Ultrastructural study of epitheliocystis organisms from gill epithelium of the fish Sparus aurata (L.) and Liza ramada (Risso) and their relation to the host cell

Abstract

Abstract. Ultrastructural study of epitheliocystis organisms from gills of Sparus aurata (L.) and Liza ramada (Risso) revealed in each fish a new form of the organism which differed from epitheliocystis organisms previously described. In their size range, the presence of a plasma membrane, a trilaminated cell wall and a central nucleoid, these organisms resembled chlamydial organisms (PLT). However they differed from them in the following respects: in both species several morphological forms were recognized; hyphae or mycelium‐like forms and individual units, not comparable to any of the successive units described for Chlamydia organisms. Both organisms were contained within an inclusion in the host cell, but in epitlieliocysts from S. aM7‐ata apparently intracytoplasmic forms were also observed. Ultrastructural studies of the cytoplasmic wall of the epitheliocystis inclusion in S. aurata suggest that the epitheliocystis cyst remains contained in a single unruptured hypertrophied cell, while in i. ramada the final cyst is formed through the coalescence of several epithelial cells.