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Diseases of Aquatic Organisms

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DAO 30:209-215 (1997)  -  doi:10.3354/dao030209

Differential phagocytic ability of the circulating haemocyte types of the carpet shell clam Ruditapes decussatus (Mollusca: Bivalvia)

Carmen López1, María J. Carballal1, Carlos Azevedo2, Antonio Villalba1

1Centre of Marine Research, Ministry of Fisheries and Aquaculture of Galicia, POB 208, E-36600 Vilagarcía de Arousa, Pontevedra, Spain
2Department of Cell Biology, Institute of Biomedical Sciences, University of Porto, P-4000 Porto, Portugal

Phagocytosis of foreign materials by haemocytes is an important aspect of the internal defence of bivalve molluscs. Two main haemocyte types can be distinguished in the haemolymph of the clam Ruditapes decussatus: granulocytes and hyalinocytes. The ability of clam haemocytes to phagocytose zymosan particles, Vibrio P1 cells and trophozoites of the protistan parasite Perkinsus atlanticus was demonstrated by means of in vitro assays. However, clam haemocytes did not phagocytose P. atlanticus zoospores in the assays. Granulocytes showed the highest phagocytic capacity in each assay. Phagocytic capacity of haemocytes was not significantly affected by clam age. An ultrastructural study of phagocytosis showed the following sequence of events: engulfment of particles by pseudopods, formation of a phagocytic vacuole, fusion of lysosomes with the phagocytic vacuole, and digestion of the particles giving rise to residual bodies that might be discharged.

Ruditapes decussatus · Haemocytes · Phagocytosis · Vibrio P1 · Perkinsus atlanticus

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