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Anthropogenic habitat disturbances can dramatically alter ecological community interactions, including host-pathogen dynamics. Recent work has highlighted the potential for habitat disturbances to alter host-associated microbial communities, but the associations between anthropogenic disturbance, host microbiomes, and pathogens are unresolved. Amphibian skin microbial communities are particularly responsive to factors like temperature, physiochemistry, pathogen infection, and environmental microbial reservoirs. Through a field survey on wild populations of Acris crepitans (Hylidae) and Lithobates catesbeianus (Ranidae), we assessed effects of habitat disturbance on environmental bacterial resevoirs, Batrachochytrium dendrobatidis (Bd) infection, and skin microbiome composition. We found higher measures of microbiome dispersion (a measure of community stability) in A. crepitans from more disturbed ponds, supporting the hypothesis that disturbance increases stochasticity in biological communties. We also found that habitat disturbance limited microbiome similarity between locations for both species, suggesting less bacterial exchange in more disturbed areas. Higher disturbance was associated with lower Bd prevalence for A. crepitans, which could signify suboptimal microclimates for Bd in disturbed habitats. In this system we use microbiome dispersion as a metric of population health. Combined, our findings show that reduced microbiome stability stemming from habitat disturbance could compromise population health, even in the absence of pathogenic infection.

The ability of an organism to tolerate seasonal temperature changes, such as extremely cold temperatures during the winter, can be influenced by their pathogens. We tested how exposure to a virulent fungal pathogen, Batrachochytrium dendrobatidis (Bd), affected the critical thermal minimum (CTmin) of two frog species, Hyla versicolor (gray treefrog) and Lithobates palustris (pickerel frog). The CTmin is the minimum thermal performance point of an organism, which we estimated via righting response trials. For both frog species, we compared the righting response of Bd‐exposed and Bd‐unexposed individuals in either a constant (15ºC) environment or with decreasing temperatures (−1°C/2.5 min) starting from 15°C. The CTmin for both species was higher for Bd‐exposed frogs than unexposed frogs, and the CTmin of H. versicolor was higher than L. palustris. We also found that Bd‐exposed frogs of both species righted themselves significantly fewer times in both decreasing and constant temperature trials. Our findings show that pathogen exposure can reduce cold tolerance and limit the thermal performance range of hosts, which may lead to increased overwintering mortality., We tested how exposure to a virulent fungal pathogen, Batrachochytrium dendrobatidis, affected the critical thermal minimum of two frog species. In both frog species, exposure to the fungal pathogen increased the critical thermal minimum. Our findings show that pathogen exposure can reduce cold tolerance and limit the thermal performance range of hosts.

Dispersal following metamorphosis is critical for sustaining anuran metapopulations. Mink Frog (Lithobates septentrionalis) is a primarily aquatic species that is common in eastern Canada. The species is not well studied, and little is known about the terrestrial dispersal of recently metamorphosed individuals. Here we present our observations on the phenology of terrestrial activity in recently metamorphosed Mink Frogs in Algonquin Provincial Park, Ontario, Canada. Despite a sampling effort of over 26 000 trap nights over two years (2010 and 2011) in an area with a known population of Mink Frogs, we observed only 35 individuals, all of which were recent metamorphs, in late summer 2011, suggesting annual variability of recruitment. Because all Mink Frogs were observed in a riparian area, it is likely that this species uses riparian corridors to disperse toward other wetlands, thus avoiding forested areas.

The bullfrog, Lithobates catesbeianus, is one of the most important invasive anurans, affecting especially native anurans due to their similar habits. Here we used a hierarchical co-occurrence model fit in a Bayesian framework to investigate the effects of the bullfrog on two native frog species from southern Brazil, testing the hypothesis that bullfrog presence changes the activity of native species and their relationship with habitat. We found that both occupancy and detection probabilities of native species were similar with bullfrog presence or absence at a site. However, we observed changes in activity and microhabitat use preferences of both native species when the bullfrog was present, suggesting that the presence of the invasive species altered the behavior of the native species. Changes induced by invasive species can result in severe long-term consequences for native species since niche differentiation may not mediate the ability of species to persist together indefinitely.

Wetlands are often created through wetland mitigation to replace lost natural wetlands, but further evaluation is needed to determine the ability of a created wetland to replace lost wetland functions, especially providing wildlife habitat. We used a mesocosm design to compare the water quality between three created wetlands and three natural wetlands in West Virginia, USA and to evaluate how the water quality from the two wetland types were able to support metamorphosis in larval spring peepers (Pseudacris crucifer) and wood frogs (Lithobates sylvaticus) across two years (2014-2015). Responses in metamorphosis rates differed between species and between years. Spring peepers displayed similar metamorphosis rates in the created and natural wetlands in both years of the study. Wood frogs displayed similar metamorphosis rates in created and natural wetlands in 2015, but in 2014 wood frogs reached metamorphosis in less time and at a larger body size in the natural wetlands, suggesting that the wood frogs that developed in the natural wetlands may have higher fitness than those that developed in the created wetlands. Water quality was largely similar between created and natural wetlands, although dissolved oxygen, conductivity, and pH varied between mesocosms and wetlands. Our study suggests that created wetlands may be providing partial mitigation in terms of water quality for amphibian development. We recommend that future monitoring of created wetlands include measures of juvenile amphibian recruitment as well as additional habitat variables to better determine the ability of created wetlands to function as amphibian habitat.

Simple Summary The American Bullfrog (Lithobates catesbeianus), known as one of the most problematic amphibians in the world, was introduced to South Korea in the 1970s. Although it has spread very rapidly over the past 50 years, there is no focused strategy to manage the frogs. With the introduction of American Bullfrogs into nature, numerous native species (mostly amphibians) are rapidly decreasing due to predation, a transmission of infectious diseases, and crossbreeding. In particular, the critically endangered Suwon treefrog (Hyla suweonensis) is the most affected by Bullfrogs. In this study, we modeled what environment the American Bullfrog settled in and how it could spread in the future. It was confirmed that the distribution of the two species overlaps in many areas at present, and the distribution of the American Bullfrog may spread to the distribution area of the Suwon treefrog according to future climate change. Through the results of this study, we intend to suggest a management direction for the spread of invasive species and the protection of endangered species. Our result could contribute to many countries that have problems with the American Bullfrogs at present and in the future. Abstract The American Bullfrog (Lithobates catesbeianus) has been imported into South Korea in earnest for food since the 1970s and introduced into nature due to release and escape. Accordingly, the influx and spread of American Bullfrogs are expected to have a direct impact on native species, but few related studies have been conducted on this. We predicted changes in the potential distribution and future distribution based on climate change scenarios to analyze how those changes affect critically endangered Suwon treefrogs. Suwon treefrog sites (63.9%, 78/122) overlapped with the distribution of Bullfrogs. According to the prediction of the future distribution of Bullfrogs, the overlapping of American Bullfrogs and Suwon treefrog will remain similar to the current level in the Representative Concentration Pathway (RCP) 4.5 scenario. On the other hand, in the RCP 8.5 scenario, the number of overlapping sites will increase to 72.1% (88/122) due to the spreading of the American Bullfrogs. The results show that climate change directly affects the distribution expansion of the American Bullfrogs but also indirectly can lead to an increased threat to Suwon treefrogs. In conclusion, our results strongly suggest why climate change should be actively addressed in terms of the spread of invasive species and the protection of endangered species.

