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Abstract Deepening droughts and unprecedented wildfires are at the leading edge of climate change. Such events pose an emerging threat to species maladapted to these perturbations, with the potential for steeper declines than may be inferred from the gradual erosion of their climatic niche. This study focused on two species of amphibians—Philoria kundagungan and Philoria richmondensis (Limnodynastidae)—from the Gondwanan rainforests of eastern Australia that were extensively affected by the “Black Summer” megafires of 2019/2020 and the severe drought associated with them. We sought to assess the impact of these perturbations by quantifying the extent of habitat affected by fire, assessing patterns of occurrence and abundance of calling males post‐fire, and comparing post‐fire occurrence and abundance with that observed pre‐fire. Some 30% of potentially suitable habitat for P. kundagungan was fire affected, and 12% for P. richmondensis. Field surveys revealed persistence in some burnt rainforest; however, both species were detected at a higher proportion of unburnt sites. There was a clear negative effect of fire on the probability of site occupancy, abundance and the probability of persistence for P. kundagungan. For P. richmondensis, effects of fire were less evident due to the limited penetration of fire into core habitat; however, occupancy rates and abundance of calling males were depressed during the severe drought that prevailed just prior to the fires, with the reappearance of calling males linked to the degree of rehydration of breeding habitat post‐fire. Our results highlight the possibility that severe negative impacts of climate change for montane rainforest endemics may be felt much sooner than commonly anticipated under a scenario of gradual (decadal‐scale) changes in mean climatic conditions. Instead, the increased rate of severe stochastic events places these narrow range species at a heightened risk of extinction in the near‐term.

Abstract Consumptive effects (CEs) of predation have been well‐studied in most aquatic systems, but nonconsumptive effects (NCEs) on prey have only recently received limited attention. As aquatic consumers, tadpoles have traditionally been considered strict herbivores, leaving their predatory impacts via CEs and NCEs largely unexplored. We quantified omnivory among wood frog (Lithobates sylvaticus) tadpoles and characterized their CEs and NCEs on invertebrate communities. Tadpoles from natural ponds were dissected to quantify the frequency of omnivory generally, as well as specifically in relation to pond size and tadpole morphology. Additional tadpoles were employed in a mesocosm experiment that manipulated tadpole presence (absent, caged, or free‐swimming) to quantify CEs and NCEs on freshwater zooplankton and macroinvertebrate communities. Over 70% of tadpoles in natural ponds engaged in omnivory, primarily on zooplankton, and tadpoles with wider heads and deeper tails were more likely to be omnivorous. Tadpoles in mesocosms exhibited CEs and NCEs on invertebrate communities, with stronger effects exerted on zooplankton than macroinvertebrates. The NCEs of tadpoles on invertebrates likely included production of predatory chemical cues that influenced invertebrate behavior, abundance, and community composition. Because tadpoles are often the dominant vertebrate predators in ephemeral aquatic ecosystems, this study stresses their ecological importance in structuring aquatic communities.

Background: Functional diversity is important to maintain ecosystem functioning. Species with different ecomorphological traits may display distinct functional roles in ecosystems. Accordingly, functionally extreme species are more important as they can exhibit specific strategies. However, little is known about the distribution patterns of functionally extreme species at a local scale and whether the prior extinction of extreme species can cause significant effects on functional diversity. In addition, no empirical studies have been conducted on the microhabitat determinants of extreme species to maintain the functional diversity. Results: This study collected 1470 tadpoles belonging to 6 families and 20 anuran species. These species were subsequently divided into 65 functional entities based on their developmental stages to incorporate intraspecific traits variability. As a result, we detected seven extreme functional entities, accounting for 10.7% of the total number of entities. Moreover, the prior extinction of extreme entities can lead to a significant decrease in functional diversity compared with the random extinction of entities. Microhabitat variables such as conductivity, water depth, and current velocity determined the distribution of extreme entities. Conclusion: Although the functionally extreme entities only represented a small proportion of the total number of tadpoles, they played irreplaceable roles in maintaining functional diversity. Their extinction may induce high functional vulnerability in tadpole communities. Therefore, anuran species with extreme tadpole traits need to be projected for amphibian conservation. [ABSTRACT FROM AUTHOR]

Simple Summary: Here, we provide the information derived from the first monitoring activities performed on the endangered Sette Fratelli cave salamander, Speleomantes sarrabusensis. Adopting two different monitoring schemes, we estimated the abundance of four populations of S. sarrabusensis, providing important data for future status assessments of the species. In this study, we performed the first monitoring activities on one of the most endangered amphibians in Europe, the Sette Fratelli cave salamander Speleomantes sarrabusensis. The data presented here are derived from two monitoring activities aiming to assess the status and abundance of four populations of S. sarrabusensis. With the first monitoring, we surveyed the well-known population occurring within artificial springs during the period 2015–2018, providing monthly data on the number of active individuals. With the second monitoring performed during spring to early summer of 2022, we surveyed four populations at three time points (the one from artificial springs and three from forested areas) and we provided the first estimation of the populations' abundance. Furthermore, we analyzed for the first time the stomach contents from a population of S. sarrabusensis only occurring in forested environments. With our study, we provided the first information on the abundance of different populations of S. sarrabusensis, representing the starting point for future status assessments for this endangered species. [ABSTRACT FROM AUTHOR]

Animals capable of moving in different environments might face conflicting selection on morphology, thus posing trade-offs on the relationships between morphology and locomotor performance in each of these environments. Moreover, given the distinct ecological roles of the sexes, these relationships can be sexually dimorphic. In this article, I studied the relationships between morphological traits and locomotor performance in male and female semiaquatic Pleurodeles waltl newts in their aquatic and their terrestrial stages. Morphology was sexually dimorphic: males have proportionally longer limbs and tails, as well as a better body condition (only in the aquatic phase), whereas females were larger and had greater body mass in both phases. Nonetheless, these morphological differences did not translate into sexual divergence in locomotor performance in either stage. This finding suggests other functions for the morphological traits measured, among which only SVL showed a positive relationship with locomotor performance in both stages, whereas the effect of SMI was negative only in the terrestrial stage, and that of tail length was positive only in the aquatic stage. In any case, the morphological correlates of terrestrial and aquatic locomotion did not conflict, which suggests no trade-off between both locomotory modes in the newts studied. [ABSTRACT FROM AUTHOR]

Population genetics can reveal whether colonization of created habitats has been successful and inform future strategies for habitat creation. We used genetic analysis to investigate spotted salamander (Ambystoma maculatum) colonization of created vernal pools and explored the impact of habitat characteristics on the genetic diversity and connectivity of the pools. Our first objective was to examine genetic structure, differentiation, diversity, and potential for a founder effect. Our second objective was to determine if habitat characteristics were associated with effective number of breeders, relatedness, or genetic diversity. We sampled spotted salamander larvae in 31 created vernal pools (1–5 years old) in Monongahela National Forest (WV) in May and June 2015 and 2016. The youngest pools exhibited genetic differentiation, a founder effect, and low effective number of breeders. Effective number of breeders was positively associated with pool age, vegetation cover, pool diameter, and sample size. Vegetation cover was also negatively associated with relatedness. Genetic diversity did not have strong environmental predictors. Our results indicated the effective number of breeders increased and genetic differentiation decreased within 4–5 years of pool creation, a sign of rapid colonization and potential population establishment. Our research also showed that higher vegetative cover within the pool and larger pool diameters could impact habitat quality and should be incorporated into future pool creation. [ABSTRACT FROM AUTHOR]

