Effects of chlorothalonil on development and growth of amphibian embryos and larvae.

Chlorothalonil is a broad spectrum fungicide widely used in agricultural and urban environments, yet little is known regarding its effects on amphibians. We examined effects of chlorothalonil on growth, malformations, and mortality in embryos and larvae of Xenopus laevis and Spea multiplicata, and assessed variation in sensitivity among aquatic organisms using a species sensitivity distribution (SSD). Chlorothalonil induced gut malformations in X. laevis embryos and inhibited growth. Tail degeneration was observed in larvae of both species and reduced tail length to total length ratios occurred at environmentally relevant concentrations (5.9 and 11.0 μg/L). The mechanism of tail degeneration is unclear, but alteration in the expression of genes involved in tail resorption is a hypothesized mechanism. Larval amphibians were more sensitive than invertebrates and fish. Based on our results and the range of reported environmental concentrations, chlorothalonil may pose a risk to larval amphibians in certain habitats and scenarios.