Some wetlands in the northern Great Plains support hundreds to thousands of late-stage tadpoles providing important sources of recruitment to the Wood Frog (Lithobates sylvaticus) population while many other wetlands produce none. Relationships between water quality and late-stage tadpole abundance were determined to identify the water quality parameters associated with tadpole abundance. Water samples were collected, and late-stage tadpole abundances were assessed once each year in late June for 12 years in 26 wetlands. Catch or abundance was the number of tadpoles captured in 30 min with a dip-net. The catch of tadpoles was variable both among wetlands and over the long-term for individual wetlands, and ranged from 0 to several hundred individuals. Wood Frog tadpoles were especially sensitive to sodium and chloride concentrations. At Cl concentrations less than 5 mg/L, occupancy for late-stage tadpoles was 84%, and declined by about 8% for each 5 mg/L increase in Cl to 40.1 mg/L Cl, the maximum concentration associated with the detection of tadpoles. Optimal water quality for late-stage Wood Frog tadpoles included low concentrations of Na $$(\overline{x }$$ = 8.1 mg/L), and Cl $$(\overline{x }$$ = 4.2 mg/L) relative to total dissolved solids and other ions, and high concentrations of phosphorus. In a landscape where ion concentrations in wetlands can range over 3 orders of magnitude, water quality analyses suggest that abundant Wood Frog tadpole populations occur in wetlands dominated by snow-melt runoff with its characteristic low ion concentrations. The present study highlights the importance to amphibian conservation of the water quality environment of tadpole habitat.

Amphibian species are highly vulnerable to climate change with significant species decline and extinction predicted worldwide. However, there are very limited studies on amphibians in South Korea. Here, we assessed the potential impacts of climate change on different habitat groups (wetland amphibians, Group 1, migrating amphibians, Group 2, and forest-dwelling amphibians, Group 3) under future climate change and land cover change in South Korea using a maximum entropy modelling approach. Our study revealed that all amphibians would suffer substantial loss of suitable habitats in the future, except Lithobates catesbeianus, Kaloula borealis, and Karsenia koreana. Similarly, species richness for Groups 2 and 3 will decline by 2030, 2050, and 2080. Currently, amphibian species are widely distributed across the country, however, in future, suitable habitats for amphibians would be concentrated along the Baekdudaegan Mountain Range and the southeastern region. Among the three groups, Group 3 amphibians are predicted to be the most vulnerable to climate change, therefore, immediate conservation action is needed to protect them. We expect this study could provide crucial baseline information required for the government to design climate change mitigation strategies for indigenous amphibians.

Conventional larvicide delivery strategies originally developed for permanent and floodwater mosquitoes have proved suboptimal in the small, scattered, and cryptic larval habitats preferred by container-inhabiting Aedes mosquitoes. New methods such as autodissemination, wherein adult mosquitoes spread insecticides to their own larval habitats, have been under study. Another novel delivery method termed heterodissemination, i.e. larvicide delivery by other species sharing the same habitats, has also been proposed. We conducted a proof-of-concept study with four independent experiments using American bullfrogs (Lithobates catesbeianus) and green frogs Lithobates clamitans as carriers of pyriproxyfen, an insect growth regulator, under semi-field conditions in three different locations, two in New Jersey, and one in Utah. Frogs with attached slow-release pyriproxyfen tablets were introduced into outdoor enclosures with water containers. Water samples from the containers were periodically tested using larval Aedes albopictus and Culex pipiens mosquitoes to assess mortality and percent eclosure inhibition. Overall pupal mortality [95% credible intervals] estimated by Bayesian analysis for the treatment group was 73.4% [71.3–75.2] compared to 4.1% [2.9–5.5] for the control group. Mortality within treatment groups in four different experiments ranged from 41 to 100%, whereas control mortalities ranged from 0.5% to 11%. We conclude that heterodissemination is a promising and effective approach deserving of further study.

Taxonomic identification can be difficult when two or more species appear morphologically similar. DNA barcoding based on the sequence of the mitochondrial cytochrome c oxidase 1 gene (COI) is now widely used in identifying animal species. High‐resolution melting analysis (HRM) provides an alternative method for detecting sequence variations among amplicons without having to perform DNA sequencing. The purpose of this study was to determine whether HRM of the COI barcode can be used to distinguish animal species. Using anurans as a model, we found distinct COI melting profiles among three congeners of both Lithobates spp. and Hyla spp. Sequence variations within species shifted the melting temperature of one or more melting domains slightly but do not affect the distinctness of the melting profiles for each species. An NMDS ordination plot comparing melting peak profiles among eight Anuran species showed overlapping profiles for Lithobates sphenocephala and Gastrophryne carolinensis. The COI amplicon for both species contained two melting domains with melting temperatures that were similar between the two species. The two species belong to two different families, highlighting the fact that COI melting profiles do not reveal phylogenetic relationships but simply reflect DNA sequence differences among stretches of DNA within amplicons. This study suggests that high‐resolution melting analysis of COI barcodes (COI‐HRM) may be useful as a simple and rapid method to distinguish animal species that appear morphologically similar., Taxonomic identification can be difficult when two or more species appear morphologically similar. DNA barcoding based on the mitochondrial cytochrome c oxidase 1 gene (COI) is widely used in identifying animal species. High‐resolution melting analysis of COI barcodes (COI‐HRM) provides a simple and rapid method to identify or distinguish animal species without the need to sequence DNA.

