Some haemato-immunological parameters in the mussel Perna perna

The aim of this study was to establish the normal pattern of some haemato-immunological parameters in the mussel Perna perna to serve as a reference for further studies using this species as a biological indicator of environmental contaminants. We investigated the morphology and cytochemistry of the circulating haemocytes of P. perna , their role in phagocytosis and superoxide anion production, their numbers and composition, the agglutinin concentration in the plasma and the presence of phenoloxidase activity. Two blood cell types, hyalinocytes (HY) and granulocytes (GR), were found in the haemolymph of P. perna . HY were agranular cells with a basophilic cytoplasm, whereas GR contained abundant eosinophilic granules. HY comprised approximately 60% of the blood cell types in the circulation. Both haemocyte types, but especially the GR were actively phagocytic and contained acid phosphatase. After stimulation with zymosan, the blood cells were able to reduce NBT to formazan, suggesting the generation of the superoxide anion. Glycogen was not histochemically detectable in either haemocyte type. The number of cells in circulation (THC) did not significantly vary with sex or size of the mussels (3,145·5 and 3,668·5 cells/mm3in males and females respectively). The mussel plasma had an agglutinating activity against different mammalian erythrocytes. A phenoloxidase activity was not encountered either in the haemocyte fraction or in the mussel plasma, even after induction with the protease trypsin or non-self molecules, such as LPS from Gram-negative bacteria and β-1, 3-glucans from fungi.