmood; Bolanos, Federico; Chaves, Gerardo; Savage, Jay M.; Donnelly, Maureen A.
Although the ecological consequences of species invasions are well studied, the ecological impacts of genetic introgression through hybridization are less understood. This is particularly true of the impacts of hybridization on “third party” community members not genetically involved in hybridization. We also know little about how direct interactions between hybrid and parental individuals influence fitness. Here, we examined the ecological effects of hybridization between the native, threatened California Tiger Salamander (Ambystoma californiense) and the introduced Barred Tiger Salamander (Ambystoma tigrinum mavortium). Native x introduced hybrids are widespread in California, where they are top predators in seasonal ponds. We examined the impacts of early generation hybrids (first 2 generations of parental crosses) and contemporary hybrids derived from ponds where hybrids have been under selection in the wild for 20 generations. We found that most classes of hybrid tiger salamander larvae dramatically reduced survival of 2 native community members, the Pacific Chorus Frog (Pseudacris regilla) and the California Newt (Taricha torosa). We also found that native A. californiense larvae were negatively impacted by the presence of hybrid larvae: Native survival and size at metamorphosis were reduced and time to metamorphosis was extended. We also observed a large influence of Mendelian dominance on size, metamorphic timing and predation rate of hybrid tiger salamanders. These results suggest that both genetic and ecological factors are likely to influence the dynamics of admixture, and that tiger salamander hybridization might constitute a threat to additional pond-breeding species of concern in the region.
Ryan, Maureen E.; Johnson, Jarrett R.; Fitzpatrick, Benjamin M.
The objectives of the present study are to elucidate the effects of rearing temperatures on early larval development and the occurrence of metamorphosis-related morphological abnormalities in hatchery-reared brown sole Pseudopleuronectes herzensteini. Newly hatched larvae were reared through metamorphosis at different temperatures (6, 9, 12, 15, 18, 21, and 24 °C). Growth and development of larvae were accelerated concomitant with higher
Masato Aritaki; Tadahisa Seikai
Road traffic causes significant amphibian and reptile mortality, which could be mitigated through the installation of road crossing structures that facilitate safe passage, but only if reptiles and amphibians are willing to use them. Through a series of behavioral choice experiments with frogs and turtles, we examined how aperture diameter, substrate type, length, and light permeability influenced individuals’ preferences for
Hara W. Woltz; James P. Gibbs; Peter K. Ducey
Coverboards are a useful inventory tool for many species of amphibians and reptiles, and provide a simple and effective method to involve the public in scientific research. The Davidson College Catawba River Corridor Coverboard Program (CRCCP) was initiated in 2003 to help coordinate the efforts of public and private sectors in surveying amphibians and reptiles. Fourteen sites were established within
SHANNON E. PITTMAN; MICHAEL E. DORCAS
There are many human activities that put species at risk, including development, agriculture, and forestry. Risk is not simply a linear function of habitat loss, and species reach thresholds where risk increases exponentially. The most threatened groups of organisms in Canada are the amphibians and reptiles, with over 30% of their species at risk. Three sets of studies of amphibians
|The protocols used in a research project on amphibian and reptile diversity at Cool Springs Environmental Education Center near New Bern, North Carolina is described. An increasing or stable number of amphibians and reptiles would indicate that the forest has a balance of invertebrates, leaf litter, moisture, pH, debris, burrows and habitat…
Tomasek, Terry M.; Matthews, Catherine E.; Hall, Jeff
Amphibian populations are declining globally in uplands. Stream-dwelling tadpoles are potentially important herbivores, and their loss is expected to cause significant changes in structure and function of lotic ecosystems. This study is part of a collaborative effort to measure changes in trophic structure associated with amphibian extirpations. We used stable isotopes to elucidate trends in Panamanian highland streams at two
M. E. Hunte-Brown; S. S. Kilham; M. R. Whiles; K. Lips; C. Pringle; C. Colon; R. Brenes; S. Connelly
Deicing agents, primarily road salt, are applied to roads in 26 states in the United States and in a number of European countries, yet the scale of impacts of road salt on aquatic organisms remains largely under-studied. The issue is germane to amphibian conservation because both adult and larval amphibians are known to be particularly sensitive to changes in their
Nancy E. Karraker; James P. Gibbs; James R. Vonesh
Increased traffic volumes worldwide are con- tributing to amphibian declines, and measures to reduce the occurrence of road kills are needed. One possible measure is the construction of underpasses through which animals can pass under roads, but little is known about whether amphibians will choose tunnels if given a choice or about their preferences for different tunnel types. We tested
David Lesbarrères; Thierry Lodé; Juha Merilä
|The Nature Conservancy's Berkshire Program involves community volunteers in monitoring migration routes of amphibians that rely on vernal pools for breeding success. Vernal-pool workshops provide basic knowledge of amphibian lifecycles and detailed monitoring instructions. Nighttime field trips for adults and children and monitoring experiences…
Daigle, Cheryl Perusse
Innate immune mechanisms of defense are especially important to ectothermic vertebrates in which adaptive immune responses may be slow to develop. One innate defense in amphibian skin is the release of abundant quantities of antimicrobial peptides. Chytridiomycosis is an emerging infectious disease of amphibians caused by the skin fungus, Batrachochytrium dendrobatidis. Suscept- ibility to chytridiomycosis varies among species, and mechanisms
D. C. Woodhams; K. Ardipradja; R. A. Alford; G. Marantelli; L. K. Reinert; L. A. Rollins-Smith
There has been significant recent activity related to testing amphibians in a regulatory setting. Much of this has emanated from interest by the US Environmental Protection Agency (EPA) and the Office of Economic Cooperation and Development (OECD) in utilizing amphibians in scree...