A monogenean flatworm Gyrodactylus jennyae Paetow, Cone, Huyse, McLaughlin & Marcogliese, 2009 was previously described as a pathogen on bullfrog Lithobates catesbeianus Shaw, 1802, in a Canadian captive population originating in Missouri, U.S.A. The ITS barcoding of G. jennyae showed relatedness to Asian Gyrodactylus macracanthus Hukuda 1940, a parasite of the Asian loach Misgurnus anguillicaudatus Cantor, 1842. The resulting suggestion that the globally invasive pet-trade of fish may be a mechanism for arrival of Gyrodactylus species to North America provided the framework for the current study. The present study was undertaken following the discovery of two other species of Gyrodactylus in a population of illegally introduced M. anguillicaudatus in New York State. Here the invasion hypothesis was tested via DNA sequencing of the ITS of the two Gyrodactylus species obtained from M. anguillicaudatus from New York, termed Gyrodactylus sp. A and Gyrodactylus sp. B. Both Gyrodactylus sp. A and Gyrodactylus sp. B were closely related to G. jennyae and G. macracanthus, and all belong to a molecularly well-supported monophyletic Asian freshwater group. In conclusion, this invasive fish has trafficked at least three parasite species to the U.S.A., one of them also found on frog. This route from the Asian wetlands to other continents is similar to that of amphibian chytrid fungi of genus Batrachochytrium Longcore, Pessier & Nichols, 1999.

Metapopulation‐structured species can be negatively affected when landscape fragmentation impairs connectivity. We investigated the effects of urbanization on genetic diversity and gene flow for two sympatric amphibian species, spotted salamanders (Ambystoma maculatum) and wood frogs (Lithobates sylvaticus), across a large (>35,000 km2) landscape in Maine, USA, containing numerous natural and anthropogenic gradients. Isolation‐by‐distance (IBD) patterns differed between the species. Spotted salamanders showed a linear and relatively high variance relationship between genetic and geographic distances (r = .057, p, Landscape genetic analyses reveal contrasting patterns of genetic diversity and differentiation for wood frogs and spotted salamanders across an overlapping region of their ranges that includes numerous natural and anthropogenic gradients. Urban landscape elements have detectable, but differing effects on each species. The scale dependence of isolation‐by‐distance (IBD) patterns is empirically investigated, revealing how IBD inferences vary depending on the spatial extent considered.

To detect an effect of landscape context on a species’ response, the landscape variables need to be measured within the appropriate distance from the species’ response, i.e. at the scale of effect. However, it is not clear what factors determine the scale of effect. Our objective was to test the prediction that the scale of effect should be smallest when the species’ response is fecundity, larger for abundance, and larger still for occurrence. We compared the scale of effect of two landscape variables (road density, forest proportion) on the three responses (fecundity, abundance, occurrence) for the wood frog (Lithobates sylvaticus) in eastern Ontario, Canada. We used egg mass surveys of 34 ponds to estimate fecundity (mean eggs/mass), abundance (number of masses), and occurrence (presence/absence of egg masses). We then empirically estimated the scale of effect of each landscape variable on each response. The scale of effect differed among responses, from 0.2 to 3.0 km radii; however, it did not vary in the predicted order. Furthermore, the order was not consistent between the two landscape variables. Our results show that the scale of effect of a landscape variable on a given species can differ for different response variables. However, they also suggest that these differences in the scale of effect are not predictable. Thus, the most reliable way to ensure a landscape context study is conducted at the correct spatial extent is to estimate the scale of effect empirically, rather than ‘guesstimating’ the extent a priori.

Urbanization is known to extirpate many species, but far less is known about how suburbanization may affect amphibian populations. We studied wood frogs (Lithobates sylvaticus) to test the effects of site characteristics (within-pool conditions and land cover indicative of suburbanization within 1000 m) and larval morphology on newly emerged froglets and post-breeding males across a suburbanization gradient in 15 pools in greater Bangor, Maine, USA. We raised field-captured larvae in microcosms and examined froglet morphology and locomotor performance at emergence and one month post-emergence. Larval mass was positively correlated with 50% of froglet responses (survival, size, and locomotor performance) but was negatively associated with adult size. Among site characteristics, egg density had the most salient influence with negative effects on larval survival and morphology as well as on 11 of 14 froglet responses. Vegetation, hydrology, and suburban-associated cover near pools also influenced froglet performance, and hydrology and suburban-associated cover was associated with larger and smaller adult morphology. However the influence of suburban-associated cover on froglet performance and adult morphology was small compared to that of within-pool characteristics. Specifically, our findings support the idea that within-pool conditions experienced by larvae can influence terrestrial stages with potentially life-long consequences. Nevertheless, in suburban landscapes where there is evidence of population declines, it is likely that suburbanization has the greatest impact on populations via direct effects on terrestrial stages. We encourage planners to maintain high-quality habitat for aquatic and terrestrial stage wood frogs in suburbanizing landscapes to avoid extirpation.

Conboy Lake National Wildlife Refuge (CLNWR) in Washington State supports one of the largest remaining populations of federally listed Oregon Spotted Frogs (OSF; Rana pretiosa). Invasive American Bullfrogs (Lithobates catesbeianus [Rana catesbeiana]), implicated in amphibian declines, are also abundant at CLNWR. Owing to the likely negative effect of this aquatic invader on the highly aquatic OSF, bullfrog control strategies are needed. One method is to limit habitat used by bullfrogs while retaining or enhancing OSF habitat, but for such an approach to be implemented, the 2 species must partition habitat sufficiently. We used radiotelemetry to characterize OSF and bullfrog active-season and pre-overwintering habitat in the human-engineered ditch system at CLNWR. We tracked 12 OSF and 10 bullfrogs from mid-to-late summer, recorded data on frog location and habitat, and analyzed movement patterns, niche breadth, and spatial differences between species. Based on minimum convex polygons, bullfrogs overlapped extensively with OSF habitat space in the ditch system. During the active season, niche analyses also showed extensive overlap in the species' vegetation associations, with selected exceptions at the microhabitat scale. However, each species used distinct pre-overwintering habitats. The small differences in active-season microhabitats and pre-overwintering habitats, and our relatively narrow study conditions, create uncertainty about these species' habitat use in a broader context. Nonetheless, these results underscore the challenge of managing an invasive species that is both a habitat generalist and congener and expose the need for further research to guide management approaches to favor OSFs at CLNWR.

La mayoría de los parásitos representan un problema socioeconómico grave, porque afectan a las mascotas, a los animales criados para la venta y a los animales salvajes, y algunos también son zoonóticos. La pérdida de peso, retraso del crecimiento, la predisposición a otras enfermedades y la muerte son los síntomas presentados por los animales parasitados. El objetivo de este estudio fue evaluar la helmintofauna en la rana-toro Lithobates catesbeianus criada para la venta. Se trabajó con cinco granjas de rana en el Vale do Paraíba, São Paulo, Brasil, y se examinaron un total de 185 animales. Las necropsias se realizaron, y todos los órganos que pueden tener parásitos fueron examinados. Exámenes de diagnóstico coproparasitológico también fueron realizados. Se encontró una sola espécie de nematodo y se identificó como Longibucca catesbeianae, con una prevalencia de 1,7%, abundancia media de 14,16 y una intensidad media de 850 (con un rango de 729 a 1.014). Teniendo en cuenta que la mayoría de los estudios de parasitología en los anfibios se llevan a cabo en animales de vida libre, más investigación en ranas en cautiverio se debe realizar con el fin de comprender mejor a estos parásitos y evitar futuros problemas en las operaciones comerciales de granjas de rana.

