Salamander Species Research Articles

Evaluation of Tagging Methods for Unique Identification of Individuals in Three Aquatic Eurycea Salamander Species

Marking or tagging salamanders increases efficiencies in the operations and management of captive populations and facilitates techniques for monitoring demographics of wild populations. Tags facilitate monitoring of longitudinal data for individual animals such as age or estimated age, growth, reproduction, and health. We evaluated three different tagging methods on Texas Blind, San Marcos, and Comal Springs Salamanders to determine success of each as a long-term marker of individual animals. For this study, we selected visible implant elastomer (VIE), visible implant alphanumeric tags (VIA), and passive integrated transponders (PIT). Of these, only VIE tagging has been evaluated in San Marcos Salamanders; none have been evaluated for use in the other two salamander species studied; and comparison studies among these tags for fully aquatic salamander species have not been performed. These tag types were selected for their effectiveness with other salamander species, ability to be quickly and easily identified tank-side, minimal negative effects on organisms, and perceived ease of implanting the tags. The VIE tags were retained by all species and had high readability scores. However, the issues of tag breakage and deterioration should be considered when using VIE tags. VIA tags were rejected in all but one San Marcos Salamander and all Comal Springs Salamanders, but 90% of Texas Blind Salamanders retained them. PIT tags were not tested on San Marcos, Comal Springs, and smaller Texas Blind Salamanders due to size of tag and low retention rate in larger salamanders. Of the tags evaluated in this study, VIE was the most effective in terms of retention, readability, and ease of insertion.

Detection of pathogenic Leptospira spp. in herpetofauna in Central Appalachia.

Leptospirosis is a water borne zoonotic disease of global significance that is caused by pathogenic species of the genus Leptospira. Pathogenic leptospires live in the kidneys of reservoir or infected animals and are shed in their urine contaminating water, soil, etc. Rodents are considered the primary reservoir of leptospirosis, but little is known about the role of herpetofauna (non-avian reptiles and amphibians) in the epidemiology of the disease. To address this, various species of amphibians and reptiles in the Cumberland Gap Region of the Central Appalachia were screened for the presence of Leptospira spp. Kidneys harvested from of a total of 116 amphibians and reptiles belonging to seven species of snakes, seven species of salamanders, seven species of frogs/toads, seven species of turtles and one species of lizards were tested using a highly specific TaqMan based qPCR that targets lipl32 gene of pathogenic Leptospira spp. Overall, 15 of the tested 116 amphibians and reptiles were positive (12.9%; 95% CI: 7.4%-20.4%). Of the 101 amphibians, 11 were positive (10.9%; 95% CI: 5.6%-18.7%), and 4 of the 15 reptiles tested positive (26.7%; 95% CI: 7.8%-55.1%). The amplified gene fragments of lipl32 from qPCR positive kidneys were sequenced and found to be identical with known pathogenic Leptospira spp. These results suggest that although the proportion of reptiles and amphibians transmitting pathogenic Leptospira spp. within the environment may be low as compared to rodents, they pose a risk to other susceptible hosts that share their habitats and may have role in maintaining a baseline infection in the environment.

Salamander braincase morphology as revealed by micro-computed tomography.

Morphological data sets are misleading in salamander (Caudata) phylogeny due to the relative homoplasy of the dermal skull observed in paedomorphic forms, leading to the trend of excluding morphology when exploring questions of salamander phylogeny. Investigations in caecilians (Gymnophiona) have demonstrated that the inclusion of braincase morphology can rescue morphological phylogenetic analyses and produce topologies congruent with molecular data sets. We scanned 28 species (25 genera) of salamander, representing all 10 families, with high-resolution micro-computed tomography to investigate braincase variation. We describe the morphology of the braincase for all 10 families and distinguish between paedomorphic and metamorphic morphologies. Our results demonstrate a general uniformity amongst metamorphic species with variation largely restricted to the occipito-otic region. A greater range of variation is observed within paedomorphic forms than would be expected when considering the homoplasy of the dermal skull. Obligate paedomorphic forms demonstrate considerably more variation in the anterior braincase than do facultative paedomorphs, which we suggest is evidence of a greater complexity in the evolution and development of these forms than neoteny alone would produce. This raises the question of character independence within morphological data sets and warrants further investigation into the correlation of other characters before morphological data are omitted.

