| Arthothelium | |
|---|---|
 | |
| Arthothelium spectabile | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Arthoniomycetes |
| Order: | Arthoniales |
| Family: | Arthoniaceae |
| Genus: | Arthothelium A.Massal. (1852) |
| Type species | |
| Arthothelium tremellosum (Eschw.) A.Massal. (1852) | |
| Synonyms [1] | |
Arthothelium is a genus of lichen-forming fungi in the family Arthoniaceae. [2]
Arthothelium is a genus of crustose lichens, which can either be immersed (embedded within the substrate ) or superficial (growing on the surface). The thallus may spread freely or be confined to specific areas. The lichen's photobiont (the algae or cyanobacteria involved in its symbiosis) can vary, including types from the genus Trentpohlia , the family Chlorococcaceae, or may be absent altogether. [3]
The reproductive structures resemble apothecia, a common form of lichen fruiting body, and come in various shapes, from flat to convex, and may be elongated or star-like. These structures, known as the disc , range in colour from red-brown to black, and can sometimes have a frosted, powdery appearance ( pruinose ). A thalline margin , which in some lichens surrounds the fruiting body, is absent in Arthothelium. The exciple , a rim of tissue found in some lichen fruiting bodies, is also absent. [3]
The uppermost layer of the apothecium, the epithecium , can be colourless, red-brown, or dark brown. Below this, the hymenium, where the spores develop, often turns blue when tested with iodine (I+). The hypothecium , the supportive tissue beneath the hymenium, is variable in thickness and ranges from dark red-brown to dark brown in colour. The hymenium contains filaments called paraphysoids , which are sparsely to densely branched and often have swollen, red-brown tips. [3]
The asci (spore-producing cells) are usually clavate (club-shaped) or ellipsoidal, containing eight spores. They are semi- fissitunicate , meaning they have two wall layers that split during spore release, and feature a large apical dome with a distinct ocular chamber. The ascospores are obovoid to ellipsoidal, colourless, and muriform , meaning they are divided by multiple internal walls, creating a brick-like pattern. This is a key distinguishing feature from similar genera like Arthonia , where the spores are only divided by transverse walls. [3]
Conidiomata (structures producing asexual spores) resemble those found in Arthonia. The genus generally lacks lichen products (secondary metabolites), in species found in Britain and Ireland, but elsewhere, species may contain xanthones or anthraquinones. [3]
Arthothelium typically grows on smooth bark in humid, undisturbed habitats, although it is rarely found on rock. The genus includes around 50 species and has a cosmopolitan distribution, with most species occurring in tropical regions. It is considered polyphyletic, meaning the genus likely includes species that do not share a common evolutionary ancestor, and further study is needed on its type species, Arthothelium tremellosum . [3]
As of October 2024 [update] , Species Fungorum (in the Catalogue of Life) accept 26 species of Arthothelium: [4]
The Arthoniales is the second largest order of mainly crustose lichens, but fruticose lichens are present as well. The order contains around 1500 species, while the largest order with lichenized fungi, the Lecanorales, contains more than 14000 species.
The Arthoniaceae are a family of lichenized, lichenicolous and saprobic fungi in the order Arthoniales. The Arthoniaceae is the largest family of Arthoniales, with around 800 species. Most species in Arthoniaceae belong in Arthonia which is the largest genus with 500 species. The second and third largest genus is Arthothelium with 80 species, and Cryptothecia with 60 species.
Bacidia is a genus of lichen-forming fungi in the family Ramalinaceae. The genus was circumscribed by Giuseppe De Notaris in 1846.
Ochrolechia is a genus of crustose lichens in the family Ochrolechiaceae. These lichens typically form uneven, often thick, crust-like growths on various surfaces and are characterised by their white to pale grey thalli, which may have a greenish tint. The genus has a long evolutionary history, with fossils dating back to the Paleogene period, about 34 million years ago. Ochrolechia species have disc-like apothecia, which are usually yellowish or brownish-pink and often covered with a fine white powdery coating. The genus is widely distributed and includes both common and rare species, with some found in extreme environments such as arctic and alpine regions. Ochrolechia lichens produce diverse secondary metabolites, including orcinol depsides, depsidones, and xanthones.
Cliostomum is a genus of lichenized fungi in the family Ramalinaceae. It has about 25 species.
Lecania is a genus of lichenized fungi in the family Ramalinaceae. The genus was circumscribed by Abramo Bartolommeo Massalongo in 1853. Lecania is widely distributed, especially in temperate regions, and contains about 64 species.
Micarea is a genus of lichen-forming fungi in the family Pilocarpaceae. The widely distributed genus contains 142 species and new species are described actively. Species in the genus are crustose lichens and their photobiont is a single-celled green alga.
Enterographa is a genus of lichens in the family Roccellaceae.
Mazosia is a genus of lichen-forming fungi in the family Roccellaceae.
Lecanographa is a genus of about 40 species of lichens in the family Lecanographaceae. It was circumscribed in 1994 by José M. Egea and Pilar Torrente, with Lecanographa lyncea as the type species.
Anisomeridium is a genus of lichens in the family Monoblastiaceae. The type species was originally named Arthopyrenia xylogena by Swiss botanist Johannes Müller Argoviensis in 1883; in 1928, Maurice Choisy defined the genus Anisomeridium, designating A. xylogena the type species.
Tylophoron is a genus of lichen-forming fungi in the family Arthoniaceae. The genus was circumscribed in 1862 by the Finnish lichenologist William Nylander.
Synarthonia is a genus of lichen-forming fungi in the order Arthoniales. The genus has not been placed into a family. Synarthonia was circumscribed by Swiss lichenologist Johannes Müller Argoviensis in 1891.
Megalaria is a genus of lichen-forming fungi in the family Ramalinaceae. It contains 44 species of crustose lichens, the majority of which grow on bark.
Catillaria is a genus of crustose lichens in the family Catillariaceae. The genus was circumscribed by Italian lichenologist Abramo Bartolommeo Massalongo in 1852. It is the type genus of Catillariaceae, which was circumscribed by Austrian lichenologist Josef Hafellner in 1984.
Halecania is a genus of fungi in the family Leprocaulaceae. It has 22 species. The genus was circumscribed by Austrian lichenologist Michaela Mayrhofer in 1987, with Halecania alpivaga assigned as the type species. She created Halecania to contain species, formerly placed in Lecania, with the following characteristics: uniformly amyloid apical domes, paraphyses with dark brown apical caps, and halonate ascospores.
Coniocarpon is a genus of lichen-forming fungi in the family Arthoniaceae. It has eight species of corticolous (bark-dwelling) lichens. This genus is distinct for its crystalline orange, red, and purple quinoid pigments in the ascomata that turn purple in potassium hydroxide solution, its colourless, transversely septate ascospores with large apical cells, and its rounded to lirellate ascomata.
Arthonia radiata, the asterisk lichen, is a common and widepspread species of corticolous (bark-dwelling), crustose lichen in the family Arthoniaceae.
