We evaluated the effects of dietary vitamin E on the reproductive performance and antioxidant capacity of Macrobrachium nipponense female shrimp. Prawns were fed 0, 40, 80, 160, 320 or 640 mg vitamin E/kg diet for 60 days. The 80 mg/kg group had the highest weight gain and lowest feed conversion rates. And the highest spawning rates were observed in the 80 mg/kg group with no significant differences among the groups. The highest activities of lysozyme, acid phosphatase and alkaline phosphatase in hepatopancreas were obtained in the 160 mg/kg group. The activities of superoxide dismutase, catalase and glutathione peroxidase showed a decreasing trend in the hepatopancreas. The lowest content of malondialdehyde was obtained with 80 and 160 mg/kg vitamin E. Histological results showed that the number of restzellen cells in hepatopancreas and a number of follicular cells in ovaries increased with 160 mg/kg vitamin E. However, 640 mg/kg vitamin E resulted in damaged hepatopancreas tubules and oocytes. The highest vitellogenin and vitellogenin receptor gene expressions were observed with 160 mg/kg vitamin E. These results provide evidence that dietary vitamin E with 80 and 160 mg/kg plays a positive impact on reproductive performance and antioxidant capacity of female shrimp.

We evaluated the effects of dietary vitamin E on growth, immunity and regulation of the hepatopancreas in male oriental river prawn, Macrobrachium nipponense. Shrimps were fed 0, 40, 80, 160, 320 or 640 mg vitamin E/kg for 60 days. The 80 mg/kg group had the highest weight gain rate, specific growth rate and lowest feed conversion rate while there were no significant differences in survival rate and hepatosomatic index.The highest crude fat and lowest crude protein content were observed in the 160 mg/ kg group. In the hepatopancreas, lysozyme, acid phosphatase and alkaline phosphatase activities were highest in the 160 mg/kg group, while superoxide dismutase, catalase and glutathione peroxidase activities decreased with increasing vitamin E levels. Malondialdehyde content initially decreased then increased with vitamin E levels, whereas the reverse was seen with total antioxidant capacity. Linoleic acid, DPA, DHA, total n-3 polyunsaturated fatty acid and total polyunsaturated fatty acid first increased then decreased, while EPA and total saturated fatty acid rose with vitamin E levels. Total n-6 polyunsaturated fatty acid content declined while there were no significant differences in linolenic and total monounsaturated fatty acid content.Following a toxicity test with Aeromonas hydrophila, hepatopancreas ultrastructure revealed that appropriate vitamin E levels promote an increase in mitochondria, endoplasmic reticulum and Golgi bodies, but excess vitamin E can damage cell structure.These results provide evidence that 80-160 mg/kg dietary vitamin E has a positive impact on growth, immunity and regulation of the hepatopancreas in male shrimp. K E Y W O R D S enzyme activity, fatty acid, growth, Macrobrachium nipponense male shrimp, ultrastructure, vitamin E

Ammonia is a major environmental pollutant in the aquatic system that poses a great threat to the health of shrimp. Macrobrachium nipponense, as one of the large‐yield farmed shrimp, is facing germplasm degradation. Genetic improvement through hybridization is one of the effective methods to solve this problem. However, there are few studies on the effects of ammonia nitrogen on the germplasm resources of M. nipponense. In this study, the broodstock populations (Dianshan, DS) and hybrid offspring (DS ♀ × CD [Changjiang, CJ ♂ × Dongting, DT ♀], SCD) were exposed to 0, 5, or 20 mg/L of ammonia for 96 h. The survival rate of the SCD group was greater than the DS group, although there were no significant differences in weight gain rate and length gain rate (p > 0.05). The number of positive cells and apoptosis rates in the DS group were significantly greater than in the SCD group after ammonia exposure (p < 0.05). As the ammonia concentration increased, the antioxidant enzyme activities in the SCD group were significantly higher than DS group, while the hepatotoxicity enzyme activities in the SCD group were significantly lower than DS group (p < 0.05). The trends in the expression of antioxidant‐ and immune‐related genes were generally consistent with the activities of antioxidant enzymes. Our study found that the hybrid population had stronger stress resistance than their parent populations at the same ammonia concentration. This study confirms our speculation that hybrid population has a greater advantage in antioxidant immunity, which also provides reference for the follow‐up study of chronic ammonia toxicity.

Ammonia nitrogen is an important source of water pollution that severely limits the development of aquaculture. Macrobrachium nipponense is widely cultivated due to its delicious meat, strong reproductive ability and short reproductive cycle, but the problems caused by germplasm degradation are becoming increasingly concerning.Hybridization is an efficient means to solve this problem. In this study, the parental population, Dianshan Lake (DS) and the hybrid population, DS ♀ × CD (Changjiang, CJ ♂ × Dongting, DT ♀ [SCD]) were exposed to 0, 1 or 10 mg/L total ammonia nitrogen (TAN) for 28 days. Our results indicated that the number of gill-positive cells and the apoptosis rate of the two groups showed an upward trend with the ammonia nitrogen concentration increased. The ammonia metabolism-related substance levels and the detoxifying enzyme activities in the gills of shrimp in the SCD group exposed to 10 mg/L of TAN were significantly higher than shrimp in the DS group (p < 0.05). As the TAN concentration increased, the respiratory-related genes displayed a downward trend and the nitrogen metabolism-related genes presented an upward trend.Our results suggest that the SCD population had a stronger detoxifying capacity and a greater stress resistance ability than the DS population when subjected to the same concentration of ammonia nitrogen stress.