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Diseases of Aquatic Organisms

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DAO 30:223-225 (1997)  -  doi:10.3354/dao030223

Some observations on an amoeba, destructive agent of the gills of Cerastoderma edule (Mollusca, Bivalvia)

Carlos Azevedo

Department of Cell Biology, Institute of Biomedical Sciences and IMAR - Institute of Marine Research, University of Oporto, Largo A. Salazar no. 2, P-4050 Porto, Portugal

The fine structure of an amoeba, a destructive agent found in sub-epithelial tissues of the gills of Cerastoderma edule (Mollusca, Bivalvia), is described. The uninuclear amoeba reached a diameter of 18 to 20 µm, and contained a prominent nucleolus about 3 µm in diameter which seemed to be locus of active rRNA synthesis. Several dense extra-nucleolar bodies found at the periphery of the nuclear envelope may represent a nucleolar segregation, i.e. a structure similar to the nucleolus-like bodies. The appearance of these structures suggests they may be involved in the continuous transport of ribonucleoproteins. Histopathology associated with these cells revealed haemocytic infiltration and necrotic cells, which were interpreted as a sign that this amoeba was pathogenic to the host.

Ultrastructure · Amoeba · Destructive agent · Bivalves

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