Abundant amphibian remains were encountered at Duinefontein 2, a late mid-Quaternary fossil site with Acheulean artifacts. The amphibians are distributed in concentric bands that suggest shoreline lags around the southeast rim of an interdunal pond, part of which has been exposed by very extensive excavations. The pond community was dominated by ranids and pipids, both requiring less than a meter
C Garth Sampson
Q1 Abstract: Despite the continuing loss of wetland habitats and associated declines in amphibian populations, attempts to translate wetland losses into measurable losses to ecosystems have been lacking. We estimated the potential productivity from the amphibian community that would be compromised by the loss of a single isolated wetland that has been protected from most industrial, agricultural, and urban impacts
J. WHITFIELD GIBBONS; CHRISTOPHER T. WINNE; D. E. Scott; J. D. Willson; X. Glaudas; K. M. Andrews; B. D. Todd; L. A. Fedewa; L. Wilkinson; R. N. Tsaliagos; S. J. Harper; J. L. Greene; T. D. Tuberville; B. S. Metts; M. E. Dorcas; J. P. Nestor; C. A. Young; T. Akre; R. N. Reed; K. A. Buhlmann; J. Norman; D. A. Croshaw; C. Hagen; B. B. Rothermel
Alford et al. question the working model underlying our test for a link between global warming and amphibian disappearances, and Di Rosa et al. criticize our emphasis on a single proximate agent, the chytrid fungus Batrachochytrium dendrobatidis. Both teams report key pieces of the amphibian-decline puzzle and new evidence from different parts of the world that climate change is a
J. Alan Pounds; Martín R. Bustamante; Luis A. Coloma; Jamie A. Consuegra; Michael P. L. Fogden; Pru N. Foster; Enrique La Marca; Karen L. Masters; Andrés Merino-Viteri; Robert Puschendorf; Santiago R. Ron; G. Arturo Sánchez-Azofeifa; Christopher J. Still; Bruce E. Young
Amphibians are among the most endangered animals on Earth, and climatic shifts are among the hypothesized factors in their decline. We used spatial patterns of recent amphibian declines in Italy to test hypotheses pertaining to three potential, nonexclusive factors: climate change, habitat alteration, and high levels of incident solar radiation. This study was based on patterns of presence in a
Manuela D’Amen; Pierluigi Bombi
Amphibians stand at the forefront of a global biodiversity crisis. More than one-third of amphibian species are globally threatened, and over 120 species have likely suffered global extinction since 1980. Most alarmingly, many rapid declines and extinctions are occurring in pristine sites lacking obvious adverse effects of human activities. The causes of these ''enigmatic'' declines remain highly contested. Still, lack
Steven M. Whitfield; Kristen E. Bell; Thomas Philippi; Mahmood Sasa; Federico Bolanos; Gerardo Chaves; Jay M. Savage; Maureen A. Donnelly
Amphibians are a bellwether for environmental degradation, even in natural ecosystems such as Yellowstone National Park in the western United States, where species have been actively protected longer than anywhere else on Earth. We document that recent climatic warming and resultant wetland desiccation are causing severe declines in 4 once-common amphibian species native to Yellowstone. Climate monitoring over 6 decades,
Sarah K. McMenamin; Elizabeth A. Hadly; Christopher K. Wright
Pesticides have long been proposed as a possible cause of amphibian pop- ulation declines, but due to a number of challenges there has been relatively little ecotox- icological research on pesticides and declines in natural populations. My study examines the association between the spatial patterns of declines for five California amphibian species and historical patterns of pesticide use in California
In Ambohitantely the rainforest is divided distinctly by pseudosteppe into more than 500 fragments. The amphibian faunas of seven such fragments varying in size from 0.16 to 1250 ha were examined. Twenty-eight amphibian species of two families (Ranidae and Microhylidae) were recorded in the rainforest fragments. The species numbers in the fragments were positively correlated with fragment area and form
The persistence of pond-breeding amphibians in highly fragmented land- scapes may be constrained by the need for connectivity between aquatic breeding sites and suitable terrestrial habitat, an example of landscape complementation. Although migratory ability determines the spatial scale at which landscape complementation operates, the factors influencing migratory success of amphibians, especially of juveniles, are poorly understood. This study is the
Betsie B. Rothermel
The disease chytridiomycosis, which is caused by the chytrid fungus Batrachochytrium dendrobatidis ,i s associated with recent declines in amphibian populations. Susceptibility to this disease varies among amphib- ian populations and species, and resistance appears to be attributable in part to the presence of antifungal microbial species associated with the skin of amphibians. The betaproteobacterium Janthinobacterium lividum has been isolated