Dam construction affects freshwater ecosystems worldwide. While there is much focus on large impoundments, farm ponds are overlooked despite their near-ubiquity across human-altered landscapes. Within the Great Plains of North America, there are millions of farm ponds, yet little is known about the fish communities and factors structuring them. We propose a conceptual model where fish, amphibian, and crayfish abundances differ along a pond size and water permanency gradient and are further influenced by interactions among species. In the summer of 2021, we sampled 100 farm ponds across central Kansas, primarily on private land. Pond size and permanency explained community structure with smaller and less permanent ponds being dominated by amphibians and crayfish while larger ponds were dominated by stocked sportfish. Distribution modeling revealed a negative correlation between stocked fish and other community components indicating potential interactions. If we are to conserve headwater stream species, especially those that are threatened or endangered, strategies that integrate farm ponds seem necessary given their prevalence on the landscape. [ABSTRACT FROM AUTHOR]

The amygdala is a complex brain structure in the vertebrate telencephalon, essential for regulating social behaviors, emotions, and (social) cognition. In contrast to the vast majority of neuron types described in the many nuclei of the mammalian amygdala, little is known about the neuronal diversity in non-mammals, making reconstruction of its evolution particularly difficult. Here, we characterize glutamatergic neuron types in the amygdala of the urodele amphibian Pleurodeles waltl. Our single-cell RNA sequencing data indicate the existence of at least ten distinct types and subtypes of glutamatergic neurons in the salamander amygdala. These neuron types are molecularly distinct from neurons in the ventral pallium (VP), suggesting that the pallial amygdala and the VP are two separate areas in the telencephalon. In situ hybridization for marker genes indicates that amygdalar glutamatergic neuron types are located in three major subdivisions: the lateral amygdala, the medial amygdala, and a newly defined area demarcated by high expression of the transcription factor Sim1. The gene expression profiles of these neuron types suggest similarities with specific neurons in the sauropsid and mammalian amygdala. In particular, we identify Sim1+ and Sim1+ Otp+ expressing neuron types, potentially homologous to the mammalian nucleus of the lateral olfactory tract (NLOT) and to hypothalamic-derived neurons of the medial amygdala, respectively. Taken together, our results reveal a surprising diversity of glutamatergic neuron types in the amygdala of salamanders, despite the anatomical simplicity of their brain. These results offer new insights on the cellular and anatomical complexity of the amygdala in tetrapod ancestors. [ABSTRACT FROM AUTHOR]

Visual communication is apparently widespread among anurans, but these behaviours in many Neotropical species remain unstudied. We provide the first descriptions of visual displays in males of the Neotropical treefrog Dendropsophus carnifex (Hylidae) from three populations at Mindo, in northwestern Ecuador. We describe hind-foot lifting, foot-flagging, arm waving, toe trembling, body raising, and throat exposure for D. carnifex. All visual displays include exposure of flash colours in hidden surfaces of body and legs. Vocalisations were not emitted simultaneously with visual displays but were intercalated. [ABSTRACT FROM AUTHOR]

Tropical forests harbour the highest levels of terrestrial biodiversity and represent some of the most complex ecosystems on Earth, with a significant portion of this diversity above ground. Although the vertical dimension is a central aspect of the ecology of forest communities, there is little consensus as to prominence, evenness, and consistency of community‐level stratification from ground to canopy. Here, we gather the results of 62 studies across the tropics to synthesise and assess broad patterns of vertical stratification of abundance and richness in vertebrates, the best studied taxonomic group for which results have not been collated previously. Our review of the literature yielded sufficient data for bats, small mammals, birds and amphibians. We show that variation in the stratification of abundance and richness exists within and among all taxa considered. Bat richness stratification was variable among studies, although bat abundance was weighted towards the canopy. Both bird richness and abundance stratification were variable, with no overriding pattern. On the contrary, both amphibians and small mammals showed consistent patterns of decline in abundance and richness towards the canopy. We descriptively characterise research trends in drivers of stratification cited or investigated within studies, finding local habitat structure and food distribution/foraging to be the most commonly attributed drivers. Further, we analyse the influence of macroecological variables on stratification patterns, finding latitude and elevation to be key predictors of bird stratification in particular. Prominent differences among taxa are likely due to taxon‐specific interactions with local drivers such as vertical habitat structure, food distribution, and vertical climate gradients, which may vary considerably across macroecological gradients such as elevation and biogeographic realm. Our study showcases the complexity with which animal communities organise within tropical forest ecosystems, while demonstrating the canopy as a critical niche space for tropical vertebrates, thereby highlighting the inherent vulnerability of tropical vertebrate communities to forest loss and canopy disturbance. We recognise that analyses were constrained due to variation in study designs and methods which produced a variety of abundance and richness metrics recorded across different arrangements of vertical strata. We therefore suggest the application of best practices for data reporting and highlight the significant effort required to fill research gaps in terms of under‐sampled regions, taxa, and environments. [ABSTRACT FROM AUTHOR]

Understanding attributes of phenology beyond the mean date of a life history event, such as variability among individuals within a population, is critical to predict how climate‐induced phenological shifts may alter population dynamics. Identifying how phenological variability impacts organisms is especially needed to better understand how phenological shifts affect trophic dynamics (e.g., shifts in variability of top predators affecting primary production). To better understand the effects of phenological variability on both populations and communities, we examined how variation in egg hatching synchrony of predatory marbled salamanders (Ambystoma opacum) impacted intraspecific interactions at the larval stage, ultimately affecting demographic traits and survival through metamorphosis. We also examined how hatching synchrony affected overall trophic dynamics (e.g., primary consumers and producers) in pond food webs. We experimentally manipulated the degree of hatching synchrony of embryonic A. opacum and subsequently reared larvae in outdoor mesocosms. We monitored demographic traits such as larval growth, size at and time to metamorphosis, and survival. To assess trophic dynamics, we monitored zooplankton abundance and phytoplankton biomass during the experiment. Larvae exhibited greater variability in body size in medium and low hatching synchrony treatments compared to high synchrony treatments. Larval body size variation diminished over time to ultimately result in no differences in most life history traits at metamorphosis or survival among hatching synchrony treatments. We also found no differences among treatments in zooplankton abundance or phytoplankton biomass, likely because of minimal variation in A. opacum survival among treatments that would induce top‐down changes. Overall, we found that phenological variation may be context dependent in its influence on demography and overall community structure. Because of concerns for how phenological shifts will affect species interactions, greater scrutiny into conditions that would promote changes in population and community dynamics is needed. [ABSTRACT FROM AUTHOR]

Contemporary forest management often requires meeting diverse ecological objectives including maintaining ecosystem function and promoting biodiversity through timber harvesting. Wildlife are essential in this process by providing ecological services that can facilitate forest resiliency in response to timber harvesting. However, the mechanisms driving species' responses remain ambiguous. The goal of this study was to assess mechanisms influencing eastern red-backed salamander (RBS; Plethodon cinereus) response to overstory cover removal. We evaluated two mitigation strategies for the RBS in response to overstory removal. We used a before-after-control-impact design to study how (1) retaining residual trees or (2) eliminating soil compaction affected RBS surface counts and body condition index (BCI) up to two-years post-treatment. Additionally, we assessed how surface counts of RBS were influenced by overstory tree cover. Surface counts of RBS were not strongly influenced by overstory removal when tree residuals were retained. Body condition index increased in treatments where harvest residuals were retained. In treatments where soil compaction was eliminated, surface counts and BCI were inversely related. Finally, surface counts from both mitigation strategies were not strongly influenced by overstory cover. Overall, both mitigation techniques appeared to ameliorate impacts of overstory removal on RBS. These results highlight the importance of understanding mechanisms driving species' responses to forest management. To reduce the perceived negative effects of overstory removal on RBS, incorporating these mitigation measures may contribute to the viability and stability of RBS populations. Incorporating species' life history traits into management strategies could increase continuity of ecological function and integrity through harvesting. [ABSTRACT FROM AUTHOR]

