To seek or not to seek sunlight? That is the question.
Blaustein, Andrew 1, Kats, Lee2, 1 Oregon State University, Corvallis, Oregon, USA2 Pepperdine University, Malibu, California, USA
ABSTRACT- Numerous recent experimental studies have shown that many amphibian species are harmed by ultraviolet-B (UV-B; 280-315 nm) radiation. Exposure to UV-B can cause death and sublethal damage. Sublethal affects include physiological and anatomical malformations and behavioral changes. However, the effects of UV-B exposure vary among species, populations and life stages. Moreover, the effects of UV-B on amphibians are context and dose dependent and can vary spatially and temporally. UV-B may interact synergistically with numerous agents including contaminants and pathogens. The behavior of some amphibian species makes them less likely to be exposed to UV-B and other defense mechanisms limit the adverse effects of UV-B after exposure. For example, some species limit the exposure of their eggs to sunlight by laying them in deep or murky water. In some species, mobile larvae and adults avoid sunlight. Moreover, some species have molecular mechanisms that provide them with some protection after exposure to UV-B. Nevertheless, many species actively seek sunlight for thermoregulation. This is especially critical for species living in ephemeral ponds that must grow, develop and undergo metamorphosis before their pond dries or freezes. Therefore, amphibians are faced with conflicting selection pressures regarding sunlight. Should they seek it or avoid it? Some recent reports fail to recognize these conflicting selection pressures. Furthermore, some recent reports do not incorporate into their ecological scenarios, context dependent conditions, sublethal effects and life history stage, regarding UV-B radiation and amphibians. This has led to some inaccurate conclusions and false impressions concerning the overall effects of UV-B radiation on amphibians.
Key words: amphibians, ultraviolet radiation, sunlight
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