Developmental toxic effects of monocrotophos, an organophosphorous pesticide, on zebrafish (Danio rerio) embryos

The present study examined the response of zebrafish embryos exposed to different concentrations (10, 20, 30, 40, 50, and 60 mg/L) of monocrotophos under static conditions for 96 h. We found that mortality had occurred within 48 h at all test concentrations, later insignificant mortality was observed. Monocrotophos (MCP) can be rated as moderately toxic to the Zebrafish embryos with a 96-h median lethal concentration (LC₅₀) of 37.44 ± 3.32 mg/L. In contrast, it greatly affected the development of zebrafish embryos by inducing several developmental abnormalities like pericardial edema, altered heart development, spinal and vertebral anomalies in a concentration-dependent manner. A significant percent reduction in length by 9–48 % and heart beats by 18–51 % was observed in hatchlings exposed to LC₁₀and LC₅₀concentrations at 96 h when compared to controls. The process of looping formation of heart at embryonic stage was greatly affected by the LC₅₀concentration of MCP. The neurotoxic potentiality of MCP was assessed by using a marker enzyme, acetylcholinesterase in both in vitro and in vivo experiments. MCP was found to be the most potent inhibitor of AChE in vitro with an IC₅₀value of 4.3 × 10⁻⁴ M. The whole-body AChE enzyme activity in vivo was significantly inhibited during the exposure tenure with the maximum inhibition of 62 % at 24 h.