Matthew H. Becker; Robert M. Brucker; Christian R. Schwantes; Reid N. Harris; Kevin P. C. Minbiole
Summary 1. This review examines the intraspecific patterns and differences in life-history traits of amphibian populations living at different altitudes and latitudes. Specifically we examined differences in development and growth (physiological constraints) and reproductive ecology (plasticity in reproductive traits). 2. Research published to date suggests that amphibian populations at higher altitudes and latitudes tend to: (a) have shorter activity periods,
Clare Morrison; Jean-Marc Hero
Chytridiomycosis is an emerging fungal disease of amphibians responsible for mass mortalities and population declines globally. One hypothesis for its recent emergence is anthropogenic introduction of the causative agent Batrachochytrium dendrobatidis through trade in amphibians for pets, food and biocontrol. In this study, we examined histological samples from apparently healthy American bullfrogs Rana catesbeiana that have been introduced into the
Rhea Hanselmann; Argelia Rodr??guez; Margarita Lampo; Laurie Fajardo-Ramos; A. Alonso Aguirre; A. Marm Kilpatrick; Jon Paul Rodr??guez; Peter Daszak
Coarse woody debris (CWD) has been identified as a key microhabitat component for groups that are moisture and temperature sensitive such as amphibians and reptiles. However, few experimental manipulations have quantitatively assessed amphibian and reptile response to varying CWD volumes within forested environments. We assessed amphibian and reptile response to large-scale, CWD manipulation within managed loblolly pine stands in the
Audrey K. Owens; Kurtis R. Moseley; Timothy S. McCay; Steven B. Castleberry; John C. Kilgo; W. Mark Ford; Castleberry; Steven
We surveyed 104 potential amphibian-breeding sites in northwest Indiana for the presence and abundance of amphibians, habitat parameters, and water chemistry. Linear regression was used as an exploratory analysis, and stepwise multiple regression and ANOVA were used to model factors that best explained amphibian species richness, abundance, and number of years with breeding populations. The most important breeding site factors
Robert Brodman; Jill Ogger; Tracey Bogard; Amanda J. Long; Rachel A. Pulver; Katherine Mancuso; Denise Falk
It is now widely accepted that a shift towards renewable energy production is needed in order to avoid further anthropogenically induced climate change. The ocean provides a largely untapped source of renewable energy. As a result, harvesting electrical power from the wind and tides has sparked immense government and commercial interest but with relatively little detailed understanding of the potential environmental impacts. This study investigated how the sound emitted from an underwater tidal turbine and an offshore wind turbine would influence the settlement and metamorphosis of the pelagic larvae of estuarine brachyuran crabs which are ubiquitous in most coastal habitats. In a laboratory experiment the median time to metamorphosis (TTM) for the megalopae of the crabs Austrohelice crassa and Hemigrapsus crenulatus was significantly increased by at least 18 h when exposed to either tidal turbine or sea-based wind turbine sound, compared to silent control treatments. Contrastingly, when either species were subjected to natural habitat sound, observed median TTM decreased by approximately 21-31% compared to silent control treatments, 38-47% compared to tidal turbine sound treatments, and 46-60% compared to wind turbine sound treatments. A lack of difference in median TTM in A. crassa between two different source levels of tidal turbine sound suggests the frequency composition of turbine sound is more relevant in explaining such responses rather than sound intensity. These results show that estuarine mudflat sound mediates natural metamorphosis behaviour in two common species of estuarine crabs, and that exposure to continuous turbine sound interferes with this natural process. These results raise concerns about the potential ecological impacts of sound generated by renewable energy generation systems placed in the nearshore environment. PMID:23240063
Pine, Matthew K; Jeffs, Andrew G; Radford, Craig A
It is now widely accepted that a shift towards renewable energy production is needed in order to avoid further anthropogenically induced climate change. The ocean provides a largely untapped source of renewable energy. As a result, harvesting electrical power from the wind and tides has sparked immense government and commercial interest but with relatively little detailed understanding of the potential environmental impacts. This study investigated how the sound emitted from an underwater tidal turbine and an offshore wind turbine would influence the settlement and metamorphosis of the pelagic larvae of estuarine brachyuran crabs which are ubiquitous in most coastal habitats. In a laboratory experiment the median time to metamorphosis (TTM) for the megalopae