HEMOLYMPH CELL-TYPES OF THE MUSSEL MYTILUS-GALLOPROVINCIALIS

Two types of circulating hemocytes were identified in Mytilus gallopro vincialis hemolymph: hyalinocytes and granulocytes. The hyalinocytes a re agranular cells and show a central nucleus surrounded by relatively small cytoplasm. The granulocytes are larger than hyalinocytes and ha ve smaller nuclei. Three classes of granulocytes (acidophilic granuloc ytes, basophilic granulocytes and granulocytes containing both types o f granules) were distinguished based on staining properties of their c ytoplasmic granules. At the ultrastructural level, the hyalinocytes sh ow characteristics of undifferentiated cells. The granulocytes are mor e differentiated and have membrane-limited cytoplasmic granules. Some granulocytes contain only small granules; others have numerous large g ranules and some of them contain a mix of granule sizes. Density gradi ent centrifugation allowed the separation of acidophilic granulocytes from the other types. Immunocharacterization demonstrated that the gra nulocytes are an antigenically heterogeneous population.