Electron microscopy on a nematode-trapping fungus, Acaulopage pectospora

Trapping organs of Acaulopage pectospora Drechsler, a nematode-destroying fungus, were examined by electron microscopy at various stages of infection. The trapping organs arise from sparsely developed nonseptate hyphae as short, lateral branches, each with a slightly inflated terminal knob. Nematodes arc captured by adhesive secreted from the knob. Electron microscopy revealed the following ultrastructural aspects: (i) the trap's cytoplasm is occupied by large electron-dense vesicles (0.5–0.9 μm) before secretion of the adhesive; (ii) the secreted adhesive derived from the large vesicles has a high electron density and contains a number of bubbles; (iii) the cell wall of the traps becomes doubled after the secretion of adhesive and an aliquot of the adhesive remains in the intervening space between the outer and inner cell wall; (iv) the outer wall of the terminal knob exhibits a rimose appearance. Ultrastructural evidence indicates that Acaulopage pectospora is very similar to Zoophagus insidians Sommerstorff.