of the crabs Austrohelice crassa and Hemigrapsus crenulatus was significantly increased by at least 18 h when exposed to either tidal turbine or sea-based wind turbine sound, compared to silent control treatments. Contrastingly, when either species were subjected to natural habitat sound, observed median TTM decreased by approximately 21–31% compared to silent control treatments, 38–47% compared to tidal turbine sound treatments, and 46–60% compared to wind turbine sound treatments. A lack of difference in median TTM in A. crassa between two different source levels of tidal turbine sound suggests the frequency composition of turbine sound is more relevant in explaining such responses rather than sound intensity. These results show that estuarine mudflat sound mediates natural metamorphosis behaviour in two common species of estuarine crabs, and that exposure to continuous turbine sound interferes with this natural process. These results raise concerns about the potential ecological impacts of sound generated by renewable energy generation systems placed in the nearshore environment.
Pine, Matthew K.; Jeffs, Andrew G.; Radford, Craig A.
Like many metazoans, the freshwater prawn Macrobrachium rosenbergii begins its post-embryonic life with a set of morphologically distinct planktonic larval stages, followed by a benthic post-larval stage during which the maturing organism differs from the larvae both ecologically and physiologically. Understanding of the molecular basis underlying morphogenesis in crustaceans is limited to the observation that methyl farnesoate, the non-epoxidated form of the insect juvenile hormone, acts as the active crustacean juvenoid. Molt steroids were also linked to morphogenesis and several other molecular pathways, such as Hedgehog and Wnt, are known to underlie morphogenesis in all metazoans examined and, as such, are thought to do the same in crustaceans. Using next generation sequencing, we deep-sequenced the transcriptomes of several larval and post-larval stages. De novo assembly, followed by bioinformatics analysis, revealed that many novel transcripts are over-expressed in either larvae- or post-larvae-stage prawn, shedding light on the molecular basis underlying M. rosenbergii metamorphosis. Fast larval molting rates and periodic morphological changes were reflected in over-expression of transcripts annotated to the cell cycle, DNA replication and morphogenic pathways (i.e., Hedgehog and Wnt). Further characterization of transcripts assigned to morphogenic pathways by real-time RT-PCR reconfirmed their over-expression in larvae, albeit with a more complex expression pattern when examined in the individual developmental stages. The expression level of an orthologue of cytochrome P450, 15A1, known to epoxidize methyl farnesoate in insects, was increased in the late larval and early post-larval stages, in accordance with the role of methyl farnesoate in crustacean metamorphosis. This study exemplifies the applicability of a high-throughput sequencing approach for studying complex traits, including metamorphosis, providing new insight into this unexplored area of crustacean research.
Ventura, Tomer; Manor, Rivka; Aflalo, Eliahu D.; Chalifa-Caspi, Vered; Weil, Simy; Sharabi, Omri; Sagi, Amir
Insect larvae metamorphose to winged and reproductive adults either directly (hemimetaboly) or through an intermediary pupal stage (holometaboly). In either case juvenile hormone (JH) prevents metamorphosis until a larva has attained an appropriate phase of development. In holometabolous insects, JH acts through its putative receptor Methoprene-tolerant (Met) to regulate Krüppel-homolog 1 (Kr-h1) and Broad-Complex (BR-C) genes. While Met and Kr-h1 prevent precocious metamorphosis in pre-final larval instars, BR-C specifies the pupal stage. How JH signaling operates in hemimetabolous insects is poorly understood. Here, we compare the function of Met, Kr-h1 and BR-C genes in the two types of insects. Using systemic RNAi in the hemimetabolous true bug, Pyrrhocoris apterus, we show that Met conveys the JH signal to prevent premature metamorphosis by maintaining high expression of Kr-h1. Knockdown of either Met or Kr-h1 (but not of BR-C) in penultimate-instar Pyrrhocoris larvae causes precocious development of adult color pattern, wings and genitalia. A natural fall of Kr-h1 expression in the last larval instar normally permits adult development, and treatment with an exogenous JH mimic methoprene at this time requires both Met and Kr-h1 to block the adult program and induce an extra larval instar. Met and Kr-h1 therefore serve as JH-dependent repressors of deleterious precocious metamorphic changes in both hemimetabolous and holometabolous juveniles, whereas BR-C has been recruited for a new role in specifying the holometabolous pupa. These results show that despite considerable evolutionary distance, insects with diverse developmental strategies employ a common-core JH signaling pathway to commit to adult morphogenesis.