Comparative Studies on Wet Attaching Abilities of Different Salamander Species

Comparative Studies on Wet Attaching Abilities of Different Salamander Species

GENETIC DIVERSITY OF CYSTODISCUS SPECIES IN AMPHIBIANS IN THE SOUTHERN UNITED STATES.

Myxosporean species in the genus Cystodiscus are parasites of amphibians and have been reported from several continents. Typically used for the identification of myxozoans, the spores produced by these species are similar to one another, possessing 2 polar capsules and being ovoid. The number of transverse depressions on the spore can be useful for delineating species, but these can sometimes be difficult to distinguish. In North America, Cystodiscus serotinus and Cystodiscus melleni have been described, and for C. serotinus in particular, numerous reports and a wide range of hosts have been associated with this species. Given the challenges of identifying some of these species, we questioned whether all encounters of Cystodiscus species can be attributed to these 2 described species, or if there may be additional undescribed species or cryptic species. Over 7 yr, 383 amphibians representing 13 species of toads, frogs, and salamanders were collected from sites in Oklahoma and Arkansas. Cystodiscus infections were found in 56 individuals (14.6%). Tissues from these infected individuals were preserved in alcohol for genetic analysis. The small subunit (SSU) and large subunit (LSU) ribosomal RNA genes were partially sequenced and analyzed phylogenetically. Nine distinct SSU sequence types and 7 distinct LSU sequence types were identified. Phylogenetically, sequence types were attributable to C. serotinus, C. melleni, Cystodiscus axonis, and an undescribed species. For the previously described species, there were multiple SSU sequence types: 4 for C. serotinus and 2 for both C. melleni and C. axonis. Phylogenetic patterns were similar for the LSU sequence analysis using a shorter sequence than the SSU, and we propose that the LSU is useful for initial barcoding of Cystodiscus species in any future surveys. In our qualitative assessment of sequence types compared to geography and host species, SSU types C1 and C2 (C. axonis) were only found in Union County, Arkansas, and McCurtain County, Oklahoma, respectively. Also, salamanders were only infected with SSU types B or D (C. melleni), and type B was only found in salamanders. Our finding of C. axonis in North America is notable because this species was described in Australia and is associated with host pathology. Our work reveals that there are cryptic species of Cystodiscus in the United States, one of which may be a pathogen, highlighting the importance of genetic analysis for future surveys of these species.

Social Behavior, Community Composition, Pathogen Strain, and Host Symbionts Influence Fungal Disease Dynamics in Salamanders.

The emerging fungal pathogen, Batrachochytrium dendrobatidis (Bd), which can cause a fatal disease called chytridiomycosis, is implicated in the collapse of hundreds of host amphibian species. We describe chytridiomycosis dynamics in two co-occurring terrestrial salamander species, the Santa Lucia Mountains slender salamander, Batrachoseps luciae, and the arboreal salamander, Aneides lugubris. We (1) conduct a retrospective Bd-infection survey of specimens collected over the last century, (2) estimate present-day Bd infections in wild populations, (3) use generalized linear models (GLM) to identify biotic and abiotic correlates of infection risk, (4) investigate susceptibility of hosts exposed to Bd in laboratory trials, and (5) examine the ability of host skin bacteria to inhibit Bd in culture. Our historical survey of 2,866 specimens revealed that for most of the early 20th century (~1920–1969), Bd was not detected in either species. By the 1990s the proportion of infected specimens was 29 and 17% (B. luciae and A. lugubris, respectively), and in the 2010s it was 10 and 17%. This was similar to the number of infected samples from contemporary populations (2014–2015) at 10 and 18%. We found that both hosts experience signs of chytridiomycosis and suffered high Bd-caused mortality (88 and 71% for B. luciae and A. lugubris, respectively). Our GLM revealed that Bd-infection probability was positively correlated with intraspecific group size and proximity to heterospecifics but not to abiotic factors such as precipitation, minimum temperature, maximum temperature, mean temperature, and elevation, or to the size of the hosts. Finally, we found that both host species contain symbiotic skin-bacteria that inhibit growth of Bd in laboratory trials. Our results provide new evidence consistent with other studies showing a relatively recent Bd invasion of amphibian host populations in western North America and suggest that the spread of the pathogen may be enabled both through conspecific and heterospecific host interactions. Our results suggest that wildlife disease studies should assess host-pathogen dynamics that consider the interactions and effects of multiple hosts, as well as the historical context of pathogen invasion, establishment, and epizootic to enzootic transitions to better understand and predict disease dynamics.

