''Arthonia radiata'', the asterisk lichen, is a common and widepspread species of

corticolous This glossary of mycology is a list of definitions of terms and concepts relevant to mycology, the study of fungi. Terms in common with other fields, if repeated here, generally focus on their mycology-specific meaning. Related terms can be found ...

(bark-dwelling),

crustose lichen Crustose lichens are lichens that form a crust which strongly adheres to the Substrate (biology), substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. The basic structure of crustose lichen ...

in the family

Arthoniaceae The Arthoniaceae are a family (biology), family of lichenized, Lichenicolous fungus, lichenicolous and saprobic fungi in the order Arthoniales. The Arthoniaceae is the largest family of Arthoniales, with around 800 species. Most species in Arthon ...

Taxonomy

''Arthonia radiata'' is the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

of the genus ''

Arthonia ''Arthonia'' is a genus of lichens in the family Arthoniaceae. 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.Field Guide to California ...

''. It was first

formally described A species description is a formal scientific description of a newly encountered species, typically articulated through a scientific publication. Its purpose is to provide a clear description of a new species of organism and explain how it differ ...

Christiaan Hendrik Persoon Christiaan Hendrik Persoon (31 December 1761 – 16 November 1836) was a Cape Colony mycologist who is recognized as one of the founders of mycology, mycological Taxonomy (biology), taxonomy. Early life Persoon was born in Cape Colony at ...

in 1794, who called it ''Opegrapha radiata''.

Erik Acharius Erik Acharius (10 October 1757 – 14 August 1819) was a Swedish botanist who pioneered the Taxonomy (biology), taxonomy of lichens and is known as the "father of lichenology". Acharius was famously the last pupil of Carl Linnaeus. Life Ac ...

transferred it to the genus ''

'' in 1808. It has been known by many names in its lengthy

taxonomic 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation ...

history. The

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

of ''Arthonia radiata'' has been

sequenced In genetics and biochemistry, sequencing means to determine the primary structure (sometimes incorrectly called the primary sequence) of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a sequence which succi ...

and assembled. The draft genome is approximately 33.5

megabase A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...

s in size, contains 6,931 annotated genes, and consists of 16.65% repeat sequences, predominantly LTR elements.

Description

''Arthonia radiata'' is a

with an immersed

thallus Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...

, 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 . Its reproductive structures, called

apothecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. As ...

, 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-. Arthonia radiata 182556268

Under a microscope, the apothecia have a thin (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 The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in oth ...

(spore-producing layer) and a hypothecium (the layer beneath) that is also colourless to pale olive-brown. The (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. ''Arthonia radiata'' produces spores that are cylindric-obovoid to cylindrical, with 3 internal walls (

septa SEPTA, the Southeastern Pennsylvania Transportation Authority, is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly four million people througho ...

) 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 A pycnidium (plural pycnidia) is an asexual fruiting body produced by mitosporic fungi, for instance in the order Sphaeropsidales ( Deuteromycota, Coelomycetes) or order Pleosporales (Ascomycota, Dothideomycetes). It is often spherical or inve ...

, 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 A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...

(asexual spores), about 4–5 μm long. No

secondary metabolite Secondary metabolites, also called ''specialised metabolites'', ''secondary products'', or ''natural products'', are organic compounds produced by any lifeform, e.g. bacteria, archaea, fungi, animals, or plants, which are not directly involved ...

s, often used to identify lichen species, have been detected in ''Arthonia radiata'' using

thin-layer chromatography Thin-layer chromatography (TLC) is a chromatography technique that separates components in non-volatile mixtures. It is performed on a TLC plate made up of a non-reactive solid coated with a thin layer of adsorbent material. This is called the sta ...

Habitat and distribution

''Arthonia radiata'' is a widespread and common species. It grows on the smooth bark of many trees and shrubs.

Species interactions

Lichenicolous fungi A lichenicolous fungus is a member of a specialised group of fungi that live exclusively on lichens as their host (biology), host organisms. These fungi, comprising over 2,000 known species across 280 genera, exhibit a wide range of ecological st ...

that have been recorded growing on ''Arthonia radiata'' include '' Muellerella polyspora'', '' Stigmidium arthoniae'', and an undescribed species of '' Opegrapha''.

References

{{Taxonbar , from1=Q10497183 , from2=Q108122283 Arthoniomycetes Lichen species Lichens described in 1794 Taxa named by Christiaan Hendrik Persoon

Taxonomy

Description

Habitat and distribution

Species interactions

See also

References