Background Previous work showed that miRNAs play key roles in the regulation of metamorphosis in the hemimetabolan species Blattella germanica. To gain insight about which miRNAs might be important, we have constructed two miRNA libraries, one of the penultimate, pre-metamorphic nymphal instar (N5) and the other of the last, metamorphic nymphal instar (N6). Results High throughput sequencing gave 61 canonical miRNAs present in the N5 and N6 libraries, although at different proportions in each. Comparison of both libraries led to the identification of three and 37 miRNAs significantly more expressed in N5 and N6 respectively. Twelve of these 40 miRNAs were then investigated further by qRT-PCR and results indicated that miR-252-3p was well expressed in N5 but not in N6, whereas let-7-5p, miR-100-5p and miR-125-5p showed the reverse pattern. 20-Hydroxyecdysone (20E) tended to stimulate miRNA expression, whereas juvenile hormone (JH) inhibited the 20E stimulatory effect. Expression of let-7, miR-100 and miR-125 was increased by 20E, which has also been observed in D. melanogaster. The only miRNA that was inhibited by 20E was miR-252-3p. The involvement of let-7, miR-100 and miR-125 in metamorphosis has been demonstrated in other insects. Depletion of miR-252-3p caused growth and developmental delays, which suggests that this miRNA is involved in regulating these processes prior to metamorphosis. Conclusions The comparative analysis of miRNA libraries from pre-metamorphic (N5) and metamorphic stages (N6) of B. germanica proved to be a useful tool to identify miRNAs with roles in hemimetabolan metamorphosis. Three miRNAs emerged as important factors in the metamorphic stage (N6): let-7-5p, miR-100-5p and miR-125-5p, whereas miR-252-3p appears to be important in the pre-metamorphic stage (N5).
Background The steroid hormone 20-hydroxyecdysone (20E) triggers the major developmental transitions in Drosophila, including molting and metamorphosis, and provides a model system for defining the developmental and molecular mechanisms\\u000a of steroid signaling. 20E acts via a heterodimer of two nuclear receptors, the ecdysone receptor (EcR) and Ultraspiracle,\\u000a to directly regulate target gene transcription.\\u000a \\u000a \\u000a \\u000a \\u000a Results Here we identify the genomic transcriptional response to
Robert B Beckstead; Geanette Lam; Carl S Thummel
Three years after a serious cerebral contusion a patient became delirious for a period of several months. During that time he pretended to turn into a cock. This theme is interpreted as a metaphorical expression rather than as a firm belief in a real metamorphosis. The feelings of strangeness considered as a matricial condition of delirious phenomenons are debated. Of first importance are the lesions of the right hemisphere upon which are often added more diffuse impairments of the frontal lobes and of the brain stem. The rarity of this phenomenon is to be emphasized whereas the references to animals seem to haunt human soul. PMID:2412284
Numerous studies have documented the decline of amphibian populations over the past decade and no single factor has been the linked to these widespread declines. Determining the causes of declining amphibian populations worldwide has proven difficult because of the variety of anthropogenic and natural suspect agents. A Wingspread workshop, convened by The Society of Environmental Toxicology and Chemistry (SETAC), brought together individuals with expertise in the areas of amphibian biology, ecotoxicology, natural resource management, and environmental policy. This workshop had three objectives: 1) create a network for future discussions on multiple Stressor causes of declines; 2) characterize and prioritize technical issues critical to the analysis of the decline problem; and 3) identify and develop resource management approaches to promote sustainable and healthy amphibian populations. The workshop proceedings will be summarized in a book entitled, "Multiple Stressors and Declining Amphibian Populations: Evaluating Cause and Effect." This paper summarizes the results of the workshop.
Krest, S. K.; Linder, G.; Sparling, D. W.