Amphibian diseases and invasive amphibian species are both generally introduced through the wildlife trade, either for human consumption or for the pet trade. However, adequate regulations can prevent such introductions. In the Republic of Korea, the establishment of invasive Lithobates catesbeianus populations resulted in the alteration of native species’ ecology and in an increase in Batrachochytrid load on local species. While not exemplified yet, the same risk arises from all species in the trade, some of which are already found in the wild despite the potential threats to the ecosystems. While regulations exist for the trade of wildlife in general, they are not directly addressing the amphibian trade, especially newly traded species. Thus, we recommend a restriction on the trade of amphibians in Korea.

Animals have a long history of assessing ecosystem responses to environmental disturbances, and amphibians stand out for presenting themselves as good animal model and bioindicators of environmental quality. The main purpose of the present work was to investigate the cellular effects of contamination of waters of the Marrecas River, located in the southwest of the state of Parana, Brazil. Therefore, the objective of the present study was to investigate and monitor the cytotoxic and mutagenic effect, with bullfrog tadpoles, and to discuss these effects with land use along this hydrographic basin. Mutagenic effects were determined by micronucleus assay, and cytotoxicity by other nuclear changes, such as segmented cells, binucleated cells, cells with buds and reniform cells. Water samples were obtained at nine sites along the Marrecas River, covering areas with rural and urban hydrological contribution. For each site, four samples were collected, along the years 2017 and 2018, encompassing the four seasons (summer, autumn, winter, and spring). The results showed mutagenic and cytotoxic effect in four sampling sites, and only cytotoxic effect in other four sites. These effects may be due, possibly, to the use of different agrochemicals across the hydrographic basin region, which have predominant hydrological contributions from crops. Data of this study indicate the presence of cytotoxic and mutagenic contaminants in the waters of the Marrecas River, which can generate environmental problems on the river fauna/flora, and can also affect the local population health.

The American bullfrog (Lithobates catesbeianus Shaw, 1802), an amphibian species native to eastern North America, is considered one of the 100 most harmful invasive species in the world. Previous studies document several feral populations in the Amazon and Andean regions of Ecuador. However, only few adults have been reported in the Coast region, despite some evidence suggesting its introduction 31 years ago. Using visual and auditory cues, we explored a 490-hectare wetland area at Santay Island, a protected sanctuary and a Ramsar site on the Ecuadorian Coast. Bullfrogs were detected in seven out of 15 sampled ponds in all types of habitats except for mangroves. The low abundance of adults and juveniles suggests a recently established population. This is the first record of a feral population inside a protected area or Ramsar site in Ecuador. In accordance with the Ramsar Convention mission of preserving wetlands, we propose two strategies to manage bullfrogs at Santay Island.

Although amphibians use human-created habitats in urban landscapes, few studies have investigated the quality of these habitats. To assess habitat quality of stormwater management ponds and adjacent urban uplands for wood frogs (Lithobates sylvaticus) and American toads (Anaxyrus americanus), we compared life history characteristics between populations breeding across an urbanization gradient. Specifically, we compared body size, ages of breeding adults, and female reproductive investment among urban, suburban, and rural populations in Baltimore County, Maryland, USA. Although there was variation in age at maturity among populations, ages of breeding adults did not differ among urban, suburban, and rural areas. Maternal body size strongly influenced reproductive investment in both species, but relationships did not vary among urban, suburban, and rural populations. Adult wood frogs and American toads from more urbanized landscapes were significantly smaller at age than conspecifics from rural landscapes; the magnitude of differences was similar across adult age classes. Our results suggest that in the urban and rural landscapes that we studied, adult habitats are similar in quality, but either larval or juvenile habitats may be of lower quality in urban areas.

Habitat loss and degradation linked to urbanization threaten amphibian populations globally, yet studies examining amphibian behaviour and habitat use in cities are rare. Through the use of radiotelemetry, we examined the postbreeding (May–October) movement behaviour and habitat use of adult Wood Frogs (Lithobates sylvaticus (LeConte, 1825)) at natural and constructed urban wetlands in Edmonton, Alberta, located in the semiarid, aspen parkland of Canada. Movement from breeding wetlands was limited, with most tracked individuals remaining within 25 m of ponds in grassy riparian areas. Long-distance migratory movements were rare and only occurred at natural sites with relatively high proportions of forested land surrounding wetlands. In general, tracked frogs showed a preference for habitat close to water that provided shelter from desiccation and predation (e.g., unmowed grass and stands of shrubs). Our findings have implications for the management of wetlands and conservation of amphibian populations in urban environments.

Many reptiles and amphibians are gaining recognition as harmful invaders, highlighted by well-known examples such as the Brown Tree Snake (Boiga irregularis), Cane Toad (Rhinella marina), American Bullfrog (Lithobates catesbeianus), and Burmese Python (Python molurus bivittatus). In 2003, an introduced population of Seal Salamanders (Desmognathus monticola) was found in Spavinaw Creek, within the Ozark Plateau of northwest Arkansas. Genetic evidence confirmed an introduction from northern Georgia. Very little is known about the status of this non-native population; thus, the objective of this study was to assess the current distribution and abundance of non-native D. monticola along Spavinaw Creek. We conducted repeated, low-intensity visual surveys along the 30 km extent of Spavinaw Creek in Arkansas and used a hierarchical Bayesian analysis to model the occupancy response of D. monticola and five native salamander species relative to river mile and habitat covariates. We also conducted a short-term clos...

Global amphibian biodiversity has declined dramatically in the past 4 decades, and many amphibian species have declined to near extinction as a result of emergence of the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd). However, persistent or recovering populations of several amphibian species have recently been rediscovered, and such populations may illustrate how amphibian species that are highly susceptible to chytridiomycosis may survive in the presence of Bd. We conducted field surveys for Bd infection in 7 species of Costa Rican amphibians (all species that have declined to near extinction but for which isolated populations persist) to characterize infection profiles in highly Bd-susceptible amphibians post-decline. We found highly variable patterns in infection, with some species showing low prevalence (~10%) and low infection intensity and others showing high infection prevalence (>80%) and either low or high infection intensity. Across sites, infection rates were negatively associated with mean annual precipitation, and infection intensity across sites was negatively associated with mean average temperatures. Our results illustrate that even the most Bd-susceptible amphibians can persist in Bd-enzootic ecosystems, and that multiple ecological or evolutionary mechanisms likely exist for host-pathogen co-existence between Bd and the most Bd-susceptible amphibian species. Continued monitoring of these populations is necessary to evaluate population trends (continuing decline, stability, or population growth). These results should inform efforts to mitigate impacts of Bd on amphibians in the field.

