RESUMO
Objective To evaluate the molluscicidal effect of niclosamidate against Oncomelania hupensis in laboratory and explore its mechanism by determining the enzyme activities of six important enzymes in snail soft tissues.Methods O.hupensis snails were treated with niclosamidate at the concentration of 1.25 mg/L for 24 h and the snail soft tissues were separated and pre-pared for analysis.The enzyme activities of NOS,AChE,SDH,LDH,ACP and AKP were determined by ultraviolet spectropho-tometry.The morphology of the snail soft tissue was also observed.Results Niclosamidate exhibited a potent molluscicidal ef-fect against O.hupensis at the concentration of 5.00 mg/L with a mortality of 96.67% by the immersion method in laboratory.Af-ter immersed with niclosamidate(1.25 mg/L)for 24 h,the enzyme activities of NOS,AChE,ACP and AKP were significantly decreased compared with those of the controls(all P<0.01).There were no significant changes observed in the enzyme activi-ties of SDH and LDH(both P>0.05).Conclusion Niclosamidate possesses a potent molluscicidal effect against O.hupensis and its molluscicidal mechanism is probably by affecting the transmission of neurotransmitters,interfering with the circulation, metabolism and motor functions that require NO,and hindering the digestion and absorption of nutriments,which eventually re-sult in the death of the snails.