Genus of lichens
Astrothelium is a large genus of corticolous (bark-dwelling) lichens in the family Trypetheliaceae. The genus is characterized by a corticate thallus and diverse ascomata structures, which can be simple, aggregated, or forming ;dfn id="" ;pseudostromata ;/dfn ;. "Astrothelium" is also notable for the ;dfn id="" ;carbonized ;/dfn ; walls of its ascomata, the so-called " ;dfn id="" ;textura intricata ;/dfn ;" (i.e., tightly interwoven) arrangement of cells in these walls, and various forms of ;dfn id="" ;distoseptate ;/dfn ;, transparent spores.
Taxonomy.
The genus was circumscribed in 1824 by German botanist Franz Gerhard Eschweiler, with "Astrothelium conicum" assigned as the type species.
Description.
The thallus, or the vegetative body of "Astrothelium", is ;dfn id="" ;corticate ;/dfn ;, meaning it is covered by a protective ;dfn id="" ;cortex ;/dfn ;. The ascomata, which are the fruiting bodies containing the reproductive spores, can appear in various forms such as simple, aggregated, or forming ;dfn id="" ;pseudostromata ;/dfn ;. These structures often differ in their composition and colour, and can be used as ;dfn id="" ;characters ;/dfn ; to distinguish between species. The ascomata can range from being immersed within the thallus to prominently displayed on the surface. The ostioles, or small openings that allow the release of spores, can be located at the apex or eccentrically on the ascomata and may appear as either simple or fused structures.
"Astrothelium" is also notable for its ascomatal wall, which is made up of hyphal cells and is typically carbonized. The wall features a ;dfn id="" ;textura intricata ;/dfn ;, a term used to describe a tightly interwoven arrangement of cells.
Within the ;dfn id="" ;hamathecium ;/dfn ;, the tissue that houses the asci (spore-producing structures), the cells are either clear or filled with oil droplets. The ;dfn id="" ;ascospores ;/dfn ;, which are the sexual spores responsible for reproduction, are ;dfn id="" ;distoseptate ;/dfn ; and hyaline in appearance. They can also exhibit a variety of forms, including transversely septate or ;dfn id="" ;muriform ;/dfn ;, reflecting their segmented or multi-cellular nature.
Species.
As of January 2024[ [update]], Species Fungorum accepts 267 species in "Astrothelium".
References.
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