Cooler temperatures slow the repair of DNA damage in tadpoles exposed to ultraviolet radiation: Implications for amphibian declines at high altitude

Effects of atrazine on movement, metabolism and gene expression in Pelophylax nigromaculatus larvae under global warming

Global warming and environmental pollutants both pose a threat to the behavior and physiology of animals, but research on the combined effects of the two is limited. Atrazine, a widely used herbicide, has toxic effects on organisms. In this study, the effects of environmental concentrations of atrazine exposure (100 μg/L) for seven days on the movement, metabolism and gene expression related to motility of Pelophylax nigromaculatus larvae (GS8) were investigated under global warming. The results showed that compared to the optimal growth temperature (18 °C), atrazine treatment under global warming (21 °C) significantly increased the average speed (about 11.2 times) and maximum acceleration (about 1.98 times) of P. nigromaculatus larvae, altered the relative abundance of 539 metabolites, including Formyl-5-hydroxykynurenamine, 2,4-Dihydroxybenzophenone, and FAPy-adenine, and changed the nucleotide metabolism, pyrimidine metabolism, glycerophospholipid metabolism, and purine metabolism, as well as increased the gene expression of SPLA2 (about 6.46 times) and CHK (about 3.25 times). In summary, atrazine treatment under global warming caused metabolic disorders in amphibian larvae and increased the expression of some movement-related genes in the brain, resulting in abnormally active.

Limited contribution of photoenzymatic DNA repair in mitigating carry-over effects from larval UVB exposure: Implications for frog recruitment

Solar ultraviolet-B (UVB) radiation has increased due to stratospheric ozone depletion, climate and ecosystem changes and is a driver of amphibian population declines. Photoenzymatic repair (PER) is a critical mechanism for limiting UVB lethality in amphibian larvae. However, the link between PER and the UVB-induced effects remains understudied through long-term investigations in vivo. Here, we assessed how larval PER determines the lethal and sublethal effects induced by environmentally relevant acute UVB exposure until the juvenile phase in the Neotropical frog Odontophrynus americanus. We conducted laboratory-based controlled experiments in which tadpoles were or were not exposed to UVB and subsequently were exposed to light (for PER activation) or dark treatments. Results showed that the rates of mortality and apoptosis observed in post-UVB dark treatment are effectively limited in post-UVB light treatment, indicating PER (and not dark repair, i.e. nucleotide excision repair) is critical to limit the immediate genotoxic impact of UVB-induced pyrimidine dimers. Nonetheless, even tadpoles that survived UVB exposure using PER showed sublethal complications that extended to the juvenile phase. Tadpole responses included alterations in morphology, chromosomal instability, increased skin susceptibility to fungal proliferation, as well as increased generation of reactive oxygen species. The short-term effects were carried over to later stages of life because metamorphosis time increased and juveniles were smaller. No body abnormalities were visualized in tadpoles, metamorphs, and juveniles, suggesting that O. americanus is UVB-resistant concerning these responses. This study reveals that even frog species equipped with an effective PER are not immune to carry-over effects from early UVB exposure, which are of great ecological relevance as late metamorphosis and smaller juveniles may impact individual performance and adult recruitment to breeding. Future ecological risk assessments and conservation and management efforts for amphibian species should exercise caution when linking PER effectiveness to UVB resistance.

Effects of climate change and mixtures of pesticides on the Amazonian fish Colossoma macropomum

