MORPHOLOGICAL AND CYTOCHEMICAL CHARACTERISTICS OF HEMOCYTES OF MERETRIX LUSORIA (Bivalvia: Veneridae)

MORPHOLOGICAL AND CYTOCHEMICAL CHARACTERISTICS OF HEMOCYTES OF MERETRIX LUSORIA (Bivalvia: Veneridae)

To help understand the cellular defense mechanism of Meretrix lusaria hemocytes withdrawn from the posterior adductor muscle were classified on the basis of their morphology, cytochemistry and phagocytic characteristics under a light microscope. Two cell types, granulocytes and hyalinocytes, were found in the hemoctyes. Granulocytes, 13.1±2.6㎛ 16.2±3.3㎛ in size, contain some large or small eosinophlic granules in their cytoplasm. Granuloctyes were subclassified into small eosinophilic granulocytes and large eosinophilic granulocytes based on the size of the granules. Granulocytes were positive to PAS, acid phosphatase and phenol oxidase but negative to Sudan black B. Granulocytes showed posphagocytic activity to zymosan particles. Hyalinocytes, that is, agranulocyles that did not contain granules in the basophilic small cytoplasm, were 11.3 :t 2.8 ~m in diameter and had an oval or irregular nucleus at the center of the cell. The ratio of nucleus to the cytoplasm was very high. Hyalinocytes were weakly positive to PAS but negative to Sudan black B and acid phosphatase. Phenoloxidase acivity was not detected in hyalinocytes. Hyalinocytes phagocytized zymosan particles but the activity was very low compared with that of granulocytes.