The American bullfrog Lithobates catesbeianus is an invasive species that can strongly affect native amphibian communities through competition, predation, or introduction of diseases. This frog has invaded multiple areas in South America, for which niche models predict suitable environments across much of the continent. This paper reveals the state of the invasion of this species in Uruguay and its possible relationship with the chytrid pathogenic fungus, Batrachochytrium dendrobatidis. Surveys at invaded sites were conducted from 2007 to 2015, identified two populations undergoing recent range expansion (one of them exponential), two populations that failed to establish, and a new record in an urban area of the capital city, Montevideo. In all the analysed feral populations, chytridiomycosis was found. Our data suggest that the invasion of L. catesbeianus in Uruguay is at an early stage, with very localized populations, which might allow for the implementation of cost-effective management plans, with eradication constituting a plausible option.

Large quantities of road salts are used for de-icing in temperate climates but often leach into aquatic ecosystems where they can cause harm to inhabitants, including reduced growth and survival. However, the implications of road salt exposure for aquatic animal susceptibility to pathogens and parasites have not yet been examined even though infectious diseases can significantly contribute to wildlife population declines. Through a field survey, we found a range of NaCl concentrations (50-560mg/L) in ponds known to contain larval amphibians, with lower levels found in sites close to gravel- rather than hard-surfaced roads. We then investigated how chronic exposure to environmentally-realistic levels of road salt (up to 1140mg/L) affected susceptibility to infection by trematode parasites (helminths) in larval stages of two amphibian species (Lithobates sylvaticus - wood frogs, and L. pipiens - northern leopard frogs) by considering effects on host anti-parasite behavior and white blood cell profiles. Wood frogs exposed to road salt had higher parasite loads, and also exhibited reduced anti-parasite behavior in these conditions. In contrast, infection intensity in northern leopard frogs had a non-monotonic response to road salts even though lymphocytes were only elevated at the highest concentration. Our results indicate the potential for chronic road salt exposure to affect larval amphibian susceptibility to pathogenic parasites through alterations of behavior and immunocompetence, with further studies needed at higher concentrations, as well as that of road salts on free-living parasite infectious stages.

Carry-over effects influence trait responses in later life stages as a result of early experience with environmental cues. Predation risk is an influential stressor and selection exists for early recognition of threats. In particular, invasive species may benefit from carry-over effects by preemptively recognizing and responding to novel predators via latent developmental changes and embryonic learning. In a factorial experiment, we conditioned invasive American bullfrog embryos (Lithobates catesbeianus) to the odor of a novel fish predator, largemouth bass (Micropterus salmoides) alone or in combination with injured conspecific cues. We quantified developmental carryover in the larval life stage and found that individuals conditioned to the highest risk (fish and injured conspecific cues) grew into longer bodied larvae relative to larvae from lower risk treatments. We also assessed embryonic learning, a behavioral carry-over effect, and found an interaction between embryonic conditioning and larval exposure. Behavioral responses were only found in scenarios when predation risk varied in intensity across life history stages, thus requiring a more flexible antipredator strategy. This indicates a potential trade-off between the two strategies in larval growth and development rates, and time until metamorphosis. Our results suggest that early predator exposure and carry-over effects have significant impacts on life history trajectories for American bullfrogs. This research contributes to our understanding of a potentially important invasion mechanism in an anuran species of conservation concern.

Of the 37 species of the European Union concern eight are already present and two present a future potential risk for Romania. This paper brings updated information regarding these species in Romania. The presence of eight invasive alien species of concern to the European Union have already been recorded in Romania: two plant speciesCabomba carolinianaandHeracleum sosnowskyi, two crustaceansOrconectes limosusandEriocheir sinensis, two fish speciesPseudorasbora parvaandPerccottus glenii, one reptileTrachemys scriptaand one mammalMyocastor coypus. Other two species of Union concern (Lithobates catesbeianusandProcyon lotor) may soon become invaders in Romania. We emphasize the urgent need to assess their current distribution and impact or potential to establish and possible impact at national level.

Insular Newfoundland has no native amphibians. While global amphibian populations are declining at alarming rates, populations of introduced anurans (frogs and toads) continue to expand in western Newfoundland, Canada. We expected the establishment and dispersal of the most recently introduced species, Mink Frog (Lithobates septentrionalis), to be influenced by the presence in the region of the previously introduced and ecologically similar Green Frog (L. clamitans). We used a combination of anuran calling surveys and pond-edge visual surveys to assess the ongoing dispersal, relative regional distribution, and local habitat use for these two species in western Newfoundland. The recently established Mink Frog has dispersed ∼3.8 km/year northeast from the original (2001) discovery location and ∼2.6 km/year southwest; co-occurrence analyses revealed that this population displayed habitat and spatial separation from long-established Green Frog populations, at both landscape and local scales. Although cause an...

Identification of essential habitat is a fundamental component of amphibian conservation; however, species with complex life histories frequently move among habitats. To better understand dynamic habitat use, we evaluated Wood Frog (Lithobates sylvaticus (LeConte, 1825)) habitat selection and movement patterns during the spring migration and foraging periods and described the spatiotemporal variability of habitats used during all annual life-history periods. We radio-tracked 71 frogs in Maine during 2011–2013 and evaluated spring migration, foraging activity center (FAC), and within-FAC habitat selection. Telemetered frogs spent the greatest percentage of each field season in hibernacula (≥54.4%), followed by FACs (≥25.5%), migration habitat (≥16.9%), and breeding sites (≥4.5%). FACs ranged 49 – 1 335 m2 (568.0 ± 493.4 m2) and annual home ranges spanned 1 413 – 32 165 m2 (11 780.6 ± 12 506.1 m2). During spring migration, Wood Frogs exhibited different movement patterns (e.g., turn angles), selected different habitat features, and selected habitat features less consistently than while occupying FACs, indicating that the migration and foraging periods are ecologically distinct. Habitat-use studies that do not discriminate among annual life-history periods may obscure true ecological relationships and fail to identify essential habitat necessary for sustaining amphibian populations.

