Salinity(sodium chloride,NaCl)from anthropogenic sources is a persistent contaminant that negatively affects freshwater taxa.Amphibians can be susceptible to salinity,but some species are innately or adaptively tolera...Salinity(sodium chloride,NaCl)from anthropogenic sources is a persistent contaminant that negatively affects freshwater taxa.Amphibians can be susceptible to salinity,but some species are innately or adaptively tolerant.Physiological mechanisms mediating tolerance to salinity are still unclear,but changes in osmoregulatory hor-mones such as corticosterone(CORT)and aldosterone(ALDO)are prime candidates.We exposed larval barred tiger salamanders(Ambystoma mavortium)to environmentally relevant NaCl treatments(<32–4000 mg·L-1)for 24 days to test effects on growth,survival,and waterborne CORT responses.Of those sampled,we also quantified waterborne ALDO from a subset.Using a glucocorticoid antagonist(RU486),we also experimentally suppressed CORT signaling of some larvae to determine if CORT mediates effects of salinity.There were no strong differ-ences in survival among salinity treatments,but salinity reduced dry mass,snout–vent length,and body condition while increasing water content of larvae.High survival and sublethal effects demonstrated that salamanders were physiologically challenged but could tolerate the experimental concentrations.CORT signaling did not attenuate sublethal effects of salinity.Baseline and stress-induced(after an acute stressor,shaking)CORT were not influ-enced by salinity.ALDO was correlated with baseline CORT,suggesting it could be difficult to decouple the roles of CORT and ALDO.Future studies comparing ALDO and CORT responses of adaptively tolerant and previously unexposed populations could be beneficial to understand the roles of these hormones in tolerance to salinity.Nev-ertheless,our study enhances our understanding of the roles of corticosteroid hormones in mediating effects of a prominent anthropogenic stressor.展开更多
Species with especially close dependence on the environment to meet physiological requirements,such as ectotherms,are highly susceptible to the impacts of climate change.Climate change is occurring rapidly in the Suba...Species with especially close dependence on the environment to meet physiological requirements,such as ectotherms,are highly susceptible to the impacts of climate change.Climate change is occurring rapidly in the Subarctic and Arctic,but there is limited knowledge on ectotherm physiology in these landscapes.We investigated how environmental conditions and habitat characteristics influence the physiological conditions and habitat use of wood frogs(Rana sylvatica)in a Subarctic landscape near Churchill,Manitoba(Canada).We used plaster models to estimate water loss rates and surface body temperatures among different habitat types and at specific locations used by radio-tracked frogs.Water loss(R2=0.67)and surface temperature(R2=0.80)of plaster models was similar to that of live frogs.Model-based water loss rates were greater in tundra habitat than in boreal forest and ecotone habitat.Habitat use of wood frogs was strongly tied with available surface moisture and decreased water loss rates that were observed with plaster models.Environmental conditions,such as wind speed and ground tem-perature,explained 58%and 91%of the variation in water balance and temperature of plaster models.Maintaining physiological conditions may be challenging for semi-aquatic ectotherms in environments vulnerable to future cli-mate change.The ability to predict physiological conditions based on environmental conditions,as demonstrated in our study,can help understand how wildlife will respond to climatic changes.展开更多
基金funded by University of Montana,U.S.Geological Survey(USGS RWO#103 to CWB),National Science Foundation(NSF-DEB 1754474 to EJC)the Nelson Schwab Family Foundation。
文摘Salinity(sodium chloride,NaCl)from anthropogenic sources is a persistent contaminant that negatively affects freshwater taxa.Amphibians can be susceptible to salinity,but some species are innately or adaptively tolerant.Physiological mechanisms mediating tolerance to salinity are still unclear,but changes in osmoregulatory hor-mones such as corticosterone(CORT)and aldosterone(ALDO)are prime candidates.We exposed larval barred tiger salamanders(Ambystoma mavortium)to environmentally relevant NaCl treatments(<32–4000 mg·L-1)for 24 days to test effects on growth,survival,and waterborne CORT responses.Of those sampled,we also quantified waterborne ALDO from a subset.Using a glucocorticoid antagonist(RU486),we also experimentally suppressed CORT signaling of some larvae to determine if CORT mediates effects of salinity.There were no strong differ-ences in survival among salinity treatments,but salinity reduced dry mass,snout–vent length,and body condition while increasing water content of larvae.High survival and sublethal effects demonstrated that salamanders were physiologically challenged but could tolerate the experimental concentrations.CORT signaling did not attenuate sublethal effects of salinity.Baseline and stress-induced(after an acute stressor,shaking)CORT were not influ-enced by salinity.ALDO was correlated with baseline CORT,suggesting it could be difficult to decouple the roles of CORT and ALDO.Future studies comparing ALDO and CORT responses of adaptively tolerant and previously unexposed populations could be beneficial to understand the roles of these hormones in tolerance to salinity.Nev-ertheless,our study enhances our understanding of the roles of corticosteroid hormones in mediating effects of a prominent anthropogenic stressor.
基金approved by IACUC at Southeast Missouri State University and funded by Earthwatch Institute,the Northern Research Fund from the Churchill Northern Studies Centre,and the Office of Student Research at Appalachian State University。
文摘Species with especially close dependence on the environment to meet physiological requirements,such as ectotherms,are highly susceptible to the impacts of climate change.Climate change is occurring rapidly in the Subarctic and Arctic,but there is limited knowledge on ectotherm physiology in these landscapes.We investigated how environmental conditions and habitat characteristics influence the physiological conditions and habitat use of wood frogs(Rana sylvatica)in a Subarctic landscape near Churchill,Manitoba(Canada).We used plaster models to estimate water loss rates and surface body temperatures among different habitat types and at specific locations used by radio-tracked frogs.Water loss(R2=0.67)and surface temperature(R2=0.80)of plaster models was similar to that of live frogs.Model-based water loss rates were greater in tundra habitat than in boreal forest and ecotone habitat.Habitat use of wood frogs was strongly tied with available surface moisture and decreased water loss rates that were observed with plaster models.Environmental conditions,such as wind speed and ground tem-perature,explained 58%and 91%of the variation in water balance and temperature of plaster models.Maintaining physiological conditions may be challenging for semi-aquatic ectotherms in environments vulnerable to future cli-mate change.The ability to predict physiological conditions based on environmental conditions,as demonstrated in our study,can help understand how wildlife will respond to climatic changes.
