in agreement with the change in inorganic P level in the muscle. AEC may be a direct indicator of energy metabolic activity during the moult cycle. ATPyADP and ATPyAMP ratios in premoult and postmoult stages were higher than that in intermoult stage. Naq –Kq -ATPase activities of gills, muscles and hepatopancreatic of prawns were higher in early postmoult and late premoult animals, whereas they were lower in late postmoult, intermoult and early premoult animals. Gill residual ATPase activity was significantly higher in postmoult animals, while the peak value of hepatopancreatic residual ATPase activity appeared in intermoult stage.

Growth, hemolymph osmolality, tissue water, ribonucleic acid (RNA)/deoxyribonucleic acid (DNA) ratio, protein-bound amino acids and free amino acids (FAA) of Macrobrachium nipponense were investigated, after they were acclimated to 0‰,7‰,14‰and 20‰ for 14 days. Growth was significantly (P < 0.05) influenced by salinity. The highest weight gain of prawns ( P < 0.05) was achieved at a salinity of 14‰.The RNA/DNA ratio, total protein-bound amino acid (TAA) and FAA concentrations in the muscle of prawns increased by hyperosmotic stress. The osmolality of prawns haemolymph increased slightly in salinities from 0‰ to14‰. A sharp increase in haemolymph osmotic concentration occurs between 14‰ and 21‰ the isosmotic point being reached at 15‰ (450 mOsm). It is noted that the relationship of total FAA concentration in muscle and salinity in the range of 0 – 20‰ revealed a positive linear correlation. The correlation coefficient (R2) is 0.98. During adaptation, the FAA pool (mainly glycine, alanine and proline) of muscle seems to be directly related to osmoregulation, while the percentage change in alanine in prawns transferred from freshwater to diluted seawater (20x was most pronounced (116% approx.). These results are compared with those of M. rosenbergii.

The 24 h, 48 h and 96-h LC50 of nitrite and the effects on reactive oxygen intermediates (ROIs) in haemocytes, superoxide dismutase (SOD) activity, catalase (CAT) activity, glutathione peroxidase (GPX) activity, in muscle of Penaeus vannamei fed the basal and higher selenium diet exposed to ambient nitrite were investigated. The results showed that, in prawns that were fed higher selenium diet, there was a significant decrease in the 24 h, 48 h and 96-h LC50 of nitrite, suggesting increase toxicity of nitrite to prawn when dietary higher selenium was added to feed. A significantly increased ROIs value was found in prawn fed the basal and higher selenium diet (P b 0.05) exposed to nitrite shock and increased with increased ambient nitrite concentration. Exposure to a sublethal concentration of nitrite for 24 h, ROIs in prawn fed the basal and higher selenium diet increased by 43.5% and 47.2% compared with that of prawn exposed to control nitrite concentration, whereas SOD, GPX and CAT activity decreased 66.6% and 71.13%; 70% and 81.3%; 34.7% and 28% in prawn fed the basal and higher selenium diet respectively. The results show that an imbalance between prooxidant forces and antioxidant defenses is one of the toxicity mechanisms of nitrite on prawn, P. vannamei, and that supplementation of diets with higher levels of selenium is harmful for prawn and increases toxicity of nitrite to prawn.

chium nipponense exposed to ambient ammonia were investigated. The results showed that the 96-h LC50 of ammonia-N was 36.6 mg 11 for the freshwater prawn, M. nipponense, at pH 8.0. When prawns were exposed to high ambient ammonia-N concentrations, the oxygen consumption rate increased and ammonia excretion decreased. Dietary vitamin C supplementation led to higher oxygen consumption and lower ammonia excretion. Na+/K+ ATPase activity increased with increased ambient ammonia-N exposure in the range of 0 – 18.3 mg l 1, and then was reduced at ambient ammonia-N 36.6 mg l 1. Na+/K+ ATPase activities of prawns fed a vitamin C-supplemented diet were significantly lower than those of prawns fed a diet which was not supplemented with vitamin C.

A cell culture system was devised for muscle cell of Macrobrachium nipponense in the study. The juvenile and adult shrimps were held in laboratory aquaria with penicillin 1000 IU/ml and streptomycin 1000 g/ml for 12–24 hours. Cell cultures were established in medium 199 supple-mented with 20% fetal bovine serum, 1 g/L glucose, 5.2 g/L NaCl, 1.43 g/L CaCl2, 0.05 g/L MgCl2, 100 IU/mL penicillin and 100 g/ml streptomycin. Fibroblast-like cells were passaged up to three times and survived for 54 days. The results showed the optimum for subculture in vitro was in medium 199 with pH 7.6. Moreover, basal medium supplemented with Zn2+ 60 g/L could enhance the growth of the muscle cells. It was found that better results for cell culture would be obtained more easily with juvenile shrimps caught in spring than adults in summer or autumn; and shrimps caught within 12 hours after ecdysis could grow much better than the intermoult shrimps.