Amphibian Declines Research Articles

Chytrid prevalence and infection intensity in treefrogs from three environments with different degrees of conservation in Mexico

AbstractChytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), has been related to rapid population declines and extinction in amphibians around the world. Bd has been associated with a severe decline in amphibian populations in southern Mexico. We compare the prevalence and intensity of Bd infection in two tree frogs in southern Mexico with similar life habits (Plectrohyla matudai and Ptychohyla euthysanota), inquiring if they differ across habitat types with different degrees of disturbance: preserved cloud forest, secondary cloud forest and anthropized riparian vegetation, and across three seasons. We examine the relationship between infection prevalence and intensity with biotic and abiotic variables. Infection prevalence differed between the two species, but not among environments, despite their similar life habits. Among seasons, prevalence decreased significantly at the end of the rainy season. There was no indication of significant changes in infection intensity between species, environments, and seasons. Moreover, the interaction among extrinsic factors (canopy cover, temperature, relative humidity) and factors intrinsic factors (body condition) explains the dynamics of Bd infection in the region. In our sample, we found no disease‐affected individuals, which may indicate that both species are resistant to the effects of the pathogen under field conditions. Finally, our results found no evidence to indicate that open canopies and anthropized habitats of the Sierra Madre de Chiapas are a refuge that prevents high prevalence or infection of Bd in stream breeders' amphibians.Abstract in Spanish is available with online material.

Genotoxic risk assessment of solar UV radiation in tadpoles from Brazilian wetlands

Solar ultraviolet (UV) radiation is an environmental genotoxic factor linked to amphibian decline. Here we assessed the genotoxic risk of UVB and UVA exposure for tadpoles from open ponds in southern Brazil, a mid-latitude region influenced by stratospheric ozone depletion. Daily UV doses were measured on the surface of a pond in Taim Ecological Station (TAIM; 32°49’24’’S; 52°38’31’’W) on a cloudless summer day to predict the worst-case scenario for UV-induced DNA damage. Pond descriptors were related to the use of microhabitats by Boana pulchella tadpoles in two ponds over the climate seasons of 2013 and 2014. Our results indicate that shaded microhabitats were more frequent than unshaded ones in autumn, winter, and spring but not in summer. Hence, the penetration of UV radiation into the water of unshaded microhabitats was evaluated through laboratory experiments with artificial UV sources and pond water samples. Physical and biological sensors were applied in the experiments to measure the incident UV radiation and its genotoxic action. By integrating field and laboratory data, we demonstrate that low doses of biologically effective UV radiation reached the tadpoles in autumn, winter, spring, and early summer due to a high proportion of shaded microhabitats and a high concentration of solids in unshaded microhabitats. However, the relative reduction of shaded microhabitats jointly with a declining water level in late summer may have exposed tadpoles to high UV doses. Our experiments also indicate that solar UVB radiation, but not UVA, is primarily responsible for the induction of DNA pyrimidine dimers in organisms living under the surface of aquatic ecosystems. The present work highlights the determinant role of wetland descriptors for minimizing the genotoxic potential of UV radiation and its consequences for amphibians.

Identification of a novel secreted metabolite cyclo(phenylalanyl-prolyl) from Batrachochytrium dendrobatidis and its effect on Galleria mellonella.

The fungus, Batrachochytrium dendrobatidis, is the causative agent of chytridiomycosis and a leading cause of global decline in amphibian populations. The first stages of chytridiomycosis include: inflammation, hyperkeratosis, lethargy, loss of righting reflex, and disruption of internal electrolyte levels leading to eventual death of the host. Previous work indicates that B. dendrobatidis can produce immunomodulatory compounds and other secreted molecules that regulate the growth of the fungus. In this study, filtrates of the fungus grown in media and water were subjected to ultra-performance liquid chromatography-mass spectrometry and analyzed using Compound Discoverer 3.0. Identification of cyclo(phenylalanyl-prolyl), chitobiose, and S-adenosylmethionine were verified by their retention times and fragmentation patterns from B. dendrobatidis supernatants. Previous studies have analyzed the effects of B. dendrobatidis on amphibian models, in vitro, or in cell culture. We studied the effects of live B. dendrobatidis cells, spent culture filtrates containing secreted metabolites, and cyclo(pheylalanyl-prolyl) on wax moth larvae (Galleria mellonella). Concentrated filtrates caused melanization within 24h, while live B. dendrobatidis caused melanization within 48h. Here we show B. dendrobatidis produces secreted metabolites previously unreported. The impacts of these chemicals were tested on an alternate non-amphibian model system that has been used for other fungi to study pathogenicity traits in this fungus.

