Ultrastructure of the ascospore formation of Arthroderma simii

Ascospore formation of Arthroderma simii was observed using electron microscopy. Using scanning electron microscopy, many round asci were observed inside the gymnothecia obtained by 4 weeks of incubation after mating. Ascospores were produced inside the asci, then discoid-shaped mature ascospores were observed through the degenerate and disrupted ascus cell wall. Disseminated ascospores were observed outside the gymnothecium 7 weeks after inoculation. Using transmission electron microscopy, the enveloping membrane system of two unit membranes invaginated and delimited the cytoplasm. The inner membranes were found to have changed into ascospore plasma membranes, whereas the outer membranes and intercisternal space were changed into ascus cell wall. The subcellular events of ascospore formation were found to be essentially similar to those of other dermatophytes.