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Toxocysts of the genus Pleurotus are blastoconidia-like ovoid structures surrounded by a liquid droplet containing a toxin that paralyzes nematodes. This study investigated toxocyst development using a strain S396 of Pleurotus cystidiosus subsp. abalonus (subgen. Coremiopleurotus). The surface of the liquid droplet was found to be an elastic envelope. When a nematode touches the toxocyst, the envelope adheres to the worm and bursts. Toxocysts are induced simultaneously with coremia formation in the absence of nematodes and developed only from aerial hyphae in which nuclear division had ceased. In the early stage of toxocyst development, liquid springs repeatedly from the tip of the sterigma-like stipe before ovoid (blastoconidium-like structure) formation. A certain substance in the liquid might polymerize to form the envelope while the ovoid simultaneously budded in the droplet. The nucleus tends to locate near the toxocyst, especially in early stage of toxocyst development. Each dikaryotic cell predominantly formed one or two toxocyst(s) while each monokaryotic cell predominantly formed one. In rare cases, a nucleus existed in the toxocyst, suggesting the possibility that the toxocyst is a vestigial blastoconidium.

This study was carried out to elucidate the poorly understood processes of arthroconidiation through coremium formation using Pleurotus cystidiosus subsp. abalonus. The coremia exclusively produced dikaryotic arthroconidia with the remnant of a clamp connection. Cells in the subapical zone of the hyphal bundle reduced their length by division before arthroconidiation. Approximately 400000 arthroconidia were produced by a coremium in 1 day, with constant productivity over a 2-week period. Continuous cell extension and division in the coremium stipe supplied cells for arthroconidiation at the coremium apex, which is surrounded by a liquid droplet (coremioliquid). Maintenance of moisture with coremioliquid was necessary for arthroconidiation. The coremioliquid formation was performed by active liquid transportation in the hyphae, a process that was blocked by the microtubule depolymerization agent thiabendazole.