Ascus
sexual spore-bearing cell produced in ascomycete fungi
An ascus (from Ancient Greek ἀσκός (askós) 'skin bag, wineskin'; pl.: asci) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or species can occur in numbers of one (e.g. Monosporascus cannonballus), two, four, or multiples of four. In a few cases, the ascospores can bud off conidia that may fill the asci (e.g. Tympanis) with hundreds of conidia, or the ascospores may fragment, e.g. some Cordyceps, also filling the asci with smaller cells. Ascospores are nonmotile, usually single celled, but not infrequently may be coenocytic (lacking a septum), and in some cases coenocytic in multiple planes. Mitotic divisions within the developing spores populate each resulting cell in septate ascospores with nuclei. The term ocular chamber, or oculus, refers to the epiplasm (the portion of cytoplasm not used in ascospore formation) that is surrounded by the "bourrelet" (the thickened tissue near the top of the ascus).
“Ascus” enters the record as sexual spore-bearing cell produced in ascomycete fungi. Crown Archives preserves that source wording while asking what Ascus, sexual and spore-bearing can confirm, complicate or overturn.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated May 19, 2025. The linked authority identifier is Q723425. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Ascus” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.