Seasonal changes in blood cells of Arctic char (Salvelinus alpinus L.) from a high mountain lake

Seasonal changes in blood erythrocytes and lymphocytes were investigated in Arctic char from a remote high mountain lake at an altitude of 2344 m. Des pite striking seasonal differences of environmental conditions the erythroc yte numbers remained constant during the year. Lymphocytes, however, displa yed a distinct seasonal pattern with low abundance during the period of ice -cover (about 7 months) and high abundance in summer. During winter the cir culating blood contained lymphocytes with damaged organelles and membranes, and almost exclusively mature red cells with a high density. With rising w ater temperature in July/August (11 degreesC), however, high-density (old) cells almost disappeared, the proportion of immature cells dramatically inc reased, and the capacity to responding to handling stress decreased. We con clude that in summer the accelerated erythropoiesis (recruitment of red blo od cells) compensates for the reduced lifespan of red blood cells.