Previously melittin, the ?-helical basic honey bee venom peptide, was shown to inhibit F1-ATPase by binding at the ?-subunit DELSEED motif of F1Fo ATP synthase. Herein, we present the inhibitory effects of the basic ?-helical amphibian antimicrobial peptides, ascaphin-8, aurein 2.2, aurein 2.3, carein 1.8, carein 1.9, citropin 1.1, dermaseptin, maculatin 1.1, maganin II, MRP, or XT-7, on purified F1 and membrane bound F1Fo E. coli ATP synthase. We found that the extent of inhibition by amphibian peptides is variable. Whereas MRP-amide inhibited ATPase essentially completely (~96% inhibition), carein 1.8 did not inhibit at all (0% inhibition). Inhibition by other peptides was partial with a range of ~13% to 70%. MRP-amide was also the most potent inhibitor on molar scale (IC50 ~3.25 µM). Presence of an amide group at the c-terminal of peptides was found to be critical in exerting potent inhibition of ATP synthase (~20–40% additional inhibition). Inhibition was fully reversible and found to be identical in both F1Fo membrane preparations as well as in isolated purified F1. Interestingly, growth of Escherichia coli was abrogated in the presence of ascaphin-8, aurein 2.2, aurein 2.3, citropin 1.1, dermaseptin, magainin II-amide, MRP, MRP-amide, melittin, or melittin-amide but was unaffected in the presence of carein 1.8, carein 1.9, maculatin 1.1, magainin II, or XT-7. Hence inhibition of F1-ATPase and E. coli cell growth by amphibian antimicrobial peptides suggests that their antimicrobial/anticancer properties are in part linked to their actions on ATP synthase.
Laughlin, Thomas F.; Ahmad, Zulfiqar
Ectothermic species living in temperate regions can experience rapid and potentially stressful changes in body temperature driven by abrupt weather changes. Yet, among amphibians, the physiological impacts of short-term temperature variation are largely unknown. Using an ex situ population of Cryptobranchus alleganiensis, an aquatic North American salamander, we tested the hypothesis that naturally occurring periods of temperature variation negatively impact amphibian health, either through direct effects on immune function or by increasing physiological stress. We exposed captive salamanders to repeated cycles of temperature fluctuations recorded in the population's natal stream and evaluated behavioral and physiological responses, including plasma complement activity (i.e. bacteria killing) against Pseudomonas aeruginosa, Escherichia coli and Aeromonas hydrophila. The best-fit model (?AICc=0, wi=0.9992) revealed 70% greater P. aeruginosa killing after exposure to variable temperatures and no evidence of thermal acclimation. The same model predicted 50% increased E. coli killing, but had weaker support (?AICc=1.8, wi=0.2882). In contrast, plasma defenses were ineffective against A. hydrophila, and other health indicators (leukocyte ratios, growth rates and behavioral patterns) were maintained at baseline values. Our data suggest that amphibians can tolerate, and even benefit from, natural patterns of rapid warming/cooling. Specifically, temperature variation can elicit increased activity of the innate immune system. This immune response may be adaptive in an unpredictable environment, and is undetectable by conventional health indicators (and hence considered cryptic). Our findings highlight the need to consider naturalistic patterns of temperature variation when predicting species' susceptibility to climate change. PMID:23948472
Terrell, Kimberly A; Quintero, Richard P; Murray, Suzan; Kleopfer, John D; Murphy, James B; Evans, Matthew J; Nissen, Bradley D; Gratwicke, Brian
Widespread reports of amphibian declines have been considered a warning of large-scale environmental degradation, yet the reasons for these declines remain unclear. This study suggests that exposure to ultraviolet radiation may act as an environmental stressor that affects population breeding success or susceptibility to disease. Ultraviolet radiation is attenuated by dissolved and particulate compounds in water, which may be of either terrestrial or aquatic origin. UV attenuation by dissolved organic carbon (DOC) is primarily due to compounds in the fulvic acid fraction, which originate in soil environments. These terrestrially-derived fulvic acids are transported to during hydrologic flushing events such as snowmelt and episodic precipitation and play an important role in controlling UV exposure in surface waters. As part of a previously published project, amphibian surveys were conducted at seventeen sites in Rocky Mountain National Park both during, and subsequent to, a three-year drought (1988 - 1990). During this period, ten sites lost one amphibian species, while only one site gained a previously unreported species. One possible explanation for these localized species losses is increased exposure to UV radiation, mediated by reduced terrestrial DOC inputs during dry periods. Several subsequent years of water chemistry data showed that the sites with documented species losses were characterized by a range of DOC concentrations, but tended to have a greater proportion of terrestrial DOC than sites that did not undergo species loss. This suggests that terrestrial inputs exert a strong control on DOC concentrations that may influence species success. We used physical environmental factors to develop a classification scheme for these sites. There are many physical factors that can influence terrestrial DOC inputs, including landscape position, geomorphology, soil type, and watershed vegetation. In addition, we considered the possible effects on internal aquatic inputs, such as nutrient status, food web composition, and aquatic vegetation. Finally, we examined other sites in Rocky Mountain National Park to determine their susceptibility to species loss.
O'Reilly, C. M.; Brooks, P. D.; Corn, P. S.; Muths, E.; Campbell, D. H.; Diamond, S.; Tonnessen, K.
