Search

Aim: For many endemic species with limited dispersal capacities, the relationship between landscape changes and species distributions is still unclear. We characterized the population structure of the endemic ringed salamander (Ambystoma annulatum) across its distribution in the Central Interior Highlands (CIH) of North America, an area of high species endemism, to infer the ecological and evolutionary history of the species. Methods: We sampled 498 individuals across the species distribution and characterized the population genetic structure using nuclear microsatellite and mitochondrial DNA (mtDNA) markers. Results: Ambystoma annulatum exist in two strongly supported nuclear genetic clusters across the CIH that correspond to a northern cluster that includes the Missouri Ozark populations and a southern cluster that includes the Arkansas and Oklahoma Ozarks and the Ouachita Mountains. Our demographic models estimated that these populations diverged approximately 2,700 years ago. Pairwise estimates of genetic differentiation at microsatellite and mtDNA markers indicated limited contemporary gene flow and suggest that genetic differentiation was primarily influenced by changes in the post‐Pleistocene landscape of the CIH. Main Conclusions: Both the geologic history and post‐European settlement history of the CIH have influenced the population genetic structure of A. annulatum. The low mtDNA diversity suggests a retraction into and expansion out of refugial areas in the south‐central Ozarks, during temperature fluctuations of the Pleistocene and Holocene epochs. Similarly, the estimated divergence time for the two nuclear clusters corresponds to changes in the post‐Pleistocene landscape. More recently, decreased A. annulatum gene flow may be a result of increased habitat fragmentation and alteration post‐European settlement. [ABSTRACT FROM AUTHOR]

Amphibians are one of the most vulnerable groups of tetrapods with 41% of species considered threatened with extinction. In amphibians, an increase in stress level is an early physiological response to factors associated with habitat degradation. In vertebrates, stress increases the susceptibility to parasite infections and is associated with changes in the number of blood cells, and therefore the proportion of the leukocytes, neutrophils to lymphocytes (N/L ratio) is used as a proxy measure of stress hormones. In this study, we used such leukocyte profiles to analyze stress levels and evaluate parasite load to elucidate the health condition of the endangered Mexican stream salamander, Ambystoma ordinarium. The habitat quality of streams inhabited by A. ordinarium was evaluated by Rapid Bioassessment Protocols (RBPs). We selected three streams with the highest RBPs scores as the undisturbed streams and three with the lowest scores as the disturbed streams. In each stream, we determined leukocyte profile and searched for ecto/endoparasites on sampled individuals. We report for the first time the leukocyte profile of A. ordinarium. A significantly higher N/L ratio was found in salamanders from disturbed vs. undisturbed streams. We also found a higher parasitic infection in salamanders from disturbed streams. Our results suggest that low habitat quality can increase stress levels and susceptibility to parasitic infections, thereby compromising the long-term persistence of populations of this species in disturbed habitats. [ABSTRACT FROM AUTHOR]

In order to better understand the impacts and treatment of infection with Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal) it is important to document host species, the effect of infection and response to treatment protocols. Here we report asymptomatic Bd infection detected through duplex qPCR screening of three Mexican ambystomatid salamanders; Ambystoma andersoni, Ambystoma dumerilii and Ambystoma mexicanum at three zoo collections, and A. andersoni and A. mexicanum in a private collection. Bsal was tested for but not detected. We also report the effectiveness and side effects of five treatment protocols in these species. Using the antifungal agent itraconazole, A. dumerilii were cleared of infection without side-effects using the granulated preparation (Sporanox). Morbidity and mortality occurred when A. dumerilii and A. andersoni were treated using a liquid oral preparation of the itraconazole (Itrafungol); infection was successfully cleared in surviving specimens of the latter species. Ambystoma mexicanum was successfully cleared without any side-effects using Itrafungol. Mortality and morbidity were likely caused by toxic effects of some component on the liquid preparation of itraconazole, but aspects of water quality and husbandry cannot be ruled out. [ABSTRACT FROM AUTHOR]

The populations of ambystomatid salamanders around Mexico City are subject to a variety of threats, and some populations may be in decline. Three Ambystoma species found around Mexico City and in central Mexico are A. altamirani, A. leorae, and A. rivulare, and these three species are subject to a variety of conservation threats. We compiled a database of localities for these ambystomatid salamanders. The compiled observations of these three species of endangered salamanders suggest several patterns: 1) most localities for all three species are in the Estado de México, including several for A. altamirani within the borders of Mexico City; 2) there is little, if any, geographical overlap among these three species; 3) the relatively few documented sites for A. leorae and A. rivulare highlight their tenuous conservation status. Our hope is that this presentation of a map of documented locations of these three Mexican Ambystoma has created a starting point for future studies on these salamanders. [ABSTRACT FROM AUTHOR]

