''Astrothelium macrostomum'' 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 ...

. It is found in

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

, Guyana, and

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in ...

Taxonomy

The species was formally described as new to science in 2016 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 l ...

. The type collection was made by

Harrie Sipman Henricus (Harrie) Johannes Maria Sipman (born 1945) is a Dutch lichenologist. He specialises in tropical and subtropical lichens, and has authored or co-authored more than 250 scientific publications. He was the curator of the lichen herbarium ...

in ,

Minas Gerais Minas Gerais () is a state in Southeastern Brazil. It ranks as the second most populous, the third by gross domestic product (GDP), and the fourth largest by area in the country. The state's capital and largest city, Belo Horizonte (literall ...

, Brazil, on 16 September 1997.

Description

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 ...

of ''Astrothelium macrostomum'' is , smooth, somewhat shiny, and continuous, covering areas up to 7 cm in diameter and less than 0.1 mm thick. It appears olive-green to olive-grey, typically lacking a , and 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, causing the lower bark or

cambium A cambium (plural cambia or cambiums), in plants, is a tissue layer that provides partially undifferentiated cells for plant growth. It is found in the area between xylem and phloem. A cambium can also be defined as a cellular plant tissue from ...

layer to swell and erupt through the upper bark. Ascomata are (pear-chaped), about 0.6–1.2 mm in diameter, usually aggregated in groups of 2–5, and mostly immersed in the bark tissue. The wall is , up to approximately 80

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 ...

thick. Ostioles are eccentric and fused, with a flat, white- appearance, surrounded by a whitish zone. The does not contain oil lobules.

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 ...

each contain eight . These ascospores 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 ...

, 5–7-septate, , measuring 65–85 by 16–19 μm, with pointed ends and diamond-shaped , not surrounded by a gelatinous layer. were not observed to occur in this species.

Chemistry

The thallus surface of ''Astrothelium macrostomum'' is UV−, while the

medulla Medulla or Medullary may refer to: Science * Medulla oblongata, a part of the brain stem * Renal medulla, a part of the kidney * Adrenal medulla, a part of the adrenal gland * Medulla of ovary, a stroma in the center of the ovary * Medulla of ...

is K−. The ostiolar region has a UV+ (yellow) reaction.

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 ...

indicates the presence of

lichexanthone Lichexanthone is an organic compound in the structural class of chemicals known as xanthones. Lichexanthone was first isolated and identified by Japanese chemists from a species of leafy lichen in the 1940s. The compound is known to occur in ma ...

, a

xanthone Xanthone is an organic compound with the molecular formula O 6H4sub>2CO. It is a white solid. In 1939, xanthone was introduced as an insecticide and it currently finds uses as ovicide for codling moth eggs and as a larvicide. Xanthone is also ...

compound that fluoresces when lit with a long-wavelength UV light.

Similar species

''Astrothelium macrostomum'' is similar to ''

Astrothelium eustomum ''Astrothelium'' is a genus of corticolous (bark-dwelling) lichens in the family Trypetheliaceae. The genus was circumscribed in 1824 by German botanist Franz Gerhard Eschweiler, with ''Astrothelium conicum'' assigned as the type species. Spe ...

'', but can be differentiated by its 5–7-septate , as opposed to the 3–5-septate and smaller ascospores of ''A. eustomum''. '' Astrothelium diplocarpoides'' shares some similar characteristics, but differs in having an inspersed and the presence of

throughout the thallus.

Habitat and distribution

''Astrothelium macrostomum'' grows on the smooth bark of trees within rainforests. It is known to occur in Brazil, Guyana, and Venezuela.

References

{{Taxonbar, from=Q95573604 macrostomum Lichen species Lichens described in 2016 Lichens of Brazil Lichens of Guyana Lichens of Venezuela Taxa named by André Aptroot