Herpothallon | |
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Herpothallon rubrocinctum | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Arthoniomycetes |
Order: | Arthoniales |
Family: | Arthoniaceae |
Genus: | Herpothallon Tobler (1937) |
Type species | |
Herpothallon sanguineum (Vain.) Tobler (1937)
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Species | |
See text | |
Synonyms[1] | |
Herpothallon is a genus of crustose lichens in the family Arthoniaceae. It has about 50 species.[2]
The genus was circumscribed in 1930 by German lichenologist Friedrich Tobler, with Herpothallon sanguineum assigned as the type species. Tobler erroneously believed that the fungus was a member of the Basidiomycota.[3][4] After it was recognized as an ascolichen, it was referred to either Chiodecton (family Roccellaceae) or Cryptothecia (family Arthoniaceae).[5]
In 2009, Herpothallon was resurrected following a publication by André Aptroot, Göran Thor, Robert Lücking, and John Elix, in which they recognized 29 species worldwide.[6] The type species is now known as Herpothallon rubrocinctum,[7] or in the vernacular as the "Christmas lichen".[8]
Herpothallon is characterized by the byssoid (a wispy or cottony texture) prothallus (i.e., the first purely fungal layer upon which an algae-containing thallus develops) and hypothallus (i.e., a growth of undifferentiated purely fungal mycelium present as a distinct layer on the underside of the thallus). The texture of the thallus is somewhat felt-like, and its form is heteromerous, meaning that more or less distinct tissues are present, in particular, the mycobiont and photobiont components occur in well-marked layers, with the photobiont in a more or less distinct zone between the upper cortex and the medulla. Another thallus feature common to all species is the felty pseudoisidia; these are isidia-like outgrowths that, unlike true isidia, lack internal differentiation and have no distinct cortex. The thallus also has pustules (blister-like elevations), and granules ranging in form and size from soredia-like to minute. The photobiont partner of the Herpothallon lichen is from Trentepohlia, a genus of green algae.[9] In Herpothallon, the asci do not develop in true ascomata. Only two members of the genus, H. fertile and H. inopinatum, are known to be fertile.[10]
As of January 2022[update], Species Fungorum accepts 42 species of Herpothallon.