Genetic and morphological data demonstrate hybridization and backcrossing in a pair of salamanders at the far end of the speciation continuum.

Deeply diverged yet hybridizing species provide a system to investigate the final stages of the speciation process. We study a hybridizing pair of salamander species—the morphologically and genetically drastically different newts Triturus cristatus and T. marmoratus—with a panel of 32 nuclear and mitochondrial genetic markers. Morphologically identified hybrids are mostly of the F1 generation and mothered by T. cristatus. The sex ratio of the F1 hybrid class is reciprocally skewed, with a preponderance of females in T. cristatus‐mothered hybrids and males in T. marmoratus‐mothered hybrids. This amounts to the Haldane effect operating in one direction of the cross. Deeper generation hybrids are occasionally produced, possibly including F1 hybrid × backcross hybrid offspring. Interspecific gene flow is low, yet skewed toward T. cristatus. This asymmetry may be caused by hybrid zone movement, with the superseding species being predisposed to introgression. The persisting gene flow between deeply differentiated species supports the notion that full genetic isolation may be selected against. Conversely, published morphological data suggest that introgressive hybridization is detrimental, with digital malformations occurring more frequently in the area of sympatry. Finally, to assist field identification, both within the area of natural range overlap and concerning anthropogenic introductions elsewhere, we document the phenotypical variation of two generations of hybrids compared with both parental species. We suggest that fluctuating range boundaries, ecological segregation, cytonuclear incompatibilities and hybrid breakdown through Bateson–Dobzhansky–Muller incompatibilities all contribute to species integrity, despite incomplete isolation during secondary contact.

Quantifying Inter- and Intrasexual Head-Shape Polymorphism in Eurycea cf. wilderae (Blue-Ridge Two-Lined Salamanders)

Distinct morphological differences between and within sexes may reflect reproductive behaviors that have evolved under natural and sexual selection. In some members of the Eurycea bislineata (Two-Lined Salamander) species complex, inter- and intrasexual variation in head morphology result from secondary sexual characters used in locating, courting, and guarding mates. In populations of Eurycea cf. wilderae (Blue-Ridge Two-Lined Salamander), males possess one of two suites of morphological traits corresponding to alternative reproductive tactics. “Searching” males appear to be adapted for locating and courting females in terrestrial habitats and are characterized by the seasonal development of mental glands, protruding premaxillary teeth, and elongate cirri. “Guarding” males appear to be adapted for aggressively guarding females in aquatic habitats, lack all three aforementioned traits, and are instead characterized by seasonally enlarged jaw musculature. Traditionally, males have been categorized by treating these traits as binary (i.e., present or absent), but this fails to capture any continuous variation. Here, we evaluated the utility of geometric morphometric methods to quantify and describe differences in head morphology among female, searching male, and guarding male E. cf. wilderae. In the left-lateral view, we found significant pairwise differences among all three morph–sex groups. In the ventral view, we found significant pairwise differences between searching males and guarding males and between searching males and females, but not between guarding males and females. Deformation grids clearly demonstrated the enlarged jaw musculature of guarding males and wider, flatter rostrum of searching males. Our results demonstrate utility of geometric morphometric methods for describing head shape differences among these alternative reproductive tactics and provide baseline data for future studies of spatial and temporal variation.

