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.

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.

Superoxide dismutase (SOD; EC 1.15.1.1) is an enzyme that protects against oxidative stress from superoxide radicals in living cells. This enzyme had been isolated, purified and partially characterized from muscle tissue of the shrimp Macrobrachium nipponense. The purification was achieved by heat treatment, ammonium sulfate fractionated precipitation and column chromato-graph on DEAE-cellulose 32. Some physiological and biochemical characterization of it was tested. The molecular weight of it was about 21.7 kDa, as judged by SDS–polyacrylamide gel electrophoresis. The purified enzyme had an absorption peak of 278 nm in ultraviolet region, and the enzyme remained stable at 25–45℃ within 90 min. However, it was rapidly inactivated at higher temperature. Treatment of the enzyme with 1 mM ZnCl2, SDS and 1mM or 10mM mercaptoethanol showed some increasing activity. However, the enzyme activity was obviously inhibited by 10mM CaCl2, CuSO4, ZnCl2 and 1mM CaCl2 and 10mM K2Cr2O7. SOD activity did not show significantly variation after incubated with 1mM CaCl2, EDTA and 10mM SDS. The enzyme was insensitive to cyanide and contained 1.03F0.14 atoms of manganese per subunit shown in atomic absorption spectroscopy, which revealed that purified SOD was Mn superoxide dismutase.

The 24-, 48- and 96-h LC50 of nitrite and the effects on reactive oxygen intermediates (ROIs) in haemocytes and muscle, superoxide dismutase (SOD) activity, catalase (CAT) activity, glutathione peroxidase (GPX) activity, in muscle of Macrobrachium nipponense exposed to ambient nitrite were investigated. The 24-, 48- and 96-h LC50 values of nitrite at pH 8.0 were 46, 26 and 13.3 mg l 1. A significantly increased ROIs value was found in prawn (P < 0.05) exposed to nitrite shock and increased with increased ambient nitrite concentration. Exposure to a sublethal concentration of nitrite for 24 h, increased ROIs by 97% compared with that of prawn exposed to control nitrite concentration, whereas SOD, CAT and GPX activity decreased 67%, 80.6% and 82.7%, respectively. The results showed that an imbalance between prooxidant forces and antioxidant defenses is one of the toxicity mechanisms of nitrite on prawn.

This study examined the effects of temperature on growth, adenosine phosphates, ATPase and cellular defense response of juvenile shrimps Macrobrachium nipponense. The results showed that specific growth rates in the temperature range 22–32℃ were significantly (P < 0.05) greater than that at 16 and 20℃, and were highest at 25℃. The average (0.513 ± 0.032) of hepatopancreas Na+–K+ ATPase activities in the temperature range 16–22℃ were enhanced 1.38-fold than that (0.216 ± 0.069) of hepatopancreas Na+–K+ ATPase activities in the temperature range 25–32℃ (P < 0.05). The adenylate energy charge (AEC) in muscle showed higher value (P < 0.05) at 16°C and 20°C compared to in the temperature range 22–32℃. ROIs level of abdominal muscle at 25℃ was the lowest (P < 0.05). Moreover, SOD activity of abdominal muscle at 22–30℃ was higher (P < 0.05) than that at 16 and 32℃. 2006 Elsevier B.V. All rights reserved.

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.

The effects of supplemental vitamin C, in the form L-ascorbyl-2-polyphosphate (APP) in enriched live food dietary (Artemia) on reactive oxygen intermediates (ROIs) and free radical scavenging enzymes (such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione transferase) activities in muscle of Penaeus vannamei exposed to ambient ammonia-N were investigated. The results showed ROIs values of shrimps fed the starved and enriched Artemia increased with increased ammonia-N concentration. The ROIs value of shrimps fed the enriched Artemia exposed to increasing ammonia-N concentration were 37.4%, 26.4% and 31.1% lower (P b 0.05) compared with those of shrimps fed the starved Artemia exposed to the same ammonia-N concentration. Total SOD, CAT, GPX, GST and GR activities of shrimps fed the enriched Artemia exposed to ammonia-N (2.568–3.852 mmol/l), were all higher (P b 0.05) than that of shrimps fed the starved Artemia exposed to the same ammonia-N concentration. In addition, total SOD, CAT, GPX, GST and GR activities of shrimps of both dietary treatments decreased (P b 0.05) with increased ammonia-N concentration. The results demonstrated that supplementation of ascorbic acid in enriched live food (Artemia) enhanced the anti-oxidant capacity of shrimp, increasing its defense system that may fight against environmental stress leading to reduced ammonia toxicity.

Penaeus chinensis (Osbeck) juveniles were maintained for 14 days at pH 6.0, 7.0, 7.6, 8.0 and 8.5, respectively. The effects of pH on survival, phosphorus concentration, adenylate energy charge (AEC) and Na+ –K+ adenosine triphosphatase (ATPase) activities of prawns were investigated. The results showed that survival of P. chinensis was impaired at low and high pH levels. The total phosphate level and AEC in abdominal muscle increased with pH level in range of 6.0–7.6 reaching the maximum values at pH 7.6. Thereafter, the levels declined with increasing pH level in range of 7.6–8.5. The change of Na+ –K+ ATPase activity in gill of prawn was similar to that of total phosphorus content and AEC in muscle of prawn at different pH. The effect of pH on Na+ –K+ ATPase activity in the muscle was lower than on that in gill.