Toxic Effects Of Monocrotophos On Monopterus Albus

The aims of the present study were to assess the toxic effects of the sublethal concentrations of monocrotophos (an organophosphorus pesticide) on freshwater fish, Monopterus albus. The results showed that at 20±2℃, the LC50 of MCP for 96 h were 3.27 mg·L-1 to Monopterus albus.Effects of monocrotophos on activities of brain AChE , liver and kidney CaE,ALP,ACP of Monopterus albus were studied via a static toxicity experiment. The results show that after being exposed to the monocrotophos at the concentration of 0.25 mg·L-1, 0.50 mg·L-1, 1.00 mg·L-1 and 2.00 mg·L-1 for 96 hours at the temperature (20±2)℃, the activities of liver and kidney CaE and brain AChE would be remarkably impeded and even inhibited in different inhibition patterns. Particularly significant was the effect with the activity of CaE in the liver and kidney tissues, which were inhibited (P<0.01) in all the treatment concentrations. But the inhibition of the activity of brain AChE remained just at 0.25 mg·L-1of monocrotophos (P<0.05), though it was extremely significant at the other different concentrations (P<0.01). The activities of liver and kidney CaE actually exhibited a pattern that the inhibition extent would be smaller with the increase of the exposure content while the activities of brain AChE showed an opposite tendency. Moreover, the activity of ALP was accelerated with the liver, but inhibited with the kidney. At the same time, the activities of ACP were found to be increased in both liver and kidney of Monopterus albus.The results demonstrated that liver and kideney carboxylesterase (CaE) in fish played a vital role on the detoxification owing to its high-affinity to monocrotophos. Thus, the presence of CaE could protect brain acetylcholinesterase (AChE), which was pathological target enzyme, from attacking by toxicant. The ALP and ACP may play an important role in the resistance of fish to the poison of organophosphorus pesticides, and elucidation of the mechanism needs further research.