Arthonia radiata
| Arthonia radiata | |
|---|---|
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Scientific classification 
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| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Arthoniomycetes |
| Order: | Arthoniales |
| Family: | Arthoniaceae |
| Genus: | Arthonia |
| Species: | A. radiata
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| Binomial name | |
| Arthonia radiata | |
| Synonyms[2] | |
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List
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Arthonia radiata, the asterisk lichen,[3] is a common and widepspread species of corticolous (bark-dwelling), crustose lichen in the family Arthoniaceae.[4]
Taxonomy
[edit | edit source]Arthonia radiata is the type species of the genus Arthonia. It was first formally described by Christiaan Hendrik Persoon in 1794, who called it Opegrapha radiata.[5] Erik Acharius transferred it to the genus Arthonia in 1808.[6] It has been known by many names in its lengthy taxonomic history.[2]
The genome of Arthonia radiata has been sequenced and assembled. The draft genome is approximately 33.5 megabases in size, contains 6,931 annotated genes, and consists of 16.65% repeat sequences, predominantly LTR elements.[7]
Description
[edit | edit source]Arthonia radiata is a crustose lichen with an immersed thallus, often separated from its surroundings by a thin brown line. The thallus is typically pale, ranging from white to pale grey, sometimes with a brown or olive tinge, and often forms a mosaic-like pattern on its substrate. Its reproductive structures, called apothecia, are black and can appear in various shapes—rounded, star-like (stellate), or elongated. These apothecia can measure between 0.15 and 2.2 mm across, and are usually flat or slightly convex. They lack a frosted appearance, often referred to as being non-pruinose.[8]
Under a microscope, the apothecia have a thin epithecium (the upper layer) that is brown or olive-brown, reacting to certain chemical tests by turning pale green. The internal structure includes a clear hymenium (spore-producing layer) and a hypothecium (the layer beneath) that is also colourless to pale olive-brown. The paraphysoids (sterile filaments within the hymenium) are narrow, 1–2 μm wide, but can expand to 3 μm, and they are often capped with darker brown tips.[8]
Arthonia radiata produces spores that are cylindric-obovoid to cylindrical, with 3 internal walls (septa) dividing the spore into 4 cells. These ascospores measure between 15 and 20 μm long and 4.5 to 6 μm wide, and the uppermost cell is not enlarged. While its asexual reproductive structures, pycnidia, are rare, they are immersed in the thallus and black, with a pale green reaction in chemical tests. These structures release small, rod-like conidia (asexual spores), about 4–5 μm long.[8]
No secondary metabolites, often used to identify lichen species, have been detected in Arthonia radiata using thin-layer chromatography.[8]
Habitat and distribution
[edit | edit source]Arthonia radiata is a widespread and common species. It grows on the smooth bark of many trees and shrubs.[8]
Species interactions
[edit | edit source]Lichenicolous fungi that have been recorded growing on Arthonia radiata include Muellerella polyspora, Stigmidium arthoniae, and an undescribed species of Opegrapha.[8]
See also
[edit | edit source]References
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