The ecotoxicological risk to vertebrates posed by zinc oxide nanoparticles (ZnO NPs) is still poorly understood, especially in animals with a biphasic life cycle, which have aquatic and terrestrial phases, such as amphibians. In the present study, we investigated whether acute exposure (7 days) to ZnO NPs and zinc chloride (ZnCl2) at three environmentally relevant concentrations (0.1, 1.0, and 10 mg L−1) induces changes in the morphology, chondrocranium, and behavior of the tadpoles of Lithobates catesbeianus (Anura: Ranidae). Tadpoles exposed to both forms of Zn did not undergo any morphological or behavioral changes at the lowest concentrations (0.1 and 1.0 mg L−1). However, the animals exposed to the highest concentration (10 mg L−1) lacked oral disc structures, were smaller in size, had a longer tail, and presented changes in the position and coiling of the intestine and malformations of the chondrocranium in comparison with the control group. This indicates that ZnO NPs and ZnCl2 altered the development of the tadpoles, causing delays in their metamorphosis and even reducing individual fitness. The tadpoles exposed to both forms of Zn at 10 mg L−1 also had reduced mobility, especially in the presence of conspecifics. Based on these findings, we emphasize the importance of studying morphological, skeletal, and behavioral biomarkers to evaluate the toxic effects of metal-based nanoparticles in amphibians. [ABSTRACT FROM AUTHOR]

Sympatric distribution and potentially long larval development time make the assignment of tadpoles confusing in Asian-horned frogs of the subfamily Megophryinae. In this study, we used molecular data to identify four syntopic megophryinid tadpoles from Mangshan on the border between Hunan and Guangdong provinces in southern China: Brachytarsophrys popei, Boulenophrys shimentaina, Bo. cf. ombrophila, and Bo. nanlingensis. A detailed re-description of the Br. popei tadpoles is provided as well as the first descriptions of three Boulenophrys tadpoles based on external morphology and coloration. An effort is attempted to distinguish these tadpoles by coloration patterns: the dorsal pattern, ventral pattern, and pattern on tail are useful for field identification of these tadpoles. However, the variation of color pattern could sometimes make species delineation difficult. Researchers are encouraged to document coloration in life with photographs and the collection of tadpoles of different development stages and sizes advocated in order to better understand how color may change during larval development. [ABSTRACT FROM AUTHOR]

While most anuran species are highly vocal, few of them seem to be endowed with a complex call repertoire. Odorrana tormota, combines a remarkable vocalization complexity with auditory sensitivity over an extended spectral range spanning from audible to ultrasonic frequencies. This species is also exceptional for its ability to modify its middle ear tuning by closing the Eustachian tubes (ET). Using scanning laser Doppler vibrometry, the tympanal vibrations were measured to investigate if the tuning shift caused by the ET closure contributes to intraspecific acoustic communication. To gain insight into the inner ear frequency selectivity and sensitivity of this species, distortion product otoacoustic emissions were recorded at multiple frequency-level combinations. Our measurements of inner ear responses indicated that in O. tormota each sex is more sensitive to the frequencies of the other sex's vocalizations, female ears are more sensitive to 2–7 kHz, while male ears are more sensitive to 3–15 kHz. We also found that in both sexes the ET closure impacts the sensitivity of the middle and inner ear at frequencies used for communication with conspecifics. This study broadens our understanding of peripheral auditory mechanisms contributing to intraspecific acoustic communication in anurans. [ABSTRACT FROM AUTHOR]

Although research has focused on density‐dependent responses of hosts to single‐parasite infections, hosts are exposed to numerous parasites simultaneously under natural conditions and if these exposures lead to infections, they can threaten host populations and ecosystem stability. Moreover, spatiotemporal variation in abundance of co‐occurring parasites might influence host infection intensity. If interactions are consistent between different coinfecting parasites, then these patterns could give managers another tool to control disease spread and even predict problematic disease emergences.We investigated how parasite density and identity alter within‐host coinfection dynamics. To test this, we simultaneously exposed Cuban treefrogs Osteopilus septentrionalis as a model amphibian species to all pairwise combinations of three problematic parasites that commonly coinfect amphibians: the fungus Batrachochytrium dendrobatidis (Bd), the nematode Aplectana hamatospicula and Ranavirus. Hosts were exposed to one parasite at a fixed dose and another parasite at a range of five doses.Higher doses of Bd decreased Ranaviral and A. hamatospicula loads, but Bd load was not influenced by the dose of either parasite. Ranaviral load was negatively associated with A. hamatospicula dose, but A. hamatospicula load was not affected by Ranaviral dose. We found that all the pairwise coinfections were dependent on parasite density and that pairwise interactions were highly asymmetric—strong in one direction and weak in the other—consistent with interactions dominating food webs.Synthesis and applications: We also revealed that the exposure dose of A. hamatospicula was positively associated with host tolerance to Bd infection and negatively associated with Ranaviral load in hosts. Ranavirus and Bd cause mass die‐offs in amphibians, but A. hamatospicula does not. Therefore, in systems where these parasites coexist, maintaining or increasing densities of A. hamatospicula could reduce the negative effects of Bd and Ranavirus infections. Additionally, if these asymmetric and density‐dependent patterns from community ecology are applicable to other amphibian coinfections or coinfections in other systems, this should allow conservation organizations and resource managers to predict outbreaks and manage host declines associated with deadly parasites by modifying the abundance of coinfecting parasites that might be easier to manage. [ABSTRACT FROM AUTHOR]

The cortical bones of mammals, birds, and reptiles are composed of a complex of woven bone and lamellar bone (fibrolamellar bone) organized into a variety of different patterns; however, it remains unclear whether amphibians possess similar structures. Importantly, to understand the evolutionary process of limb bones in tetrapods, it is necessary to compare the bone structure of amphibians (aquatic to terrestrial) with that of amniotes (mostly terrestrial). Therefore, this study compared the cortical bones in the long bones of several frog species before and after metamorphosis. Using micro‐computed tomography (CT), we found that the cortical bones in the fibrolamellar bone of Xenopus tropicalis (Pipoidea superfamily) and Lithobates catesbeianus (Ranoidea superfamily) froglets are dense, whereas those of Ceratophrys cranwelli (Hyloidea superfamily) are porous. To clarify whether these features are common to their superfamily or sister group, four other frog species were examined. Histochemical analyses revealed porous cortical bones in C. ornata and Lepidobatrachus laevis (belonging to the same family, Ceratophryidae, as C. cranwelli). However, the cortical bones of Dryophytes japonicus (Hylidae, a sister group of Ceratophryidae in the Hyloidea superfamily), Microhyla okinavensis (Microhylidae, independent of the Hyloidea superfamily), and Pleurodeles waltl, a newt as an outgroup of anurans, are dense with no observed cavities. Our findings demonstrate that at least three members of the Ceratophryidae family have porous cortical bones similar to those of reptiles, birds, and mammals, suggesting that the process of fibrolamellar bone formation arose evolutionarily in amphibians and is conserved in the common ancestor of amniotes. [ABSTRACT FROM AUTHOR]

