Nuclear bodies in the egg cells of a Gyrodactylus species (Platyhelminthes, Monogenea).

The presence and ultrastructure of distinctive nuclear bodies in a mature 'egg cell' of a Gyrodactylus sp. are described. These electron-dense granular bodies, which appear in section as open or closed rings or as a solid mass are not membrane-bound and lie in clusters close to the nucleolus. The nuclear bodies are compared with the nuclear-inclusion bodies previously reported in platyhelminths. The possible origin, significance and role of the nuclear bodies in this Gyrodactylus sp. are discussed.