Changing in Plasma Factors in Sobaity, Sparidentex hasta in Different Environmental Salinities

144 juvenile Sobaity, Sparidentex hasta, after acclimation to laboratory conditions in sea water (40ppt) for one week, sea water was replaced with different salinities (5, 20 and 60ppt) and seawater (40ppt) as control. Samplings were performed at 6 and 12 hours, 1, 2, 7 and 14 days after the time of changing in environmental salinities. Blood samples were collected for plasma cortisol, glucose and electrolytes analysis. According to the results, plasma levels of cortisol showed significant increases in 5 and 60 ppt environment in relation to control and 20ppt groups 12 hours from the beginning of the experiment. However in 24h samples up to the end of the experiment (14days) there were no significant differences among treatments. Plasma glucose levels showed a significant increase only at 12h sampling time in relation to 6 and 24hours in fish adapted to 5 and 60ppt. Plasma Ca++ concentrations had no significant changes during experiment. Plasma Mg++ amounts decreased significantly in 5 and 20 ppt groups in relation with control at 24 h sampling time. In conclusion, cortisol has important role in adaptation to both 5 and 60ppt at the beginning of the exposure, because of its significant increase at just 12 hours in 5 and 60 ppt than the controls, but the role of cortisol has been replaced with other changes in osmoregulatory related tissues and cells according to the plasma cortisol amounts in 5 and 60ppt that returned to the basic levels.