Environmental and Anthropogenic Factors Shape the Skin Bacterial Communities of a Semi-Arid Amphibian Species

The amphibian skin microbiome is important in maintaining host health, but is vulnerable to perturbation from changes in biotic and abiotic conditions. Anthropogenic habitat disturbance and emerging infectious diseases are both potential disrupters of the skin microbiome, in addition to being major drivers of amphibian decline globally. We investigated how host environment (hydrology, habitat disturbance), pathogen presence, and host biology (life stage) impact the skin microbiome of wild Dhofar toads (Duttaphrynus dhufarensis) in Oman. We detected ranavirus (but not Batrachochytrium dendrobatidis) across all sampling sites, constituting the first report of this pathogen in Oman, with reduced prevalence in disturbed sites. We show that skin microbiome beta diversity is driven by host life stage, water source, and habitat disturbance, but not ranavirus infection. Finally, although trends in bacterial diversity and differential abundance were evident in disturbed versus undisturbed sites, bacterial co-occurrence patterns determined through network analyses revealed high site specificity. Our results therefore provide support for amphibian skin microbiome diversity and taxa abundance being associated with habitat disturbance, with bacterial co-occurrence (and likely broader aspects of microbial community ecology) being largely site specific.

A Variety of Fungal Species on the Green Frogs' Skin (Pelophylax esculentus complex) in South Banat.

In the last several decades, amphibian populations have been declining worldwide. Many factors have been linked to global amphibian decline, including habitat destruction, pollution, introduced species, global environmental changes, and emerging infectious diseases. Recent studies of amphibian skin infections were mainly focused on the presence of chytridiomycosis, neglecting other members of the frogs' skin communities. The diversity pattern of fungal dwellers on the skin of green frogs (Pelophylax esculentus complex) was investigated. A total of 100 adults were sampled from three localities in South Banat (northern Serbia) over three consecutive years and detected fungal dwellers were identified using light microscopy and ITS and BenA gene sequencing. Structures belonging to fungi and fungus-like organisms including a variety of spores and different mycelia types were documented in the biofilm formed on amphibian skin, and are classified into 10 groups. In total, 42 fungal isolates were identified to species, section, or genus level. The difference in mycobiota composition between sampling points (localities and green frog taxa) was documented. The highest number of fungal structures and isolates was recorded on the hybrid taxon P. esculentus and locality Stevanove ravnice. Parental species showed a markedly lower diversity than the hybrid taxon and were more similar in diversity patterns and were placed in the same homogenous group. The locality Stevanove ravnice exhibited more pronounced differences in diversity pattern than the other two localities and was placed in a distinct and separate homogenous group. Among the fungal isolates, the highest isolation frequency was documented for Alternaria alternata, Aspergillus sp. sect. Nigri, Epicoccum nigrum, Fusarium proliferatum, and Trichoderma atroviride. Among the documented species, dematiaceous fungi, causative agents of chromomycosis in amphibians, were also recorded in this research with high isolation frequency. Also, some rare fungal species such as Quambalaria cyanescens and Pseudoteniolina globosa are documented for the first time in this research as microbial inhabitants of amphibian skin.

Addressing conservation measures through fine-tuned species distribution models for an Italian endangered endemic anuran

