Comparison of Growth Performance and Biochemical Components between Low-Salinity-Tolerant Hybrid and Normal Variety of Pacific White Shrimp (Penaeus vannamei)

Penaeus vannamei, a high-yield economical shrimp, is confronting germplasm degradation in the culture environments found in China, which results in a sharp drop in production. Genetic improvement by hybridization is an effective way to solve this problem. In this study, we selected the hybrid species adapted to low-salinity culture obtained by intraspecific crossing as the experimental group. The control group consisted of normal variety from the Hainan Lutai Company. The two groups of shrimps were cultured for three months under salinities of 1 PSU, 5 PSU, and 15 PSU. Growth-performance-related indicators, biochemical composition, and molting-related gene expression were examined. The results showed that at salinities of 1 PSU and 5 PSU, the survival rate and growth performance of the low-salt breeding group were better than those of the normal variety population. The digestive enzyme activity in the low-salt breeding group was higher, which was consistent with its better growth performance, and was also associated with higher triglyceride, total cholesterol, and glycogen content. Lower levels of lactic acid indicated less anaerobic metabolism and better adaptability to the environment. The amino acid and fatty acids analysis showed that levels of essential amino acids and high unsaturated fatty acids were both higher in the low-salt breeding group than in the normal variety shrimp cultured in a low-salinity environment. The expression levels of genes associated with molting (CHS, CaMKI, RXR, EcR, HSP60, and HSP70) were also higher in the low-salt breeding group than in the control group. The results indicated that the hybrid shrimp showed better growth performance and nutritional advantages compared with the normal shrimp under salinities of 1 PSU and 5 PSU. This research provides a valuable reference for subsequent genetic breeding and shrimp culture.