Toxicity of endosulfan to aquatic stages of anuran amphibians

Abstract

AbstractThe toxicity of endosulfan insecticide to wood frog (Rana sylvatica) embryos and tadpoles of wood frogs, American toads (Bufo americanus), and green frogs (R. clamitans) was examined in the laboratory. Following exposures to 0.03 to 0.4 mg/L endosulfan for 96 h, sublethal effects and postexposure mortality were assessed. In another experiment, premetamorphic American toad tadpoles (with developing hindlimbs but unerupted front legs) were exposed to 0.3 mg/L endosulfan for 96 h. The exposed wood frog embryos hatched successfully and were morphologically indistinguishable from the unexposed animals at the end of the 10‐d postexposure period. However, extensive paralysis of exposed tadpoles of all three species occurred; all but one of the exposures resulted in 100% of the tadpoles experiencing paralysis at some point during the exposure or recovery period. Postexposure mortality of tadpoles was high and occurred at the lowest exposure concentrations (0.041–0.053 mg/L) for each species exposed as 2‐week‐old tadpoles. Newly hatched American toad tadpoles were more tolerant than tadpoles of the other two species, but no clear species differences in sensitivity of 2‐week‐old tadpoles was apparent. American toad premetamorphs exposed to endosulfan did not recover from the effects of the exposure. Our results indicate that the aquatic stages of anuran amphibians may be sensitive to levels of the pesticide endosulfan that could reach their habitat by means of direct applications or drift from aerial spraying.