Age-Related and Seasonal Dynamics of Hemocyte Population in the Mussel <i>Crenomytilus grayanus</i> (Dunker, 1853)

Abstract

The cellular composition of the hemolymph of the mussel Crenomytilus grayanus is represented by hemoblasts, hyalinocytes, basophilic, neutrophilic and acidophilic granulocytes with a significant predominance of the latter. With the age of the mollusk, the average values of the size and granularity of hemocytes increased due to accumulation of granulocytes in the hemolymph (up to 100% of all cells) and their mature highly differentiated acidophilic forms (up to 99% of all cells); this indicates a decrease in the rate of renewal of the cell population. During the autumn period of sexual inertia, the number of cells in the hemolymph of mussels decreased with increasing age of mollusks but without any correlation with the shell size. However, in summer, during the spawning period, the concentration of hemocytes either did not change or increased with increasing body size, directly correlating with the number of young basophilic granulocytes. This correlation may indicate either a relationship between the number of hemocytes and the ability of mussels to reach large sizes, or a higher potency in aged mussels for emergency mobilization of the immune system in the summer season through rapid replenishment of the pool of circulating cells with subsequent redistribution of young and mature cell forms between hemolymph and the internal organs.