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As a result, the ascus will contain four pairs of spores. Then the ascospores are released from the ascus. In many cases the asci are formed in a regular layer, the hymenium, in a fruiting body which is visible to the naked eye, here called an ascocarp or ascoma. In other cases, such as single-celled yeasts, no such structures are found.
There are 2000 identified genera and 30,000 species of Ascomycota. The unifying characteristic among these diverse groups is the presence of a reproductive structure known as the ascus, though in some cases it has a reduced role in the life cycle. Many ascomycetes are of commercial importance.
Ascus (Ancient Greek: Ἄσκος) was a giant from ancient Greek mythology, who in conjunction with Lycurgus of Thrace chained the god Dionysus and threw him into a river. The god Hermes (or, according to other tellings, Zeus ) rescued Dionysus, conquered (ἐδαμασεν) the giant, flayed him, and made a bag (ἄσκος) of his skin.
The ascus itself forms as a radiating spur branch at the top of the hook. Each nucleus divides, resulting in the formation of a pair of compatible nuclei, i.e. a dikaryon, in the ascus, which is now the penultimate space. Two sister nuclei remain, one in the basal cell and the other in the crozier tip.
Usnea filipendula – one of about 20,000 described species of lichen. The following outline provides an overview of and topical guide to lichens.. Lichen – composite organism made up of multiple species – a fungal partner, one or more photosynthetic partners, which can be either green algae or cyanobacteria, and, in at least 52 genera of lichens, a yeast. [1]
Many are free-living but there are some species that are parasites on other lichens, while one marine species always lives together with a leafy green alga. Several characteristics of the spore -bearing structures, the ascomata , define the family, including their perithecioid form–more or less spherical or flask-shaped, with a single opening ...
Pezizomycotina is the largest subdivision of Ascomycota, containing the filamentous ascomycetes and most lichenized fungi. It is more or less synonymous with the older taxon Euascomycota. [2]
The generic name polyascus (poly "many" + ascus "bag") refers to the typical presence of multiple external sac-like female bodies, known as externae. In Polyascus species, these originate from asexual reproduction.