| Water is shrimp living environment, so water quality have a direct impact on the growth and economic benefits of shrimp. In ammonia N, pH, dissolved oxygen, temperature and salinity physiochemical indexs, pH is one of important physiochemical index and one of synthesis reaction index of water chemical traits, can affect water biological productivity. At present, the study about pH stress on shrimp growth, ion transport enzyme and immune related indexs have reported in the domestic and foreign. However, the comprasion study of pH stress in Fenneropenaeus chinensis , Litopenaeus vannamei, Marsupenaeus japonicus havn't seen until now. this thesis selected pH as the experimental change factor and studied comprasion of pH stress on growth, survival rate and activity of ion-transport enzyme, immune related factors in F. chinensis , L. vannamei, M. japonicas. This study include three parts.The first part: The survival rate, gill Na~+-K~+-ATPase activities, serum iNOS, PO, SOD, GSH-PX, LSZ activities and muscle RNA/DNA were compared in F. chinensis, L. vannamei and M. japonicus which were reared under control group (pH 8.2), low (pH 7.2), and high (pH 9.2) pH stress conditions in this study. Results showed that there were no negative effect among three species of shrimps when reared in the control group for 96h. Under low or high pH stress conditions, the survival rates of M. japonicus, L. vannamei and F. chinensis for 96h were 96.7% and 97.0%, 60.1% and 54.6%, 58.6% and 13.3%, respectively. With respect to gill Na~+-K~+-ATPase activity, L. vannamei showed highest level and M. japonicus was lowest under control group. The change on gill Na~+-K~+-ATPase activity of F. chinensis was the biggest. While that of M. japonicas was smallest under both low and high pH stress conditions. Also, all three species of shrimps tend to change much more in gill Na~+-K~+-ATPase activity under pH 9.2. In the control, the activities of nonspecific immunity related enzymes of both L. vannamei and M. japonicus were significantly higher than that of F. chinensis and PO and SOD activities of M. japonicus were markedly higher than that of L. vannamei, while the LSZ activity of L. vannamei was higher than that of M. japonicus. The changes in nonspecific immunity related enzymatic activities for F. chinensis and L. vannamei were much higher than that for M. japonicus both in low and high pH stress conditions for 96h and serum PO, SOD and iNOS activity in F. chinensis tended to change much more under high pH stress. Compared with control group, muscle RNA/DNA ratio declined with pH stress time prolonged, and shrimps growth was inhibited.The second part: This paper compares the gene expressions of ion-transport enzyme (Na~+-K~+-ATPase), proPO and Mn-SOD of F. chinensis, L. vannamei and M. japonicus which were reared under different pH stress conditions. The main results were as follows: (1) Under different pH stress groups, the expression of three species of shrimps gill Na~+-K~+-ATPase increased gradually and after reaching maximum level decreased gradually. It was significant difference with control group (P<0.05). Compared among pH stress groups, high pH stress groups (pH8.7 pH9.2 groups) made the expression of F. chinensis gill Na~+-K~+-ATPase changed much more than the low pH stress groups. Compared among three species of shrimps, Na~+-K~+-ATPase expression of F. chinensis varied much more than that of L. vannamei, and M. japonicas Na~+-K~+-ATPase expression changed relatively small. (2) Under different pH stress groups, proPO expressions of F. chinensis and L. vannamei tend to increase gradually and reach maximum level after a period of time, and then decrease gradually, and showed two or three expression peak (P<0.05). However, except pH9.2 groups proPO expression of M. japonicas tend to induce down-regulated and then increase with pH stress time prolonged. When reached maximum level, the expression decreased also. Compared among pH stress groups, high pH stress groups had an more effect on proPO expressions of F. chinensis and L. vannamei than that of others. pH6.7 and 7.2 groups had an more effect on proPO expressions of M. japonicas than that of others. Compared among three species of shrimps, F. chinensis proPO expression changed much more than that of L. vannamei, and the proPO expression of M. japonicus changed relatively small. (3) Under different pH stress groups, the F. chinensis and M. japonicus Mn-SOD expression showed increasing at the beginning and reached expression peak, then decreased gradually, and appeared two or three expression peaks(P<0.05). Low pH stress groups (pH6.7 pH7.2 groups) L. vannamei Mn-SOD expression tend to increase slightly and then down-regulated when reached maximum level. However high pH stress groups the expression of L. vannamei Mn-SOD showed decreased gradually. Compared among pH stress groups, pH7.2 groups had an more effect on F. chinensis Mn-SOD expression than that of other groups and pH8.7 pH9.2 groups had an more effect on L. vannamei Mn-SOD expression than that other groups. pH7.7 and pH8.7 groups high ad an more effect on M. japonicus Mn-SOD expression than that other groups. Compared among three species of shrimps, M. japonicus Mn-SOD expression varied much more than that of F. chinensis, and L. vannamei Mn-SOD expression changed relatively small.The third part: In the paper, F. chinensis, L. vannamei and M. japonicus were chosen as experimental materials. On the basis of anatomy, this part analyzed three species of shrimps gill and liver external symptoms and microstructure changes after pH stress 72h. The results show that shrimp gill color looked dim, some looked black and congested gill looked swelling, some gill cell represented inflammation. Epithelial layer became incrassation and gaps between layer was reduced, some area appeared adhesion. pH8.7 and pH9.2 groups of F. chinensis, M. japonicus gill were more damaged than that of pH6.7 and pH7.2 groups. pH6.7 groups of L. vannamei gill was more damaged than that of other groups. After pH stress 72h, liver color became black red from bright red, which was damaged broadly. Liver tube arranged disorderly, which boundary became ambiguous and tube space became smalling. Conjunctive tissue and epithelial cells between liver tube was damaged, and some cells was disjointed and nucleolus appeared pyknosis or disappear. pH8.7 and pH9.2 groups of F. chinensis, M. japonicus liver histopathological were injured more seriously than that of other groups. pH6.7 and pH7.2 groups of L. vannamei liver was damaged more seriously than that of other groups.From above results, compared among three species of shrimps, F. chinensis survivl rates was the smallest, then was L. vannamei and M. japonicus survival rates was the biggest. Compares among pH stress groups,pH9.2 groups of F. chinensis gill Na~+-K~+-ATPase and serum PO activities and Na~+-K~+-ATPase, proPO gene expression and gill micrograph changed more seriously than that other groups. This results reconcile with shrimp survival rates, and can speculate Na~+-K~+-ATPase, PO index interrelated with pH strss. Compared among three species of shrimps, F. chinensis is sensitive to pH stress and have a weak tolerance, then is L. vannamei. M. japonicus has the strongest tolerance for pH stress. |
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