%0 Journal Article %J Ecological Applications %D 1999 %T DNA repair and resistance to UV-B radiation in western spotted frogs %A Andrew R Blaustein %A John B Hays %A Peter D Hoffman %A Chivers, DP %A Kiesecker, J M %A Leonard WP %A Marco, A %A Reaser, JK %A Anthony, RG %B Ecological Applications %8 1999 %G eng %N 9:3:1100-1105 %0 Journal Article %J Environmental Toxicology %D 1997 %T The significance of Ultraviolet-B radiation to amphibian population declines. Reviews in Toxicology %A Andrew R Blaustein %A Kiesecker, J M %A Peter D Hoffman %A John B Hays %B Environmental Toxicology %V 147-165 %8 1997 %G eng %0 Journal Article %J Photochem Photobiol %D 1996 %T Developmental responses of amphibians to solar and artificial UVB sources: a comparative study. %A John B Hays %A Andrew R Blaustein %A Kiesecker, J M %A Peter D Hoffman %A Pandelova, I %A Coyle, D %A Richardson, T %K Amphibians %K Animals %K Deoxyribodipyrimidine Photo-Lyase %K DNA %K DNA Repair %K Female %K Ovum %K Radiation Tolerance %K Sunlight %K Ultraviolet Rays %X

Many amphibian species, in widely scattered locations, currently show population declines and/or reductions in range, but other amphibian species show no such declines. There is no known single cause for these declines. Differential sensitivity to UVB radiation among species might be one contributing factor. We have focused on amphibian eggs, potentially the most UVB-sensitive stage, and compared their resistance to UVB components of sunlight with their levels of photolyase, typically the most important enzyme for repair of the major UV photoproducts in DNA, cyclobutane pyrimidine dimers. Photolyase varied 100-fold among eggs/oocytes of 10 species. Among three species-Hyla regilla, Rana cascadae, and Bufo boreas-for which resistance of eggs to solar UVB irradiance in their natural locations was measured, hatching success correlated strongly with photolyase. Two additional species, Rana aurora and Ambystoma gracile, now show similar correlations. Among the low-egg-photolyase species, R. cascadae and B. boreas are showing declines, and the status of A. gracile is not known. Of the two high-photolyase species, populations of H. regilla remain robust, but populations of R. aurora are showing declines. To determine whether levels of photolyase or other repair activities are affected by solar exposures during amphibian development, we have initiated an extended study of H. regilla and R. cascadae, and of Xenopus laevis, laboratory-reared specimens of which previously showed very low photolyase levels. Hyla regilla and R. cascadae tadpoles are being reared to maturity in laboratories supplemented with modest levels of UV light or light filtered to remove UVB wavelengths. Young X. laevis females are being reared indoors and outdoors. Initial observations reveal severe effects of both UVA and UVB light on H. regilla and R. cascadae tadpoles and metamorphs, including developmental abnormalities and high mortalities. Assays of photolyase levels in the skins of young animals roughly parallel previous egg/oocyte photolyase measurements for all three species.

%B Photochem Photobiol %V 64 %P 449-56 %8 1996 Sep %G eng %N 3 %0 Conference Proceedings %B Proceedings International Congress of Photobiology, Vienna, Austria %D 1996 %T Responses of amphibians to solar and artificial UV light: photorepair, survival, and developmental effects %A John B Hays %A Andrew R Blaustein %A Kiesecker, J M %A Peter D Hoffman %A Pandelova, I %B Proceedings International Congress of Photobiology, Vienna, Austria %8 09/1996 %G eng %0 Journal Article %J Journal of Cellular Biochemistry %D 1995 %T Differences in DNA-repair activity and sensitivity to UV-B light among eggs and oocytes of declining and stable amphibian species %A John B Hays %A Peter D Hoffman %A Andrew R Blaustein %B Journal of Cellular Biochemistry %8 1995 %G eng %N 296 %0 Journal Article %J Proc Natl Acad Sci U S A %D 1994 %T UV repair and resistance to solar UV-B in amphibian eggs: a link to population declines? %A Andrew R Blaustein %A Peter D Hoffman %A Hokit, D G %A Kiesecker, J M %A Walls, S C %A John B Hays %K Animals %K Anura %K Bufonidae %K Deoxyribodipyrimidine Photo-Lyase %K DNA %K DNA Damage %K DNA Repair %K Female %K Models, Biological %K Ovum %K Population Dynamics %K Radiation Tolerance %K Ranidae %K Species Specificity %K Ultraviolet Rays %X

The populations of many amphibian species, in widely scattered habitats, appear to be in severe decline; other amphibians show no such declines. There is no known single cause for the declines, but their widespread distribution suggests involvement of global agents--increased UV-B radiation, for example. We addressed the hypothesis that differential sensitivity among species to UV radiation contributes to these population declines. We focused on species-specific differences in the abilities of eggs to repair UV radiation damage to DNA and differential hatching success of embryos exposed to solar radiation at natural oviposition sites. Quantitative comparisons of activities of a key UV-damage-specific repair enzyme, photolyase, among oocytes and eggs from 10 amphibian species were reproducibly characteristic for a given species but varied > 80-fold among the species. Levels of photolyase generally correlated with expected exposure of eggs to sunlight. Among the frog and toad species studied, the highest activity was shown by the Pacific treefrog (Hyla regilla), whose populations are not known to be in decline. The Western toad (Bufo boreas) and the Cascades frog (Rana cascadae), whose populations have declined markedly, showed significantly lower photolyase levels. In field experiments, the hatching success of embryos exposed to UV radiation was significantly greater in H. regilla than in R. cascadae and B. boreas. Moreover, in R. cascadae and B. boreas, hatching success was greater in regimes shielded from UV radiation compared with regimes that allowed UV radiation. These observations are thus consistent with the UV-sensitivity hypothesis.

%B Proc Natl Acad Sci U S A %V 91 %P 1791-5 %8 1994 Mar 01 %G eng %N 5