Acute Toxicity and Neurotoxicity of Chlorpyrifos in Black Tiger Shrimp, Penaeus monodon

Acute toxicity and neurotoxicity of chlorpyrifos were determined in black tiger shrimp, P. monodon. LC50 values after 24 to 96 h of exposure were between 149.55 and 59.16 nmol/L. To determine the neurotoxicity of chlorpyrifos, the inhibition of acetylcholinesterase was monitored in the gill of the shrimps exposed to lethal (0.019, 0.194, and 1.942 μmol/L) and sub-lethal (0.019, 0.194, and 1.942 nmol/L) concentrations of chlorpyrifos. In lethal dose exposure, the AChE activities observed in shrimp exposed to 0.194, and 1.942 μmol/L of chlorpyrifos were significantly lower (1.7 and 3.3 times) than that of control shrimp after 30 min of exposure (p<0.05). In sub-lethal exposure tests, the AChE activity of shrimp was significantly lower (1.9 times) than that of control shrimp after exposure to 1.942 nmol/L of chlorpyrifos for 72 h (p<0.05). The sensitive reduction of AChE activity at the sub-lethal concentration, which was 30 times lower than 96 h LC50 value found in this study, indicates the potential use as a biomarker of chlorpyrifos exposure.