Phagocytic activity of scallop (Pecten maximus) haemocytes maintained in vitro

Haemocytes from the great scallop,Pecten maximus, were maintained for several weeksin vitroin media based on filtered natural and artificial seawater. Cell monolayers were achieved after washing and mechanical removal of aggregates. Haemocyte function was assayed by measuring phagocytosis, applying a double staining method allowing a simultaneous viewing of intracellular (phagocytosed) and extracellular bacteria by fluorescence microscopy. Phagocytosis was observed immediately after addition of bacteria, and the percentage of phagocytic haemocytes increased with increasing incubation periods. Similar phagocytic activities were measured in homologous haemolymph immediately after sampling, and in artificial medium after different incubation periods. Differences in the percentage of phagocytosing haemocytes were observed between individual scallops. Haemocytes with different morphology and fluorescence were observed.