New locality record of the critically endangered and endemic species, Lyciasalamandra billae (Franzen & Klewen, 1987) (Amphibia: Salamandridae) from Turkey

Objective: The Bille’s Lycian Salamander, Lyciasalamandra billae is an endemic salamander species of Turkey and it has a very narrow distribution area in the Antalya province of the country. A limited number of the reported populations of this critically endangered species are known. The present study aims to show that the distribution of the species extends towards the northeast of Antalya province. Materials and Methods: Two adult individuals (1 ♂ and 1 ♀) were caught from the Sarısu (Antalya, Turkey) population. The morphometric features of the individuals were measured using a digital caliper. After morphometric measurements of the individuals were taken without performing any anesthetic procedure and killing any animals, the salamanders were released back to the habitat where they were caught.  Results: We recorded a new locality of the species located about 11 km northeast of Gedeller village. The habitat of the individuals from Sarısu consisted of a forested area. Vegetation of the habitat generally comprised pine trees and dwarf scrub plants. Rostrum– Anus length (RA) was 59.68 mm in the female individual and 59.03 mm in the male. The tail length (TL) was 50.14 mm in the female and 47.12 mm in the male.  Conclusion: The morphometric characters and color-pattern features of the specimens were compared with the specimens reported in the literature. We found that the morphometric proportions and ratios of the Sarısu population were similar to the results of the specimens in literature, except a slightly higher HW/HL ratio of the Sarısu population. Based on our morphological findings, we concluded that our specimens belonged to the L. b. billae. However, our conclusion was not dependent on molecular data.

A Guide to Sexing Salamanders in Central Appalachia, United States

Abstract Documenting the sex of individuals encountered during wildlife research and monitoring activities is important for understanding and tracking changes in populations. However, sexing salamanders can be particularly difficult because secondary sex characters are often subtle or only visible during the breeding season, and guidance on species-specific sex determination is lacking from most field guides. The purpose of this guide is to provide a reference to assist biologists in the Central Appalachian region with identifying sex of live adult salamanders. In the main text we provide summary tables and figures to serve as concise references in the field. We provide individual species accounts that contain concise yet comprehensive information for each species based on the published literature, as well as many images depicting sexually dimorphic characters. Our focal region encompasses partial or entire distributions for 56 species of salamanders in 5 families (Ambystomidae, Cryptobranchidae, Plethodontidae, Proteidae, and Salamandridae). We identified seven morphological characters that are strongly sexually dimorphic and useful for sexing live, nonanesthetized, adult salamanders in the field, with males of individual species exhibiting one to five of the characters. We identified more than 20 additional characters that are weakly sexually dimorphic, difficult to distinguish in the field, or species-specific. Our guide serves as a synthesis of sexually dimorphic characters for salamanders in Central Appalachia, and we anticipate it will have broad value for researchers, monitoring programs, and salamander enthusiasts in eastern and central North America.

Impact of climate and land cover changes on the potential distribution of four endemic salamanders in Mexico

Anthropogenic changes, such as land use and climate change, are the greatest threats to biodiversity, especially for amphibians, which are the most endangered vertebrate class worldwide. Species distribution modelling was applied to assess how expected future climate and land cover change scenarios might influence the geographic distribution and habitat connectivity of four salamanders endemic to Mexico: Aquiloeurycea cephalica (Cope, 1865), Isthmura bellii (Gray, 1850), Pseudoeurycea robertsi (Taylor, 1939), and Pseudoeurycea leprosa (Cope, 1869). For this, the Community Climate System Model (CCSM4) with two Representative Concentration Pathways (RCP 45 and RCP 85) and two modelling methods (Maxent in ENMeval and an ensemble model in biomod2) were used. The most important environmental variables explaining the distribution of the target species, as well as the environmental niche overlap between them, were also determined. Abies forest cover was one of the most important variables explaining the current distribution of P. robertsi (contribution of 39%), P. leprosa (contribution of 18%), and A. cephalica (contribution of 22%) with a positive effect. The distribution of these three species was also limited by maximum temperatures, whereas the I. bellii distribution was more limited by minimum temperatures. The environmental niches of P. leprosa and A. cephalica were significantly similar (D = 0.637, I = 0.801, p-value = 0.02), as well as the environmental niches of P. robertsi and P. leprosa (D = 0.640, I = 0.797, p-value = 0.01). As expected, all salamander species were predicted to face a reduction in their potential distribution (reductions between 2.64 and 32.16%) and landscape connectivity (reductions between 4.93 and 73.92%) under future scenarios of climate and land cover change. Different models and scenarios were inconsistent in determining which species’ distribution would suffer the biggest reduction in the future. However, P. robertsi suffered the largest reduction in connectivity under both scenarios of climate change. Similarly, our results suggest that Sierra de las Cruces and Corredor Biológico Chichinautzin are very important areas in terms of connectivity. Unfortunately, great losses of Abies and Pinus forests were also predicted to occur in these areas between 2011 and 2014. According to these findings, the preservation of Abies forests of the Trans-Mexican Volcanic Belt is essential to preserve P. robertsi, P. leprosa, and A. cephalica salamanders, whereas the preservation of Corredor Biológico Chichinautzin and Sierra de las Cruces is essential to maintain landscape connectivity for P. leprosa, A. cephalica, and I. bellii. Thus, these areas should be prioritized in conservation programs.

