Toxicity of the Insecticide Etofenprox to Three Life Stages of the Grass Shrimp, Palaemonetes pugio

Opportunities for environmental contamination by the insecticide etofenprox are increasing as its uses expand from primarily indoor residential to rice cultivation and mosquito control. To provide toxicity data for sensitive saltwater species, effects of etofenprox were assessed using three life stages of the estuarine grass shrimp, Palaemonetes pugio. Adults, larvae, and embryos were tested in aqueous exposures, while adults and larval shrimp were also tested in the presence of sediment. In addition, sublethal cellular stress biomarkers, glutathione and lipid peroxidation, were examined. Larval shrimp was the most sensitive life stage, with 96-h median lethal concentration (LC₅₀) of 0.89 μg/l, compared with 1.26 μg/l for adults and 100 μg/l for embryos. Presence of sediment significantly decreased toxicity of etofenprox to both adult and larval shrimp. Etofenprox exposure (100 μg/l) increased time to hatch in embryos. Lipid peroxidation levels were reduced in adult and larval shrimp after 96 h exposure to etofenprox, while no effect on glutathione was detected. The results of this study provide new information on the toxicity of etofenprox to estuarine invertebrates. These data may prove beneficial to the regulation of this pesticide and management of its uses in coastal areas.