BELDEN, L.K.*; MOORE, I.T.; BLAUSTEIN, A.R.: Survival and the physiological stress response in Cascades frog tadpoles exposed to ambient UV-B radiation in the field

Global environmental changes, including increases in ultraviolet-B radiation (UV-B; 280-320 nm), are receiving attention from biologists interested in how these changes will alter community and ecosystem structure and function. However, we know little about how factors such as UV-B affect animals physiologically. Amphibians provide a good model system for examining the physiological effects of UV-B exposure because basic studies documenting both lethal and sublethal effects have been completed on a wide array of species at many life history stages. In this study, we examined the physiological stress response, as measured by glucocorticoid hormones, and survival of Cascades frog tadpoles, Rana cascadae, exposed to ambient UV-B in the field for 6 weeks. There were no differences in corticosterone levels between exposed and non-exposed tadpoles, although survival was significantly higher in the tadpoles shielded from UV-B. Even though UV-B exposure can be lethal for Rana cascadae tadpoles, in this study we did not observe a physiological stress response. However, the stress response in this species is poorly understood and there are several factors, including the length of the study, the ability of tadpoles to perceive UV-B, and the timing of development of the stress axis, that could explain the lack of a physiological stress response.