The early evolution of salamanders, which are one of the three living groups of lissamphibians, is not well known. Both stem- and crown-group salamanders first appeared in the Middle Jurassic (Bathonian), but subsequently had different evolutionary histories: stem salamanders were thought to have gone extinct in the Late Jurassic, while crown salamanders persist to the present day. Here, I report the discovery of an indeterminate stem salamander in the Lower Cretaceous (Aptian-Albian) Ilek Formation of Western Siberia. This is new evidence that the most basal salamanders survived beyond the Jurassic-Cretaceous boundary and co-existed with crown-group salamanders during approximately the first 40 million years of the known history of salamanders. The recognition of stem salamanders in the Early Cretaceous of Western Siberia adds to the inventory of taxa that suggest this area was a refugium for various groups of vertebrates with Jurassic affinities. [ABSTRACT FROM AUTHOR]

Ambystoma altamiranoi is an endangered endemic salamander found in the Transvolcanic Belt of Mexico. Unfortunately, relatively little is known about its ecology. Here we report on the diet of larval A. altamiranoi from a population in Llano de los Axolotes, Sierra de las Cruces, State of México, Mexico. Empty stomachs were found in 13.3% of individuals. Ostracods and gastropods dominated the diet of A. altamiranoi, together accounting for 89.9% of prey items consumed. The remainder of the diet consisted primarily of insects. Our observations suggest that the diet of A. altamiranoi is relatively narrow and that resources may be limited (relatively high frequency of empty stomachs), suggesting that factors that could impact the availability of ostracods and gastropods might have serious consequences for these endangered salamanders. [ABSTRACT FROM AUTHOR]

Eleven female Jefferson Salamanders (Ambystoma jeffersonianum) and five female Spotted Salamanders (A. maculatum) were collected during 28 February-17 March 2011 from the same vernal pool in south-central Pennsylvania for comparison of reproductive characteristics. Mean clutch size (169.5 eggs) and relative clutch mass (12.9%) of A. jeffersonianum was larger than those values of A. maculatum (130.8 eggs and 9.4%, respectively) despite an 8.9% smaller body size of the former. However, mean egg diameter was larger in A. maculatum. Greater fecundity, even if at the cost of egg size, could provide A. jeffersonianum with an added reproductive advantage in areas of syntopy with A. maculatum, where it is known to be a superior competitor and predator of A. maculatum at the larval stage. [ABSTRACT FROM AUTHOR]

Introduction Many species of ambystomatid salamanders are dependent upon highly variable temporary wetlands for larval development. High larval densities may prompt the expression of a distinct head morphology that may facilitate cannibalism. However, few studies have characterized structural cannibalism within natural populations of larval salamanders. In this study we used two species of larval salamanders, long-toed (Ambystoma macrodactylum) and ringed salamanders (A. annulatum). Head morphometrics and stable isotopic values of carbon (δ13C) and nitrogen (δ15N) were used to identify the presence or absence of structural cannibalism. Weather conditions were also analyzed as a potential factor associated with the expression of cannibalistic morphology. Results Populations of salamander larvae did not consistently exhibit cannibalistic morphologies throughout collection periods. Larval long-toed salamanders exhibited trophic polymorphisms when relatively lower precipitation amounts were observed. Larval ringed salamanders were observed to be cannibalistic but did not exhibit polymorphisms in this study. Conclusions Structural cannibalism may be transient in both species; however in long-toed salamanders this morphology is necessary for cannibalism. Ringed salamanders can be cannibalistic without morphological adaptations; however the cannibal morph may prolong the viable time period for cannibalism. Additionally, weather conditions may alter pond hydroperiod, subsequently influencing head morphology and cannibalism. [ABSTRACT FROM AUTHOR]

The article describes a case study that presents a new species of Aplectana in Ambystoma velasci found in Mexico. Topics covered include the identified species of Ambystoma, the materials and methods used to examine the specimens of Ambystoma velasci collected from Lago de Tecocomulco in Hidalgo, Mexico, and the description of the new species of Aplectana. It also discusses the taxonomic summary relating to Aplectana found in Ambystoma velasci.

During fieldwork conducted between end of February and mid-April 2012 14 new localities were ascertained for four different taxa of the amphibian genus Lyciasalamandra (L. l. basoglui, L. l. finikensis, L. arikani and L. atifi). This paper represents the first record of L. l. basoglui from Muğla province (Saklıkent, Fethiye). Unlike the common belief in previous researches based on literature we determined that there are almost no gaps between the distributional areas of the known subspecies of L. luschani, moreover the subspecies were found in contact. The recently discovered populations of L. arikani and L. atifi were found to have some distinctive morphological differences compared to other populations of the respective species. [ABSTRACT FROM AUTHOR]

The movements of 52 cave salamanders (Speleomantes strinatii) were studied from May to October 2012, in NW Italy. Cave salamanders, caught inside an artificial cave, were individually marked with fluorescent visible implant elastomers and displaced 20 m from the capture site. A total of 27 (52% of displaced individuals) were recaptured in the cave by the end of the experiment. Six (11.5%) of these were recaptured inside the cave within two nights and ten (19%) within five nights. There were no sex or body size differences between returning or non-returning salamanders. These preliminary results suggest the existence of homing behaviour in S. strinatii [ABSTRACT FROM AUTHOR]

