Effects of acclimation to high environmental temperatures on intermediary metabolism and osmoregulation in the sub-Antarctic notothenioid Eleginops maclovinus

Abstract

Eleginops maclovinus is a sub-Antarctic fish endemic to the South American coast and is a monotypic species of the Eleginopidae family. A scarce amount of scientific information exists regarding the effects of temperature on E. maclovinus physiology. In this study, E. maclovinus specimens were acclimated for 2 weeks at 10 °C (control), 14, and 18 °C. Posterior assessments were performed for the intermediary metabolism of carbohydrates, lipids, and amino acids (in the plasma, liver, gills, and kidney) and on the osmoregulatory capacity [plasma osmolality and gill, kidney, and foregut Na+, K+-ATPase (NKA) activities]. In the plasma, only lactate and total amino acid levels were affected by the temperature. NKA activity presented a linear relationship with the increased temperatures. The liver exhibited no change in the carbohydrates metabolism, but the glycogen/glucose metabolite levels did differ. Amino acid metabolism showed a direct relationship between temperature and GDH and Asp-AT activities, and an inverse relationship between temperature and Ala-AT activity. Lipid metabolism was similar to Ala-AT. In the gills, carbohydrate metabolism (G6PDH and HK activities) presented a direct relationship with the increased temperatures. In the kidney, carbohydrate metabolism (only G6PDH activity) was greater at higher temperatures, and amino acid metabolism (GDH activity) showed a direct relationship with temperature. Lipid metabolism (G3PDH activity) was greatest at 14 °C, presenting significant differences compared to 10 °C. The obtained results suggest that E. maclovinus can acclimate to the projected thermal increase of climate change, with a reorganization of the intermediary metabolism components being tissue-dependent and osmoregulatory effects being affected by NKA activity and greater rates of nitrogenous waste extrusion.