Dehiscence and active spore release in pathogenic strains of the yeast Metschnikowia bicuspidata var. australis: possible predatory implication.

Strains of Metschnikowia bicuspidata var. australis, pathogenic to brine shrimp (Artemia salina), were observed to form asci which, upon reaching maturity, forcibly expelled their needle-shaped spores. The mechanical force responsible apparently originates from the formation of an ectoplasmic mucilage capable of exerting pressure over all of the ascus contents; when the apex of the peduncle ruptures, the ascospores are violently released. Cytochemical analyses indicated that the gel is a substance highly resistant to chemical and enzymatic hydrolysis. Its chemical nature is not known as yet. The morphogenetic events of this process are described, and its ecological implication, the possibility of active mechanical predation in yeast, is discussed.