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

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

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 ...

, first described in 2016. It is known to occur in Sri

Lanka Lanka (, ) is the name given in Hindu epics to the island fortress capital of the legendary asura king Ravana in the epics of the ''Ramayana'' and the ''Mahabharata''. The fortress was situated on a plateau between three mountain peaks kn ...

Taxonomy

The species was formally described in 2016 by lichenologists Gothamie Weerakoon and

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 ...

. 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 Rilhena, Sri Lanka.

Description

''Astrothelium conjugatum'' is characterized by its ascomata, which are and arranged with 2–8 chambers joined with eccentric, fused

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. Typically, 3–10 fused ascomata are grouped within one . The pseudostromata are about 1–5 mm in diameter, to prominent, with an irregularly to linear outline. They are completely covered by a thallus layer that is thick and opaque at the sides. The top of the pseudostromata can be similar in appearance or thinner and translucent, in which case the black ascoma wall is visible through it. The thallus itself is , pale yellowish brown, rather smooth, covering areas of up to in diameter, and lacks a prothallus. Ascomata are about 0.5–0.7 mm in diameter. The is clearly but sparsely interspersed with hyaline oil droplets. The ascospores have an form. They are

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 ...

, 3-septate, fusiform to

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, measuring 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 Uni ...

, and have diamond-shaped when mature. were not observed to occur in the species. The thallus and pseudostroma of ''Astrothelium conjugatum'' react UV− and K− in chemical spot tests, and

thin-layer chromatography Thin-layer chromatography (TLC) is a chromatography technique used to separate non-volatile mixtures. Thin-layer chromatography is performed on a sheet of an inert substrate such as glass, plastic, or aluminium foil, which is coated with a t ...

did not detect any

lichen product Lichen products, also known as lichen substances, are organic compounds produced by a lichen. Specifically, they are secondary metabolites. Lichen products are represented in several different chemical classes, including terpenoids, orcinol de ...

s. This species is closely related to ''

Astrothelium straminicolor ''Astrothelium'' is a genus of corticolous lichen, corticolous (bark-dwelling) lichens in the family Trypetheliaceae. The genus was circumscription (taxonomy), circumscribed in 1824 by German botanist Franz Gerhard Eschweiler, with ''Astrothelium ...

'', which is found in India, Malaysia, and Sarawak. The primary distinguishing feature of ''A. conjugatum'' is the presence of a thallus layer on top of the pseudostromata, a feature absent in ''A. straminicolor''.

Habitat and distribution

''Astrothelium conjugatum'' is known only from its

type locality Type locality may refer to: * Type locality (biology) * Type locality (geology) See also * Local (disambiguation) * Locality (disambiguation) {{disambiguation ...

in Sri Lanka, where it was found on tree bark in a wet lowland

tropical rainforest Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equatori ...

References

{{Taxonbar, from=Q107503694 conjugatum Lichen species Lichens described in 2016 Lichens of Sri Lanka Taxa named by André Aptroot Taxa named by Gothamie Weerakoon