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

Abstract

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.

Keywords

Green sturgeon Salinity acclimation Tissue microarray NKCC SF Bay-Delta 

Abbreviations

DPS

Distinct population segment

TMA

Tissue microarray

LSC

Laser scanning cytometry

NKA

Na+, K+-ATPase

NKCC

Na+, K+, 2Cl co-transporter

VHA

Vacuolar-type H+-ATPase

MRC

Mitochondrion-rich cell

g/l

Grams per liter

°C

Degrees celsius

FW

Freshwater

SW

Seawater

EST

Estuary water

BAY

SF Bay water

NEM

N-Ethylmaleimide

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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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