Several studies highlighted the complexity of mixing pesticides present in Amazonian aquatic environments today. There is evidence that indicates that ongoing climate change can alter the pattern of pesticide use, increasing the concentration and frequency of pesticide applications. It is known that the combination of thermal and chemical stress can induce interactive effects in aquatic biota, which accentuates cell and molecular damage. However, considering that the effects of climate change go beyond the increase in temperature the objective of this study was to evaluate the effect of climate change scenarios proposed by 6 th IPCC report and a mixture of pesticides on the tambaqui (Colossoma macropomum). The hypothesis of this study is that the negative effects will be accentuated by the combination of an extreme climate changes scenario and a mixture of pesticides. To test the hypothesis, juvenile tambaqui were exposed to a combination of four pesticides (chlorpyrifos, malathion, carbendazim and atrazine) in two scenarios, one that simulates current environmental conditions and another that predicted the environmental scenario for the year 2100. Fish were subjected to the experimental conditions for 96 h. At the end of the experiment, samples of blood, gills, liver, brain, and muscle were obtained for hematological, genotoxic, biochemical, and histopathological analyses. The results demonstrate that environmentally realistic concentrations of pesticides, when mixed, can alter the biochemical responses of tambaqui. The extreme scenario promotes hematological adjustments, but impairs branchial antioxidant enzymes. There is an interaction between the mixture of pesticides and the extreme scenario, accentuating liver tissue damage, which demonstrates that even increased activity of antioxidant and biotransformation enzymes were not sufficient to prevent liver damage.

Population structure and adaptability analysis of Schizothorax o'connori based on whole-genome resequencing

BACKGROUND

Schizothorax o'connori is an endemic fish distributed in the upper and lower reaches of the Yarlung Zangbo River in China. It has experienced a fourth round of whole gene replication events and is a good model for exploring the genetic differentiation and environmental adaptability of fish in the Qinghai-Tibet Plateau. The uplift of the Qinghai-Tibet Plateau has led to changes in the river system, thereby affecting gene exchange and population differentiation between fish populations. With the release of fish whole genome data, whole genome resequencing has been widely used in genetic evolutionary analysis and screening of selected genes in fish, which can better elucidate the genetic basis and molecular environmental adaptation mechanisms of fish. Therefore, our purpose of this study was to understand the population structure and adaptive characteristics of S. o'connori using the whole-genome resequencing method.

RESULTS

The results showed that 23,602,746 SNPs were identified from seven populations, mostly distributed on chromosomes 2 and 23. There was no significant genetic differentiation between the populations, and the genetic diversity was relatively low. However, the Zangga population could be separated from the Bomi, Linzhi, and Milin populations in the cluster analysis. Based on historical dynamics analysis of the population, the size of the ancestral population of S. o'connori was affected by the late accelerated uplift of the Qinghai Tibet Plateau and the Fourth Glacial Age. The selected sites were mostly enriched in pathways related to DNA repair and energy metabolism.

CONCLUSION

Overall, the whole-genome resequencing analysis provides valuable insights into the population structure and adaptive characteristics of S. o'connori. There was no obvious genetic differentiation at the genome level between the S. o'connori populations upstream and downstream of the Yarlung Zangbo River. The current distribution pattern and genetic diversity are influenced by the late accelerated uplift of the Qinghai Tibet Plateau and the Fourth Ice Age. The selected sites of S. o'connori are enriched in the energy metabolism and DNA repair pathways to adapt to the low temperature and strong ultraviolet radiation environment at high altitude.

Sublethal consequences of ultraviolet radiation exposure on vertebrates: Synthesis through meta-analysis

Ultraviolet radiation (UVR) from the sun is a natural daytime stressor for vertebrates in both terrestrial and aquatic ecosystems. UVR effects on the physiology of vertebrates manifest at the cellular level, but have bottom-up effects at the tissue level and on whole-animal performance and behaviours. Climate change and habitat loss (i.e. loss of shelter from UVR) could interact with and exacerbate the genotoxic and cytotoxic impacts of UVR on vertebrates. Therefore, it is important to understand the range and magnitude of effects that UVR can have on a diversity of physiological metrics, and how these may be shaped by taxa, life stage or geographical range in the major vertebrate groups. Using a meta-analytical approach, we used 895 observations from 47 different vertebrate species (fish, amphibian, reptile and bird), and 51 physiological metrics (i.e. cellular, tissue and whole-animal metrics), across 73 independent studies, to elucidate the general patterns of UVR effects on vertebrate physiology. We found that while UVR's impacts on vertebrates are generally negative, fish and amphibians were the most susceptible taxa, adult and larvae were the most susceptible life stages, and animals inhabiting temperate and tropical latitudes were the most susceptible to UVR stress. This information is critical to further our understanding of the adaptive capacity of vulnerable taxon to UVR stress, and the wide-spread sublethal physiological effects of UVR on vertebrates, such as DNA damage and cellular stress, which may translate up to impaired growth and locomotor performance. These impairments to individual fitness highlighted by our study may potentially cause disruptions at the ecosystem scale, especially if the effects of this pervasive diurnal stressor are exacerbated by climate change and reduced refuge due to habitat loss and degradation. Therefore, conservation of habitats that provide refuge to UVR stress will be critical to mitigate stress from this pervasive daytime stressor.