Environmental DNA as a detection and quantitative tool for stream‐dwelling salamanders: A comparison with the traditional active search method

AbstractAs amphibians are showing significant signs of decline, adequate information and understanding of target species are essential for taking appropriate conservation measures. In recent years, environmental DNA has seen notable growth as a monitoring tool and testing this emergent method with various species has become an important step toward a better understanding of its benefits and limits for studying specific taxa. This study focused on using species‐specific qPCR assays developed in our research group to test the eDNA method for three stream‐dwelling salamander species of the Plethodontidae family: the Spring salamander (Gyrinophilus porphyriticus), the Northern dusky salamander (Desmognathus fuscus), and the Northern two‐lined salamander (Eurycea bislineata). The traditional active search method and the eDNA method were compared for both their ability to detect species as well as to provide a quantitative assessment of populations in 24 headwater streams in Québec, eastern Canada. For all three species, eDNA was detected in every stream where the target species was observed during the active search method. Moreover, eDNA was detected in nine streams where the target species was not identified with the active search. A marginally significant association was found between eDNA concentration and salamander density for D. fuscus only. All species showed high variability for eDNA concentration between qPCR technical replicates and between samples of a given stream. The results of this study lead us to conclude that eDNA can be an excellent method for detection of stream‐dwelling salamanders. Given the inconsistent quantitative aspect of eDNA with the studied species, the future of these stream‐dwelling salamander monitoring most likely lies in the combined use of both eDNA and active search methods. Hence, active search could continue to offer useful small‐scale detection and reliable quantitative data while eDNA could be implemented as an efficient and promising tool for large‐scale detection.

Comparative development and ocular histology between epigean and subterranean salamanders (Eurycea) from central Texas.

The salamander clade Eurycea from the karst regions of central Texas provides an ideal platform for comparing divergent nervous and sensory systems since some species exhibit extreme phenotypes thought to be associated with inhabiting a subterranean environment, including highly reduced eyes, while others retain an ancestral ocular phenotype appropriate for life above ground. We describe ocular morphology, comparing three salamander species representing two phenotypes—the surface-dwelling Barton Springs salamander (E. sosorum) and San Marcos salamander (E. nana) and the obligate subterranean Texas blind salamander (E. rathbuni) - in terms of structure and size of their eyes. Eyes were examined using confocal microscopy and measurements were made using ImageJ. Statistical analysis of data was carried out using R. We also provide a developmental series and track eye development and immunolocalization of Pax6 in E. sosorum and E. rathbuni. Adult histology of the surface-dwelling San Marcos salamander (E. nana) shows similarities to E. sosorum. The eyes of adults of the epigean species E. nana and E. sosorum appear fully developed with all the histological features of a fully functional eye. In contrast, the eyes of E. rathbuni adults have fewer layers, lack lenses and other features associated with vision as has been reported previously. However, in early developmental stages eye morphology did not differ significantly between E. rathbuni and E. sosorum. Parallel development is observed between the two phenotypes in terms of morphology; however, Pax6 labeling seems to decrease in the latter stages of development in E.rathbuni. We test for immunolabeling of the visual pigment proteins opsin and rhodopsin and observe immunolocalization around photoreceptor disks in E. nana and E. sosorum, but not in the subterranean E. rathbuni. Our results from examining developing salamanders suggest a combination of underdevelopment and degeneration contribute to the reduced eyes of adult E. rathbuni.

Clinging ability is related to particular aspects of foot morphology in salamanders.

