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

. It is characterized by its conical black , which contrast sharply with the

thallus Thallus (plural: 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. Many of these organisms ...

. This lichen species has been found only in Brazil and is unique in its appearance, superficially resembling a ''

Pyrenula ''Pyrenula'' is a genus of lichen-forming fungi in the family Pyrenulaceae. The genus has a widespread distribution, especially in tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the ...

'' species.

Taxonomy

Astrothelium nigrum was formally described as a new species in 2016 by lichenologists

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 l ...

and Marcela Cáceres. The

type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

was collected in Rondônia, at the Estação Ecológica de Cuniã, on tree bark in

primary 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 rainforest ...

. The species is known for its distinctive conical black that contrast sharply with the thallus, giving it a superficial resemblance to ''

Pyrenula infraleucotrypa ''Pyrenula'' is a genus of lichen-forming fungi in the family Pyrenulaceae The Pyrenulaceae are a family of fungi in the order Pyrenulales. The family was first named by German botanist Gottlob Ludwig Rabenhorst in 1870. Species in the famil ...

''.

Description

The

of ''Astrothelium nigrum'' is corticate, smooth, somewhat shiny, and continuous, with an ochraceous green color. It covers areas up to in diameter and is approximately 0.1 mm thick. The thallus is surrounded by a black

prothallus A prothallus, or prothallium, (from Latin ''pro'' = forwards and Greek ''θαλλος'' (''thallos'') = twig) is usually the gametophyte stage in the life of a fern or other pteridophyte. Occasionally the term is also used to describe the young ...

line about 0.4 mm wide, and it induces

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external Tissue (biology), tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissu ...

formation on the host bark. The ascomata are , 0.2–0.4 mm wide and 0.5–0.7 mm high, mostly aggregated and immersed in conical to hemispherical pseudostromata with a black, non-corticated surface. The pseudostromata are distinctly raised above the thallus, regular in outline, with sloping sides, and up to 2 mm in diameter and 0.7 mm high. The wall of the ascomata is all around, up to 100 μm thick. The

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 ...

s are eccentric, fused, flat to convex, black, and surrounded by a dull grey rim. The is not with oil globules. The

asci ASCI or Asci may refer to: * Advertising Standards Council of India * Asci, the plural of ascus, in fungal anatomy * Accelerated Strategic Computing Initiative * American Society for Clinical Investigation * Argus Sour Crude Index * Association of ...

contain 8 ascospores, which are hyaline, , have 3

septa The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates transit bus, bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people ...

, and measure 19–21 by 7–8 μm in size, with rounded ends and diamond-shaped .

Habitat and distribution

''Astrothelium nigrum'' is found on smooth bark of trees in

primary forest An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance, and thereby exhibits unique ecological featur ...

s and is currently known only from Brazil.

References

{{Taxonbar, from=Q107503920 nigrum Lichen species Lichens described in 2016 Lichens of Brazil Taxa named by André Aptroot Taxa named by Marcela Cáceres