Arthonia | |
---|---|
Arthonia quintaria | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Arthoniomycetes |
Order: | Arthoniales |
Family: | Arthoniaceae |
Genus: | Arthonia Ach. (1806) |
Type species | |
Arthonia radiata | |
Species | |
Synonyms [1] | |
List
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Arthonia is a genus of lichens in the family Arthoniaceae. [2] It was circumscribed by Swedish botanist Erik Acharius in 1806.
It is a genus of thin crustose lichen of widely varying forms, commonly called comma lichens. [3] : 222
Arthonia species are typically crustose lichens, forming thin, often inconspicuous patches that can be either flush with the surface ( immersed ) or sitting on top (superficial). The thallus—the main body of the lichen—may spread without clear boundaries or sometimes be neatly outlined by thin brown lines. In some species, the thallus may be absent altogether. Under chemical tests, the fungal filaments (hyphae) in the thallus can show distinctive reactions, turning red or pale blue when stained with iodine (I+) and then blue with a potassium iodine (K/I) solution. [4]
The photosynthetic partner ( photobiont ) is most commonly a green alga belonging to the genus Trentepohlia . In some cases, however, a less well-known type of green alga is involved, and a few species are only weakly lichenised or even live partly by breaking down dead organic matter (saprophytic) or parasitising other lichens (lichenicolous). [4]
The reproductive structures of Arthonia are ascomata, which are often similar to apothecia (open, disc-like fruiting bodies) but can have a wide range of shapes. They may be round, elongated, linear, or even star-shaped, and on bark they often develop a subtle, thin rim of tissue that includes both lichen and host bark cells. The exposed surface of these structures (the disc ) can be reddish-brown to black, and sometimes appears dusted with pale or white powder ( pruina ). Unlike many lichens, Arthonia usually lacks a thalline exciple (a protective rim made of thallus tissue) and often also lacks a true exciple (a layer of fungal tissue), though a few species develop a well-defined, carbonised boundary. [4]
Internally, the top layer ( epithecium ) can range from colourless to reddish or dark brown. The main spore-producing region (hymenium) typically reacts to the same chemical tests as the thallus hyphae, and these reactions help distinguish Arthonia from other lichens. Beneath the hymenium, a distinct hypothecium (a supporting layer) may be absent or difficult to separate from the hymenium. Thread-like fungal elements ( paraphysoids ) weave through a gel-like matrix, becoming more intricately branched and pigmented near their tips, where they often form small, dark "caps". [4]
The asci, or spore-bearing cells, usually contain eight spores and have a characteristic Arthonia-type structure. They are often semi- fissitunicate (splitting in a controlled way when releasing spores) and possess a large, domed apex with a specialised "ocular chamber" that may show subtle colour changes with chemical tests. The ascospores themselves are typically oval or elongated, divided into one to seven segments (septa), and start off colourless and smooth. As they mature and age, they may darken and become slightly roughened. Initially, the spores can have a very thin, colourless outer layer ( epispore ). [4]
In addition to sexual reproduction via ascospores, Arthonia often produces tiny, inconspicuous, flask-shaped structures called pycnidia. These generate small, colourless, single-celled spores (conidia) that are usually rod-shaped but occasionally ellipsoidal or thread-like. [4]
From a chemical standpoint, many Arthonia species do not contain distinct lichen products, but others produce a variety of substances, including xanthones and certain anthraquinones. These chemical differences, along with the various structural features, help distinguish different species within the genus. [4]
Porina is a genus of crustose lichens in the family Porinaceae. As of August 2024, Species Fungorum accepts 161 species of Porina.
Mazosia is a genus of lichen-forming fungi in the family Roccellaceae.
Megaspora is a genus of lichen-forming fungi in the family Megasporaceae. It contains four species of crustose lichens that typically grow on soil, bryophytes, or plant litter on chalky substrates.
Teuvoa is a genus of lichen-forming fungi in the family Megasporaceae. It was first classified by lichenologists Mohammad Sohrabi and Steven Leavitt in 2013, with Teuvoa uxoris assigned as the type species. This genus was delineated from the larger genus, Aspicilia, following a molecular phylogenetic analysis which revealed that the Aspicilia uxoris species group constituted a distinct lineage in the Megasporaceae. Initially containing three species, two additional species native to China were added in 2018. Teuvoa is characterised by its small ascospores and conidia, and the absence of secondary metabolites.
