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

Abstract

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‰, 10‰, 20‰, and 40‰ to investigate its physiological and molecular responses. Our results revealed that serum osmolality, Na + , and Clconcentrations 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 α1) rapidly responded to changes in salinity levels. In the gills, the expression of Tonka α1 was markedly upregulated at 2 h in all the experimental groups (0‰, 10‰, 20‰, and 40‰). In the kidney, Tonka α1 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 α1 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‰ and 40‰ groups than in the control group (0 h). Interestingly, Na + /K + -ATPase activity was lowest in the 20‰ 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. changes in concentrations of sodium (Na + ), chloride (Cl-), potassium (K + ), and serum osmolality (Shui et al., 2018). Salinity changes also has a direct influence on hematological and biochemical variables, such as growth hormone, cortisol and thyroxine, which provides essential information regarding clinical status and energy of fish (Arnason et al., 2013).Osmoregulation is the main process by which aquatic animals respond to changes in salinity, especially in fish . Osmolality increases with increased salinity during the adaptation (Schmitz et al., 2017). Euryhaline teleost fishes regulate and maintain their plasma ionic composition and osmotic concentration following changes in the environmental salinity (Yamaguchi et al., 2018). In a hypotonic environment, to maintain ionic homeostasis, teleosts absorb ions through the gills and intestine and excrete excess water, and filter solute to form diluted urine through renal reabsorption. In contrast, in hypertonic environments, teleosts passively lose water and gain excess ions. Therefore, teleosts actively secrete ions and drinking water to maintain homeostasis (Urbina et al., 2013). However, the acclimation to changing environmental salinity is a complex process involved a set of physiological and molecular responses based on the function of several osmoregulatory organs (e.g., gills, kidney and intestine), such as active ion transport of concentration gradients using various molecular ...