Two primer set/probe combinations targeting variable regions on the 23S rRNA gene were designed to detect and quantify chlamydiae in DNA extracted from brain swabs of the endangered Houston toad (Anaxyrus houstonensis) using SYBRGreen- and Taqman-based quantitative polymerase chain reaction (qPCR). Prevalence and abundance values for samples were generally different between SYBRGreen- and Taqman-based detection methods, with higher specificity observed for Taqman-based detection. Of the 314 samples analyzed, initial screening with SYBRGreen-based qPCR retrieved 138 positive samples, of which 52 were confirmed by Taqman-based analyses as chlamydiae. All of these samples were subsequently identified as Chlamydia pneumoniae by specific qPCR and confirmed by comparative sequence analyses of 23S rRNA gene amplicons. These results demonstrate the usefulness of our developed qPCR methods to screen for and verify prevalence of chlamydiae in DNA of brain swabs, and ultimately specifically identify and quantify chlamydiae, specifically C. pneumoniae in these samples. [ABSTRACT FROM AUTHOR]

The gut microbiome is important for host health and can be influenced by environmental and hormonal changes. We studied the interactions between anthropogenic land use, glucocorticoid hormones, and gut bacterial communities in common toads (Bufo bufo). We sampled tadpoles from ponds of three habitat types (natural, agricultural, and urban ponds), examined gut microbiome composition using amplicon sequencing of the 16S rRNA gene, and measured the associated stress physiology using water-borne hormones. Tadpoles from different habitat types significantly differed in bacterial composition. However, bacterial richness, Shannon diversity, and Firmicutes to Bacteroidota ratio did not vary with habitat type. In contrast with other studies, we found a positive correlation between baseline corticosterone release rate and bacterial diversity. Stress response and negative feedback were not significantly correlated with bacterial diversity. These results suggest that, despite alterations in the composition of intestinal bacterial communities due to land-use change, common toad tadpoles in anthropogenic habitats may maintain their physiological health in terms of the "gut-brain axis". [ABSTRACT FROM AUTHOR]

The Chiricahua leopard frog (Lithobates chiricahuensis) is a threatened species endemic to the southwestern United States and Northern Mexico. Captive breeding programs were established to support reintroduction efforts, yet reproductive output has been lower than needed for recovery of the species. This study aimed to evaluate the effects of captivity on amphibian reproduction by (1) determining if captive, semi‐captive, and wild male L. chiricahuensis produce sperm at similar rates and concentration in response to hormone treatment; and (2) evaluating the quality of sperm obtained over time from these populations. Males from captive, semi‐captive, and wild locations were administered a combination of human chorionic gonadotropin and gonadotropin‐releasing hormone to stimulate sperm production and release. A high percentage of males in the captive (60%), semi‐captive (100%), and wild (95.3%) populations produced sperm following treatment. Sperm quality (forward progressive motility and total sperm motility) did not differ between groups. However, sperm quantity (sperm/ml) differed (p <.05) between populations, with semi‐captive and wild males producing higher concentrations of sperm than captive males. These results suggest that Chiricahua leopard frog sperm quantity, but not quality, may become negatively impacted by long‐term captivity in indoor, controlled settings. [ABSTRACT FROM AUTHOR]

Ranavirosis is a disease of high concern for amphibians due to widespread documentation of its lethal and sublethal impacts and its high transmission potential across populations and species. We investigated whether spotted salamander (Ambystoma maculatum) ranavirus prevalence and viral load were associated with habitat characteristics, genetic diversity, corticosterone levels, and body size. In 2015 and 2016, we sampled 34 recently created vernal pools in the Monongahela National Forest, West Virginia, USA. We collected tail clippings from 1,128 spotted salamander larvae and waterborne hormone samples from 436 of those larvae, along with eight environmental characteristics of the pools. Over the 2-yr period, we detected ranavirus in 62% of pools, with prevalence ranging from 0% to 63% (mean, 7.68%). Spotted salamander size was positively correlated with ranavirus presence and viral load; however, we did not find associations between ranavirus prevalence or viral load and habitat characteristics, spotted salamander genetic diversity, relatedness, effective number of breeders, or corticosterone levels. The widespread occurrence of ranavirus in the vernal pools illustrates the potential for rapid natural introduction of the pathogen to created wetlands. Managers could consider monitoring local distributions of ranavirus before creation of new vernal pools to guide strategic placement of the wetlands to minimize occurrence and prevalence of this pathogen. [ABSTRACT FROM AUTHOR]

Novel infectious diseases, particularly those caused by fungal pathogens, pose considerable risks to global biodiversity. The amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) has demonstrated the scale of the threat, having caused the greatest recorded loss of vertebrate biodiversity attributable to a pathogen. Despite catastrophic declines on several continents, many affected species have experienced population recoveries after epidemics. However, the potential ongoing threat of endemic Bd in these recovered or recovering populations is still poorly understood. We investigated the threat of endemic Bd to frog populations that recovered after initial precipitous declines, focusing on the endangered rainforest frog Mixophyes fleayi. We conducted extensive field surveys over 4 years at three independent sites in eastern Australia. First, we compared Bd infection prevalence and infection intensities within frog communities to reveal species‐specific infection patterns. Then, we analyzed mark‐recapture data of M. fleayi to estimate the impact of Bd infection intensity on apparent mortality rates and Bd infection dynamics. We found that M. fleayi had lower infection intensities than sympatric frogs across the three sites, and cleared infections at higher rates than they gained infections throughout the study period. By incorporating time‐varying individual infection intensities, we show that healthy M. fleayi populations persist despite increased apparent mortality associated with infrequent high Bd loads. Infection dynamics were influenced by environmental conditions, with Bd prevalence, infection intensity, and rates of gaining infection associated with lower temperatures and increased rainfall. However, mortality remained constant year‐round despite these fluctuations in Bd infections, suggesting major mortality events did not occur over the study period. Together, our results demonstrate that while Bd is still a potential threat to recovered populations of M. fleayi, high rates of clearing infections and generally low average infection loads likely minimize mortality caused by Bd. Our results are consistent with pathogen resistance contributing to the coexistence of M. fleayi with endemic Bd. We emphasize the importance of incorporating infection intensity into disease models rather than infection status alone. Similar population and infection dynamics likely exist within other recovered amphibian‐Bd systems around the globe, promising longer‐term persistence in the face of endemic chytridiomycosis. [ABSTRACT FROM AUTHOR]

The extensive clearing and modification of forests by anthropogenic activities is a major driver of biodiversity loss. Declines of common species are especially concerning because of the potentially large cascading effects they might have on ecosystems. Regrowth of secondary forests may help reverse population declines by restoring habitats to similar conditions prior to land conversion but the value of these secondary forests to fauna is not well understood. We compared the abundance of a direct-developing terrestrial frog, Craugastor stejnegerianus , in riparian and upland habitats of pasture, secondary forest, and mature forest sites. Mean abundance per transect was lower in upland pasture compared to mature forest. Secondary forest had similar abundance to mature forest regardless of age. We show that conversion of forest habitat to pasture represents a conservation threat to this species. However, riparian buffers help mitigate the negative effect of conversion of forest to pasture, and regrowth of secondary forest is an effective management strategy for restoring the abundance of this common leaf-litter species. [ABSTRACT FROM AUTHOR]

Non-invasive methods are important to the field of conservation physiology to reduce negative effects on organisms being studied. Glucocorticoid (GC) hormones are often used to assess health of individuals, but collection methods can be invasive. Many amphibians are imperiled worldwide, and saliva is a non- or semi-invasive matrix to measure GCs that has been partially validated for only four amphibian species. Validation ensures that assays are reliable and can detect changes in saliva corticosterone (sCORT) after exposure to stressors, but it is also necessary to ensure sCORT concentrations are correlated with plasma concentrations. To help validate the use of saliva in assessing CORT responses in amphibians, we captured uniquely marked Columbia spotted frogs (Rana luteiventris) on sequential days and collected baseline and stress-induced (after handling) samples. For a subset of individuals, we collected and quantified CORT in both saliva and blood samples, which have not been compared for amphibians. We tested several aspects of CORT responses and, by collecting across separate days, measured repeatability of CORT responses across days. We also evaluated whether methods common to amphibian conservation, such as handling alone or handling, clipping a toe and tagging elevated sCORT. Similar to previous studies, we show that sCORT is reliable concerning parallelism, recovery, precision and sensitivity. sCORT was weakly correlated with plasma CORT (R2 = 0.21), and we detected elevations in sCORT after handling, demonstrating biological validation. Toe clipping and tagging did not increase sCORT over handling alone, but repeated handling elevated sCORT for ~72 hours. However, sCORT responses were highly variable and repeatability was low within individuals and among capture sessions, contrary to previous studies with urinary and waterborne CORT. sCORT is a semi-invasive and rapid technique that could be useful to assess effects of anthropogenic change and conservation efforts, but will require careful study design and future validation. [ABSTRACT FROM AUTHOR]