Climate and land cover changes are the two most important stressors causing the decline of amphibians’ populations worldwide. Within the Mediterranean area, one of the global biodiversity hotspots, the endemic Italian yellow-bellied toad ( Bombina pachypus ) suffered the same fate, as the decreases and local extinctions proved over time. Since the need to preserve this Apennine endemic species is evident, we take advantage of a novel approach combining climate-based ecological niche models and post-modelling GIS techniques (i.e., the weighted overlay framework) to produce finer species distribution models for B. pachypus . In doing so, we coupled climate variables with topographic-, hydrologic-, and habitat-related predictors, sharpening the potential species’ distribution at its whole range scale. Our findings show a latitudinal subdivision in predicted suitability: Central Apennines populations are expected to suffer more than the Northern ones, with considerable potential future losses of genetic diversity. On the contrary, Southern Apennines’ suitability is predicted to remain stable over time, preserving the vast diversity. When assessing the coverage that protected areas offer to the locations of suitable habitats for B. pachypus , the protected sites of the Central Apennines result in slightly less suitable conservation areas than those in the Northern and Southern Apennines. The overall protected areas coverage is currently low (∼20%) and predicted in the future to narrow towards medium suitability values, except in Southern Apennines, where an increase is inferred. In light of our spatially-explicit results, we suggest that a national-scale conservation strategy should consider different management options according to the sub-territories that our analyses highlighted. Our coupled “weighted modelling – spatialised genetic inference” approach permits us to support different conservation policies at all spatial scales, capitalising on relatively few input data. Also, in-depth spatial analyses should be performed to support effective protection strategies and management for the conservation stakeholders. • Fine-tuned SDMs deepen knowledge and strongly uphold Bombina pachypus conservation. • Changes will differently affect biogeographic sectors’ suitability for B. pachypus. • Protected areas’ policy should base on predicted local responses to future changes.

Skeletal morphology and fluctuating asymmetry of the European green toad, Bufotes viridis, in contrasting habitats

Abstract Current environment changes and global amphibian decline suggest specific responses assuming urbanisation potential of the species. Amphibians are generally considered to be suitable bio-indicators of environmental health due to their ecological requirements. Therefore, fluctuating asymmetry (FA), a measure of small random deviations from bilateral symmetry is used for assessing morphological disruptions and parallelly the environment health. We measured the snout-vent length and lengths of five skeletal traits of limbs (humerus, radioulna, femur, tibiofibula, calcaneus) among the five European green toad populations from two contrasting habitats (urban and rural). We did not confirm our hypothesis that urban populations would exhibit higher level of FA as an indicator of higher environmental stress comparing to rural populations. However, asymmetry measured on forelimb bones was significantly larger than on hindlimbs. In addition, one urban population had significantly longer limbs comparing to the other sites.

Winterkill in Lotic Systems May Be an Important Driver of Amphibian Population Declines

Studies of frogs overwintering in ice-covered ponds and lakes have documented large winterkills, suggesting that winter can be a time of great stress and may be a serious threat to rare and endangered frog species that overwinter in these systems. Lotic systems are assumed to be better oxygenated and therefore less subject to overwinter mortality than lentic systems, but few studies of the winter ecology of ranids in stream ecosystems exist. We investigated the habitat use and survival of Columbia Spotted Frogs (Rana luteiventris) overwintering in a stream system in the Toiyabe Mountains of Nevada. We radio-tracked 13 Spotted Frogs from October 2000 to March 2001 to locate hibernacula and document winter habitat use. During the winter, frogs moved up to 191 m under the ice, often upstream against the current. We marked 1,763 frogs from 2000 to 2001 and found evidence of winterkill (population decreases of 66% to 86.5%) at four out of five sites while the fifth site showed no evidence of winterkill. This corresponded to an actual observation of winterkill of 88% of the frogs at one of the sites, making this one of a few studies directly tying observed wintertime mortality to mark–recapture estimates of decreases in ranid populations and the first to do so for amphibians overwintering in a lotic system. Amphibian winter ecology in lotic systems, the severity and frequency of winterkill events in these systems, and their effect on population size and structure is in need of further study over a wide range of species and should be considered in conservation plans for ranids in lotic systems.

National eDNA-based monitoring of Batrachochytrium dendrobatidis and amphibian species in Norway

Freshwaters represent the most threatened environments with regard to biodiversity loss and, therefore, there is a need for national monitoring programs to effectively document species distribution and evaluate potential risks for vulnerable species. The monitoring of species for effective management practices is, however, challenged by insufficient data acquisition when using traditional methods. Here we present the application of environmental DNA (eDNA) metabarcoding of amphibians in combination with quantitative PCR (qPCR) assays for an invasive pathogenic chytrid species (Batrachochytrium dendrobatidis -Bd), a potential threat to endemic and endangered amphibian species. Statistical comparison of amphibian species detection using either traditional or eDNA-based approaches showed weak correspondence. By tracking the distribution of Bd over three years, we concluded that the risk for amphibian extinction is low since Bd was only detected at five sites where multiple amphibians were present over the sampled years. Our results show that eDNA-based detection can be used for simultaneous monitoring of amphibian diversity and the presence of amphibian pathogens at the national level in order to assess potential species extinction risks and establish effective management practices. As such our study represents suggestions for a national monitoring program based on eDNA.

