Effects of gradual salinity increase on osmoregulation in Caspian roach Rutilus caspicus |
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Authors: | Malakpour Kolbadinezhad S Hajimoradloo A Ghorbani R Joshaghani H Wilson J M |
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Affiliation: | Gorgan University of Agricultural Sciences and Natural Resources (GUASNR), College of Fisheries and Environment, Shahid Beheshti Ave, Gorgan 49138-15739, Iran. |
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Abstract: | This study was carried out to determine the effects of gradual salinity increase on osmoregulatory ability of the Caspian roach Rutilus caspicus, under conditions which mimic stocking conditions of hatchery-raised fish. Initially, 30 juvenile fish (mean ± S.D. 3.20 ± 0.34 g) were transferred to 20 l circular tanks, in which salinities were changed in a stepwise fashion, from 0 to 5, 10 or 15 at 48 h intervals. The fish at salinity 15 were held for an additional 48 h at this salinity. Forty-eight hours after salinity transfer, survival rate, haematocrit, plasma Cl(-) , Na(+) and K(+) concentrations, osmolality and gill Na(+) /K(+) -ATPase (NKA) activity were measured. The only effect of exposure to 5 was a significant reduction in haematocrit compared to the freshwater control group. Exposure to salinity 10 raised haematocrit, Cl(-) and Na(+) concentrations and osmolality. At 48 h exposure to salinity 15, haematocrit, Cl(-) and Na(+) concentrations and osmolality were significantly higher than freshwater controls, and gill NKA activity was significantly lower, but the effect on NKA was no longer evident at 96 h exposure. There were no effects on survival. These results indicate that R. caspicus juveniles experience an initial non-lethal iono-osmotic perturbation following salinity increase but can adapt to brackish water at salinity 15. |
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Keywords: | brackish water gill Na+/K+‐ATPase NKA osmolality |
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