The interaction between morphology, performance, and ecology has long been studied in order to explain variation in the natural world. Within arboreal salamanders, diversification in foot morphology and microhabitat use are thought to be linked by the impact of foot size and shape on clinging and climbing performance, resulting in an ability to access new habitats. We examine whether various foot shape metrics correlate with stationary cling performance and microhabitat to explicitly quantify this performance gradient across 14 species of salamander, including both arboreal and nonarboreal species. Clinging performance did not correlate with foot shape, as quantified by landmark‐based geometric morphometrics, nor with microhabitat use. Mass‐corrected foot centroid size and foot contact area, on the other hand, correlated positively with clinging performance on a smooth substrate. Interestingly, these foot variables correlated negatively with clinging performance on rough substrates, suggesting the use of multiple clinging mechanisms dependent upon the texture of the surface. These findings demonstrate that centroid size and foot contact area are more functionally relevant for clinging in salamanders than foot shape, suggesting that foot shape need not converge in order to achieve convergent performance. More broadly, our results provide an example of how the quantification of the performance gradient can provide the appropriate lens through which to understand the macroevolution of morphology and ecology.

Cranial skeletogenesis of one of the largest amphibians, Andrias japonicus, provides insight into ontogenetic adaptations for feeding in salamanders

Abstract Skeletal development in salamanders is greatly influenced by their complex life history. Although the relationship between skull development and life history has been investigated in a variety of salamander species, few studies have compared skull development among lineages. Here, we describe the cranial skeletogenesis of the Japanese giant salamander, Andrias japonicus (family Cryptobranchidae), for the first time. To conduct interspecific comparisons, we also describe the cranial skeletogenesis of Hynobius nebulosus (Hynobiidae), Pleurodeles waltl (Salamandridae) and Ambystoma mexicanum (Ambystomatidae). Our comparative analyses reveal interspecific differences in cranial skeletogenesis, particularly in the timing of the onset of ossification, the direction of ossification (e.g. from anterior to posterior) and the ossification pattern of the hyobranchial skeleton. The early onset of jaw ossification, posterior extension of the maxilla and posterolateral inclination of the squamosal in An. japonicus might be adaptations that allow An. japonicus to gulp feed, primarily using the suction force generated by opening the mouth wide, while also supplementing that force by depressing the hyobranchial skeleton. Multivariate regression of skull shape on log10-transformed centroid size revealed that the unique skull shape of adult and subadult An. japonicus forms through hypermorphosis.

Plataforma para el Inventario de la Herpetofauna de México

This review presents a new free access platform that contains the Inventory of the Herpetofauna of Mexico, the first virtual space in Mexico and in which Herpetología Mexicana publishes a complete list of species to contribute to the knowledge, study, conservation and outreach of the commonly known “amphibians and reptiles”. Its format is accessible and downloadable, both for specialized and non-specialized users, and is updated immediately after the appearance of studies that modify the herpetofaunal biodiversity of the country. The quantification of species in the inventory allows, among other aspects, to highlight, reaffirm and compare with data from other references that Mexico is not only one of the most biodiverse countries in Herpetofauna, but is also the richest nation in species of Mesoamerican salamanders and in snakes on the planet.

The impact of climate change on western Plethodon salamanders' distribution.

AimGiven that salamanders have experienced large shifts in their distributions over time, we determined how each species of Plethodon in the Pacific Northwest would respond to climate change. We incorporated several greenhouse scenarios both on a species‐by‐species basis, and also using phylogenetic groups, with the aim to determine the best course of action in managing land area to conserve diversity in this group.LocationPacific Northwest of the United States (northern CA, OR, WA, ID, and MT).Major taxa studiedWestern Plethodon salamanders.MethodsSpecies distribution models were estimated using MaxEnt for the current time period and for several future climate scenarios using bioclimatic data layers. We used several methods to quantify the change in habitat suitability over time from the models. We explored aspects of the climate layers to determine whether we can expect a concerted response to climate change due to similarity in ecological niche or independent responses that could be harder to manage.ResultsThe distribution of western Plethodon salamander species is strongly influenced by precipitation and less so by temperature. Species responses to climate change resulted in both increases and decreases in predicted suitable habitat, though most species ranges do not contract, especially when taken as a phylogenetic group.Main conclusionsWhile some established habitats may become more or less climatically suitable, the overall distribution of species in this group is unlikely to be significantly affected. Clades of Plethodon species are unlikely to be in danger of extirpation despite the possibility that individual species may be threatened as a result of limited distributions. Grouping species into lineages with similar geographic ranges can be a viable method of determining conservation needs. More biotic and dispersal information is needed to determine the true impact that changes in climate will have on the distribution of Plethodon species.

