DNA repair and resistance to UV-B radiation in western spotted frogs

We assessed DNA repair and resistance to solar radiation in eggs of members of the western spotted frog complex (Rana pretiosa and R. luteiventris), s pecies whose populations are suffering severe range reductions and declines . Specifically, we measured the activity of photoreactivating enzyme (photo lyase) in oocytes of spotted frogs. In some species, photoreactivation is t he most important mechanism for repair of UV-damaged DNA. Using field exper iments, we also compared the hatching success of spotted frog embryos at na tural oviposition sites at three elevations, where some embryos were subjec ted to ambient levels of UV-B radiation and others were shielded from UV-B radiation. Compared with other amphibians, photolyase activities in spotted frogs were relatively high. At all sites, hatching success was unaffected by UV-B. Our data support the interpretation that amphibian embryos with re latively high levels of photolyase are more resistant to UV-B radiation tha n those with lower levels of photolyase. At the embryonic stage, UV-B radia tion does not presently seem to be contributing to the population declines of spotted frogs.