In vitrostudy of phagocytic ability ofMytilus galloprovincialisLmk. haemocytes

In vitroassays were performed to assess the phagocytic ability of mussel haemolymph cell types. Among the haemocyte types, the granulocytes showed an important phagocytic activity whereas the hyalinocytes did not, thus indicating that mussel haemocytes are functionally heterogeneous. Phagocytic activity of acidophilic granulocytes was higher than basophilic ones. Ultrastructural study showed thatVibrioP1 cells were internalised in phagosomes and then digested. As a result of the digestive process, concentric lamellae and other degraded materials were produced inside the phagosomes, and non degraded materials gave rise to residual bodies which could be discharged from the cells. Similar events were observed in the phagocytic process of zymosan particles. The study of influence of temperature on phagocytosis activity revealed that the percentage of phagocytic cells was lower at 10° C than at 20° C and 30° C. Phagocytosis activity was higher in the assays performed at 15 ppt than those at 25 ppt and 36 ppt. No significant differences on percentage of phagocytic cells were found between young and adult mussels. Generation of superoxide anion by haemocytes using zymosan as a phagocytosis stimulant was demonstrated through the nitroblue tetrazolium reduction test.