Adaptive alterations on gill Na+, K+-ATPase activity and mitochondrion-rich cells of juvenile Acipenser sinensis acclimated to brackish water

Abstract

Understanding the physiological changes and osmoregulatory strategy is critical for anadromous species to adapt to large changes between freshwater and marine environments. In this study, juvenile Chinese sturgeon (Acipenser sinensis) were acclimated for 2 months to freshwater (FW, c. 0‰) and brackish water (BW, 15‰). Blood was assessed for changes in osmolality and ions. Gill tissue was assayed for Na(+), K(+)-ATPase (NKA) activity and immunohistochemical analysis on mitochondria-rich cells (MRCs). Serum osmolality and ions concentrations (Na(+), Cl(-) and K(+)) examined, except K(+), increased significantly in those specimens adapted to BW. However, the variations were within the range of effective hyperosmotic adaptation. The specific activity of gill NKA of juveniles adapted to BW was significantly higher (c. 1.6 times) than that of fish adapted to FW. MRCs were mainly presented in the interlamellar region of the filament and at the base of the lamella in either FW- or BW-acclimated individuals. In BW, the number and size of MRCs on filaments greatly increased. However, there was no significant difference in the number and size of the MRCs at the lamella region. Results show that juvenile Chinese sturgeon keep osmotic homeostasis in hyperosmotic environments by increasing gill NKA activity and MRCs' size and number, which is similar to other sturgeons and euryhaline teleosts.

The positive effects of taurine on growth performance, immunohaematological parameters and stress response of farmed beluga ( Huso huso ) in both fresh water and brackish water

“…In another study on Chinese sturgeon (Omn, 190 g), osmolality, sodium, chloride increased and potassium decreased in the serum of fish farmed in BW (15 ppt) as compared with FW (Zhao et al, 2016).…”

“…These results were compatible with our data showing that increasing osmolality and inorganic ions are strategies to cope with salinity. Zhao et al (2016) mentioned that elevated serum osmolality in sturgeon of this size/age may be normal and does not necessarily mean the occurrence of a stressful situation. In our study, higher growth in BW as compared to FW indicated that fish had no problem and could do salinity acclimation well.…”