Branchiate Ambystoma talpoideum (Mole Salamanders) in fishless ponds can be large enough to act as predators, rather than competitors, during the spring breeding season of other amphibians. Food habits of high-density Mole Salamander populations from 2 proximate woodland ponds in Clark County, AR were examined before and after egg-laying by frogs, with an expectation that the salamanders likely would consume hatching tadpoles. However, salamanders instead commonly fed on the novel item of freshly-laid frog eggs. Results from both ponds indicated that the salamanders, perhaps due to food limitation, consumed smaller prey items than would be expected and heavily consumed frog eggs, a novel item. [ABSTRACT FROM AUTHOR]

Spatial autocorrelation (SAC) is often observed in species distribution data, and can be caused by exogenous, autocorrelated factors determining species distribution, or by endogenous population processes determining clustering such as dispersal. However, it remains debated whether SAC patterns can actually reveal endogenous processes. We reviewed studies measuring dispersal of the salamander Salamandra salamandra, to formulate a priori hypotheses on the scale at which dispersal is expected to determine population distribution. We then tested the hypotheses by analysing SAC in distribution data, and evaluating whether controlling for the effect of environmental variables can reveal endogenous processes. We surveyed 565 streams to obtain species distribution data; we also recorded landscape and microhabitat features known to affect the species. We used multiple approaches to tease apart endogenous and exogenous SAC: the analysis of residuals of logistic regression models considering different environmental variables; the analysis of eigenvectors extracted by several implementations of spatial eigenvector mapping. In capture-mark-recapture studies, 98% of individuals moved 500 m or less. Both species distribution and environmental features were strongly autocorrelated. The residuals of logistic regression relating species to environmental variables were autocorrelated at distances up to 500 m; analyses considering different sets of environmental variables, or assuming non-linear species habitat relationships, yielded identical results. The results of spatial eigenvector mapping strongly depended on the matrix of distances used. Nevertheless, the eigenvectors of models with best fit were autocorrelated at distances up to 200-500 m. The concordance between multiple approaches suggests that 500 m is the scale at which dispersal connects breeding localities, increasing probability of occurrence. If exogenous variables are correctly identified, the analysis of SAC can provide important insights on endogenous population processes, such as the flow of individuals. SAC analysis can also provide important information for conservation, as the existence of metapopulations or population networks is essential for long term persistence of amphibians. [ABSTRACT FROM AUTHOR]

The achójki is an Ambystomatidae salamander, this species is endemic and inhabit exclusively at lake Pátzcuaro, Michoacán; it presents paedogenesis, and is a generalist carnivorous that probably has interspecific competition with some freshwater fish, such as: Bulldog Goodeid (Alloophorus robustus), Mexican Silverside (Menidia estor) and Largemouth Black Bass (Micropterus salmoides). For p'urhépecha people, this species has an alimentary use, cooking by broth or fried, by their high protein content and also is considered medicinal, prescripted for respiratory diseases and supplying energy for anemic children and breastfeeding women. This paper is divided in two issues, ecology and cultural use of this species, based on bibliographical search and interviews on field work. Most of the adults had knowledge of use of achójki, and claim the population reduction. Currently is considered a threatened species and is registered in national and international lists of conservation. The main factors that have contributed to the species decrease are: lake pollution, decrease of the water level, introduction of exotic species and overexploitation of resources. Were founded are three UMAs or reproduction sites: UMA Jimbani Erandi, PIMVS Jimbani Tzípekua and UMA Dumerilii. Development programs that involve local initiatives should be done for the survival of the species with a sustainable perspective. The general aim of the present paper is to recognize the ecological and cultural importance of the achójki (Ambystoma dumerilii) in Patzcuaro's lake. [ABSTRACT FROM AUTHOR]

Abstract: Axolotls (Ambystoma mexicanum) are aquatic salamanders that are widely used in research. Axolotls have been bred in laboratories for nearly 150years, yet little is known about the basic biology of reproduction in these animals. We investigated the effects of changing day length, time of year, and food availability on levels of circulating estradiol and androgens in adult female and male axolotls, respectively. In addition, we examined the effects of these variables on the mass of ovaries, oviducts, and eggs in females and on mass of testes in males relative to each individual’s body weight, to calculate a form of gonadosomatic index (GSI). In both sexes, GSI was not correlated with levels of circulating steroids. In female axolotls, estradiol levels were influenced by food availability, changes in day length, and season, even when animals were held at a constant temperature and day length was decorrelated with calendar date. In addition, the mass of ovaries, oviducts, and eggs varied seasonally, peaking in the winter months and declining during the summer months, even though our animals were not breeding and shedding eggs. In males, levels of androgens appeared to vary independently of external conditions, but GSI varied dramatically with changes in day length. These results suggest that reproduction in axolotls may vary seasonally, as it does in many other ambystomid species, although both male and female axolotls are capable of reproducing several times each year. The physiological basis of this ability remains enigmatic, given the indications of seasonality contained in our data. [Copyright &y& Elsevier]