The regulation of river systems alters hydrodynamics and often reduces lateral connectivity between river channels and floodplains. For taxa such as frogs that rely on floodplain wetlands to complete their life cycle, decreasing inundation frequency can reduce recruitment and increase the probability of local extinction. We virtually reconstructed the inundation patterns of wetlands under natural and regulated flow conditions and built stochastic population models to quantify the probability of local extinction under different inundation scenarios. Specifically, we explored the interplay of habitat size, inundation frequency, and successive dry years on the local extinction probability of the threatened southern bell frog Litoria raniformis in the Murray River floodplains of South Australia. We hypothesized that the changes to wetland inundation resulting from river regulation are driving L. raniformis declines in this semiarid system. Regulation has reduced the inundation frequency of essential habitats below critical thresholds for the persistence of many fresh water‐dependent species. Successive dry years raise the probability of local extinction, and these effects are strongest in smaller wetlands. Larger wetlands and those with more frequent average inundation are less susceptible to these effects. Elucidating these trends informs the prioritization of intervention sites and the frequency of conservation interventions. Environmental water provision (through pumping or the operation of flow‐regulating structures) is a promising tool to reduce the probability of breeding failure and local extinction. Our modeling approach can be used to prioritize the delivery of environmental water to L. raniformis and potentially many other frog species. [ABSTRACT FROM AUTHOR]

The Phoenix Zoo has partnered with US Fish and Wildlife Service, Arizona Game and Fish Department, US Forest Service, and other organizations for more than 25 years to help recover Chiricahua leopard frogs (Rana [=Lithobates] chiricahuensis) in Arizona, USA. This federally threatened species faces declines due to habitat loss and degradation, long-term drought, disease, and invasive species. Over 26,000 larvae, froglets, and adults, as well as 26 egg masses produced by adults held at the Phoenix Zoo have been released to the wild, augmenting and/or re-establishing wild populations. Chiricahua leopard frog-occupied sites in Arizona have increased from 38 in 2007, when the species' recovery plan was published, to a high of 155 in the last five years, as a result of ex situ and in situ conservation efforts. As one of the longest-running programs of its kind in the United States, communication among partners has been key to sustaining it. Recovery strategies and complex decisions are made as a team and we have worked through numerous management challenges together. Though Chiricahua leopard frogs still face significant threats and a long road to recovery, this program serves as a strong example of the positive effects of conservation partnerships for native wildlife. [ABSTRACT FROM AUTHOR]

In China, as elsewhere, amphibians are highly endangered. Anthropogenic environmental change has affected the distribution and population dynamics of species, and species distributions at a broad scale are strongly driven by climate and species' ability to disperse. Yet, current knowledge remains limited on how widespread human activity affects the distribution patterns of amphibians in China and whether this effect extends beyond climate. We compiled a relatively comprehensive database on the distribution of 196 amphibian species in China from the literature, public databases, and field data. We obtained 25,826 records on almost 50% of known species in China. To test how environmental factors and human activities influence the current distribution of amphibians (1960–1990), we used range filling, which is species realized ranges relative to their potential climate distribution. We used all species occurrence records to represent realized range and niche models to predict potential distribution range. To reduce uncertainty, we used 3 regression methods (beta regression, generalized boosted regression models, and random forest) to test the associations of species range filling with human activity, climate, topography, and range size. The results of the 3 approaches were consistent. At the species level, mean annual precipitation (climate) had the most effect on spatial distribution pattern of amphibians in China, followed by range size. Human activity ranked last. At the spatial level, mean annual precipitation remained the most important factor. Regions in southeastern of China that are currently moist supported the highest amphibian diversity, but were predicted to experience a decline in precipitation under climate change scenarios. Consequently, the distributions of amphibians will likely shift to the northwest in the future, which could affect future conservation efforts. [ABSTRACT FROM AUTHOR]

An increasing number of species are establishing populations outside of their native ranges, often with negative ecological and economic impacts. The detection and surveillance of invasive species presents a huge logistical challenge, given the large spatial regions in which new populations can appear. However, data collected through citizen science projects are increasingly recognised as a valuable source for detection and monitoring of invasive species. We use data from a national citizen science project, FrogID, to quantify the spread of the eastern dwarf tree frog (Litoria fallax) outside its historical native range in Australia. Of 48 012 records of L. fallax in the FrogID database, 485 were located far outside the historical native range of the species. L. fallax has established geographically large populations hundreds of kilometres away from its native range, and these appear to be spreading in extent over time. These populations have resulted in novel species co-occurrences, with L. fallax now co-occurring with at least two frog species not present in their native range. Although the impacts of the invasive populations of L. fallax remain unknown, our work highlights the value in leveraging citizen science projects to detect and monitor native species that can become invasive far outside their historical range. Up to date information on the distribution of invasive species is vital to biodiversity conservation but difficult to obtain. We use data from a national citizen science project, FrogID, to examine the distribution of the eastern dwarf tree frog (Litoria fallax) in Australia. These data reveal that the species has established populations far outside its native range and that these populations are spreading, highlighting the value of citizen science in detection and monitoring of invasive species. Photograph by Jodi Rowley. [ABSTRACT FROM AUTHOR]

Amphibians are increasingly threatened worldwide, but the availability of genomic resources that could be crucial for implementing informed conservation practices lags well behind that for other vertebrate groups. Here, we describe draft de novo genome, mitogenome, and transcriptome assemblies for the Neotropical leaf-frog Phyllomedusa bahiana native to the Brazilian Atlantic Forest and Caatinga. We used a combination of PacBio long reads and Illumina sequencing to produce a 4.74-Gbp contig-level genome assembly, which has a contiguity comparable to other recent nonchromosome level assemblies. The assembled mitogenome comprises 16,239 bp and the gene content and arrangement are similar to other Neobratrachia. RNA-sequencing from 8 tissues resulted in a highly complete (86.3%) reference transcriptome. We further use whole-genome resequencing data from P. bahiana and from its sister species Phyllomedusa burmeisteri, to demonstrate how our assembly can be used as a backbone for population genomics studies within the P. burmeisteri species group. Our assemblies thus represent important additions to the catalog of genomic resources available from amphibians. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are contaminants widely distributed in the environment and biota. Previously, most studies focused on identifying and characterizing microplastics in the marine environment, while their impact on freshwater ecosystems remains to be determined. This review summarizes recent findings regarding MPs physiological, immunological, and genetic effects on amphibians based upon the biological relevance of this species as indicators of freshwater pollution. Data demonstrated that MPs contamination may potentially alter various physiological processes in aquatic animals, mainly in the embryonic stages. It is worthwhile noting that adverse effects might be enhanced in synergy with other pollutants. However, amphibians might counteract the effect of MPs and other pollutants through microbiota present both in the intestine and on the skin. In addition, amphibian microbial composition might also be altered by MPs themselves in a manner that leads to unpredicted health consequences in amphibians. [ABSTRACT FROM AUTHOR]