Amphibian collapses increased malaria incidence in Central America *

Biodiversity in ecosystems plays an important role in supporting human welfare, including regulating the transmission of infectious diseases. Many of these services are not fully-appreciated due to complex environmental dynamics and lack of baseline data. Multicontinental amphibian decline due to the fungal pathogen Batrachochytrium dendrobatidis (Bd) provides a stark example. Even though amphibians are known to affect natural food webs—including mosquitoes that transmit human diseases—the human health impacts connected to their massive decline have received little attention. Here we leverage a unique ensemble of ecological surveys, satellite data, and newly digitized public health records to show an empirical link between a wave of Bd-driven collapse of amphibians in Costa Rica and Panama and increased human malaria incidence. Subsequent to the estimated date of Bd-driven amphibian decline in each ‘county’ (canton or distrito), we find that malaria cases are significantly elevated for several years. For the six year peak of the estimated effect, the annual expected county-level increase in malaria ranges from 0.76 to 1.1 additional cases per 1000 population. This is a substantial increase given that cases country-wide per 1000 population peaked during the timeframe of our study at approximately 1.5 for Costa Rica and 1.1 for Panama. This previously unidentified impact of biodiversity loss illustrates the often hidden human welfare costs of conservation failures. These findings also show the importance of mitigating international trade-driven spread of similar emergent pathogens like Batrachochytrium salamandrivorans.

Cultivable microbiota of Proteus anguinus from underground habitats and animals accidently washed to the surface in Croatia

Proteus anguinus (olm) is an amphibian endemic to underground cave systems of the Dinaric karst of Central Europe, adapted to a life in complete darkness. Recent studies have demonstrated the global decline of amphibians due to poorly understood microbiological diseases, emphasizing just how little is known about the natural microflora of amphibians. Not much is known about the olm’s microbiota in their cave habitats, and nothing is known about the microbiology of animals washed to the surface. This observational study describes the microbiological analysis of the skin, cloaca and oral cavity of six olms collected from their cave habitats, and 16 collected after being washed out by flows from two springs, to learn more about the olm’s normal microbiota and possible changes after contact with the different environmental conditions on the surface. Standard microbiological procedures, MALDI-TOF and Real-Time PCR were used for microbiological species identification. All animals tested negative for Ranavirus, Batrachochytrium dendrobatidis, Batrachochytrium salamandrivorans and Chlamydia spp. The most abundant fungi isolated were Penicillium spp. and Cladosporium spp. The washed out animals showed a higher diversity of bacterial flora than those from cave habitats, with Acinetobacter johnsonii, Aeromonas hydrophila, Bacillus spp. and Janthinobacterium lividum as the most frequently identified isolates.

Effects of isolated and combined exposures of Boana curupi (Anura: Hylidae) tadpoles to environmental doses of trichlorfon and ultraviolet radiation

The biodiversity collapse strongly affects the amphibian group and many factors have been pointed out as catalytic agents. It is estimated that several events in the amphibian population decline worldwide may have been caused by the interaction of multiple drivers. Thus, this study aimed to evaluate the stressful effects of the exposure to environmental doses of trichlorfon (TCF) pesticide (0.5 μg/L; and an additional 100-fold concentration of 50 µg/L) and ultraviolet radiation (UV) (184.0 kJ/m² of UVA and 3.4 kJ/m² of UVB, which correspond to 5% of the daily dose) in tadpoles of the Boana curupi species (Anura: Hylidae). The isolated and combined exposures to TCF happened within 24 h of acute treatments under laboratory-controlled conditions. In the combined treatments, we adopted three different moments (M) of tadpole irradiation from the beginning of the exposures to TCF (0 h – M1; 12 h – M2; and 24 h – M3). Then, we evaluated tadpole survival, change in morphological characters, induction of apoptotic cells, lipid peroxidation (LPO), protein carbonyl content (PCC), glutathione S-transferase (GST), non-protein thiols (NPSH), and acetylcholinesterase (AChE), as well as the induction of genomic DNA (gDNA) damage. UVB treatment alone resulted in high mortality, along with a high level of apoptosis induction. Both UVA, UVB, and TCF increased LPO, PC, and AChE, while decreased GST activity. Regarding co-exposures, the most striking effect was observed in the interaction between UVB and TCF, which surprisingly decreased UVB-induced tadpole mortality, apoptosis, and gDNA damage. These results reinforce the B. curupi sensitivity to solar UVB radiation and indicate a complex response in face of UVB interaction with TCF, which may be related to activation of DNA repair pathways and/or inhibition of apoptosis, decreasing UVB-induced tadpole mortality.

