Journal of Comparative Physiology B

, Volume 179, Issue 3, pp 383–390 | Cite as

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

Original Paper


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.


Green sturgeon Salinity acclimation Tissue microarray NKCC SF Bay-Delta 



Distinct population segment


Tissue microarray


Laser scanning cytometry


Na+, K+-ATPase


Na+, K+, 2Cl co-transporter


Vacuolar-type H+-ATPase


Mitochondrion-rich cell


Grams per liter


Degrees celsius






Estuary water


SF Bay water





This work was supported by a CALFED SeaGrant postdoctoral fellowship awarded to BAS, and a CALFED Science program grant (SP2006-1035) awarded to DK. We would like to sincerely acknowledge Serge Doroshov, Silas Hung, Robert Kaufmann, and Joel van Eenennaam for their successful effort at spawning green sturgeon in captivity. We also would like to thank Paul Lutes and Erik Hallen of the Center for Aquatic Biology, and Aquaculture, Enio Sanmarti, Amanda Schwabe, and Cesar Morales of the Department of Animal Science, as well as Christa Woodley and Joseph Cech Jr in the Department of Wildlife, Fish, and Conservation Biology at UC Davis.


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.Department of Animal ScienceUniversity of California, DavisDavisUSA

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