HAEMOCYTES OF THE FRESHWATER MUSSEL, DREISSENA POLYMORPHA PALLAS: CYTOLOGY, CYTOCHEMISTRY AND X-RAY MICROANALYSIS

Abstract

The haemocytes of Dreissena polymorpha were examined by light and electron microscopy. On the basis of cytology and cytochemistry, three main haemocyte types were identified' agranular haemocytes or hyalinocytes, granular haemocytes represented by the neutrophihc granulocytes and the large basophilic haemocytes (LBH). These cell types correspond to the haemocyte classification scheme commonly established for bivalve molluscs: the granular haemocytes (granulocytes) and the nongranular haemocytes (hyalinocytes) Hydrolytic enzyme activities, such as acid phosphatase and non-specific esterases, were demonstrated within the cytoplasmic inclusions of the neutrophilic granulocytes and the LBH- f} glucuronidase activity was also detected in the cytoplasnuc granules and vacuoles of the LBH. Ultrastructural and phosphatase reactivity was revealed within the matrix of the cytoplasmic granules. The presence of a range of hydrolytic enzymes, including hydrolases and glycosidases in the granules, suggests that these organelles belong to the lysosomal system X-ray microanalysis showed the presence of P, S, Si, Mg, Ca and heavy metals such as Cu, Zn, Pb and Fe in the matrix of the granules of the haemocytes in a natural population of zebra mussels. The occurrence of trace metals sequestrated in the lysosomes suggests the involvement of the granular haemocytes in metal accumulation, transport and detoxication mechanisms.