Effects Of Beta-cypermethrin On Immunotoxicity Of Procambarus Clarkii

In recent years, the widespread use of pesticides has caused severe environmental pollution in the word. Beta-cypermethrin, a synthetic pyrethroid insecticide, has become a widely used new pesticide due to its efficient, broad-spectrum, low toxicity and low-residue. Although pyrethroid pesticides is low toxicity to some non-target organisms, such as human or mammals, but its toxicity is very high to fish, shrimp, crab and other aquatic animals.To investigate the immunotoxicity effect of beta-cypermethrin on Procambarus clarkii, the crayfishes were exposed to various concentrations of beta-cypermethrin (0,0.005,0.01,0.02and0.04μg/L) until96h according to the96h LC50values (0.2μg/L) measured previously. The total hemocyte counts (THC), hemocyte respiratory burst activity (RB) and the activities of humoral immunity factor, including serum antibacterial activity (Ua), bacteriolytic activity (Ub) and phenol oxidase (PO), were investigated at24h,48h,72h and96h, respectively. The contents of reactive oxygen species (ROS), malondialdehyde (MDA) and protein carbonyl content (PCO) and the activities of superoxide dismutase (SOD) and catalase (CAT) in the serum, gill and hepatopancreas of crayfishes were measured to indicate the oxidative damages. In order to preliminarily explore the pathological physiology changes of crayfishes, the activities of Na+-K+-ATPase in gill and hepatopancreas and hepatopancreas histopathology were determined. This study preliminary illustrates the immunotoxicity of beta-cypermethrin on Procambarus clarkii.(1) When the crayfishes were exposed to beta-cypermethrin, the total hemocyte counts were reduced during96h period; hemocyte respiratory burst activities (RB) first increased then declined; the activities of antibacterial, lysozyme and phenol oxidase enzymes in serum were significantly inhibited. The results showed that beta-cypermethrin had significant negative effects on cellular and humoral immunity of Procambarus clarkii during the96h exposure.(2) After96h exposed, the activities of antioxidant enzymes, such as SOD and CAT, in gill and hepatopancreas of crayfish were restrained due to excessive production of ROS; the contents of MDA and tissue protein carbonyl (PCO) increased significantly, causing lipid peroxidation and protein oxidative damage of crayfishes. The results shows that the gill and hepatopancreas were subject to oxidative damage.(3) Beta-cypermethrin can inhibit the activities of Na+-K+-ATPase in hepatopancreas and gill of Procambarus clarkii. Compared with control group, the activities of Na+-K+-ATPase in hepatopancreas and gill at0.04μg/L treatment decreased by45.7%and18%after96h, respectively; In hepatopancreas, the vacuolar increased, lumen expansion, epithelial cells were separated with the basement until the epithelial cells necrosis and shedding into the lumen.When the Beta-cypermethrin concentrations exceed0.02μg/L, it would be caused an obvious damage on microstructure of hepatopancreas in Procambarus clarkii, thus affecting its physiological function.In summary, sub-lethal doses (0.005-0.04μg/L)of beta-cypermethrin has immunotoxicity to Procambarus clarkii. Because beta-cypermethrin mainly be absorbed into the hemolymph through the gills and then reached throughout the body. This caused the function decline of cellular and humoral immune in Procambarus clarkii. After the primary detoxification of hepatopancreas, the beta-cypermethrin would produce stress response to crayfish. The excessive production of ROS would inhibite antioxidant enzyme activities in gill and hepatopancreas, then resulting in lipid peroxidation and protein oxidative damage. Meanwhile, as the concentration of beta-cypermethrin increased, it had an obvious damage on microstructure of hepatopancreas.