Daily patterns of blood electrolytes in sea bass adapted to different osmotic media at different times of the year

Juvenile sea bass were kept at three different salinities during two months. Ca2+, Mg2+, Na+and K+were determined in blood samples obtained at the beginning and at the end of the experimental period. Sea bass have a marked ability to regulate plasma electrolytes over a wide range of salinities. Different salinities induce acute changes in the rhythmicity levels and amplitude of plasma electrolytes. We observed a variation of the circadian rhythms in plasma electrolytes. On a seasonal basis, different photoperiods induce a plasma shift of the circadian rhythm of plasma electrolytes of seas bass adapted to seas water. The findings are discussed from the point of view of osmoregulation linked with the reproductive cycle of sea bass.