Electron microscopy of an endoparasitic fungus, Gonimochaete pyriforme, infecting nematodes

Abstract

Gonimochaete pyriforme Barron was studied using the electron microscope. Protoplasm in the pyriform-shaped aplanospore is filled with electron-dense vesicles (0.1–0.3 μm) except at the base where it is vacuolated. The globose knob at the apical end of the spore is covered with a very thin adhesive layer (ca. 0.1 μm) whose electron density is slightly enhanced by ruthenium red staining but which does not show a fibrillose appearance. After attachment to the nematode's cuticle, a narrow germ tube (0.15 μm) arises from the globose knob and penetrates through the adhesive layer and the host's cuticle into the nematode body. The adhesive knob of the aplanospore in G. pyriforme is very similar in ultrastructure to the encysted zoospore of Myzocytium humicola Barron and Percy in the Lagenidiales after the cyst has germinated.