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
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.
