Abstract: Acute toxicity of chlorpyrifos(CPF) on crayfish(Procambarus clarkii) was studied with the static test method.In the acute exposure experiment,crayfish was exposed to CPF at the following concentrations,0,2,10,20,40,and 80 μg·L^-1.Results show that the higher the CPF concentration,the higher the toxicity to the crayfish.The 24,48 and 96 h ρ(LC₅₀) was(28.24±2.81),(19.50±2.03) and(13.13±1.70) μg·L^-1,respectively,and the safe concentration was(2.79±0.31) μg·L^-1.The lethal concentration of CPF to 50% of crayfish [ρ(LC₅₀)] decreased significant with time,which fitted a hyperbolic decay model(r=0.999 9,P<0.000 1).Histopathological observation of the crayfish revealed that CPF pollution caused serious damages to its main organs,such as epithelial hyperplasia of the heart,impregnation of cardiac muscle bundles with haemocytes;swollen neorones,chromatolysis,change of cells from multipolar to round shape,necrosis and disorganization of nerve fibres,constriction and congestion of hepatopancreas tubules with more vacuoles;vacuolation surface deposition of melanin and impregnation with haemocytes of gill tissues and atrophy and dissolution of muscle fibers.The study enriched the database of aquatic toxicology and helped accumulate basic data for control of proliferation of CPF pollution and development of ecological farming of crayfish P.clarkii. 

Key words: chlorpyrifos(CPF), Procambarus clarkii, acute toxicity, histopathology