Effects Of The Environmental Factors On Physiology-biochemistry Of Scylla Paramamosain

The effects of the environment factor(ammonia-N,nitrite,pH,salinity) stress on the physiological-biochemical parameters(THC,SOD,GSH-PX,ACP,AKP,U_α,U_L and ATPase) and histological structures of gill and hepatopancreas of mud crab Scylla paramamosain were studied by enzyme analysis and histology technique in order to evaluate the physiological-biochemical responses and mechanisms of immune defense of S.paramamosain under environmental stress.The findings will provide theoretical guidance to water quality management for mud crab aquaculture,and will contribute basic data regarding the environmental physiology of crustaceans.The main results and conclusions of the study were as follows:1.Physiological-biochemical parameters and the histological structure of gill and hepatopancreas in mud crabs were significantly affected by ammonia-N stress.The effects of ammonia-N(0mg·L^-1(control),10mg·L^-1,20mg·L^-1,30mg·L^-1,40 mg·L^-1) on the physiological-biochemical parameters and on the histological structure of gill and hepatopancreas in mud crabs were studied.PO activity of S.paramamosain increased with ammonia-N concentration after 24h and 48h of exposure,with the peak of PO activity at 48h.The lowest PO activity was seen at 72h.This trend was also seen in THC levels,except the lowest THC was seen at 96h.Moreover,THC in C30 and C40 groups were lower.The SOD activity of gill in S.paramamosain increased with ammonia-N concentration at 24 and 48h and decreased with the ammonia-N concentration at 72 and 96h.In contrast,the SOD activity in the C40 group was consistently decreased during experimental time.SOD activiy of serum had a similar trend;the only difference was in the peak value of SOD activity after 48h compared to gills' value. The changes of SOD activity in hepatopancreas and muscle of all groups of crabs had the same trend.Furthermore,the SOD activity in gill and muscle had the same trend compared to PO and THC.The GSH-PX activity was related inversely with ammonia-N concentration,increasing after 24h,48h and 72h,but had a positive relation after 96h.The GSH-PX activity of serum was opposite that of gill.The GSH-PX activity in hepatopancreas and muscle of all group crabs had the same change trend as SOD activity in hepatopancreas,U_α,U_L in serum had the same change trend as hepatopancreas' SOD activity too.Na⁺-K⁺-ATPase activity in gill of S.paramamosain decreased at 24h,and increased at 48h,72h,and 96h with ammonia-N concentration increasing.In contrast,the Na⁺-K⁺-ATPase activity of the gill in C40 group was consistently decreased during experimental time,which was the same change trend as the THC of C40 group crabs;Ca²⁺-Mg²⁺-ATPase activity had similar change trend too,but that of C40 group crabs increased with ammonia-N stress time prolonging,which was possible signal that it's time for ecdysis.ACP activity in gill and hepatopancreas of S.paramamosain had the same change trend as the Ca²⁺-Mg²⁺-ATPase activity of gill's,ACP activity of muscle in crabs different groups decreased with ammonia-N concentration increasing and ammonia-N stress time prolonging;AKP activity in gill of S.paramamosain decreased with ammonia-N concentration at 24h,72h,96h,but increased at stressed 48h;AKP activity of hepatopancreas and muscle in crabs of different groups had the same change trend as the SOD activity of serum.The histological structure changes of gills and hepatopancreas in S.paramamosain under ammonia-N stress were studied by microscopy.The results showed that there were oxidative injuries to the structure of epithelium of gill and hepatopancreatic tubules in mud crabs under ammonia-N stress,the physiological functions of tissues, organs in mud crabs depressed and the structures of gill and hepatopancreas damaged. It was more obviously injured in structures of gill and hepatopancreas in mud crab with the ammonia-N concentration increasing.2.Physiological-biochemical parameters were affected by nitrite stress. The effects of nitrite-N(0.00 mg·L^-1,0.25 mg·L^-1,0.50 mg·L^-1,1.00 mg·L^-1,1.50 mg·L^-1,2.00 mg·L^-1) on the physiological-biochemical parameters of mud crabs were studied.The results showed that PO activity of serum,SOD,U_α,AKP activities of muscle and U_L of hepatopancreas were decreased with nitrite concentrations increasing and the time elapsing,while the activities of ACP,AKP in hepatopancreas and U_L in muscle were increased.3.Physiological-biochemical parameters were affected by pH stress.The effects of pH values(4.5,6.0,7.5,9.0,10.5) stress on the physiological biochemical parameters of S.paramamosain were studied.The results showed that the activities of PO,SOD and U_αin serum increased significantly at different pH groups(P＜0.05),and SOD activity in muscle and hepatopancreas increased significantly(P＜0.05).SOD activity in hepatopancreas increased significantly(P＜0.05) at same pH group.4.Physiological-biochemical parameters were affected by salinity stress.The effects of the salinity(5,15,25 and 35) stress on the physiological-biochemical parameters of S.paramamosain were studied.The activities of PO and SOD showed obvious time-effect,the SOD activity of muscle in S.paramamosain increased significantly for crabs transferred to 5,15 and 35.The SOD activity in the hepatopancreas of crabs in same salinity group decreased with the stressed time prolonging before 72h.The activities of Na⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase increased with the salinity decreasing.Na⁺-K⁺-ATPase activity in each treatment tended to stabilization with the passing time.ACP activity of muscle decreased slightly with the salinity increasing.AKP activity in muscle and hepatopancreas increased with the salinity increasing.The AKP activity increased with time prolonging in the same group.The activities of ACP and AKP in hepatopancreas were higher than those in muscle.In conclusions,the environmental factors significantly affect physiological biochemical response and immune of S.paramamosain.It should control range of ammonia,nitrite,pH,salinity,which maintain S.paramamosain normal metabolism and health.