BLAUSTEIN, A.R.; BELDEN, L.K.: Amphibian Defenses Against Ultraviolet-B Radiation

Environmental changes, including those associated with the atmosphere, may significantly affect individual animals, populations and ultimately, communities. Ultraviolet-B (UV-B) radiation, increasing due to stratospheric ozone depletion, has been suggested as causing mortality and a variety of sublethal effects in a number of organisms, including amphibians. As part of the overall “Biodiversity Crisis”, populations of amphibians have been declining throughout the world. There appears to be no single cause for the declines. However, the diversity of locations where amphibian populations have declined has lead to studies examining the role of atmospheric factors such as increasing UV-B radiation in declines. Results from laboratory and field studies illustrate considerable interspecific differences in sensitivity of amphibian eggs and developing embryos to UV-B radiation. However, few studies have investigated the mechanisms regulating differential sensitivity to UV-B radiation. Amphibians can cope with potentially dangerous UV-B radiation by using behavioral, physiological, and molecular mechanisms, to prevent or limit damage. Thus, females may lay eggs in areas devoid of sunlight. The jelly matrix/coat surrounding eggs may prevent UV damage by absorbing damaging wavelengths before they reach the embryo. Egg pigments may also prevent penetrance of UV to the embryo. If damage does occur, several pathways may allow an amphibian to repair the damage at the molecular level. We will discuss the results of laboratory and field experiments that have examined the effects of UV-B radiation on amphibian eggs and embryos. We will also discuss various defenses used by amphibians in early life stages to cope with UV-B radiation.