The kinetics of the bioaccumulation of malathion ( O,O-dimethyl phosphorodithioate of diethyl mercaptosuccinate) and the biological impact of exposure for tiger salamanders, Ambystoma tigrinum, were assessed through exposure to soil surface contaminated with 50 μg/cm2 or 100 μg/cm2 malathion and ingestion of an earthworm exposed to soil contaminated with 200 μg/cm2 malathion. Malathion and malaoxon burdens in salamanders sampled at different times after exposure(s) were measured by gas chromatography in four tissue/organ subgroups: liver, epaxial muscle, pooled viscera (except the liver and brain), and pooled avisceral carcass (muscle, skin, and bone). The total tiger salamander xenobiotic burdens were calculated from these data. The malathion/malaoxon burden 1 day after exposure was greatest in the avisceral carcass and 2 days after exposure was greatest in the viscera. Bioconcentration and bioaccumulation factors remained less than unity throughout the experiment and did not support the hypothesis of bioaccumulation of malathion in the tiger salamander. Biological impact was assessed with a colorimetric brain cholinesterase microassay. Brain cholinesterase activities in salamanders exposed to malathion-contaminated soil (50 μg/cm2 or 100 μg/cm2 malathion) were suppressed ∼50–65% and 90%, respectively, compared to unexposed controls. The exposed animals did not exhibit overt clinical signs of malathion toxicosis. [ABSTRACT FROM AUTHOR]

Effective sampling of pond-dwelling larval stages of the federally listed Ambystoma cingulatum (Flatwoods Salamander) requires sufficient knowledge of when larvae are present and how best to sample them. Through systematic sampling with active and passive sampling techniques, we found dipnetting to be significantly more effective than three types of passive traps. During surveys for Flatwoods Salamander larvae at Fort Stewart Military Installation, GA in 2005 and 2006, we found that pond residency varied by at least 1.5 months between the 2 years due to the timing of pond filling. In addition, our latest capture on 23 May 2005 was about 2 weeks later than previously recorded at any site range-wide. A simple growth model was used to evaluate likely hatching dates based on significant rain events, observed sizes at capture, and likely growth rates. This analysis suggested that the primary dates of hatching occurred in late February 2005 and early January 2006, a difference that corresponds to that seen in the residency of the latest larval stages. A review of the survey records for Fort Stewart for the past 13 years shows a steep decline in the number of occupied ponds from near 20 to a single pond for the past two years (the only documented breeding success in a natural pond since 1999). [ABSTRACT FROM AUTHOR]

Animals that live in social groups have the opportunity to acquire information about foraging opportunities, mates and predators. Traditionally, social learning has been studied in birds and mammals, but few tests have been conducted on less social taxa such as amphibians. Moreover, few studies have considered cross-species learning among members of mixed-species assemblages. We examined social learning in tadpoles of the boreal chorus frog, Pseudacris maculata, and found that they do not display a fright response to the odour of predacious tiger salamanders, Ambystoma tigrinum, without prior experience with salamanders, but they can learn to recognize the salamanders when they are paired with predator-experienced woodfrog, Rana sylvatica, tadpoles. Moreover, the efficacy of learning is enhanced when the ratio of tutors-to-observers increases. Social learning has far-reaching implications for survival of individuals in mixed-species assemblages. [Copyright &y& Elsevier]

Between December 2002 and June 2004, 10 marbled salamanders, Ambystoma opacum, were examined for coccidian parasites. Salamanders were collected in Bradley (n - 2), Little River (n - 1), Miller (n x 1), and Sevier (n - 1) Counties, Arkansas; Webster Parish, Louisiana (n - 2); and Bowie (n - 1) and Nacogdoches (n - 2) Counties, Texas. Two of 10 (20%) A. opacum from Louisiana harbored an undescribed species of Eimeria. Oocysts of Eimeria trauthi n. sp. were ellipsoidal, 36.6 x 33.1 (33-40 x 29-37) xm, with a thin, single-layered wall; shape index 1.1. Polar granule(s) and micropyle were absent. Oocyst residuum was composed of hundreds of loosely packed homogenous granules of various sizes enclosing a vacuole. Sporocysts were elongate-ellipsoidal, 20.8 x 8.1 (19-22 x 7-9) μm; shape index 2.6. Sporocyst residuum was spherical and composed of a cluster of granules often membrane-bound. This is the first time a coccidium has been reported from an amphibian species in Louisiana and the second time a coccidium has been described from this salamander host. In addition, the following 26 salamanders from various counties in Arkansas, Oklahoma, and Texas were surveyed during the study period and were negative for coccidia: Ambystomatidae, 4 spotted salamanders (Ambystoma maculatum) and 7 mole salamanders (Ambystoma talpoideum); Cryptobranchidae, 4 Ozark hellbenders (Cryptobranchus alleganiensis bishopi); Plethodontidae, 6 spotted dusky salamanders (Desmognathus conanti) and 3 many-ribbed salamanders (Eurycea multiplicata multiplicata); and Salamandridae, 2 central newts (Notophthalmus viridescens louisianensis). [ABSTRACT FROM AUTHOR]

