Toxicity of the organophosphorus insecticide, chlorpyrifos, to embryos of the frog, Xenopus laevis

Xenopus laevis gastrulae and post-neurula embryos were exposed to chlorpyrifos, an organophosphorus insecticide, for periods from 1 h to 96 h. Chlorpyrifos was extremely toxic to Xenopus embryos, causing significant increases in embryo mortality and malformed embryos at concentrations ranging from 0.025 to 1.0 $\mu$g/L chlorpyrifos. The current EPA freshwater acute and chronic water quality criteria of 0.08 and 0.04 $\mu$g/L chlorpyrifos may not be protective to Xenopus and other amphibian embryos. Results indicate that chlorpyrifos could pose a significant threat to the development and survival of amphibian embryos inhabiting watersheds which receive agricultural runoff containing chlorpyrifos.