Graduate Thesis Or Dissertation
 

Sublethal effects of UV-B radiation on larval amphibians

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/th83m212d

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  • Ultraviolet-B radiation (UV-B) has been suggested as a factor contributing to global amphibian population declines. While ambient UV-B levels damage the eggs and embryos of some amphibian species, few studies have addressed how UV-B affects other life history stages or sublethal responses. My dissertation focuses on (1) investigations of sublethal effects of UV-B exposure on growth and development in larval amphibians, (2) a preliminary examination of the hormonal stress response in larval amphibians exposed to UV-B and (3) investigations of defenses that amphibians may use to prevent UV-B damage. Delayed sublethal responses to UV-B were documented for red legged frogs (Rana aurora). Larvae exposed to ambient UV-B during embryonic development were smaller and less developed one month after hatching than larvae not exposed as embryos. Exposure of larval long-toed salamanders (Ambystoma macrodactylum) to UV-B in the laboratory resulted in sublethal effects on growth for larvae from mountain sites and in decreased survival for larvae from lower elevation. Mountain populations appear to be more resistant to the detrimental effects of UV-B exposure. However, although UV-B can have various sublethal effects on growth and development, I did not observe a hormonal stress response in larvae of four species. One potential mechanism of UV-B protection is skin darkening. Larval long-toed salamanders, Northwestern salamanders (A. gracile) and roughskin newts (Taricha granulosa) implications for larval survival by manipulating skin color on black and white backgrounds during UV-B exposure. UV-B exposure resulted in reduced growth, regardless of background coloration, but there were no survivorship differences between the groups. In summary, my results suggest that even at current levels, UV-B may have impacts on amphibian life histories. While direct mortality in response to UV-B exposure may be observed for some species, there are many sublethal responses as well. These sublethal responses could be important for the long-term survival of amphibian populations.
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