Facultative paedomorphosis is the ability of a salamander to either metamorphose into a terrestrial, metamorphic adult or retain a larval morphology to become a sexually mature paedomorphic adult. It has been hypothesized that density and initial body size variation within populations are instrumental in cueing metamorphosis or paedomorphosis in salamanders, yet few studies have adequately tested these hypotheses in long-term experiments. Beginning in the spring of 2004, 36 experimental ponds were used to manipulate three body size variation levels (low, medium, high) and two density levels (low, high) of Ambystoma talpoideum larvae. Larvae were individually marked using visible implant elastomers and collected every 2 weeks in order to measure snout–vent length and mass. Bi-nightly sampling was used to collect new metamorphs as they appeared. Analysis revealed significant effects of density, size variation and morph on body size of individuals during the summer. Individuals that metamorphosed during the fall and following spring were significantly larger as larvae than those becoming paedomorphic across all treatments. These results support the Best-of-a-Bad-Lot hypothesis, which proposes that the largest larvae metamorphose in order to escape unfavorable aquatic habitats. Large larvae may metamorphose to leave aquatic habitats, regardless of treatment, due to the colder climate and lower productivity found in Kentucky, which is in the northern-most part of A. talpoideum’s range. By maintaining a long-term experiment, we have provided evidence for the transition of both larvae and paedomorphs into metamorphs during fall and spring metamorphosis events. Furthermore, the production of similar morphs under different environmental conditions observed in this research suggests that the ecological mechanisms maintaining polyphenisms may be more diverse that first suspected. [ABSTRACT FROM AUTHOR]

Pool-breeding amphibian populations operate at multiple scales, from the individual pool to surrounding upland habitat to clusters of pools. When metapopulation dynamics play a role in long-term viability, conservation efforts limited to the protection of individual pools or even pools with associated upland habitat may be ineffective over the long term if connectivity among pools is not maintained. Connectivity becomes especially important and difficult to assess in regions where suburban sprawl is rapidly increasing land development, road density, and traffic rates. We developed a model of connectivity among vernal pools for the four ambystomatid salamanders that occur in Massachusetts and applied it to the nearly 30,000 potential ephemeral wetlands across the state. The model was based on a modification of the kernel estimator (a density estimator commonly used in home range studies) that takes landscape resistance into account. The model was parameterized with empirical migration distances for spotted salamanders (Ambystoma maculatum ), dispersal distances for marbled salamanders (A. opacum ), and expert-derived estimates of landscape resistance. The model ranked vernal pools in Massachusetts by local, neighborhood, and regional connectivity and by an integrated measure of connectivity, both statewide and within ecoregions. The most functionally connected pool complexes occurred in southeastern and northeastern Massachusetts, areas with rapidly increasing suburban development. In a sensitivity analysis estimates of pool connectivity were relatively insensitive to uncertainty in parameter estimates, especially at the local and neighborhood scales. Our connectivity model could be used to prioritize conservation efforts for vernal-pool amphibian populations at broader scales than traditional pool-based approaches. [ABSTRACT FROM AUTHOR]

Skeletochronology is the most commonly used tool for evaluating the age of amphibians and reptiles. However, the accuracy of skeletochronology is questionable because few studies have utilized individuals of known age to calibrate their results. In this study, the accuracy of skeletochronology was assessed using individual Arizona Tiger Salamanders (Ambystoma tigrinum nebulosum) that were of known ages that varied from 2-15 years. Cross-sections of salamander toes were analyzed to compare the number of LAG (lines of arrested growth) to the actual age of known cohorts. Our results suggest that skeletochronology was an inaccurate tool for estimating age in this population of A. tigrinum nebulosum because it grossly underestimated age. The high intensity of endosteal resorption coupled with rapprochement of the most peripheral LAG may have produced these results. Our research indicates that skeletochronological studies that do not use individuals of known age for calibration may underestimate age. [ABSTRACT FROM AUTHOR]

