Physiological and molecular responses of golden pompano Trachinotus ovatus subjected to the acute salinity stress

Golden pompano (Trachinotus ovatus) is a commercially important marine fish and is widely cultured in the coastal area of South China. Salinity is one of the most important environmental factors influencing aquatic organisms. In this study, T. ovatus was subjected to the acute salinity stress treatments using four salinity levels of 0 parts per thousand, 10 parts per thousand, 20 parts per thousand, and 40 parts per thousand to investigate its physiological and molecular responses. Our results revealed that serum osmolality, Na+, and Cl- concentrations showed a similar decreasing trend after salinity stress at the first 2 h and then increased after 8 h. In particular, the Na+/K+-ATPase alpha 1-isoform (Tonka a1) rapidly responded to changes in salinity levels. In the gills, the expression of Tonka a1 was markedly upregulated at 2 h in all the experimental groups (0 parts per thousand, 10 parts per thousand, 20 parts per thousand, and 40 parts per thousand). In the kidney, Tonka a1 expression in these experimental groups tended first to increase but then decreased, with its values peaking at 2 h, 4 h, and 8 h, respectively. In the intestine, Tonka a1 responded rapidly to salinity changes and then changed dramatically within 4 h under salinity stress. The Na+/K+-ATPase activity was also affected by the acute salinity stress, and it was higher in the 10 parts per thousand and 40 parts per thousand groups than in the control group (0 h). Interestingly, Na+/K+-ATPase activity was lowest in the 20 parts per thousand group. Our results show the various physiological response of T. ovatus under acute salinity stress and demonstrate that under such conditions, Na+/K+-ATPase is primarily involved in the osmoregulation required to maintain homeostasis in this species.