''Astrothelium infravulcanum'' is a species of corticolous (bark-dwelling), crustose lichen in the family

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 ...

. This species was discovered in the

rainforest Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...

s of

Acre The acre is a unit of land area used in the imperial Imperial is that which relates to an empire, emperor, or imperialism. Imperial or The Imperial may also refer to: Places United States * Imperial, California * Imperial, Missouri * Imp ...

, Brazil, and is distinguished by its unique features and chemical makeup.

Taxonomy

''Astrothelium infravulcanum'' was formally described as a new species in 2022 by the Dutch lichenologist

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 ...

, in a study highlighting new lichen species from Brazil. The type specimen was collected by Marcela Cáceres and Aptroot from the Comunidade Cuidado in the Cazumbá-Iracema Extractive Reserve ( Sena Madureira,

Acre, Brazil Acre () is a state located in the west of the North Region of Brazil and the Amazonia Legal. Located in the westernmost part of the country, at a two-hour time difference from Brasília, Acre is bordered clockwise by the Brazilian states of Am ...

); there, at an elevation of , it was found growing on bark in a

. The species name ''infravulcanum'' signifies its resemblance to ''

Astrothelium vulcanum ''Astrothelium vulcanum'' is a species of corticolous (bark-dwelling) lichen in the family Trypetheliaceae. Found in Guyana, it was formally described as a new species in 2016 by André Aptroot. The type specimen was collected from the Kuyuwin ...

'' but with notably smaller spores, hence ''infra'' indicating "below" or "smaller than" in Latin, pointing to the smaller size of its spores compared to those of ''A. vulcanum''.

Description

The species showcases a pale ochraceous (yellowish-brown) thallus, which is the body of the lichen, lacking a prothallus (a preliminary growth phase or border). The thallus emits a yellow fluorescence under

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 ...

, indicating the presence of specific chemicals. Its reproductive structures, called ascomata, are to (globe to pear-shaped), measuring 0.2–0.4 mm in diameter, and mostly embedded within the thallus rather than lying on a separate supportive structure. These structures have a single, black opening (

ostiole An ''ostiole'' is a small hole or opening through which algae or fungi release their mature spores. The word is a diminutive of "ostium", "opening". The term is also used in higher plants, for example to denote the opening of the involuted ...

) at the top through which spores are released. The internal structure () is interspersed with clear, oil-like globules. Spores are produced eight per

ascus An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or s ...

, are clear (

hyaline A hyaline substance is one with a glassy appearance. The word is derived from el, ὑάλινος, translit=hyálinos, lit=transparent, and el, ὕαλος, translit=hýalos, lit=crystal, glass, label=none. Histopathology Hyaline cartilage is ...

), divided into three sections (3- septate), and measure 14–17 by 5–6

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 ...

. These spores are long-

ellipsoid An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a surface that may be defined as the ...

in shape and do not have a surrounding gelatinous layer. The species does not form pycnidia, which are structures that produce asexual spores. Chemically, the thallus reacts to UV light by turning yellow but shows negative reactions to standard

lichen spot test A spot test in lichenology is a spot analysis used to help identify lichens. It is performed by placing a drop of a chemical on different parts of the lichen and noting the colour change (or lack thereof) associated with application of the chemical ...

s (C, P, and K tests), indicating the absence of certain chemicals typically searched for in lichen studies. The only chemical detected through thin-layer chromatography is lichexanthone, a

xanthone Xanthone is an organic compound with the molecular formula O 6H4CO. It is a white solid. In 1939, xanthone was introduced as an insecticide and it currently finds uses as Insecticide, ovicide for codling moth eggs and as a larvicide. Xanthone ...

compound common in some lichens and known for its yellow fluorescence under long-wavelength UV light.

Habitat and distribution

''Astrothelium infravulcanum'' is corticolous, meaning it grows on tree bark, specifically within the humid and biodiverse ecosystem of a Brazilian rainforest. At the time of its original publication, the lichen was only known to exist in its type locality within the state of Acre, Brazil.

References

{{Taxonbar, from=Q124727702 Astrothelium Lichen species Lichens described in 2022 Lichens of Brazil Taxa named by André Aptroot