Osmo- and ionoregulatory responses of green sturgeon (Acipenser medirostris) to salinity acclimation

• Published in: Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Vol. 179; no. 3; pp. 383 - 390
• Main Authors: Sardella, Brian A., Kültz, Dietmar
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.04.2009; Springer Nature B.V
• Subjects: Acclimatization; Acclimatization - physiology; Analysis of Variance; Animal Physiology; Animals; Apoptosis; Biochemistry; Biomedical and Life Sciences; Biomedicine; California; Caspases - metabolism; Endangered & extinct species; Enzymes; Fishes - physiology; Fresh Water; Human Physiology; Hydrogen-Ion Concentration; Laser Scanning Cytometry; Life history; Life Sciences; Microarray Analysis; Migratory species; Original Paper; Physiology; Proteins; Rivers; Salinity; Seawater; Sodium-Potassium-Exchanging ATPase - metabolism; Sturgeon; Water content; Water-Electrolyte Balance - physiology; Zoology; California; United States > US; Green sturgeon; SF Bay-Delta; Tissue microarray; NKCC; Salinity acclimation
• ISSN: 0174-1578; 1432-136X
• DOI: 10.1007/s00360-008-0321-5

The green sturgeon is a long-lived, highly migratory species with populations that are currently listed as threatened. Their anadromous life history requires that they make osmo- and ionoregulatory adjustments in order to maintain a consistent internal milieu as they move between fresh-, brackish-, and seawater. We acclimated juvenile green sturgeon (121 ± 10.0 g) to 0 (freshwater; FW), 15 (estuarine; EST), and 24 g/l (SF Bay water; BAY) at 18°C for 2 weeks and measured the physiological and biochemical responses with respect to osmo- and ionoregulatory mechanisms. Plasma osmolality in EST- and BAY-acclimated sturgeon was elevated relative to FW-acclimated sturgeon ( P  < 0.01), but there was no difference in muscle water content or abundance of stress proteins. Branchial Na + , K + -ATPase (NKA) activity was also unchanged, but abundance within mitochondrion-rich cells (MRC) was greater in BAY-acclimated sturgeon ( P  < 0.01). FW-acclimated sturgeon had the greatest NKA abundance when assessed at the level of the entire tissue ( P  < 0.01), but there were no differences in v-type H + ATPase (VHA) activity or abundance between salinities. The Na + , K + , 2Cl − co-transporter (NKCC) was present in FW-acclimated sturgeon gills, but the overall abundance was lower relative to sturgeon in EST or BAY water ( P  < 0.01) where this enzyme is crucial to hypoosmoregulation. Branchial caspase 3/7 activity was significantly affected by acclimation salinity ( P  < 0.05) where the overall trend was for activity to increase with salinity as has been commonly observed in teleosts. Sturgeon of this age/size class were able to survive and acclimate following a salinity transfer with minimal signs of osmotic stress. The presence of the NKCC in FW-acclimated sturgeon may indicate the development of SW-readiness at this age/size.