Amphibians have been facing global declines over the last decades from direct and indirect effects of anthropogenic activities. A contributor to declines is waterway contamination from agricultural runoffs of pesticides such as neonicotinoids. Beyond direct and indirect effects of the pesticide, few studies have investigated the possible interactions between neonicotinoids and natural environmental stressors across larval development, which could alter the strength and direction of observed neonicotinoid effects. The present study used a fully crossed design to investigate how a concentration of imidacloprid (a neonicotinoid; 10 µg/L) measured in surface waters interacted with low and high population densities (0.33 and 1 tadpole/L, respectively), an important environmental stressor, to influence behavior and development across metamorphosis in wood frogs (Rana sylvatica), known to breed in agricultural landscapes. Behaviors were measured in the absence and presence of predation cues using open‐field tests at three distinct developmental stages, up to the metamorph stage. We found that imidacloprid did not interact with population density or independently affect behaviors in the absence of predation cues. However, individuals raised at high density compared with low density were more active at an early developmental stage but less active at metamorphic climax. Furthermore, both density and imidacloprid independently decreased the natural freezing response of tadpoles to predation cues. Finally, we found that distance traveled in the open‐field test was weakly repeatable between aquatic stages but not repeatable across metamorphosis, a pattern that was not affected by treatments. The present study provides novel insights on the ecotoxicology of imidacloprid in the presence of a natural stressor, highlighting the importance of including behavioral assays and natural stressors in studies of amphibian ecotoxicology. Environ Toxicol Chem 2022;41:2968–2980. © 2022 SETAC [ABSTRACT FROM AUTHOR]

Oviparous species that reproduce in unpredictably variable environments risk depositing their eggs in situations that may become unsuitable for offspring survival at any time. This uncertainty often leads to selection for iteroparity as a form of bet‐hedging to spread offspring development spatially and temporally, thereby improving the odds of some cohorts experiencing optimal conditions. Paradoxically, an iteroparous mode appears to be the exception for a small number of amphibians that exploit temporary aquatic systems. In this study, we provide evidence of this paradox in an Australian anuran, the sandpaper frog, Lechriodus fletcheri, which breeds almost exclusively in small, highly ephemeral pools that often dry before the completion of tadpole development. A capture‐mark‐recapture study was conducted on a population over three consecutive breeding seasons, to determine how often adults returned to breeding sites within and between years and the extent of iteroparity. We found practically no adult returns between seasons, even though recapture events often occurred within season, suggesting that this species is virtually semelparous. A similar life history is apparent in other amphibians, suggesting that some species are able to persist in unpredictable environments by likely taking advantage of other forms of bet‐hedging in the absence of iteroparity. For L. fletcheri, we suggest that an extended breeding season may lend itself to the process of cohort splitting at a population level, resulting in the future reproductive activity of offspring from each generation being spread across multiple seasons. Our study shows how an iteroparous life history is not the only way to deal with environmental uncertainty. [ABSTRACT FROM AUTHOR]

Investigating feeding patterns among species is essential to understanding and preserving populations, especially in habitats like the Amazon. This study analyzed the patterns of food resource use of two coexisting species of Hylidae, Boana geographica and B. raniceps, in Central Amazonia, Brazil. High trophic niche overlap (0.74) and differences in the most important food items were observed between the two species. For B. geographica, anuran tadpoles were the prey with the greatest volume (63.73%) and frequency (30%). For B. raniceps, the items with the highest volume were Orthoptera (53.14%) and Araneae (30.39%), and the most frequent item was Coleoptera (18.75%). The most important food items for B. geographica were tadpoles (Ix = 39.41) and for B. raniceps were Orthoptera (Ix = 25.05) and Coleoptera (Ix = 16.85). For both species, no correlation was found between predator size and mouth width in relation to the size and volume of the prey. Boana raniceps was considered a passive, generalist forager with a sit-and-wait feeding strategy like most Hylidae. On the other hand, B. geographica may be regarded as an active generalist forager due to the high consumption of tadpoles. Despite the high overlap in their diet composition, the differences in prey categories with greater dietary importance likely seem to enable these species' coexistence. [ABSTRACT FROM AUTHOR]

We describe fatal phaeohyphomycosis due to Veronaea botryosa in captive White's tree frogs (Litoria caerulea), the first confirmed report in amphibians in North America. Over 15 months, six frogs developed ulcerative dermatitis on distal extremities/ventrum, which in one animal progressed to vasculitis and necrotizing osteomyelitis. All six frogs died. Clinicopathologic findings, diagnostic challenges, and control are discussed. Emerging fungi such as V. botryosa pose serious concerns for zoonosis and potential spread through the pet trade. [ABSTRACT FROM AUTHOR]

Objective: The growth, survival, and condition factor of Ambystoma mexicanum juveniles fed with three commercial feed-based diets coated with different animal oils as potential palatability enhancers were evaluated. Methodology: Three diets were prepared using commercial feed coated with fish, chicken, and krill oil. The experiment lasted 81 days, the food was provided to the axolotls (6 per experimental unit, in triplicate) every 48 h, at 4% of the total biomass. The total weight of each experimental unit was recorded every 15 days, at the end of the experiment individual weight and height and survival were recorded. The following variables were calculated: Fulton's K, specific growth rate, coefficient of variation of final weight and size heterogeneity. Results: All three treatments showed an increase in total biomass, with a trend towards better performance in chicken and fish oil treatments compared to krill oil. When performing the statistical analysis, it was found that there were no significant differences among the treatments for any of the variables recorded. Implications: The three oils used in the present study were good palatable agents in the food intake of A. mexicanum. Conclusions: It is recommended to use chicken oil as an attractant additive in the formulation of a specific diet due to its low cost. [ABSTRACT FROM AUTHOR]

Parasite and pathogen surveillance is crucial for understanding trends in their distributions and host spectra, as well as to document changes in their population dynamics. Nevertheless, continuous surveillance is time-consuming, underfunded due to the non-charismatic nature of parasites/pathogens, and research infrastructure is usually limited to short-term surveillance efforts. Species observation data provided by the public can contribute to long-term surveillance of parasites using photographic evidence of infections shared on community science platforms. Here, we used public photo repositories to document the occurrence across space and time of Lucilia spp. (Diptera: Calliphoridae), a parasite inducing nasal toad myiasis in the European toad Bufo bufo (Anura: Bufonidae). We found a total of 262 toad myiasis observations on iNaturalist (n = 132), on GBIF (n = 86), on Flickr (n = 41), and on observation.org (n = 3). Our results indicate that the distribution of toad myiasis is regionally limited, despite its host being widely distributed and abundant across a wide region in Europe. Observations were found in 12 countries with relatively low prevalence, including Belgium (3.90%, CI 2.44–6.18), Denmark (1.26%, CI 0.89–1.80), France (0.45%, CI 0.14–1.38), Germany (1.27%, CI 0.92–1.75), Lithuania (0.50%, CI 0.13–1.98), Luxembourg (1.30%, CI 0.42–3.95), the Netherlands (2.71%, CI 1.61–4.52), Poland (0.89%, CI 0.34–2.35), Russia (Kaliningrad Oblast) (4.76%, CI 0.67–27.14), Switzerland (NA), Ukraine (0.87%, CI 0.12–5.91), and in the UK (0.45%, CI 0.28–0.72). Nevertheless, the number of uploaded observations of both parasite infection and host presence indicates a stable increase likely due to the growing popularity of community science websites. Overall, community science is a useful tool to detect and monitor certain wildlife diseases and to recognize potential changes in disease dynamics through time and space. [ABSTRACT FROM AUTHOR]