Potential Distribution and Connectivity for Two Plethodontid Salamanders: Conservation Areas and Landscape Corridors for Two Endemic Species of México and Guatemala.

Habitat loss is one of the most important threats to biodiversity; it alters the habitat connectivity of species and is among the main causes of the global amphibian extinction crisis. Identifying the potential areas of distribution and connectivity of species is of the utmost importance so that informed decisions can be made for the conservation of vulnerable amphibian populations. In this study, we performed species distribution models and used circuit theory to model omnidirectional connectivity for two plethodontid salamanders of conservation concern distributed in the forests of Chiapas, Mexico, and Guatemala (Bolitoglossa franklini and Bolitoglossa lincolni). Potential distribution maps show an affinity for well-preserved montane forests for both species. Likewise, we found that the niches of the species are not similar. The connectivity models show that the main areas of connectivity are in the Meseta Central de Chiapas, Sierra Madre de Chiapas, and the Cordillera Volcánica Guatemalense, in this last range, important areas of connectivity were located, as well as least-cost paths and barriers to the movement of both species. We identified that important areas of climatic suitability and connectivity are not within the protected natural areas and may be threatened by the increasing influence of anthropogenic activities. The results of our study show the importance of preserving the regional forests to ensure the persistence of species with arboreal habits and high sensitivity to habitat transformation, as well as to recognize and prioritize potential areas for management and protection in both southern Mexico and Guatemala.

An amphibian high fat diet model confirms that endocrine disruptors can induce a metabolic syndrome in wild green frogs (Pelophylax spp. complex)

A pre-diabetes syndrome induced by endocrine disruptors (ED) was recently demonstrated in the model amphibian Silurana (Xenopus) tropicalis and was suggested to be a potential cause of amphibian population decline. However, such effects have not been found in wild type frogs exposed to ED and the capacity of amphibians to physiologically develop diabetes under natural conditions has not been confirmed. This study showed that a high fat diet (HFD) model displaying the important characteristics of mammal HFD models including glucose intolerance, insulin resistance and nonalcoholic fatty liver disease (NAFLD) can be developed with green frogs (Pelophylax spp.). Wild green frogs exposed to 10 μg L−1 benzo [a]pyrene (BaP) for 18 h also displayed several characteristics of the pre-diabetes phenotype previously observed in Xenopus including glucose intolerance, gluconeogenesis activation and insulin resistance. The study results confirmed that metabolic disorders induced by ED in wild green frogs are typical of the pre-diabetes phenotype and could serve as a starting point for field studies to determine the role of ED in the decline of amphibian populations. From an environmental perspective, the response of wild green frogs to different ED (10 μg L−1) suggests that a simple glucose-tolerance test could be used on wild anurans to identify bodies of water polluted with metabolic disruptors that could affect species fitness.

Low temperatures lead to higher toxicity of the fungicide folpet to larval stages of Rana temporaria and Bufotes viridis.

Pesticides are one of the main drivers of the worldwide amphibian decline. Their actual toxicity depends on a number of factors, like the species in focus or the developmental stage of exposed individuals. As ectothermic species, the metabolism of amphibians is influenced by ambient temperature. Therefore, temperature also affects metabolic rates and thus processes that might enhance or reduce toxic effects. Studies about the interactive effect of temperature and toxicity on amphibians are rare and deliver contrasting results. To investigate the temperature-dependent pesticide sensitivity of larvae of two European species we conducted acute toxicity tests for the viticultural fungicide Folpan® 500 SC with the active ingredient folpet at different temperatures (6°C, 11°C, 16°C, 21°C, 26°C). Sensitivity of Rana temporaria and Bufotes viridis was highly affected by temperature: early larvae (Gosner stage 20) were about twice more sensitive to Folpan® 500 SC at 6°C compared to 21°C. Next to temperature, species and developmental stage of larvae had an effect on sensitivity. The most sensitive individuals (early stages of R. temporaria at 6°C) were 14.5 times more sensitive than the least sensitive ones (early stages of B. viridis at 26°C). Our results raise concerns about typical ecotoxicological studies with amphibians that are often conducted at temperatures between 15°C and 20°C. We suggest that future test designs should be performed at temperatures that reflect the temperature range amphibians are exposed to in their natural habitats. Variations in the sensitivity due to temperature should also be considered as an uncertainty factor in upcoming environmental risk assessments for amphibians.

