''Astrothelium vulcanum'' is a species of corticolous (bark-dwelling)

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.Trypetheliaceae The Trypetheliaceae are a family of mainly lichen-forming fungi in the order Trypetheliales. Genera *'' Alloarthopyrenia'' – 1 sp. *''Aptrootia'' – 3 spp. *'' Architrypethelium'' – 8 spp. *''Astrothelium'' – ca. 275 spp. *'' Bathel ...

. Found in

Guyana Guyana ( or ), officially the Cooperative Republic of Guyana, is a country on the northern mainland of South America. Guyana is an indigenous word which means "Land of Many Waters". The capital city is Georgetown. Guyana is bordered by the ...

, it was formally described as a new species in 2016 by

André Aptroot André Aptroot (Heemskerk, 1961) is a Dutch mycologist and lichenologist. In 1993 he did his PhD at the University of Utrecht under the supervision of Robbert Gradstein (nl). His dissertation was titled "Systematic studies on pyrenocarpous li ...

. The type specimen was collected from the Kuyuwini Landing ( Rupununi) at an elevation of ; here, in a

savannah A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the Canopy (forest), canopy does not close. The open canopy allows sufficient light to rea ...

forest, it was found growing on the smooth bark of trees. The lichen has a smooth, somewhat shiny thallus surrounded by a thin black prothallus, and covering areas up to in diameter. Its ascospores are spindle-shaped (''fusiform'') with rounded edges, with three septa and dimensions of 20–25 by 6.5–7.5

μm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

. ''Astrothelium vulcanum'' contains lichexanthone, a lichen product that causes the thallus to fluoresce when lit with a long-wavelength

UV light Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...

. '' Astrothelium infravulcanum'', found in Brazil and described as a new species in 2022, was named for its similar appearance to ''A. vulcanum'', but is distinguished by its smaller ascospores, which measure 14–17 by 5–6 μm.

References

vulcanum Lichen species Lichens described in 2016 Lichens of Guyana Taxa named by André Aptroot {{Dothideomycetes-stub