Cloning of a proenkephalin cDNA from the pelobatid anuran amphibian, Spea multiplicatus, provides additional evidence that Leu-enkephalin, although present in the brain of anuran amphibians, is not encoded by the proenkephalin gene. The S. multiplicatus proenkephalin cDNA is 1375 nucleotides in length, and the open reading frame contains the sequences of seven opioid sequences. There are five copies of the
Stephanie Lecaude; Jasem Alrubaian; Cristina Sollars; Catherine Propper; Phillip Danielson; Robert M Dores
Vertebrate genomes are comprised of isochores that are relatively long (>100 kb) regions with a relatively homogenous (either GC-rich or AT-rich) base composition and with rather sharp boundaries with neighboring isochores. Mammals and living archosaurs (birds and crocodilians) have heterogeneous genomes that include very GC-rich isochores. In sharp contrast, the genomes of amphibians and fishes are more homogeneous and they have a lower overall GC content. Because DNA with higher GC content is more thermostable, the elevated GC content of mammalian and archosaurian DNA has been hypothesized to be an adaptation to higher body temperatures. This hypothesis can be tested by examining structure of isochores across the reptilian clade, which includes the archosaurs, testudines (turtles), and lepidosaurs (lizards and snakes), because reptiles exhibit diverse body sizes, metabolic rates, and patterns of thermoregulation. This study focuses on a comparative analysis of a new set of expressed genes of the red-eared slider turtle and orthologs of the turtle genes in mammalian (human, mouse, dog, and opossum), archosaurian (chicken and alligator), and amphibian (western clawed frog) genomes. EST (expressed sequence tag) data from a turtle cDNA library enriched for genes that have specialized functions (developmental genes) revealed using the GC content of the third-codon-position to examine isochore structure requires careful consideration of the types of genes examined. The more highly expressed genes (e.g., housekeeping genes) are more likely to be GC-rich than are genes with specialized functions. However, the set of highly expressed turtle genes demonstrated that the turtle genome has a GC content that is intermediate between the GC-poor amphibians and the GC-rich mammals and archosaurs. There was a strong correlation between the GC content of all turtle genes and the GC content of other vertebrate genes, with the slope of the line describing this relationship also indicating that the isochore structure of turtles is intermediate between that of amphibians and other amniotes. These data are consistent with some thermal hypotheses of isochore evolution, but we believe that the credible set of models for isochore evolution still includes a variety of models. These data expand the amount of genomic data available from reptiles upon which future studies of reptilian genomics can build. PMID:21669806
Chojnowski, Jena L; Braun, Edward L
Hemoparasites were harvested from 993 individuals belonging to 15 reptilian and 1 amphibian species, from various Italian localities. Hemogregarins were found in 10 reptilian species while a flagellate and microfilariae were found only in Tarentola mauritanica from Lampedusa. For each host species and place of origin the frequencies of hemogregarins are reported and discussed. Longitudinal studies with periodical thin smears were carried out on 5 Tarentola mauritanica, 4 Lacerta viridis, 26 Podarcis filfolensis, 10 Podarcis muralis, 38 Podarcis sicula, 8 Chalcides ocellatus. This material, whose study has not yet been completed, is made available by the author who strongly encourages further investigations on this subject. PMID:10870559
Peptides analogous to glucagon-like peptide-1 (GLP-1) have been isolated from amphibian pancreas and intestine, and their amino acid sequences and cDNA structures elucidated. Just like their mammalian counterpart, these peptides are potent insulinotropins in mammalian pancreatic cells. We show here that these peptides also exert strong glycogenolytic actions when applied to dispersed fish hepatocytes. We compared the potencies of three synthetic GLP-1s from Xenopus laevis and two native GLP-1s from Bufo marinus in the activation of glycogenolysis in the hepatocytes of a marine rockfish (Sebastes caurinus) and two freshwater catfish (Ameiurus nebulosus and A. melas), and demonstrated their effectiveness in increasing the degree of phosphorylation of glycogen phosphorylase. We also compared the glycogenolytic potency of the peptides with those of human GLP-1 and glucagons from human and B. marinus. Sensitivity to these peptides is species-specific, with the rockfish responding at lower concentrations to GLP-1s and the two catfish reacting better to glucagons. However, the relative potency of the amphibian GLP-1s and glucagons is similar in the three species. Xenopus GLP-1C (xGLP-1C) is consistently more potent than xGLP-1B, while xGLP-1A displays the smallest activation of glycogenolysis. Similarly, Bufo GLP-1(32)-the peptide with the highest amino acid sequence identity to xGLP-1C-always shows a