CHYTRIDIOMYCOTA Olpidium vermicolaEndobiotic, Monocentric, Holocarpic The posteriorly uniflagellate zoospore is attracted to a nematode egg by chemical secretions, encysts on its surface and penetrates to the interior (endobiotic) where it produces one (monocentric), large, nonseptate, multinucleate thallus that fills the egg. All the protoplasm inside the thallus then cleaves around the nuclei (holocarpic) to form zoospores which escape through evacuation (exit) tubes at one or both ends of the thallus which has now converted to a zoosporangium. One zoospore infection results in one thallus in the egg that matures to form a zoosporangium. Three zoospores attacking an egg will resullt in three separate thalli.
Apparently multiple infections trigger a signal to produce restings spores. Multiple infections result in many infection thalli, some or all of which produce resting spores instead of zoosporangia.
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