Blood Parasites of Toads (Amietophrynus regularis) in Al-Sorojia and Jebel Aulia, Khartoum State, Sudan

The present study was conducted to detect and identify blood parasites infecting toads Amietophrynus (Bufo) regulariss and find out the association between the infection of the parasites and host factors sex, length, body weight, and age. One hundred and twenty Amietophyrnus (Bufo) regularis (99 males and 21 females) were collected from May to August 2016 in two localities in Khartoum State (Al-Sorojia and Jebel Aulia). They were examined for blood parasites using blood films stained in Giemsa’s. A total of 77 (64.16%) of specimens were infected by 880 parasitic protozoa made-up of 879 (99.89%). Apicomplexa composed of Haemogregina spp. (89.66%), Hepatozoon spp. (10.22%), and 1 (0.11%) Kinteoplastides composed of Trypanosoma spp., while 43 (35.83%) were uninfected. No nematodes were recovered. The infection rate based on sex shows that females significantly (χ2 =12.520, p≤0.05) have a higher rate of infection than males. For the toad maturity, there was a significant difference in the infection rate between the mature group and the immature (χ2 =19.471, p=0.003). The infection rate increases with decreasing of weight and length with a negative correlation (rs = –0.022, p = 0.814 and rs = –0.004, p = 0.966, respectively). This study showed a high level of parasitic infection in African common toads in Khartoum State which contributed to the decline in amphibian populations. Further research on amphibian parasitism and its threats to human health is warranted.

Microflora Influence: The Aquatic Environment Changes Grouping Risk and Development Speed of Toad Tadpoles

In addition to habitat loss and fragmentation, behavioral traits and the deterioration of water environments also contribute to the local extinction of amphibians. Abundant microflora in urban ponds may cause fatal diseases, whereas symbiotic bacteria may protect the host from pathogens; these effects may vary with group size. In this study, I monitored the growth of Japanese common toad (Bufo japonicus) larvae in Tokyo using three different group sizes: 1 (solitary), 2 (pair), and 15. Although there was no genetic bias in the major histocompatibility complex (MHC) class II genes or microsatellite loci to the survival of the larvae, the mortality risk of the larvae reared in pond water was higher than that of those reared in tap water. According to the survival analysis, the risk was more significant when the group size was 15. This result would be unwelcomed for the B. japonicus tadpoles, which have habits of social aggregation. Furthermore, larval metamorphosis took longer to complete in pond than tap water without any difference in body length or mass. These findings provide fundamental insight into the impact of the aquatic environment and the effect of the group size on animal health and conservation.

Effect of captivity and water salinity on culture-dependent frog skin microbiota and Batrachochytrium dendrobatidis (Bd) infection

ABSTRACT The world is undergoing a sixth mass extinction, and the drastic decline of amphibians in the last several decades is a major contributing factor. The spread of the deadly Batrachochytrium dendrobatidis (Bd) fungus is a major causative agent, and captive breeding programs are under way to try and save endangered populations. However, how captivity affects Bd infection and the skin microbiota is not clear. We identified the skin bacteria of the South Australian frog Crinia signifera and showed that their culture-dependent skin microbiota is moderately stable in cohorts sampled from the same location in subsequent years. Their microbiota was also structurally different to that of a sympatric frog species, Limnodynastes tasmaniensis, indicating a specific microbial signature. Twenty-four C. signifera were placed into captivity for four weeks, exposed to a range of water salinity levels, during which time there was a significant reduction in identifiable skin bacterial species diversity, richness, and a change in microbial structure. The infection intensity of Bd was also significantly reduced in captivity, with some frogs becoming completely clear of infection, whilst water salinity level was not a significant determinant of Bd infection or skin microbiota.