higher potency than Bufo GLP-1(37), which is closely related to xGLP-1B. The relative hierarchy of these glycogenolytic GLP-1s differs from their ranking as insulinotropins in mammalian beta-cells. In the rockfish system, Bufo glucagon-36, a C-terminally extended glucagon, is more potent than the shorter bovine glucagon and Bufo glucagon-29 in the activation of glycogenolysis; when tested in A. nebulosus hepatocytes, bovine and amphibian glucagons are equipotent. Amphibian GLP-1s and glucagons activate glycogenolysis in fish hepatocytes through increased phosphorylation of glycogen phosphorylase, implying involvement of the adenylyl cyclase/protein kinase A system in signal transduction. We conclude that the broad physiological effectiveness of GLP-1 has been retained throughout vertebrate evolution, and that both insulinotropic activity and glycogenolytic actions belong to the repertoire of GLP-1. PMID:11384772
Mommsen, T P; Conlon, J M; Irwin, D M
Pathogenic fungi have substantial effects on global biodiversity, and 2 emerging pathogenic species-the chytridiomycete Batrachochytrium dendrobatidis, which causes chytridiomycosis in amphibians, and the ascomycete Geomyces destructans, which causes white-nose syndrome in hibernating bats-are implicated in the widespread decline of their vertebrate hosts. We synthesized current knowledge for chytridiomycosis and white-nose syndrome regarding disease emergence, environmental reservoirs, life history characteristics of the host, and host-pathogen interactions. We found striking similarities between these aspects of chytridiomycosis and white-nose syndrome, and the research that we review and propose should help guide management of future emerging fungal diseases. PMID:23622255
Eskew, Evan A; Todd, Brian D
Topoisomerases are nuclear enzymes that play essential roles in DNA replication, transcription, chromosome segregation, and recombination. All cells have two major forms of topoisomerases: type I, which makes single-stranded cuts in DNA, and type II enzymes, which cut and pass double-stranded DNA. DNA topoisomerases are important targets of approved and experimental anti-cancer agents. The protocols described in this unit are of assays used to assess new chemical entities for their ability to inhibit both forms of DNA topoisomerase. Included are an in vitro assay for topoisomerase I activity based on relaxation of supercoiled DNA and an assay for topoisomerase II based on the decatenation of double-stranded DNA. The preparation of mammalian cell extracts for assaying topoisomerase activity is described, along with a protocol for an ICE assay for examining topoisomerase covalent complexes in vivo and an assay for measuring DNA cleavage in vitro.
Nitiss, John L.; Soans, Eroica; Rogojina, Anna; Seth, Aman; Mishina, Margarita
Background The orthologs of eukaryotic initiation factor 5C (eIF5C) are essential to the initiation of protein translation, and their regulation during development is not well known. Results A cDNA encoding a polypeptide of 419 amino acids containing an N-terminal leucine zipper motif and a C-terminal eIF5C domain was cloned from metamorphic larvae of Helicoverpa armigera. It was subsequently named Ha-eIF5C. Quantitative real-time PCR (QRT-PCR) revealed a high expression of the mRNA of Ha-eIF5C in the head-thorax, integument, midgut, and fat body during metamorphosis. Immunohistochemistry suggested that Ha-eIF5C was distributed into both the cytoplasm and the nucleus in the midgut, fat body and integument. Ha-eIF5C expression was upregulated by 20-hydroxyecdysone (20E). Furthermore, the transcription of Ha-eIF5C was down regulated after silencing of ecdysteroid receptor (EcR) or Ultraspiracle protein (USP) by RNAi. Conclusion These results suggested that during metamorphosis of the cotton bollworm, Ha-eIF5C was upregulated by 20E through the EcR and USP transcription factors.
Dong, Du-Juan; Wang, Jin-Xing; Zhao, Xiao-Fan
A nonparasitic lamprey in Japan, Lethenteron reissneri, stops feeding prior to the commencement of metamorphosis. Resumption of feeding cannot take place due to major alterations in the digestive system, including loss of the gall bladder (GB) and biliary tree in the liver. This degeneration of bile ducts is considered to depend on programmed cell death or apoptosis, but molecular evidence of apoptosis remains lacking. Using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining and immunohistochemistry with an antibody against active caspase-3, we showed that epithelial cells of the cystic duct (CD) and GB became TUNEL-positive by the early metamorphosing stage. Immunohistochemical staining of active caspase-3, a key mediator in the apoptotic cascade, showed that the apoptotic signal was initiated in the region around the CD in the late larval phase. In later stages, active caspase-3-positive epithelial cells were also observed in the large intrahepatic bile duct (IHBD) and peripheral small IHBDs. At the early metamorphosing stage, bile canaliculi between hepatocytes were dilated and displayed features resembling canaliculi in cholestasis. Onset of apoptosis around the CD, w