Inoderma is a genus of lichen-forming fungi in the family Arthoniaceae. It was resurrected for use in 2015 for a small group of species with the following features: elevated, white pruinose pycnidia, immersed to adnate white pruinose apothecia, and a weakly gelatinized hymenium. Inoderma byssaceum was assigned as the type species for the genus.
Reichlingia is a genus of lichen-forming fungi in the family Arthoniaceae. It has seven species. The genus was originally circumscribed by Paul Diederich and Christoph Scheidegger in 1996, with Reichlingia leopoldii as the type, and at that time, only species. The fungus was at first thought to be a lichenicolous (lichen-dwelling) fungus, but is now considered a lichenised hyphomycete.
Calogaya orientalis is a species of corticolous (bark-dwelling) and muscicolous lichen (moss-dwelling), crustose lichen in the family Teloschistaceae. It is found in arid steppe and desert habitats in Northwestern China, Iran, and Turkey. The thallus of this lichen is reduced, similar to species in the genus Athallia.
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.
Flavoplaca oasis is a species of saxicolous (rock-dwelling), crustose lichen in the family Teloschistaceae. It is widely distributed across Europe, and has been reported in Western Asia, China, and North Africa.
Glaucomaria is a genus of lichen-forming fungi in the family Lecanoraceae. It has seven species. The genus was circumscribed by Maurice Choisy in 1929. It contains crustose lichens formerly placed in the Lecanora rupicola species complex as defined by several previous authors.
Glaucomaria carpinea is a species of corticolous (bark-dwelling), crustose lichen in the family Lecanoraceae. It is a widely distributed species.
Myochroidea is a genus of lichen-forming fungi of uncertain familial placement in the order Lecanorales. It has four species of grey or brown-grey crustose lichens.
Carbacanthographis coccospora is a species of saxicolous (rock-dwelling) crustose lichen in the family Graphidaceae. Found in Brazil, it was described as new to science in 2002.
Porpidia macrocarpa is a species of saxicolous (rock-dwelling), crustose lichen in the family Lecideaceae.
Aspiciliella is a genus of lichen-forming fungi in the family Megasporaceae. It has four species. The genus is characterised by its crustose, rimose-areolate thallus that is partially continuous and has a K+ (red) reaction. The epihymenium is typically green to olive-green and turns light green when treated with N. Aspiciliella has eight-spored asci of the Aspicilia-type, containing ellipsoid, colourless, and simple ascospores.
Aspilidea is a fungal genus of uncertain familial placement in the subclass Ostropomycetidae. It contains the single species Aspilidea myrinii, a saxicolous (rock-dwelling) crustose lichen with a circumpolar distribution.
Gloeoheppia is a genus of lichen-forming fungi in the family Gloeoheppiaceae. It comprises five species. The genus is distinguished from similar-looking lichens like Heppia by its internal structure, the nature of its photobiont, and details of its reproductive structures.
Megaloblastenia is a genus of crustose lichen-forming fungi in the family Megalosporaceae, comprising three species. Proposed by Dutch lichenologist Harrie Sipman in 1983, the genus is characterised by its thick, ecorticate thallus ranging from pale whitish-grey to yellowish, and its disc-like fruiting bodies (apothecia) that can be biatorine or lecideine. Megaloblastenia lichens form a symbiotic relationship with Dictyochloropsis algae, produce hyaline, bicellular ascospores with polaribilocular structure, and contain chemical compounds such as zeorin, pannarin, or usnic acid. Found in Australasia and South America, these lichens typically grow as epiphytes on trees in moist forests within temperate to tropical oceanic climates.
Leprantha is a fungal genus in the family Arthoniaceae. It comprises a single species, Leprantha cinereopruinosa, a corticolous (bark-dwelling), crustose lichen.
Arthonia radiata, the asterisk lichen, is a common and widepspread species of corticolous (bark-dwelling), crustose lichen in the family Arthoniaceae.