Does a Moderately Warming Climate Compensate for the Negative Effects of UV-B Radiation on Amphibians at High Altitudes? A Test of Rana kukunoris Living on the Qinghai-Tibetan Plateau.

Simple SummaryBoth the warming climate and ultraviolet-B radiation are notable environmental factors affecting tadpole development. However, the phenotypes of tadpoles living at high altitudes may be improved by moderately warming temperatures, reducing or eliminating the negative effects of oxidative damage caused by cool temperatures or strong ultraviolet-B radiation. To verify this hypothesis, Rana kukunoris tadpoles, which live at high altitudes, were exposed to ultraviolet-B radiation and ultraviolet-B radiation-free environments at 14 (cool temperature) and 22 °C (warm temperature), respectively. Ultraviolet-B radiation and a warm temperature had opposite influences on several traits of the tadpoles, and the moderate temperature could compensate for or override the negative effects of ultraviolet-B radiation by increasing the tadpoles’ preferred body temperature and critical tolerance temperature, thus enhancing the locomotion ability and thermal sensitivity of their antioxidant systems. The dark skin coloration and aggregation behavior of R. kukunoris tadpoles may also be effective strategies for allowing them to resist ultraviolet-B radiation and helping them to better adapt to a warming environment with stronger ultraviolet-B radiation. Thus, a moderate degree of warming may increase the capacity of living organisms to adapt to environmental changes and thus have positive effects on the development of tadpoles living at high altitudes.Both the warming climate and ultraviolet-B radiation (UVBR) are considered to be notable environmental factors affecting amphibian population decline, with particular effects on tadpole development. However, the phenotypes of tadpoles living at high altitudes may be improved by moderately warming temperatures, reducing or eliminating the negative effects of oxidative damage caused by cool temperatures or strong UVBR at high altitudes. To verify this hypothesis, Rana kukunoris tadpoles, which live at high altitudes, were used to test the effect of the interaction of temperature and UVBR on their development and antioxidant systems in a fully factorial design. The tadpoles were exposed to UVBR and UVBR-free environments at 14 (cool temperature) and 22 °C (warm temperature), respectively. UVBR and a warm temperature had opposite influences on several traits of the tadpoles, including their survival, developmental rate, individual size, preferred body temperature, thermal tolerance temperature, oxidative damage, and enzymatic and nonenzymatic antioxidant systems. The moderate temperature could compensate for or override the negative effects of UVBR by increasing the tadpoles’ preferred body temperature and critical tolerance temperature, thus enhancing the locomotion ability and thermal sensitivity of their antioxidant systems. Furthermore, the dark skin coloration and aggregation behavior of R. kukunoris tadpoles may also be effective strategies for allowing them to resist UVBR and helping them to better adapt to a warming environment with stronger UVBR. Thus, it is possible that a moderate degree of warming may increase the capacity of living organisms to adapt to environmental changes and thus have positive effects on the development of tadpoles living at high altitudes.

Detecting and comparing extinction debts of amphibians in different habitats of southwestern China

As a global biodiversity hotspot, southwestern China has been increasingly disturbed by human activities and has been undergoing rapid urbanization in recent years. In order to provide recommendations for conservation strategies, this paper explores the disequilibrium between land use and amphibian diversity. Four types of suitable habitat that are suitable for amphibians to inhabit (including farmland, woodland, grassland, and water habitat) were assessed and compared. Through fitting 20 models for species–area relationships (SARs), we found that different habitat types had different best-fitted SAR models. However, the conventional power law model had the advantage of being estimated without extreme values, and the estimation usually did not involve numerical problems. As such, we compared the debt mapping patterns derived from the best-fit SAR models and the power models. Regardless of the SAR models used, current amphibian richness was more strongly correlated with the past habitat area, suggesting that amphibian extinction debt existed in the region. Distribution of debt magnitude in different habitats presented congruent results: 1) The debt magnitude predicted in different habitats varied in decreasing order with grassland, water habitats, woodland, and farmland. 2) Debt magnitude in the region near the Chengdu Plain was high, while the extinction debt magnitude in the western region near the Qinghai-Tibet Plateau was low. This followed expectations, as there is a profound impact of human activities in the Chengdu Plain that threatens the survival of amphibian species in that area. In summary, our results suggest that some specific habitats (grasslands and water) and areas (Chengdu Plain) need greater conservation effort to better protect the habitats of amphibians and reduce the extinction risks of species.