Extensive research has described the behavioral response of fishes to electrofishing, but few investigations have measured the response of frogs. As electricity continues to be used as a tool to conduct frog and other amphibian surveys, and because frogs inhabit many of the same environments where electrofishing surveys are conducted for fish species, documenting the response of frogs to electricity is important. We measured the voltage gradient and power density thresholds that resulted in immobilization of early life stages of American bullfrog, Lithobates catesbeianus, and Southern leopard frog, Lithobates sphenocephalus, for a range of pulse frequencies (15–120 Hz) and ambient water conductivities (250–1,381 μS/cm). Voltage gradients of 0.40–1.00 V/cm at power densities of 58–1,461 μW/cm3 induced immobility. The lowest power densities causing immobilization were at pulse frequencies of 60 and 120 Hz; more power was required at lower frequencies and in water with a higher conductivity.

For many species, the distribution and quantity of habitat is likely to be altered under climate change scenarios. Globally, temperatures are expected to increase, but changes in precipitation will be variable with some locations expected to receive more and other locations to receive less. The amount and timing of precipitation has a strong influence on wetland hydroperiod, which is a critical factor in determining wetland use by species of pond-breeding amphibians. Past research has focused on the direct effects of reductions in precipitation and shorter hydroperiods, such as larvae desiccation, but little attention has been given to the indirect consequences of increased precipitation and longer hydroperiods, such as changes in predation pressure. We used wood frogs (Lithobates sylvaticus), a species that typically breeds in ephemeral (temporary) wetlands, to test the hypothesis that increased precipitation and permanent wetlands would indirectly increase mortality in wood frog embryos through increases in the density of embryo predators, second-year green frog larvae (Lithobates clamitans), limnephilid and phryganeid caddisfly larvae and red-spotted newts (Notophthalmus viridescens). We conducted translocation experiments in 2014 and 2015. We monitored wood frog embryo hatch success and mortality from predation using open (predator access) and closed (predators excluded) cages in 16 wetlands in each year. We observed no difference in embryo hatch success between ephemeral and permanent wetlands, with water temperature, not pH, affecting hatch rates. Wood frog embryos in permanent wetlands with overwintered second-year green frog larvae had higher mortality from predation (0.80, 95% confidence intervals 0.65–0.91) than permanent wetlands (0.42, CI 0.26–0.60) and ephemeral wetlands (0.37, CI 0.31–0.45) that lacked predatory green frog larvae. Embryo mortality from predation increased with increasing green frog larvae density. Regression models showed that ponds with larvae densities >2.5 larvae m−2 resulted in 90% embryo mortality. Caddisfly larvae and red-spotted newt density had no effect, and pond water temperature had a weak negative effect on embryo mortality from predation. Under a wetter and warmer climate, springtime occupancy of predatory green frog larvae is likely to increase, resulting in a reduction in the amount of suitable wood frog breeding habitat. Our research suggests that indirect effects of climate change mediated through biotic interactions may play a critical role in the distribution of ephemeral wetland species.

The global decline of amphibian species is a pressing problem that has garnered much scientific attention. Annual fluctuations of amphibian populations are a common occurrence due to weather variability, reproductive failure, or other factors. Therefore, a long-term perspective through the use of historical datasets is needed to identify persistent trends. To examine the changes in the populations of Anuran (frog and toad) species in Staten Island, NY, we used the detailed notes contained in the field journals of naturalist William T. Davis (1862–1945) to form a basis of comparison to modern surveys (2010–2011). We found very substantial changes, mainly declines, in the amphibian biota of Staten Island. Of the 10 original species, 4 have apparently been extirpated and another 4 have declined in probability of occurrence (PO), most notably Anaxyrus fowleri (Fowler's Toad), whose PO decreased 1 order of magnitude. Only Lithobates clamitans (Green Frog) and Lithobates catesbeianus (Bullfrog) have in...

We used removal sampling (RS) and neutral red dye capture–mark–recapture (CMR) methods to estimate capture probabilities for larval Wood Frogs (Lithobates sylvaticus), Spring Peepers (Pseudacris crucifer), and first-year Green Frogs (Lithobates clamitans) in ponds in southern New Brunswick, Canada. We modeled capture probability as a function of environmental variables and tested whether marks were retained between surveys. We also performed simulations to understand the effect of survey effort, capture probability, and abundance on detection probabilities and the number of surveys needed to be confident of absence. Capture probabilities (P ± SD) were low and variable: Wood Frogs, P = 0.262 ± 0.128; Spring Peepers, P = 0.323 ± 0.241; and first-year Green Frogs, P = 0.159 ± 0.106. With the use of AICc, we determined a model with the proportion of non-Typha emergent vegetation to have a positive effect, whereas pond depth had a negative effort on capture probabilities in first-year Green Frog larva...

Widespread populations of the invasive species Lithobates catesbeianus (American bullfrog) are present in different parts of the world and are difficult to control. This study investigated the possibility to sterilize male individuals of this species in order to use the sterile male release technique in controlling these invasive populations. The technique can be adopted in aquaculture facilities as well to prevent new introductions by incidental releases or escapes. In order to produce sterile individuals a cold and pressure shock protocol were used on fertilized eggs to create triploid individuals. The cold shock did not result in triploid individuals while 54% triploids were obtained from pressure shock, the remaining individuals being aneuploid. The triploid and control larvae were reared for more than one year and the control larvae had a greater length after 7 and 9 months, their weight did not differ. At metamorphosis no difference in length and weight was found between the two groups. The subadult bullfrogs from both groups showed 9 months post metamorphosis a similar scaled body mass index but lower than individuals living in the wild. The pressure shock protocol needs further refinement in respect to the timing of the shock. Further research on the reproductive behavior of these sterile frogs is necessary to evaluate the possible use in the sterile male release technique. PXL University College and EU Interreg IV A project IVAVLANED- 2.31

Between March 2004 and December 2006, and again between March 2010 and June 2013, we examined a total of 70 individual herpetofaunal members from 9 counties and 4 biotic provinces of Texas for coccidians, helminths, and ectoparasites. Twenty-three of 42 (55%) of the amphibians and four of 28 (14%) of the reptiles were infected/infested including Great Plains narrowmouth toad (Gastrophryne olivacea) with Aplectana incerta; Coastal Plain toad (Incilius nebulifer) with A. incerta and Mesocoelium cf. monodi; Rio Grande leopard frog (Lithobates berlandieri) and Plains leopard frog (Lithobates blairi) with Hannemania dunni; spring peeper (Pseudacris crucifer) with acuariid larvae; prairie kingsnake (Lampropeltis calligaster calligaster) with Caryospora duszynskii; Texas blind snake (Rena dulcis) with Parapharyngodon sp.; Texas banded gecko (Coleonyx brevis) with Spauligodon sp.; and Texas patchnose snake (Salvadora grahamiae lineata) multiply infected with Renifer aniarum, Spauligodon goldbergi, and a...