Carryover effects from environmental change in early life: An overlooked driver of the amphibian extinction crisis?

Ecological carryover effects, or delayed effects of the environment on an organism's phenotype, are central predictors of individual fitness and a key issue in conservation biology. Climate change imposes increasingly variable environmental conditions that may be challenging to early life-history stages in animals with complex life histories, leading to detrimental physiological and fitness effects in later life. Yet, the latent nature of carryover effects, combined with the long temporal scales over which they can manifest, means that this phenomenon remains understudied and is often overlooked in short-term studies limited to single life-history stages. Herein, we review evidence for the physiological carryover effects induced by elevated ultraviolet radiation (UVR; 280-400 nm) as a potential contributor to recent amphibian population declines. UVR exposure causes a suite of molecular, cellular and physiological consequences known to underpin carryover effects in other taxa, but there is a lack of research linking embryonic and larval UVR exposures to fitness consequences post-metamorphosis in amphibians. We propose that the key impacts of UVR on disease-related amphibian declines are facilitated through carryover effects that bridge embryonic and larval UVR exposure with potential increased disease susceptibility post-metamorphosis. We conclude by identifying a practical direction for the study of ecological carryover effects in amphibians that could guide future ecological research in the broader field of conservation physiology. Only by addressing carryover effects can many of the mechanistic links between environmental change and population declines be elucidated.

Temperature causes species-specific responses to UV-induced DNA damage in amphibian larvae

Anthropogenic ozone depletion has led to a 2-5% increase in ultraviolet B radiation (UVBR) levels reaching the earth's surface. Exposure to UVBR causes harmful DNA damage in amphibians, but this is minimized by DNA repair enzymes such as thermally sensitive cyclobutane pyrimidine dimer (CPD)-photolyase, with cool temperatures slowing repair rates. It is unknown whether amphibian species differ in the repair response to a given dose of UVBR across temperatures. We reared larvae of three species (Limnodynastes peronii, Limnodynastes tasmaniensis and Platyplectrum ornatum) at 25°C and acutely exposed them to 80 µW cm^-2 UVBR for 2 h at either 20°C or 30°C. UVBR-mediated DNA damage was measured as larvae repaired damage in photoreactive light at their exposure temperatures. Cool temperatures increased DNA damage in two species and slowed DNA repair rate in P. ornatum. The magnitude of DNA damage incurred from UVBR was species-specific. Platyplectrum ornatum had the lowest CPDs and DNA repair rates, and the depressive effects of low temperature on photorepair were greater in L. tasmaniensis. Considering the susceptibility of most aquatic organisms to UVBR, this research highlighted a need to consider the complexity of species-specific physiology when forecasting the influence of changing UVBR and temperature in aquatic ecosystems.

UV exposure causes energy trade-offs leading to increased chytrid fungus susceptibility in green tree frog larvae

Levels of ultraviolet (UV) radiation have increased in many parts of the world due to the anthropogenic destruction of the ozone layer. UV radiation is a potent immunosuppressant and can increase the susceptibility of animal hosts to pathogens. UV radiation can directly alter immune function via immunosuppression and photoimmunotolerance; however, UV may also influence pathogen defences by affecting the distribution of energy resources among competing physiological processes. Both defence against UV damage and repair of incurred damage, as well as the maintenance of immune defences and responding to an immune challenge, are energetically expensive. These competing demands for finite energy resources could trade off against one another, resulting in sub-optimal performance in one or both processes. We examined the potential for a disease-related energy trade-off in green tree frog (Litoria caerulea) larvae. Larvae were reared under high- or low-UV conditions for 12 weeks during which time we measured growth rates, metabolic rate and susceptibility to the amphibian fungal pathogen, Batrachochytrium dendrobatidis (Bd). We found that larvae exposed to high levels of UV radiation had higher rates of energy expenditure than those exposed to low UV levels; however, UV exposure did not affect growth rates or developmental timings. Larvae exposed to high UV radiation also experienced greater Bd infection rates and carried a higher infection burden than those not exposed to elevated UV radiation. We propose that the increased energetic costs of responding to UV radiation were traded off against immune defences to protect larval growth rates. These findings have important implications for the aetiology of some Bd-associated amphibian declines, particularly in montane environments where Bd infections are most severe and where UV levels are highest.

