''Buellia lichexanthonica'' is a species of saxicolous (rock-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.Caliciaceae. Found in Brazil, it was formally described as a new species in 2017 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 li ...
and Marcela Eugenia da Silva Cáceres. The type specimen was collected by the authors near the Poço Azul (
Riachão, Maranhão
Riachão, Maranhão is a municipality in the state of Maranhão in the Northeast region of Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin ...
), at an altitude of about ; here, in Cerrado, it was found growing on sandstone. The lichen has a thin (0.1–0.2 mm), dull yellow thallus covered with
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 ...
crystals. Its ascomata are round and black, about 0.2–0.5 mm in diameter with a flat disc. The ascospores are dark brown with an
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 ...
shape, one
septum
In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate.
Examples
Human anatomy
* Interatri ...
, and measure 11–13 by 6–7.5
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 ...
. The
specific epithet
In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
''lichexanthonica'' refers to the presence of 4,5-dichlorolichexanthone, a lichexanthone derivative that is found in the cortex of the thallus.