PHOTOENHANCED TOXICITY OF A CARBAMATE INSECTICIDE TO EARLY-LIFE STAGEANURAN AMPHIBIANS

African clawed frog (Xenopus laevis) and gray tree frog (Hyla versicol or) embryos and tadpoles were exposed to sublethal levels of carbaryl, a broad-spectrum insecticide, and ultraviolet radiation to determine interactive and sublethal effects. Ultraviolet intensity (UV-B [285-32 0 nm] plus UV-A [321-400 nm]) was controlled with various types of pla stic filters and quantified with a scanning spectroradiometer. Signifi cant differences in swimming activity and mortality of both species we re evident during the 96-h experiments. UItraviolet-B radiation alone and carbaryl in the presence of UV-B significantly decreased swimming activity of both species. As little as 1.5% intensify of ambient solar UV-B radiation photoactivated carbaryl. Toxicity of 7.5 mg/L carbaryl increased by 10-fold in the presence of UV-B in all species and life stages tested. Our results indicate that photoenhancement by solar UV- B radiation should be considered when evaluating the toxicity of conta minants to amphibians and other organisms.