Induction of photolyase activity in wood frog (Rana sylvatica) embryos

Rising ultraviolet-B (UVB, 280-320 nm) radiation has been proposed as a fac tor which may explain nonnormal amphibian population declines, Accordingly research has been directed toward estimating the photolyase activity of sev eral amphibian species in order to predict a species' resilience to UV dama ge. Unfortunately, in spite of published research which demonstrated that t he activity of one of the principal photorepair enzymes, photolyase, can be induced, these estimates did not address the potential for in vivo inducti on by environmental factors present in situ, We show here that wood frog (R ana sylvatica) embryos exposed to periods of ambient solar radiation (1) di splayed significantly different photolyase activities from embryos exposed to equivalent periods of dark; and (2) were positively correlated with the UVB fluence received in vivo. Such results suggest that previous conclusion s regarding the relationship between photorepair and population decline mus t be reevaluated. Estimating amphibian photorepair is a complicated process , and caution must be exercised when interpreting such data.