Time-lapse photomicrography and electron microscopy on initiation of infection of nematodes by Dactylella ellipsospora

Abstract

Infection of nematodes by two strains of Datylella ellipsospora was observed using video photomicrography and electron microscopy. By light microscopy, each cell with adhesive knobs contained a number of particles that were distributed evenly before capture of a nematode. The cytoplasmic particles moved to and fro at random. At the moment when the knob cell came into contact with a nematode, the particles accumulated at the place where the cell wall of the knob stuck firmly to the nematode cuticle and exuded adhesive at the same time. The adhesive can be seen near the point of contact between the cell wall of the knob and the cuticle of the nematode. At that point, the knob cell produced an infection peg in most cases, and the cell showed a preference to invade the body of the nematode rather than the tail and head. During capture, accumulation of cytoplasmic particles was seen until infection-bulb formation began. In electron micrographs of ultrathin sections, most of the particles could be seen as electron-dense vesicles, 0.2–0.6μm in diameter. After attachment of the knob cell to the nematode cuticle, the vesicles were found to fuse with plasmalemma one after another to exude adhesive seen as an amorphous electron-dense substance.