The Effects Of Cd²⁺ Or Cr⁶⁺ Stress On The Nonspecific Immune Of Scylla Paramamosain

The effects of different concentrations of water-borne Cd²⁺ or Cr⁶⁺ on total haemocyte count(THC), enzymes interrelated to immune function and histological structure of gill and hepatopancreas of mud crab Scylla paramamosain were determined by enzyme analysis and histology technique during experimental time. The aim was to clarify the mechanisms of immune defence of Scylla paramamosain under Cd²⁺ or Cr⁶⁺ stress, which will provide scientific guidelines for mud crab healthy aquaculture and pile up basic data for studying on the crustacean environmental immunology. The main results and conclusion were as follows:1. Changes of total haemocyte count of Scylla paramamosain exposed to different concentrations of water-borne Cd²⁺ or Cr⁶⁺THC of Scylla paramamosain decreased significantly when exposed to different concentrations of Cd²⁺ or Cr⁶⁺ for 1d(P<0.05). The variation of THC was positive related to the Cd²⁺or Cr⁶⁺ concentration and more sensitive when exposed to Cd²⁺. The decreasing of THC induced by Cd²⁺(0.075mg/L, 0.1 mg/L) was significantly different from the controls after 9d exposure(P<0.05), but Cr⁶⁺ didn't. THC of Scylla paramamosain was approximately to control group after 9d exposed to Cr⁶⁺, however, THC still decreased after 9d exposed to Cd²⁺.2. Effects of water-borne Cd²⁺ or Cr⁶⁺ exposure on the activities of enzymes interrelated to immune function in hemolymph of Scylla paramamosainPhenoloxidase activity was significantly suppressed in hemolymph when exposed to different concentrations of Cd²⁺ for 1d(P<0.05), exposed to different concentrations of Cr⁶⁺ for 5d. Lysozyme activity was significantly elevated in hemolymph of Scylla paramamosain when exposed to the concentrations of 0.075mg/L and 0.1 mg/L Cd²⁺, or 4.0 mg/L and 8.0 mg/L Cr⁶⁺(P<0.05).The activation depended on exposure time of Cd²⁺ or Cr⁶⁺, which suggested a decrease in activation with prolongation of exposure time. The antibacterial activity was significantly inhibited in hemolymph of Scylla paramamosain(P<0.05). The effect of Cr⁶⁺ exposure on antibacterial activity showed a dose-time response relationship at some degree. 3. Effects of water-borne Cd²⁺ or Cr⁶⁺ exposure on the activities of enzymes interrelated to immune function in gill, muscle and hepatopancreas of Scylla paramamosainThe Ca²⁺-ATPase activity was significantly suppressed in gills of Scylla paramamosain when exposed to different concentrations of Cd²⁺ after 1d (P<0.05), but the changes had no relation with Cd²⁺ concentration. However, the Na⁺,K⁺-ATPaseactivity was insignificantly inhibited by Cd²⁺ compared to control group except Cd²⁺ 0.075mg/L. Na⁺,K⁺-ATPase was lower sensitive to Cd²⁺ than Ca²⁺-ATPase. The activities of Ca²⁺-ATPase and Na⁺,K⁺-ATPase were significant decreased by Cr⁶⁺ exposure in gills of Scylla paramamosain after 1d(P<0.05). The activities of Ca²⁺-ATPase and Na⁺,K⁺-ATPase were stimulated by Cd²⁺ or Cr⁶⁺ with exposure time prolonging. The superoxide dimutase(SOD) activity were significant increased by Cd²⁺ or Cr⁶⁺ exposure in gills, hepatopancreas, muscle of Scylla paramamosain (P<0.05). The SOD activity in hepatopancreas revealed a much higher sensitivity to Cd²⁺ than that in other tissues, whereas SOD activity in gills revealed a much higher sensitivity to Cr⁶⁺ exposure. Acid phosphatase activity in gills, hepatopancreas, muscle of Scylla paramamosain was significantly stimulated by Cd²⁺(P<0.05), but revealed less change to Cr⁶⁺ exposure. The alkaline phosphatase activity was significant decreased by Cd²⁺ exposure in gills, hepatopancreas, muscle of Scylla paramamosain(P<0.05), whereas Cr⁶⁺ exposure induced an increase in alkaline phosphatase activity in Scylla paramamosain.4. Effects of water-borne Cd²⁺ or Cr⁶⁺ exposure on histological microstructure of gill and hepatopancreas in Scylla paramamosainThe effect of water-borne Cd²⁺ or Cr⁶⁺ exposure on gill and hepatopancreas microstructure of Scylla paramamosain put up the dose-time effect. Some changes were observed in histolopathological microstructure of gill and hepatopancreas after 9d. The gill filament epithelium were thickened, vasal become larger compared to control group, the boundary between hepatopancreas cells were faint in Scylla paramamosain exposed to 0.lmg/L Cd²⁺ after 9d. The irregularly thickened gill lamellae epithelium disassembled were the other histolopathological effects of 8.0mg/L Cr⁶⁺ after 9d. In hepatopancreas, the basement membranes injury, the boundary between hepatic tubules was unclear, increasing hemocytes was observed.In summary, the research suggests water-borne Cd²⁺ or Cr⁶⁺ exposure caused negative effects on immune factors, led to immune disturbance in Scylla paramamosain.