Made available in DSpace on 2022-04-29T08:28:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-10-02 Fundación Agencia Aragonesa para la Investigación y el Desarrollo Even though the herpetofauna richness in the Cerrado–a vast tropical savanna ecoregion of Brazil–is one of the highest of all Brazilian biomes, it still needs to be thoroughly investigated. This study reports the first records of the emerald-eyed tree frog (Boana crepitans), amazon waterfrog (Lithobates palmipes), star-fingered frog (Pipa pipa), and hemprich’s coral snake (Micrurus hemprichii hemprichii) within the states of Maranhão in the northeastern region and Tocantins in the northern region of Brazil. The first state records of Boana crepitans, Pipa pipa and Micrurus h. hemprichii in Tocantins, and Lithobates palmipes in Maranhão, appear in highly climatically suitable areas within the Species Extent of Occurrences (EOO), as predicted in Ecological Niche Modelling (ENM). Our new records of Pipa pipa and Micrurus h. hemprichii, compared to the ENM predictions, represent their southeastern distributional range limits. Our results also suggest that the current gaps on the distributional species ranges probably result from the lack of herpetological surveys in those regions. Departamento de Química Biológica Laboratório de Herpetologia Rua Cel. Antonio Luiz Pimenta Universidade Regional do Cariri Escola de Medicina Veterinária e Zootecnia Laboratório de Anatomia Animal Universidade Federal do Tocantins Centro Colinas do Tocantins Escola SESI Departamento de Ciências Biológicas Faculdade de Ciências de Bauru–campus Bauru Universidade Estadual Paulista Departamento de Química Biológica Programde de Pós-graduação em Bioprospecção Molecular Universidade Regional do Cariri Departamento de Ciências Biológicas Faculdade de Ciências de Bauru–campus Bauru Universidade Estadual Paulista

Wood frogs (Lithobates sylvaticus) are threatened by habitat degradation associated with suburbanization. Suburban development near pools may affect larvae with ramifications for population persistence and vitality. We studied larval development and documented key vernal pool and terrestrial characteristics within 1000 m of 43 pools across the suburban development gradient near Bangor, Maine, USA. Specifically, we examined how survival and morphological characteristics (e.g., developmental phenology, condition, body length, and tail length and shape) varied with characteristics at pool and landscape scales. Secondarily, we explored associations between morphology and survival. Differences in tadpole morphology were associated with suburban land development, hydrology, within‐pool vegetation indicative of light availability at the water's surface, and density of pool‐breeding amphibian egg masses. Across all pools, tadpoles had delayed development and were larger in pools with longer hydroperiods, while tadpoles in suburban pools developed earlier and were larger than those in rural pools with comparable hydroperiods. Tadpoles developed later and had longer tails in pools with greater canopy cover. Morphology profiles also differed between rural and suburban sites and among years. Survival in suburban pools was predicted to be 15 times greater than in rural pools, but across all pools (including those at intermediate intensities of suburbanization), survival was not predicted to vary with either morphology or site characteristics. No strong relationship existed between developmental phenology and any condition or size metric. Because rural and suburban tadpoles responded similarly to within‐pool conditions, our results support the need to maintain natural hydrology and vegetation conditions in pools even in developing areas. Although we detected benefits to tadpoles with increasing suburbanization, suburbanization is well known to extirpate breeding populations; thus, it is likely that wood frog population declines associated with suburbanization are responding to stressors beyond the pool at terrestrial life stages.

Many animals depend on stable below‐the‐snow (subnivium) conditions to survive winter in seasonally cold regions. Freeze‐tolerant ectotherms may experience increased ice content and/or energy expenditure in suboptimal subnivium conditions, with implications for overwinter survival and body reserves available for spring reproduction. We used a novel mechanistic modeling approach to explore effects of winter climate on the microclimate conditions, energy expenditure, and ice dynamics of the freeze‐tolerant, subnivium‐dwelling wood frog (Lithobates sylvaticus) in the Upper Midwest and Great Lakes Basin region of the United States. We hypothesized that (1) frogs would experience the greatest energy cost to survive winter in southern regions of our study area, where air temperatures are warmer and shallower snow could allow for increased numbers of freeze–thaw cycles, and (2) frogs would be most vulnerable to lethal freezing in the cold, dry northwest portion of our study region. We found that total winter energy expenditure changed little with latitude because the effect of warmer soil temperatures (higher metabolic rates) to the south was offset by a shorter winter duration. Energy expenditures were greatest in the snowbelts of the Great Lakes, characterized by more persistent snow cover and relatively warm soil temperatures. In contrast, highest ice contents occurred in the northwest of the study region where air temperatures were coldest and snow was shallow. Thus, it appears that wood frogs experience a trade‐off between risk of lethal ice content and extensive use of body reserves across geographic space. Simulations showed that interpopulation differences in burrow depth and cryoprotectant concentration can influence risk of lethal ice content and overuse of body reserves prior to spring breeding, and those risks vary in relation to winter climate. Our mechanistic modeling approach is a novel tool for predicting risk and shifting niche space for cold‐adapted and subnivium‐dependent species.

Amphibians are declining worldwide, in part because of large-scale degradation of habitat from agriculture and pervasive pathogens. Yet a common North American amphibian, the wood frog (Lithobates sylvaticus), ranges widely and persists in agricultural landscapes. Conventional survey techniques rely on visual encounters and dip-netting efforts, but detectability limits the ability to test for the effects of environmental variables on amphibian habitat suitability. We used environmental DNA to determine the presence of wood frogs and an amphibian pathogen (ranavirus) in Prairie Pothole wetlands and investigated the effects of 32 water quality, wetland habitat, and landscape-level variables on frog presence at sites representing different degrees of agricultural intensity. Several wetland variables influenced wood frog presence, the most influential being those associated with wetland productivity (i.e., nutrients), vegetation buffer width, and proportion of the surrounding landscape that is comprised of other water bodies. Wood frog presence was positively associated with higher dissolved phosphorus (>0.4 mg/L), moderate dissolved nitrogen (0.1-0.2 mg/L), lower chlorophyll a (≤15 µg/L), wider vegetation buffers (≥10 m), and more water on the landscape (≥0.25). These results highlight the effects of environmental factors at multiple scales on the presence of amphibians in this highly modified landscape-namely the importance of maintaining wetland water quality, vegetation buffers, and surrounding habitat heterogeneity. Environ Toxicol Chem 2019;38:2750-2763. © 2019 SETAC.

