Ambient ultraviolet radiation induces DNA damage in amphibian larvae under semi-natural conditions.

Ambient sunlight contains ultraviolet radiation (UVR), a potent genotoxic stressor, yet whether natural UVR induces DNA damage in free-living amphibian larvae remains unclear. We reared striped marsh frogs (Limnodynastes peronii) in outdoor mesocosms under low versus high ambient UVR treatments for 5 days and quantified cyclobutane pyrimidine dimers (CPDs) by ELISA. Measurable CPD levels were detected under both UVR exposures, providing direct evidence that natural sunlight induces DNA damage in amphibian larvae. Although mean CPD levels did not differ between treatments, quantile regression revealed higher levels of CPDs in both the lower (τ=0.05) and upper (τ=0.95) quantiles under high UVR. This pattern suggests that while average DNA damage levels were similar, subsets of individuals experienced disproportionately high CPD burdens under increased UVR. These results highlight the value of mesocosms as a tool to bridge laboratory and field contexts to evaluate the effects of UVR on aquatic fauna, particularly as UV environments shift with climate change.