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 Summary

Both 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.

Abstract

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.

The role of abiotic variables in an emerging global amphibian fungal disease in mountains

The emergence of the chytridiomycete fungal pathogen Batrachochytrium dendrobatidis (Bd), causing the disease chytridiomycosis, has caused collapse of amphibian communities in numerous mountain systems. The health of amphibians and of mountain freshwater habitats they inhabit is also threatened by ongoing changes in environmental and anthropogenic factors such as climate, hydrology, and pollution. Climate change is causing more extreme climatic events, shifts in ice occurrence, and changes in the timing of snowmelt and pollutant deposition cycles. All of these factors impact both pathogen and host, and disease dynamics. Here we review abiotic variables, known to control Bd occurrence and chytridiomycosis severity, and discuss how climate change may modify them. We propose two main categories of abiotic variables that may alter Bd distribution, persistence, and physiology: 1) climate and hydrology (temperature, precipitation, hydrology, ultraviolet radiation (UVR); and, 2) water chemistry (pH, salinity, pollution). For both categories, we identify topics for further research. More studies on the relationship between global change, pollution and pathogens in complex landscapes, such as mountains, are needed to allow for accurate risk assessments for freshwater ecosystems and resulting impacts on wildlife and human health. Our review emphasizes the importance of using data of higher spatiotemporal resolution and uniform abiotic metrics in order to better compare study outcomes. Fine-scale temperature variability, especially of water temperature, variability of moisture conditions and water levels, snow, ice and runoff dynamics should be assessed as abiotic variables shaping the mountain habitat of pathogen and host. A better understanding of hydroclimate and water chemistry variables, as co-factors in disease, will increase our understanding of chytridiomycosis dynamics.

HREM, RNAseq and Cell Cycle Analyses Reveal the Role of the G2/M-Regulatory Protein, WEE1, on the Survivability of Chicken Embryos during Diapause

Avian blastoderm can enter into diapause when kept at low temperatures and successfully resume development (SRD) when re-incubated in body temperature. These abilities, which are largely affected by the temperature and duration of the diapause, are poorly understood at the cellular and molecular level. To determine how temperature affects embryonic morphology during diapause, high-resolution episcopic microscopy (HREM) analysis was utilized. While blastoderms diapausing at 12 °C for 28 days presented typical cytoarchitecture, similar to non-diapaused embryos, at 18 °C, much thicker blastoderms with higher cell number were observed. RNAseq was conducted to discover the genes underlying these phenotypes, revealing differentially expressed cell cycle regulatory genes. Among them, WEE1, a negative regulator of G2/M transition, was highly expressed at 12 °C compared to 18 °C. This finding suggested that cells at 12 °C are arrested at the G2/M phase, as supported by bromodeoxyuridine incorporation (BrdU) assay and phospho-histone H3 (pH 3) immunostaining. Inhibition of WEE1 during diapause at 12 °C resulted in cell cycle progression beyond the G2/M and augmented tissue volume, resembling the morphology of 18 °C-diapaused embryos. These findings suggest that diapause at low temperatures leads to WEE1 upregulation, which arrests the cell cycle at the G2/M phase, promoting the perseverance of embryonic cytoarchitecture and future SRD. In contrast, WEE1 is not upregulated during diapause at higher temperature, leading to continuous proliferation and maladaptive morphology associated with poor survivability. Combining HREM-based analysis with RNAseq and molecular manipulations, we present a novel mechanism that regulates the ability of diapaused avian embryos to maintain their cytoarchitecture via cell cycle arrest, which enables their SRD.

