Evaluation of the Genotoxicity of Chlorpyrifos in Common Indus Valley Toad, Bufo stomaticus Using Alkaline Single-Cell Gel Electrophoresis (Comet) Assay

Abstract

Chlorpyrifos is a commonly used pesticide of organophosphate group, which causes toxicological effects in non-target organisms especially fish and frogs. In the present study, the genotoxicity of sublethal concentrations of chlorpyrifos was observed in the erythrocytes of common Indus valley toad, Bufo stomaticus, using the Alkaline Single-Cell Gel Electrophoresis (Comet) assay. In the first step, acute toxicity of chlorpyrifos was evaluated by exposing the tadpoles to high concentrations of the pesticide. The acute LC 50 value of chlorpyrifos, calculated by Trimmed Spearman-Karber (TSK) in static bioassay, was found to be 930.0 µg/L. On the basis of acute LC 50 value, the tadpoles were exposed to three sublethal concentrations (155, 233 and 465 µg/L) of chlorpyrifos for 96 h. Blood cells were collected at every 24 h interval and were subjected to the Alkaline Single-Cell Gel Electrophoresis assay. The observed DNA damage was concentration and time-dependent, and those levels of DNA damage in between the tested concentrations and times were significantly dif-ferent (p < 0.05). The tadpoles exposed to different concentrations of chlorpyrifos also showed different morphological abnormalities. It was concluded that chlorpyrifos is a genotoxic pesticide causing DNA damage in Bufo stomaticus.