Batrachochytrium salamandrivorans (Bsal), a species related to the destructive pathogen Batrachochytrium dendrobatidis (Bd), was found and identified in Europe in 2013. Now, a decade later, a large amount of information is available. This includes data from studies in the field, reports of infection in captive amphibians, laboratory studies testing host susceptibility, and data from prospective studies that test for Bsal's presence in a location. We conducted a systematic review of the published literature and compiled a dataset of Bsal tests. We identified 67 species that have been reported positive for Bsal, 20 of which have a threatened conservation status. The distribution of species that have been found with infection encompasses 69 countries, highlighting the potential threat that Bsal poses. We point out where surveillance to detect Bsal have taken place and highlight areas that have not been well monitored. The large number of host species belonging to the families Plethodontidae and Salamandridae suggests a taxonomic pattern of susceptibility. Our results provide insight into the risk posed by Bsal and identifies vulnerable species and areas where surveillance is needed to fill existing knowledge gaps. [ABSTRACT FROM AUTHOR]

Purpose: Brazilian anurans are considered the most diverse and species rich around the world. Although in recent years there has been a strong focus on research related to this group of animals, their parasites have not received the same attention. Thus, this study aimed to provide morphological and molecular data on haemogregarines biodiversity infecting Brazilian anurans. Methods: During 2020, 116 anurans were collected from four Brazilian States and their blood and fragment of organs were screened for haemogregarine parasites. Results: From the total, seven (6.03%) animals were found infected with species of Hepatozoon and Dactylosoma. Based on the morphological and molecular analysis, four anurans were found infected with Hepatozoon latrensis. The phylogenetic analysis has shown the isolates from this study grouping with the Brazilian anuran Hepatozoon clade, also with gene similarity ranging from 99.70 to 100% to H. latrensis isolates available on GenBank. Furthermore, three specimens (Trachycephalus typhonius, Leptodactylus latrans, and Rhinella diptycha) were infected with the same species of Dactylosoma (100% genetic similarity), with a genetic similarity of 98.56% to Dactylosoma piperis the only other species described in Brazil. In support of the molecular data, different morphological characters were observed in the blood smears as compared to D. piperis, suggesting that the species of Dactylosoma from the present study infecting three different species of Brazilian anurans is an undescribed species. Conclusion: Thus, this study increases the knowledge of Brazilian anuran blood parasites and demonstrates the importance of using integrative approaches for the diagnosis of haemoparasites. [ABSTRACT FROM AUTHOR]

Otoacoustic emissions (OAE) that were sound-induced, current-induced, or spontaneous have been measured in non-mammalian land vertebrates, including in amphibians, reptiles, and birds. There are no forms of emissions known from mammals that have not also been observed in non-mammals. In each group and species, the emission frequencies clearly lie in the range known to be processed by the hair cells of the respective hearing organs. With some notable exceptions, the patterns underlying the measured spectra, input-output functions, suppression threshold curves, etc., show strong similarities to OAE measured in mammals. These profound similarities are presumably traceable to the fact that emissions are produced by active hair-cell mechanisms that are themselves dependent upon comparable nonlinear cellular processes. The differences observed—for example, in the width of spontaneous emission peaks and delay times in interactions between peaks—should provide insights into how hair-cell activity is coupled within the organ and thus partially routed out into the middle ear.

Animal behavior and welfare science can form the basis of zoo animal management. However, even basic behavioral data are lacking for the majority of amphibian species, and species-specific research is required to inform management. Our goal was to develop the first ethogram for the critically endangered frog Xenopus longipes through observation of a captive population of 24 frogs. The ethogram was applied to produce a diurnal activity budget and to measure the behavioral impact of a routine health check where frogs were restrained. In the activity budget, frogs spent the vast majority of time swimming, resting in small amounts of time devoted to feeding, foraging, breathing, and (in males) amplexus. Using linear mixed models, we found no effect of time of day or sex on baseline behavior, other than for breathing, which had a greater duration in females. Linear mixed models indicated significant effects of the health check on duration of swimming, resting, foraging, feeding, and breathing behaviors for all frogs. This indicates a welfare trade-off associated with veterinary monitoring and highlights the importance of non-invasive monitoring where possible, as well as providing candidates for behavioral monitoring of acute stress. This investigation has provided the first behavioral data for this species which can be applied to future research regarding husbandry and management practices.

Abstract Background The fungal pathogen Batrachochytrium dendrobatidis (Bd) threatens amphibian biodiversity and ecosystem stability worldwide. Amphibian skin microbial community structure has been linked to the clinical outcome of Bd infections, yet its overall functional importance is poorly understood. Methods Microbiome taxonomic and functional profiles were assessed using high-throughput bacterial 16S rRNA and fungal ITS2 gene sequencing, bacterial shotgun metagenomics and skin mucosal metabolomics. We sampled 56 wild midwife toads (Alytes obstetricans) from montane populations exhibiting Bd epizootic or enzootic disease dynamics. In addition, to assess whether disease-specific microbiome profiles were linked to microbe-mediated protection or Bd-induced perturbation, we performed a laboratory Bd challenge experiment whereby 40 young adult A. obstetricans were exposed to Bd or a control sham infection. We measured temporal changes in the microbiome as well as functional profiles of Bd-exposed and control animals at peak infection. Results Microbiome community structure and function differed in wild populations based on infection history and in experimental control versus Bd-exposed animals. Bd exposure in the laboratory resulted in dynamic changes in microbiome community structure and functional differences, with infection clearance in all but one infected animal. Sphingobacterium, Stenotrophomonas and an unclassified Commamonadaceae were associated with wild epizootic dynamics and also had reduced abundance in laboratory Bd-exposed animals that cleared infection, indicating a negative association with Bd resistance. This was further supported by microbe-metabolite integration which identified functionally relevant taxa driving disease outcome, of which Sphingobacterium and Bd were most influential in wild epizootic dynamics. The strong correlation between microbial taxonomic community composition and skin metabolome in the laboratory and field is inconsistent with microbial functional redundancy, indicating that differences in microbial taxonomy drive functional variation. Shotgun metagenomic analyses support these findings, with similar disease-associated patterns in beta diversity. Analysis of differentially abundant bacterial genes and pathways indicated that bacterial environmental sensing and Bd resource competition are likely to be important in driving infection outcomes. Conclusions Bd infection drives altered microbiome taxonomic and functional profiles across laboratory and field environments. Our application of multi-omics analyses in experimental and field settings robustly predicts Bd disease dynamics and identifies novel candidate biomarkers of infection. Video Abstract

Abstract The boreal chorus frog (Pseudacris maculata) is at risk of extinction in parts of its range in Canada. Our objectives were to quantify the influence of local and landscape characteristics on the occurrence of the species in wetlands in southern Québec. We hypothesized that site occupancy depends on local characteristics and landscape characteristics contributing to site connectivity. We developed an environmental DNA (eDNA) method to detect the species and compared the detection probability of this method to traditional call surveys. We collected water samples from a total of 180 sites (90 in 2017, 110 in 2018), whereas we surveyed a subset of 63 sites using both eDNA and call surveys in 2018. Site occupancy varied across years, but was higher in sites where the species had been previously detected during the last 12 years by other studies. Site occupancy did not vary with other local and landscape characteristics, in part due to an apparent decrease in the number of sites occupied by the species since the last 12 years. Detection probability via eDNA (0.81; 95% CI: [0.31; 0.98]) did not differ from that of call surveys (0.62; 95% CI: [0.25; 0.89]). To identify the optimal sampling period for the boreal chorus frog, future studies should estimate the detection probability of eDNA during the breeding season and the larval development period of the species.