Intergenomic interactions that include homoeologous recombinations and intergenomic translocations are commonly observed in plant allopolyploids. Homoeologous recombinations have recently been documented in unisexual salamanders in the genus Ambystoma and revealed exchanged chromosomal segments between A. laterale and A.jeffersonianum genomes in individual unisexuals. We discovered intergenomic translocations in two widespread unisexual triploids A.laterale – 2 jeffersonianum (or LJJ) and its tetraploid derivative A.laterale – 3 jeffersonianum (or LJJJ) by genomic in situ hybridization (GISH). Two different types of intergenomic translocations were observed in two unisexual populations and one contained novel chromosomes generated by an intergenomic reciprocal translocation. We also observed chromosome deletions in several individuals and these chromosome fragmentations were all derived from the A. jeffersonianum genome. These observed intergenomic reciprocal translocations are believed to be caused by non-homologous pairing during meiosis followed by breakage-rejoining events. Genomes of unisexual Ambystoma undergo complicated structural changes that include various intergenomic exchanges that offer unisexuals genetic and phenotypic complexity to escape their evolutionary demise. Unisexual Ambystoma have persisted as natural nuclear genomic hybrids for about four million years. These unisexuals provide a vertebrate model system to examine the interaction of distinct genomes and to evaluate the corresponding genetic, developmental and evolutionary implications of intergenomic exchanges. Intergenomic translocations and homoeologous recombinations appear to be frequent chromosome reconstruction events among unisexual Ambystoma. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Abstract: Ambystomatid salamanders offer several advantages for endocrine disruption research, including genomic and bioinformatics resources, an accessible laboratory model (Ambystoma mexicanum), and natural lineages that are broadly distributed among North American habitats. We used microarray analysis to measure the relative abundance of transcripts isolated from A. mexicanum epidermis (skin) after exogenous application of thyroid hormone (TH). Only one gene had a >2-fold change in transcript abundance after 2 days of TH treatment. However, hundreds of genes showed significantly different transcript levels at days 12 and 28 in comparison to day 0. A list of 123 TH-responsive genes was identified using statistical, BLAST, and fold level criteria. Cluster analysis identified two groups of genes with similar transcription patterns: up-regulated versus down-regulated. Most notably, several keratins exhibited dramatic (1000 fold) increases or decreases in transcript abundance. Keratin gene expression changes coincided with morphological remodeling of epithelial tissues. This suggests that keratin loci can be developed as sensitive biomarkers to assay temporal disruptions of larval-to-adult gene expression programs. Our study has identified the first collection of loci that are regulated during TH-induced metamorphosis in a salamander, thus setting the stage for future investigations of TH disruption in the Mexican axolotl and other salamanders of the genus Ambystoma. [Copyright &y& Elsevier]

Background: Understanding the demographic processes underlying population dynamics is a central theme in ecology. Populations decline if losses from the population (i.e., mortality and emigration) exceed gains (i.e., recruitment and immigration). Amphibians are thought to exhibit little movement even though local populations often fluctuate dramatically and are likely to go exinct if there is no rescue effect through immigration from nearby populations. Terrestrial salamanders are generally portrayed as amphibians with low migratory activity. Our study uses demographic analysis as a key to unravel whether emigration or mortality is the main cause of "losses" from the population. In particular, we use the analysis to challenge the common belief that terrestrial salamanders show low migratory activity. Results: The mark-recapture analysis of adult salamanders showed that monthly survival was high (> 90%) without a seasonal pattern. These estimates, however, translate into rather low rates of local annual survival of only ~40% and suggest that emigration was important. The estimated probability of emigration was 49%. Conclusion: Our analysis shows that terrestrial salamanders exhibit more migratory activity than commonly thought. This may be due either because the spatial extent of salamander populations is underestimated or because there is a substantial exchange of individuals between populations. Our current results are in line with several other studies that suggest high migratory activity in amphibians. In particular, many amphibian populations may be characterized by high proportions of transients and/or floaters. [ABSTRACT FROM AUTHOR]

Delimiting the boundaries of species involved in radiations is critical to understanding the tempo and mode of lineage formation. Single locus gene trees may or may not reflect the underlying pattern of population divergence and lineage formation, yet they constitute the vast majority of the empirical data in species radiations. In this study we make use of an expressed sequence tag (EST) database to perform nuclear (nDNA) and mitochondrial (mtDNA) genealogical tests of species boundaries in Ambystoma ordinarium, a member of an adaptive radiation of metamorphic and paedomorphic salamanders (the Ambystoma tigrinum complex) that have diversified across terrestrial and aquatic environments. Gene tree comparisons demonstrate extensive nonmonophyly in the mtDNA genealogy of A. ordinarium, while seven of eight independent nuclear loci resolve the species as monophyletic or nearly so, and diagnose it as a well-resolved genealogical species. A differential introgression hypothesis is supported by the observation that western A. ordinarium localities contain mtDNA haplotypes that are identical or minimally diverged from haplotypes sampled from a nearby paedomorphic species, Ambystoma dumerilii, while most nDNA trees place these species in distant phylogenetic positions. These results provide a strong example of how historical introgression can lead to radical differences between gene trees and species histories, even among currently allopatric species with divergent life history adaptations and morphologies. They also demonstrate how EST-based nuclear resources can be used to more fully resolve the phylogenetic history of species radiations. [ABSTRACT FROM AUTHOR]

To assess use of terrestrial habitat by ambystomatid salamanders, Ambystoma tigrinum (Tiger Salamanders) were monitored with radiotelemetry. Four individuals were tracked as they exited a wetland and made wide use of the surrounding landscape. Salamanders moved up to 255 m from the wetland of origin and found refugia both within forested land and wildlife food plots. Based on the extent of terrestrial movements by Tiger Salamanders, our findings support previous work demonstrating that upland habitat surrounding wetlands are critical areas in amphibian life cycles. Salamander movements did not appear to be influenced by agricultural development, as two individuals traveled through this habitat type. [ABSTRACT FROM AUTHOR]