Ranavirus is a double-stranded DNA virus associated with amphibian, fish and reptile die-offs worldwide. International trade of live animals farmed for human consumption, such as the American bullfrog (Lithobates catesbeianus), plays a key role in spreading the pathogen. In Brazil, ranavirus has only been reported in captive bullfrog farms. We found infected tadpoles of both native species and the American bullfrog in the wild, and a case of mass mortality of amphibians and fish potentially associated with ranavirus. Dead animals presented skin ulcerations, hemorrhages, and edemas. We also found an overall prevalence of 37% of the amphibian chytrid in the area, and two bullfrog tadpoles were co-infected with both pathogens. We suggest that the interaction between the two pathogens should be investigated to improve global conservation of ectothermic vertebrates.

Invasive species and habitat modification threaten California's native pond-breeding amphibians, including the federally threatened California Red-legged Frog (Rana draytonii). The relative contributions of invasive species, including the American Bullfrog (Lithobates catesbeianus), and of habitat changes to these declines are disputed. I conducted a field study over several years in central California to examine the presence/absence of these two species at 79 breeding ponds to determine the predictive role for occupancy of factors including vegetation, pond characteristics, and measures of human activity. I used a boosted regression tree approach to determine the relative value of each predictor variable. Increased measures of human activity, especially proximity to trails and roads, were the best predictors for the absence of California Red-legged Frogs and California Newts. Historical factors and habitat conditions were associated with the extent and spread of the American Bullfrog. The extent and complexity of aquatic macrophytes and pond surface area were good predictors for the presence of these and other amphibian species. Surprisingly, invasive species played a relatively small role in predicting pond occupancy by the native species. These findings can inform conservation and restoration efforts for California Red-legged Frogs, which apparently persist best in small vegetated ponds in areas of low human disturbance.

We gathered and analyzed the current knowledge of the amphibians and reptiles of the Cuatro Cienegas Basin (CCB), including their biogeographical affinities and the historical and ecological importance of the basin to the diversity of these groups in the Chihuahuan Desert (CD). The CCB has a characteristic topography with alternating highlands and basins. The degree of endemicity of the fauna within the CCB is one of the highest in North America. Morphological and genetic differentiation of these taxa suggests a quick speciation due to the isolation of the basin. Further, the restricted distribution within the CCB of some taxa indicates a high ecological dependence on aquatic microhabitats. The herpetofauna present in the CCB is composed of seven amphibian and 46 reptile species, from which 2 amphibians and 9 reptiles are endemic to the basin. Bufonidae and Colubridae are the most diverse families, while Lithobates berlandieri and Aspidoscelis inornata cienegae are the most abundant species of Amphibia and Reptilia, respectively. Twelve of the previously reported species had not been recorded recently, but we recorded five species for the first time in the CCB. Most of the species are distinctive of the CD; however, the endemic species are more closely related with taxa of the Tamaulipan province, Edwards Plateau, and the Sierra Madre Oriental province.

Poikilothermic species, such as amphibians, endure harsh winter conditions via freeze-tolerance or freeze-avoidance strategies. Freeze-tolerance requires a suite of complex, physiological mechanisms (e.g., cryoprotectant synthesis); however, behavioral strategies (e.g., hibernal habitat selection) may be used to regulate hibernaculum temperatures and promote overwintering survival. We investigated the hibernal ecology of the freeze-tolerant Wood Frog (Lithobates sylvaticus) in north-central Maine. Our objectives were to characterize the species hibernaculum microclimate (temperature, relative humidity), evaluate hibernal habitat selection, and describe the spatial arrangement of breeding, post-breeding, and hibernal habitats. We monitored 15 frogs during two winters (2011/12: N = 10; 2012/13: N = 5), measured hibernal habitat features at micro (2 m) and macro (10 m) spatial scales, and recorded microclimate hourly in three strata (hibernaculum, leaf litter, ambient air). We compared these data to...

The transition from aquatic to terrestrial phase in amphibians, called metamorphosis, is accompanied by ecological, morphological, physiological, and biochemical changes. These enable the digestive system of the animal to take up nutrients when the feeding habit changes from omnivorous/herbivorous in tadpoles to carnivorous in adults. To better understand this process, this study investigated the activity of four hydrolases in the digestive system of bullfrog (Lithobates catesbeianus) at all stages of larval development in which the animals feed from exogenous sources. Digestive enzyme activity increased from the beginning of the feeding phase until pre-metamorphosis, which is related to the maturation of the digestive system. The increase was more significant in the period of pro-metamorphosis, coinciding with the accumulation of energy reserves necessary for metamorphosis and the increased growth of the animal. During the climax of metamorphosis, the activities of digestive enzymes decreased, because th...

Temperature is a key variable affecting the timing of amphibian metamorphosis from tadpoles to tetrapods, through the production and subsequent function of thyroid hormones (TH). Thyroid function can be impaired by environmental contaminants as well as temperature. Tadpoles can experience large temperature fluctuations in their habitats and many species are distributed in areas that may be impacted by agriculture. Diuron is a widely used herbicide detected in freshwater ecosystems and may impact endocrine function in aquatic organisms. We evaluated the influence of temperature (28 and 34 °C) on the action of diuron and its metabolite 3,4-dichloroaniline (3,4-DCA) on thyroid function and metamorphosis in tadpoles of Lithobates catesbeianus. Exposure to both compounds induced more pronounced changes in gene expression and plasma 3,3′,5-triiodothyronine (T3) concentrations in tadpoles treated at higher temperature. T3 concentrations were increased in tadpoles exposed to 200 ng/L of diuron at 34 °C and an acc...

The Japanese tree frog, a representative of the Manchurian fauna, is characterized by an outstanding cold resistance among the anuran amphibian species studied so far. Almost 70% of the specimens from the population inhabiting the middle Amur River withstand the cooling down to-30°C; some animals, down to-35°C. This exceeds more than twofold the cold hardiness of the wood frog (Lithobates sylvaticus LeConte, 1825), which has been considered earlier to be the most cold-resistant species. The ability of H. japonica to survive for four months in the frozen state at low temperatures makes this species independent of the temperature overwintering conditions.

The American bullfrog, native to the eastern half of North America including southern Quebec, is considered one of the most invasive species in the world. It has been introduced in America, Asia and Europe, mainly for food purposes. A study on the age and body size of this species was carried out on individuals obtained from four introduced populations (one from Western Canada and three from France), using the skeletochronological method. Adults did not differ between sexes in mean body size or mean age, with the exception of one population in France where males were younger than females. Several differences in the mean age and body size were observed, with the individuals from the population in Canada exhibiting the highest values for both sexes. The scarcity of studies in the native range prevents the comparison of introduced versus native populations, and we focus on comparisons between introduced populations.