Date of Award

Spring 2000

Project Type

Dissertation

Program or Major

Zoology

Degree Name

Doctor of Philosophy

Abstract

In this study, I examined the effects of ultraviolet radiation, highway contamination and a synergism of both factors on the spotted salamander, Ambystoma maculatum embryos in field and laboratory experiments. There are numerous reports of amphibian population declines from around the world. There are several possible factors causing the decline, including, habitat loss, environmental pollution, disease, and ultraviolet B radiation (UVB, 290--320 nm). Results of studies conducted to date seem to indicate that the impacts of these factors vary greatly among species and across geography. Amphibians have unique characteristics and life histories that make them more vulnerable to changes in their environment then many other organisms. In particular, A. maculatum breeds in temporary wetlands in which embryos and larvae must metamorphose before the wetland dries. Factors that prolong development may reach increase mortality due to pool desiccation. Therefore, habitat degradation may be more harmful for amphibians that breed in this temporary environment.

I conducted field and laboratory experiments to test the effects of roadside runoff on A. maculatum embryos. Results indicate that embryo survival is very low roadside vernal pools contaminated with highway runoff. I also tested the effects of UVB on embryos using three radiation treatments. There was no statistically significant effect of UVB radiation on embryo size at hatching, melanin concentration, or DNA damage in field experiments. Vernal pool water was so darkly colored with dissolved organic material that UVB was quickly attenuated, therefore UVB exposure was very low for the embryos. I also tested the effects of UVB radiation, highway contamination, and the impact of a synergism between these factors in the laboratory. The impact of highway contamination was much clearer than that of UVB radiation. Highway contamination significantly affected membrane diameter, embryo length at hatching and DNA damage. UVB significantly affected embryo wet mass at hatching. Results suggested that the two factors may act synergistically to negatively affect embryos but the trends were not significant.

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