PH And Salinity Stresses On Production Of Reactive Oxygen Species And Antioxidant Defense System Of Shrimp

The penaeid shrimp virus had been reported and caused serious shrimp and economic losses. Disease is the final result of a complex interaction among the shrimp, its environment and the pathogen itself. To resolve the problem of disease must research from many aspects. Study on the environmental factors on the immune responses of penaeid shrimp is one of the strategies to control the disease radically. In order to study the effect of these environmental factors on the superoxide anion randical, antioxidant enzymes SOD, CAT, GPX, GR, GST and MDA content of shrimp, we selected some typical environmental factors including pH and salinity. The main results are as follows:Effects of different time pH stress on the O_2-·production in haemolymph and antioxidant system in muscle of penaeid shrimp were studied through simulated experiments. We chose Penaeus vannamei as experiment animals and compared with different time (48h, 74h, 96h, 120h, 144h and 168 h) pH stress (5.4, 6.7, 8.0 and 9.3) on the O_2-·production in haemolymph, antioxidant system in muscle and MDA content in heaptopancreas of the shrimp. The results indicated that the enzyme activities of SOD, GPX, CAT and GR in muscle and the level of MDA in heaptopancreas can be looked as an indicator to the effects of Ph on the immuse response of the shrimp. After 48h pH stress, the O_2-·production in haemolymph was significantly higher in pH9.3 treatment. GR activity and the content of MDA also made an increase in low pH or high pH. Similarly, significant differences in SOD, CAT and GPX were observed in the muscle of the shrimp. We found that the activities of SOD and GR compensated to each other, meanwhile, CAT and GPX activities also had a compensatory response to pH exposure.Effects of salinity stress on the O_2-·production and antioxidant defense system were studied in muscle of penaeid shrimp. We chose penaeus monodon in two different life stages as experiment animals and compared with different time (24h, 48h) salinity stress(2‰, 7‰, 20‰, 30‰, 40‰) on the O_2-·production and antioxidant system in muscle of the shrimp. The results indicated that the O_2-·production and the antioxidant system of P. monodon in two different life stages was affected by salinity stress. The O_2-·production and the GPX activity in muscle of early larval stages of p. monodon decreased and the GST activity also affected in low salinity stress. CAT activity cause an increase and GPX activity made a decreased when exposed to20‰salinity stress. SOD and GR activities increased significantly in 30‰salinity group. When exposed to high salinity of 40‰, the O_2-·production and CAT activity declined, and SOD increased significantly. However, the superoxide anion production and GPX activity dropped significantly in the muscle of juvenile when exposed to low salinity, and SOD, CAT and GR activities increased significantly.But the superoxide anion production, CAT, GPX and GST activities dropped, GR activity increased significantly in the salinity of 20%. The GPX and GST activities also dropped significantly when exposed the salinity of 30‰. While in the salinity of 40‰, the superoxide anion increased, GPX and GST activities dropped significantly. The regulation of antioxidant system in erly larval stages of Penaeus monodon is different from the juvenile when exposed to salinity stress. The level of antioxidant defense system of Penaeus monodon in two different life stages also different in natural environment.