Clearcutting and other forest management practices that remove canopy and disturb ground cover may exacerbate the risk of desiccation, particularly for newly metamorphosed amphibians. We examined dehydration rates of juvenile Mole Salamanders (Ambystoma talpoideum) in relation to burrow availability in four experimental forest management treatments. Juvenile salamanders (N = 41) were confined to small enclosures in four treatments representing a range of habitat disturbance: clearcut with coarse woody debris (CWD) removed; clearcut with CWD retained; thinning; and an unharvested control of second-growth, mature loblolly pine. Half of the salamanders in each habitat treatment were provided with artificial burrows. Water loss over 72 h was significantly higher in the clearcut with CWD retained than in the other three treatments. Most water loss occurred during the first two nights, when salamanders may have been most active. Only 40% of salamanders without burrows survived in the clearcuts, versus 90% in the thinned stand and 100% in the control. Ninety percent of the salamanders with access to a burrow survived in the clearcuts versus 100% in the thinning and control. We found no correlation between soil moisture and water loss and attribute higher desiccation rates in the clearcuts to high temperatures (> 44°C). Although habitat changes resulting from thinning did not lead to increased desiccation, complete canopy removal greatly increased risk of mortality caused by desiccation. Our results also demonstrate that this risk is strongly mediated by the availability of burrows. [ABSTRACT FROM AUTHOR]

Summary: Terrestrial salamanders have been hypothesized to play an important role in the regulation of invertebrate communities on the forest floor. Previous studies testing this hypothesis have used field enclosure or laboratory microcosm methods that may bias outcomes, and no studies have addressed the extent to which environmental heterogeneity affects the strength of salamander effects. In the present study, the effects of the red-backed salamander, Plethodon cinereus, on forest-floor invertebrates were examined in open field plots in which neither the movements of salamanders nor invertebrates were impeded. This 2-year study assessed the influence of the bottom-up effect of leaf-litter mass by comparing salamander effects in the spring when litter was abundant to autumn, just prior to leaf fall, when litter thickness was low. Plethodon cinereus was found to exert top-down effects on several mesofaunal taxa, but no effects on macrofauna were detected. Salamander effects varied among sampling periods. Leaf-litter mass and, to a lesser extent, litter moisture were the determinants of invertebrate density in spring and fall 2003, whereas salamanders were the single significant factor influencing mesofaunal density in spring 2004, when both leaf-litter mass and litter moisture were especially high. Leaf-litter mass and salamanders in combination influenced mesofaunal densities in fall 2004. The results suggest that the top-down effects of salamanders are strongest in spring when hydric conditions and availability of moisture-retaining cover enhance salamander foraging success, and when salamanders affect initial, rapid stages of mesofaunal population growth. [Copyright &y& Elsevier]

Nearly 70% of the 535 species of salamanders in the world are members of a single family, the Plethodontidae, or lungless salamanders. The centre of diversity for this clade is North and Middle America, where the vast majority (99%) of species are found. We report the discovery of the first Asian plethodontid salamander, from montane woodlands in southwestern Korea. The new species superficially resembles members of North American genera, in particular the morphologically conservative genus Plethodon. However, phylogenetic analysis of the nuclear encoded gene Rag-1 shows the new taxon to be widely divergent from Plethodon. The new salamander differs osteologically from putative relatives, especially with respect to the tongue (attached protrusible) and the derived tarsus. We place the species in a new genus on the basis of the morphological and molecular data. The distribution of the new salamander adds to the enigma of Old World plethodontids, which are otherwise restricted to the western Mediterranean region, suggesting a more extensive past distribution of the family. [ABSTRACT FROM AUTHOR]

Salamanders of the genus Ambystoma are a unique model organism system because they enable natural history and biomedical research in the laboratory or field. We developed Sal-Site to integrate new and existing ambystomatid salamander research resources in support of this model system. Sal-Site hosts six important resources: 1) Salamander Genome Project: an information-based web-site describing progress in genome resource development, 2) Ambystoma EST Database: a database of manually edited and analyzed contigs assembled from ESTs that were collected from A. tigrinum tigrinum and A. mexicanum, 3) Ambystoma Gene Collection: a database containing full-length protein-coding sequences, 4) Ambystoma Map and Marker Collection: an image and database resource that shows the location of mapped markers on linkage groups, provides information about markers, and provides integrating links to Ambystoma EST Database and Ambystoma Gene Collection databases, 5) Ambystoma Genetic Stock Center: a website and collection of databases that describe an NSF funded salamander rearing facility that generates and distributes biological materials to researchers and educators throughout the world, and 6) Ambystoma Research Coordination Network: a web-site detailing current research projects and activities involving an international group of researchers. Sal-Site is accessible at http://www.ambystoma.org. [ABSTRACT FROM AUTHOR]

