盐度对凡纳滨对虾生长、免疫、抗氧化能力及肠道健康的影响OACHSSCD

[Objective]This study aims to systematically evaluate the effects of different salinity condi-tions on growth performance,disease resistance,nonspecific immunity and antioxidant capacity,as well as intestinal digestive function and gut microbiota structure of Litopenaeus vannamei,providing theoreti-cal support for optimizing salinity management in low-salinity and saline-alkali aquaculture systems for L.vannamei.[Method]Juvenile shrimps with initial body mass of(0.38±0.01)g were reared under low(15‰,L),medium(30‰,M),and high(45‰,H)salinity conditions for 8 weeks.Growth performance parameters,including survival rate,mass gain rate,specific growth rate,and feed conversion ratio,were determined.Hepatopancreas and intestinal tissues were collected to analyze nonspecific immune and antioxidant enzyme activities,related gene expression,and intestinal digestive enzyme activities.Gut microbiota composition and function were analyzed based on 16S rRNA high-throughput sequencing.In addition,healthy shrimp were challenged by injection with Vibrio parahaemolyticus(1×10⁷ CFU/mL),and the survival was recorded continuously for 72 h.[Result]Salinity significantly affected the growth performance of L.vannamei.Compared with the M group,shrimp in the H group showed significantly lower body mass gain and specific growth rates(P<0.05),while no significant difference was observed between L and M groups(P>0.05).The survival rate of the H group was significantly higher than those of the L and M groups(P<0.05).After V.parahaemolyticus infection,the average 72 h survival of the H group was higher than that of the L and M groups,but nonsignificant differences were found among the three groups(P>0.05).For immune and antioxidant responses,alkaline phosphatase activity was high-est in the M group(P<0.05);acid phosphatase,lysozyme,and phenoloxidase activities also peaked in the M group and were lowest in the L group(P<0.05).Aspartate aminotransferase activity and gene expression were significantly elevated in the H group(P<0.05),while alanine aminotransferase activity showed no significant difference(P>0.05),though its gene expression increased significantly in the H group(P<0.05).Superoxide dismutase and catalase activities and gene expressions were significantly higher in the M and H groups than those in the L group(P<0.05),whereas malondialdehyde content showed a decrease-then-increase trend,being lowest in the M group(P<0.05).Digestive enzyme analy-sis revealed that intestinal amylase activity and lipase gene expression increased with salinity,reaching the highest levels in the H group(P<0.05),while trypsin activity and gene expression showed no signifi-cant differences among groups(P>0.05).Microbiota analysis indicated that microbial richness and diversity were significantly higher in the H group compared with the L group(P<0.05).At the genus level,the relative abundance of Vibrio was significantly lower in the H and L groups than that in the M group(P<0.05).[Conclusion]Salinity modulates the growth and health of L.vannamei by regulating immune-antioxidant status,digestive capacity,and intestinal microbiota structure.