ABSTRACT: 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.

KEY WORDS: Ultrastructure · Amoeba · Destructive agent · Bivalves

Published in DAO Vol. 30, No. 3 (1997) on September 30
ISSN: 0177-5103. Copyright © Inter-Research, Oldendorf/Luhe, 1997