Micro(nano)plastics as an emerging risk factor to the health of amphibian: A scientometric and systematic review

Although the toxicity of microplastics (MPs) and nanoplastics (NPs) is recognized at different trophic levels, our know-how about their effects on amphibians is limited. Thus, we present and discuss the current state on studies involving amphibians and plastic particles, based on a broad approach to studies published in the last 5 years. To search for the articles, the ISI Web of Science, ScienceDirect, and Scopus databases were consulted, using different descriptors related to the topic of study. After the systematic search, we identified 848 publications. Of these, 12 studies addressed the relationship "plastic particles and amphibians" (7 studies developed in the laboratory and 5 field studies). The scientometric analysis points to geographic concentration of studies in Brazil and China; low investment in research in the area, and limited participation of international authors in the studies carried out. In the systematic approach, we confirm the scarcity of available data on the toxicity of plastic particles in amphibians; we observed a concentration of studies in the Anura order, only one study explored the toxicological effects of NPs and polystyrene and polyethylene are the most studied plastic types. Moreover, the laboratory tested concentrations are distant from those of the environmentally relevant; and little is known about the mechanisms of action of NPs/MPs involved in the identified (eco)toxicological effects. Thus, we strongly recommend more investments in this area, given the ubiquitous nature of NPs/MPs in aquatic environments and their possible consequences on the dynamics, reproduction, and survival of species in the natural environment.

Polyethylene glycol acute and sub-lethal toxicity in neotropical Physalaemus cuvieri tadpoles (Anura, Leptodactylidae)

Although many polymers are known by their toxicity, we know nothing about the impact of polyethylene glycol (PEG) on anurofauna. Its presence in different products and disposal in aquatic environments turn assessments about its impact on amphibians an urgent matter. Accordingly, we tested the hypothesis that short-time exposure (72 h) of tadpoles belonging to the species Physalaemus cuvieri (Anura, Leptodactylidae) to PEG induces oxidative stress and neurotoxicity on them. We observed that polymer uptake in P. cuvieri occurred after exposure to 5 and 10 mg/L of PEG without inducing changes in their nitrite levels neither at the levels of substances reactive to thiobarbituric acid. However, hydrogen peroxide and reactive oxygen species production was higher in animals exposed to PEG, whose catalase and superoxide dismutase levels were not enough to counterbalance the production of these reactive species. Therefore, this finding suggests physiological changes altering REDOX homeostasis into oxidative stress. In addition, the increased activity of acetylcholinesterase and butyrylcholinesterase, and reduction in superficial neuromasts, confirmed PEG's neurotoxic potential. To the best of our knowledge, this is the first report on PEG's biological impact on a particular amphibian species. The study has broadened the understanding about ecotoxicological risks associated with water pollution by these polymers, as well as motivated further investigations on its impacts on amphibians' health and on the dynamics of their natural populations.

Can use of hydroxychloroquine and azithromycin as a treatment of COVID-19 affect aquatic wildlife? A study conducted with neotropical tadpole

The impacts on human health and the economic and social disruption caused by the pandemic COVID-19 have been devastating. However, its environmental consequences are poorly understood. Thus, to assess whether COVID-19 therapy based on the use of azithromycin (AZT) and hydroxychloroquine (HCQ) during the pandemic affects wild aquatic life, we exposed (for 72 h) neotropical tadpoles of the species Physalaemus cuvieri to the water containing these drugs to 12.5 μg/L. We observed that the increase in superoxide dismutase and catalase in tadpoles exposed to AZT (alone or in combination with HCQ) was predominant to keep the production of NO, ROS, TBARS and H₂O₂ equitable between the experimental groups. In addition, the uptake of AZT and the strong interaction of AZT with acetylcholinesterase (AChE), predicted by the molecular docking analysis, were associated with the anticholinesterase effect observed in the groups exposed to the antibiotic. However, the unexpected increase in butyrylcholinesterase (BChE) in these same groups suggests its constitutive role in maintaining cholinergic homeostasis. Therefore, taken together, our data provide a pioneering evidence that the exposure of P. cuvieri tadpoles to AZT (alone or in combination with HCQ) in a predictably increased environmental concentration (12.5 μg/L) elicits a compensatory adaptive response that can have, in the short period of exposure, guaranteed the survival of the animals. However, the high energy cost for maintaining physiological homeostasis, can compromise the growth and development of animals and, therefore, in the medium-long term, have a general negative effect on the health of animals. Thus, it is possible that COVID-19 therapy, based on the use of AZT, affects wild aquatic life, which requires greater attention to the impacts that this drug may represent.

