The Production of Planonts by Thin-walled Sporangia of the Fungus Coelomomyces indicus, a Parasite of Mosquitoes

Abstract

SUMMARY: Thin-walled sporangia of an African strain of Coelomomyces indicus dehisced in exposed drops of water in 1 to 2 days. Good aeration was necessary. During dehiscence granules in the sporangial contents became redistributed and a lateral bulge arose on the sporangial wall. A split opened at the crest of the bulge, and the sporangial contents cleaved into planonts. A vesicle emerged from the split, expanded, filled with planonts from within the sporangium, burst, and finally dissolved. The wall of the sporangium was initially two-layered, but a third amorphous layer continuous with the vesicle developed internally during dehiscence. Dividing nuclei were seen in the early stages of dehiscence. The nuclear membrane persisted during division and intranuclear spindle microtubules arose near differentiated pockets in the nuclear envelope adjoining the apparently unpaired centrioles. Shortly before cleavage, groups of lipid droplets in the sporangium became associated with each nucleus together with an apparently single elongated centriole. After cleavage, flagella were well developed, but the ribosomes were still dispersed throughout the cytoplasm of the planonts. They then became sequestered into large membrane-bounded nuclear caps. A single large mitochondrion was present in each planont, possibly arising by coalescence of several smaller ones. A lipid body adjoined each mitochondrion. The cytoplasm of each unliberated planont contained numerous cytoplasmic vesicles and a single crystalline body. An abnormal ‘9 + 1’ flagellum was seen.