The plasma bacterial killing ability (BKA) is modulated by the stress response in vertebrates, including amphibians. The complement system is an effector mechanism comprised of a set of proteins present in the plasma that once activated can promote bacterial lysis. Herein, we investigated whether changes in plasma BKA as a result of the acute stress response and an immune challenge are mediated by the complement system in Rhinella diptycha toads. Additionally, we investigated whether the observed changes in plasma BKA are associated with changes in plasma corticosterone levels (CORT). We subjected adult male toads to a restraint or an immune challenge (with three concentrations of Aeromonas hydrophila heat inactivated), and then evaluated the plasma BKA against A. hydrophila, in vitro. We determined the complement system activity on plasma BKA, by treating the plasma (baseline, 1 h and 24 h post-restraint, and after the immune challenge) with ethylenediaminetetraacetic acid, heat, or protease. Our results showed increased CORT 1 h and 24 h after restraint and decreased plasma BKA 24 h post-restraint. The inhibitors of the complement system decreased the plasma BKA compared with untreated plasma at all times (baseline, 1 h, and 24 h after restraint), demonstrating that the plasma BKA activity is partially mediated by the complement system. The immune challenge increased CORT, with the highest values being observed in the highest bacterial concentration, compared with control. The plasma BKA was not affected by the immune challenge but was demonstrated to be partially mediated by the complement system. Our results demonstrated that restraint and the immune challenge activated the hypothalamus-pituitary-interrenal axis, by increasing plasma CORT levels in R. diptycha. Also, our results demonstrated the complement system is participative in the plasma BKA for baseline and post-stress situations in these toads. [Display omitted] • Restraint and immune challenge increased corticosterone plasma levels • Plasma bacterial killing ability decreased 24 h after restraint • Plasma bacterial killing ability was reduced by heat, protease and EDTA • Plasma bacterial killing ability is mediated by the complement system in toads [ABSTRACT FROM AUTHOR]

Tris(2-chloroethyl) phosphate (TCEP) and tris(1-chloro-2-propyl) phosphate (TCPP) are common chlorinated organophosphorus flame retardants (OPFRs) used in industry. They have been frequently detected together in aquatic environments and associated with various hazardous effects. However, the ecological risks of prolonged exposure to these OPFRs at environmentally relevant concentrations in non-model aquatic organisms remain unexplored. This study investigated the effects of long-term exposure (up to 25 days) to TCEP and TCPP on metamorphosis, hepatic antioxidants, and endocrine function in Polypedates megacephalus tadpoles. Exposure concentrations were set at 3, 30, and 90 μg/L for each substance, conducted independently and in equal-concentration combinations, with a control group included for comparison. The integrated biomarker response (IBR) method developed an optimal linear model for predicting the overall ecological risks of TCEP and TCPP to tadpoles in potential distribution areas of Polypedates species. Results showed that: (1) Exposure to environmentally relevant concentrations of TCEP and TCPP elicited variable adverse effects on tadpole metamorphosis time, hepatic antioxidant enzyme activity and related gene expression, and endocrine-related gene expression, with their combined exposure exacerbating these effects. (2) The IBR value of TCEP was consistently greater than that of TCPP at each concentration, with an additive effect observed under their combined exposure. (3) The ecological risk of tadpoles exposed to the combined presence of TCEP and TCPP was highest in China's Taihu Lake and Vietnam's Hanoi than in other distribution locations. In summary, prolonged exposure to environmentally relevant concentrations of TCEP and TCPP presents potential ecological risks to amphibian tadpoles, offering insights for the development of policies and strategies to control TCEP and TCPP pollution in aquatic ecosystems. Furthermore, the methodology employed in establishing the IBR prediction model provides a methodological framework for assessing the overall ecological risks of multiple OPFRs. [Display omitted] • Both independent and combined exposures to TCEP and TCPP severely disrupted tadpole physiology. • TCEP posed a greater ecological risk to tadpoles than TCPP, especially when combined. • A linear model was developed to predict IBR using real TCEP and TCPP data. • Ecological risks from the combined presence of TCEP and TCPP to tadpoles were highest in China's Taihu Lake and Vietnam's Hanoi. [ABSTRACT FROM AUTHOR]

Among tetrapod (terrestrial) vertebrates, amphibians remain more closely tied to an amphibious lifestyle than amniotes, and their visual opsin genes may be adapted to this lifestyle. Previous studies have discussed physiological, morphological, and molecular changes in the evolution of amphibian vision. We predicted the locations of the visual opsin genes, their neighboring genes, and the tuning sites of the visual opsins, in 39 amphibian genomes. We found that all of the examined genomes lacked the Rh2 gene. The caecilian genomes have further lost the SWS1 and SWS2 genes; only the Rh1 and LWS genes were retained. The loss of the SWS1 and SWS2 genes in caecilians may be correlated with their cryptic lifestyles. The opsin gene syntenies were predicted to be highly similar to those of other bony vertebrates. Moreover, dual syntenies were identified in allotetraploid Xenopus laevis and X. boreali s. Tuning site analysis showed that only some Caudata species might have UV vision. In addition, the S164A that occurred several times in LWS evolution might either functionally compensate for the Rh2 gene loss or fine-tuning visual adaptation. Our study provides the first genomic evidence for a caecilian LWS gene and a genomic viewpoint of visual opsin genes by reviewing the gains and losses of visual opsin genes, the rearrangement of syntenies, and the alteration of spectral tuning in the course of amphibians' evolution. [ABSTRACT FROM AUTHOR]

Endangered animals suffer from isolation of their habitats. Isolation leads to a reduction in population size as well as a decrease in genetic diversity and a concomitant increase in the risk of extinction. Amphibians are the most endangered vertebrate class. Besides habitat loss, fragmentation and isolation, amphibians are threatened by emerging diseases e.g., chytrid fungus or Ranavirus. By employing experiments, researchers investigate whether changes in genetic diversity within or among isolated populations affect amphibian fitness. While genetic diversity estimates are based on molecular markers, typically microsatellites, fitness is mostly measured as tadpole performance in rearing experiments often under varying environmental conditions. Tadpole performances (e.g., body mass, growth rate and survival) have been found to be negatively affected by low genetic diversity, as several studies have found a positive association between genetic diversity and these fitness traits. Moreover, infection with pathogens also seems to be more likely in individuals or populations with lower genetic diversity. Overall, these genetic–fitness correlations seem to be more pronounced or detectable in smaller, declining populations but not in larger populations. Genomic studies, which sample a larger fraction of the genome, are still scarce in the conservation genetic literature on amphibians. These are likely to increase in upcoming years and may reveal adaptive variants that protect against dangerous pathogens or environmental changes. Altogether, genetic–fitness correlation studies should be a priority in order to develop effective management plans for the genetic rescue of isolated, imperilled amphibian populations.

Causes and contributing factors of amphibious airplane accidents are examined by comparing the proportion of fatal accidents for different causes of accidents, with a focus on landings on water and low-level flying maneuvers. A set of 183 accidents involving amphibious planes from 2005 to 2020 was extracted from the National Transportation Safety Board’s online database. Amphibious airplane accidents are reported to be fatal in 34% of cases, which is higher than the average of 20% for general aviation. Logistic regression analysis shows that the maneuvering flight phase and decision-making factors are significantly more often associated with fatal accidents than other flight phases and causes. In addition, the number of accidents associated with decision-making factors significantly increased during the studied time period. Amphibious airplanes benefit from accident analysis despite the absence of denominator data and the limitations of most general aviation accident reports. Intentional low-level flying is shown to be a central area of concern that may be addressed at the operational as well as the training level. Landing accidents could be avoided by introducing additional warning systems and training regarding (retractable) landing gear as well as general awareness training of decision-making during landings on water.