Calcium regulation in wild populations of a freshwater cartilaginous fish, the lake sturgeon Acipenser fulvescens

Lake sturgeon, Acipenser fulvescens, are one of a few species of cartilaginous fishes that complete their life cycle entirely in freshwater. Sturgeons maintain very low concentrations of circulating calcium (Ca 2+) compared with other vertebrates, and therefore, face unique challenges in regard to C...

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Published in:Comparative biochemistry and physiology. Part A, Molecular & integrative physiology Molecular & integrative physiology, 2009-12, Vol.154 (4), p.437-450
Main Authors: Allen, Peter J., Webb, Molly A.H., Cureton, Eli, Bruch, Ronald M., Barth, Cameron C., Peake, Stephan J., Anderson, W. Gary
Format: Article
Language:English
Subjects:
Acipenser
Acipenser fulvescens
Animals
Calcium
Calcium - metabolism
Calcium - urine
Cartilaginous
Estradiol
Estradiol - blood
Female
Fishes - metabolism
Fishes - physiology
Fresh Water
Freshwater
Ion regulation
Male
Phosphate
Phosphates - urine
Reproduction
Sturgeon
Testosterone - analogs & derivatives
Testosterone - blood
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Summary:Lake sturgeon, Acipenser fulvescens, are one of a few species of cartilaginous fishes that complete their life cycle entirely in freshwater. Sturgeons maintain very low concentrations of circulating calcium (Ca 2+) compared with other vertebrates, and therefore, face unique challenges in regard to Ca 2+ regulation, which are likely to be magnified during vitellogenic stages of the reproductive cycle. In the present study, Ca 2+ concentrations and associated hormones of female and male lake sturgeon were examined in two wild populations, and were related to reproductive stage. In both populations, free, bound and total Ca 2+ were low, peaking in mid-late vitellogenic females. Internal Ca 2+ and phosphate (PO 4 3−) concentrations were inversely related to environmental concentrations, suggesting that these ions are preferentially retained and that mechanisms for mobilization are up-regulated under diminished environmental concentrations. Plasma 17β-estradiol, 11-ketotestosterone and testosterone, peaked in mid-late vitellogenic females, while the androgens peaked in spawning males. Urine Ca 2+ was more tightly regulated than other divalent ions and decreased in spawning fish. Therefore, the increases in free plasma Ca 2+, the very low circulating concentrations of free and total Ca 2+, and the increase in PO 4 3− and bound Ca 2+ in low Ca 2+ environments indicate unique adaptations to Ca 2+ regulation in the lake sturgeon.
ISSN:1095-6433
1531-4332
DOI:10.1016/j.cbpa.2009.07.014