Effects of Long-Term Salinity Exposure on Growth, Survival, Hepatopancreatic Health, and Intestinal Microbiota in Juvenile Chinese Mitten Crabs (Eriocheir japonica sinensis)

Abstract

Salinity is a key environmental factor in crustacean aquaculture, but its long-term effects on juvenile Chinese mitten crabs (Eriocheir japonica sinensis) remain poorly understood. Megalopae were reared for seven months at 0, 15, and 30 ppt, with three replicate tanks per treatment. Growth, survival, hepatopancreatic histology and biochemistry, multi-omics profiles, and intestinal bacterial communities were evaluated. Crabs at 0 ppt achieved the greatest growth and production. Survival was highest at 15 ppt, although growth and production were lowest, whereas survival was lowest at 30 ppt despite greater growth among survivors than at 15 ppt. Increasing salinity was associated with more pronounced hepatopancreatic lesions and TUNEL-positive signals, increased serum aminotransferase activities, and decreased albumin. Immune-related enzyme activities increased under saline conditions, whereas antioxidant capacity declined and lipid peroxidation increased. Multi-omics analyses highlighted the Lysosome and Tyrosine metabolism pathways. Intestinal bacterial diversity tended to increase with salinity, accompanied by a greater relative abundance of Vibrio and a lower abundance of Dysgonomonas. Thus, 15 ppt favored survival without supporting growth, whereas 30 ppt was associated with the poorest tissue condition and lowest survival. These findings show that survival, growth, production, and physiological health should be considered together when evaluating salinity suitability for long-term culture.