The Flatwoods Salamander (Ambystoma cingulatum) was listed as a federally threatened species because loss and alteration of adult and larval habitats caused population declines. Current management plans for this species must include maintenance of appropriate larval habitat. However, much of the natural history of this species is poorly known. Our objective was to evaluate the diet of A. cingulatum larvae. We examined stomach contents of 122 larvae collected from Florida and South Carolina. We identified and measured invertebrate prey and estimated biomass using length-mass relationships. Crustaceans, mostly isopods (Caecidotea), amphipods (Crangonyx), cyclopoid copepods, and cladocerans (primarily Simocephalus and other daphnids) were the most abundant prey. Isopods and amphipods also dominated stomach content biomass because of their relatively large size. Stomachs of small A. cingulatum larvae had significantly higher numbers and proportions of cladocerans and smaller numbers and proportions of isopods compared to larger larvae (P < 0.05). Smaller larvae also had significantly lower amounts and proportions of isopod biomass in their guts compared to large larvae (P < 0.05). We found Hedruris siredonis, a parasitic nematode, in ∼11% of stomachs examined; this is a new host record for this parasite. Our results indicate that larvae feed primarily on freshwater crustaceans, particularly isopods, copepods, cladocerans, and amphipods. Management activities that adversely impact freshwater crustacean communities in breeding habitats, such as pesticide use or introductions of predatory fish, could adversely impact remaining populations of this salamander. [ABSTRACT FROM AUTHOR]

Abstract Although much is known about the ecological significance of metamorphosis and metamorphic timing, few studies have examined the underlying genetic architecture of these traits, and no study has attempted to associate phenotypic variation to molecular variation in specific genes. Here we report on a candidate gene approach (CGA) to test specific loci for a statistical contribution to variation in metamorphic timing. Three segregating populations (SP1, SP2 and SP3) were constructed utilizing three species of paedomorphic Mexican ambystomatid salamander, including the axolotl, Ambystoma mexicanum . We used these replicated species to test the hypothesis that inheritance of alternate genotypes at two thyroid hormone receptor loci (TRα, TRβ ) affects metamorphic timing in ambystomatid salamanders. A significant TRα *SP effect indicated that variation in metamorphic timing may be influenced by TRα genotype, however, the effect was not a simple one, as both the magnitude and direction of the phenotypic effect depended upon the genetic background. These are the first data to implicate a specific gene in contributing to variation in metamorphic timing. In general, candidate gene approaches can be extended to any number of loci and to any organism where simple genetic crosses can be performed to create segregating populations. The approach is thus of particular value in ecological studies where target genes have been identified but the study organism is not one of the few well-characterized model systems that dominate genetic research. [ABSTRACT FROM AUTHOR]

Hatching success, deformity rates, and survivorship of northern red-legged frogs (Rana aurora) and northwestern salamanders (Ambystoma gracile) were assessed at three agricultural and three reference sites in the Sumas Prairie, British Columbia, Canada. In 1997 and 1998, eggs of both species and eggs of R. aurora, respectively, were placed in Nytex mesh cages (Irwindale, CA, USA) in roadside ditches at each site. Concurrently in 1997, eggs of R. aurora were reared in the laboratory but were exposed to water samples from each of the study sites. Hatching success was significantly lower at all agricultural sites compared to the reference sites for both species. However, no differences were observed in hatching success among sites for eggs of R. aurora reared in the laboratory. Water chemistry differed among all sites, but the largest differences were between reference and agricultural sites. Ammonia (maximum of 1.27 mg/L), total phosphate (maximum of 8.14 mg/L), and biological oxygen demand (maximum of 79.00 mg/L) were high at some of the agricultural sites during the development period. Results suggest that agricultural runoff may contribute to lower reproductive success and ultimately to reduced population viability of amphibian populations in the Lower Fraser Valley (BC, Canada). [ABSTRACT FROM AUTHOR]

Analyzes the TheO-linked acidic oligosaccharides of the jelly coat surrounding the eggs of Ambystoma maculatum using nuclear magnetic resonance (NMR) spectroscopy. Establishment of the major oligosaccharides; Structures of the carbohydrate chains appear to be species specific.

We screened a partial genomic library enriched for microsatellites and characterized nine loci for the Mexican species of Ambystoma for studies of population structure. We tested marker variability in two metamorphic ( A. granulosum, A. altamirani) and two paedomorphic ( A. andersoni, A. mexicanum) species of the A. tigrinum complex. Our microsatellites were developed from pooled genomic DNA from three species, and may work on all species in the A. tigrinum complex in Mexico. These markers will be important for studies of conservation genetics in this radiation. [ABSTRACT FROM AUTHOR]

The article discusses an inexpensive deep-water funnel trapping method for researchers studying ambystomatid salamanders. It reveals that unbaited minnow traps that are fully submerged do not allow the enclosed salamanders to reach the water surface to breathe at aquatic breeding sites. It also mentions uncertainty regarding the use of floating traps.