BALLISTOSPORIC CONIDIA IN BASIDIOBOLUS-RANARUM - THE INFLUENCE OF LIGHT AND NUTRITION ON THE PRODUCTION OF CONIDIA AND ENDOSPORES (SPORANGIOSPORES)

The process of endospore cleavage (sporangiospore formation) within wh at were originally ballistosporic conidia was examined with light and electron microscopy in two isolates of Basidiobolus ranarum. A pathoge nic isolate was obtained from skin ulcers on a frog (Davis isolate) an d a nonpathogenic isolate was obtained from toad feces (Toad isolate). Electron microscopy revealed that endospore formation was not the res ult of successive bipartitioning or progressive cleavage as previously described. Instead, the protoplasm of the ballistosporic conidium was bisected by a wall, thus dividing the conidium into one or more spora ngia within which endospores (sporangiospores) were delimited. The wal ls segregating the conidial cytoplasm into sporangia were continuous w ith the inner layer of the original conidial wall. As spores were dema rcated, some cytoplasmic debris was left in the space between the coni dial/sporangial walls and the spore walls. After a period of 16 hours of low light levels, turning on the laboratory lights stimulated the f ormation and discharge of conidia with a peak in conidial discharge 5- 6 hours later.