Electron Microscopic Analysis of Tunicate { Halocynthia roretzi ) Hemocytes

Hemocytes from hemolymph of the tunicate, Halocynthia roretzi were investigated by transmission electron microscopy (TEM). Nine types were identified according to their ultrastructural characteristics: phagocytes or macrophages (PH cells), granulocytes with small granules (GS cells), granulocytes with large granules (GL cells), vesicle-containing cells (VC cells), fibrous materialcontaining cells (FM cells), vacuolated cells type 1 (VA1 cells), vacuolated cells type 2 (VA2 cells), basophilic cells (BA cells) and lymphoid cells (LY cells). Among these hemocyte types VCcells and FM cells were unique and novel. One functional assay, i.e. phagocytic activity against sheep red blood cells (SRBC) and rat red blood cells (RRBC) was developed. This investigation resulting from improved fixation has served as the basis for standardizing hemocyte types and for defining future analyses that can be used in functional assays.