Combined effects of low temperature and salinity on the immune response, antioxidant capacity and lipid metabolism in the pufferfish (Takifugu fasciatus)

Abstract

To investigate the combined effects of low temperature and salinity on the physiology, lipid metabolism, oxidative stress and immunity of Takifugu fasciatus, a total of 36 independent experiments were established, including 4 (25, 21, 17 and 13 °C) × 3 (0, 10 and 20 ppt salinity) treatment combinations, and each treatment had three replicates. The concentrations of triglyceride (TGs), glucose (GLU), cortisol, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) and the expression of heat shock proteins 90 (HSP90) increased in pufferfish as temperature decreased, while the concentration of total cholesterol (T-CHO); the number of granulocytes (Grans), lymphocyte (LYMPHs), and red blood cell (RBCs); and the expression of interferon (IFN), interferon receptor (IFNR), interleukin-4 (IL-4) and interleukin-4R(IL-4R) decreased. The treatment of 13 °Cand 17 °C led to the death of T. fasciatus, but this was alleviated at the group of 10 ppt salinity. The correlation results showed that compared 1013 (10 ppt 13 °C) group with 013 (0 ppt 13 °C) group, the concentrations of ALT, AST, TGs, GLU, cortisol and IgM; the activities of catalas (CAT) and lipid peroxide (LPO); and the expression of HSP90 were significantly decreased, while the concentration of T-CHO and Lyz; the number of Grans, LYMPHs, RBCs; and the expression of IFN, IFNR, IL-4 and IL-4R were increased compared to those in control fish. In fish grown in 10 ppt salinity at 17 °C, the relevant indicators were the same as those measured at 13 °C, except for ALT and AST levels and the number of Grans and RBCs. In addition, there were no deaths in the experimental group at 21 °C, and there were a small number of deaths in the 2025 (20 ppt 25 °C) group. Correspondingly, ALT and AST levels in the serum as well as CAT and LPO activities in the liver were significantly higher in the 2025 (20 ppt 25 °C) group than in the 025 (0 ppt 25 °C) and 1025 (10 ppt 25 °C) groups. These results indicate that 10 ppt of salinity can alleviate the survival pressure on T. fasciatus at 13 °C and that at 25 °C, 20 ppt salinity stresses the organism. Our study not only indicates that salinity and low temperature regulate the physiological balance in T. fasciatus, but also provides a theoretical basis for the overwintering culture of T. fasciatus.