Regulation of Volumes of the Muscle, Liver, and Brain Erythrocytes in Crucian Carp Carassius auratus (Cyprinidae) in Response to Increase in the Osmotic Concentration in Blood Plasma

Abstract

In crucian carp Carassius auratus maintained in fresh water, osmotic concentrations in the blood plasma, muscles, liver, cerebrospinal fluid, and brain are in equilibrium with each other. In freshwater and at water salinity of 11.5 g/L, the osmotic concentration in the erythrocytes is significantly higher relative to blood plasma, which produces hydrostatic pressure inside the red blood cells. At the critical water salinity, osmotic concentration in the blood plasma of crucian carp increases owing to electrolytes by 44.3%, while it increases in erythrocytes, muscles, liver, cerebrospinal fluid, and in brain by 20.6−36.3%; the deficiency of electrolytes in these tissues is compensated by accumulation of the organic osmolytes. In the fish within the zone of critical salinity, sodium and potassium ions participate in the regulation of the volumes of erythrocytes and liver cells, while only sodium ions participate in the regulation of the volumes of muscles and brain. At critical salinity, crucian carp erythrocytes and muscle cells do not restore their volumes to the level typical for the fish in fresh water.