Metal accumulation varies with life history, size, and development of larval amphibians

Amphibian larvae are commonly used as indicators of aquatic ecosystem health because they are susceptible to contaminants. However, there is limited information on how species characteristics and trophic position influence contaminant loads in larval amphibians. Importantly, there remains a need to understand whether grazers (frogs and toads [anurans]) and predators (salamanders) provide comparable information on contaminant accumulation or if they are each indicative of unique environmental processes and risks. To better understand the role of trophic position in contaminant accumulation, we analyzed composite tissues for 10 metals from larvae of multiple co-occurring anuran and salamander species from 20 wetlands across the United States. We examined how metal concentrations varied with body size (anurans and salamanders) and developmental stage (anurans) and how the digestive tract (gut) influenced observed metal concentrations. Across all wetlands, metal concentrations were greater in anurans than salamanders for all metals tested except mercury (Hg), selenium (Se), and zinc (Zn). Concentrations of individual metals in anurans decreased with increasing weight and developmental stage. In salamanders, metal concentrations were less correlated with weight, indicating diet played a role in contaminant accumulation. Based on batches of similarly sized whole-body larvae compared to larvae with their digestive tracts removed, our results indicated that tissue type strongly affected perceived concentrations, especially for anurans (gut represented an estimated 46–97% of all metals except Se and Zn). This suggests the reliability of results based on whole-body sampling could be biased by metal, larval size, and development. Overall, our data shows that metal concentrations differs between anurans and salamanders, which suggests that metal accumulation is unique to feeding behavior and potentially trophic position. To truly characterize exposure risk in wetlands, species of different life histories, sizes and developmental stages should be included in biomonitoring efforts.

Comparative Osteology of Montane Climbing Salamanders (Plethodontidae: Bolitoglossa Subgenus Magnadigita) from Nuclear Central America

The skeletal features of six species of salamanders in the genus Bolitoglossa (subgenus: Magnadigita) were described and compared. Many osteological features of the Magnadigita subgenus were found to be highly conserved, such as the presence of bifurcated first caudal vertebrae and distal expansions on the terminal phalanges. Key traits were identified that were distinct among the species in this study, including the prefrontals and frontoparietal fenestrae; we suggest these traits may be useful in future taxonomic studies of Bolitoglossa. We also discuss the evolution of paedomorphosis and webbed feet in relation to Magnadigita. Bolitoglossa diaphora has highly webbed feet but lacks the osteological features typically associated with this paedomorphic trait, such as fused or accentuated elements, but rather has the osteological features typical of other Magnadigita.

Top-Down Effects of Salamanders on Macroinvertebrates in Fishless Headwater Streams

Salamanders are the top predators in many fishless headwater streams, and intraguild interactions among stream salamanders are well documented. However, little is known about the top-down effects of salamanders on stream food webs or how intraguild interactions mediate these effects. To investigate the effects of salamanders on macroinvertebrate communities of headwater streams, we conducted an experiment in stream mesocosms to test for effects of two stream salamander species, namely, Eurycea bislineata and Gyrinophilus porphyriticus, alone or in combination, on benthic and emerging macroinvertebrate density, biomass, and community composition. We also assessed intraguild interactions between these salamander species by comparing Eurycea bislineata survival and G. porphyriticus growth in single-species versus two-species treatments. Gyrinophilus porphyriticus reduced benthic macroinvertebrate densities when alone but not when co-occurring with E. bislineata. There were no effects of salamanders on benthic macroinvertebrate biomass or community composition and no effects on emerging macroinvertebrate density, biomass, or community composition. Eurycea bislineata survival decreased and G. porphyriticus weight increased in two-species treatments, suggesting that intraguild predation was occurring. Overall, although some of our findings are equivocal, these results suggest that salamanders can exert top-down control on macroinvertebrate communities in fishless headwater streams, decreasing benthic macroinvertebrate density. But this effect is dependent on the salamander species present, and can be removed by intraguild interactions between salamander species.