Physiology of seawater acclimation in the striped bass,Morone saxatilis (Walbaum) |
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Authors: | Steffen S. Madsen Stephen D. McCormick Graham Young Jeanette S. Endersen Richard S. Nishioka Howard A. Bern |
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Affiliation: | (1) Department of Integrative Biology, Cancer Research Laboratory and Bodega Marine Laboratory, University of California, Berkeley, California, 94720, U.S.A.;(2) Present address: Institute of Biology, Odense University, Campusvej 55, DK-5230, Odense M, Denmark;(3) Present address: Anadromous Fish Research Center, U.S. Fish and Wildlife Service, P.O. Box 796, Turners Falls, MA, 01376, U.S.A.;(4) Present address: Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand |
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Abstract: | Several experiments were performed to investigate the physiology of seawater acclimation in the striped bass, Morone saxatilis. Transfer of fish from fresh water (FW) to seawater (SW; 31–32 ppt) induced only a minimal disturbance of osmotic homeostasis. Ambient salinity did not affect plasma thyroxine, but plasma cortisol remained elevated for 24h after SW transfer. Gill and opercular membrane chloride cell density and Na+,K+-ATPase activity were relatively high and unaffected by salinity. Average chloride cell size, however, was slightly increased (16%) in SW-acclimated fish. Gill succinate dehydrogenase activity was higher in SW-acclimated fish than in FW fish. Kidney Na+, K+-ATPase activity was slightly lower (16%) in SW fish than in FW fish. Posterior intestinal Na+,K+-ATPase activity and water transport capacity (Jv) did not change upon SW transfer, whereas middle intestinal Na+,K+-ATPase activity increased 35% after transfer and was correlated with an increase in Jv (110%). As salinity induced only minor changes in the osmoregulatory organs examined, it is proposed that the intrinsic euryhalinity of the striped bass may be related to a high degree of “preparedness” for hypoosmoregulation that is uncommon among teleosts studied to data. |
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Keywords: | striped bass osmoregulation Na+,K+-ATPase chloride cell intestinal water transport cortisol thyroxine |
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