Ultraviolet-B irradiance and cumulative dose combine to determine performance and survival

Despite decades of research, the role of elevated solar ultraviolet-B radiation (UVBR; 280-315 nm) in shaping amphibian populations remains ambiguous. These difficulties stem partly from a poor understanding of which parameters of UVBR exposure - dose, irradiance, and time interval - determine UVBR exposure health risk, and the potentially erroneous assumption that effects are proportional to the dose of exposure, irrespective of the administered regime (Bunsen-Roscoe Law of Reciprocity; BRL). We tested if the BRL holds with respect to UVBR-induced physiological effects in amphibians by acutely exposing tadpoles of the Australian green tree frog (Litoria caerulea) to a combination of different UVBR irradiances and doses in a fully factorial experiment. The BRL was invalid across all metrics assessed, with UVBR irradiance influencing the effects of a given dose on growth, coloration and burst swimming performance of larvae. We demonstrated some of the first empirical evidence for beneficial physiological effects of UVBR exposure in a larval amphibian, with improvements in growth, burst swimming performance and survival at the highest UVBR doses, contrary to hypotheses. Our findings demonstrate the species-specific nature of amphibian responses to UVBR, and the importance of UVBR irradiance in influencing the long-term physiological effects of a given dose of radiation. This work enhances our understanding of which parameters of complex UVBR exposures determine amphibian health risk.

Spatial distribution and risk areas of foot and mouth disease in mainland China

Foot-and-mouth disease (FMD) is a severe infectious disease in animal, which affects regional economies and food security of many countries. A total of 109 FMD outbreaks in China (from 2010 to 2019) were assessed. To investigate whether the FMD outbreaks were significantly aggregated in China, spatio-temporal cluster analysis was performed. A MaxEnt model was established to identify high risk areas for FMD in China and to identify relevant risk factors. As a result, both the FMD serotype A and O had one cluster each. Roads density, isothermality, UV-B seasonality and railways density were identified as important factors that affect the occurrence of FMD serotype A. The minimum temperature of the coldest month contributed most to FMD serotype O outbreak, followed by railways density and markets distribution. This study may provide useful information for decision makers for the tailoring of a risk-based surveillance of FMD in China.

Effects of ultraviolet-B radiation on physiology, immune function and survival is dependent on temperature: implications for amphibian declines

Multiple environmental changes are thought to be contributing to the widespread decline of amphibians in montane regions, but interactions between drivers of decline are not well understood. It has been proposed previously that elevated ultraviolet-B radiation (UBVR) and low temperatures may interact in their negative effects on health, immune function and disease susceptibility in exposed amphibians. In the present study, we chronically exposed larvae of the striped-marsh frog (Limnodynastes peronii) to a factorial combination of high and low UVBR and high and low temperature to assess interactive effects on growth, survival and indices of immune function. The high UVBR treatment reduced growth and survival of larvae compared to the low UVBR treatment at both temperatures, but the effects were significantly enhanced at low temperature. High UVBR exposure also induced a chronic inflammatory response as evidenced by an increase in the leucocyte proportion of total cells and altered the ratio of neutrophils to lymphocytes in the blood, highlighting a potential mechanistic basis for increased disease susceptibility in amphibians living at high altitudes. Our findings stress the importance of investigating environmental factors in combination when assessing their effects and highlight the mechanistic basis for how key environmental drivers in montane regions affect amphibian health. Continuation of this work is necessary for the development of targeted conservation strategies that tackle the root causes of montane amphibian declines.