''Acolium'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

ized

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

in the family

Caliciaceae The Caliciaceae are a family (taxonomy), family of mostly lichen-forming fungus, fungi belonging to the class (taxonomy), class Lecanoromycetes in the division (mycology), division Ascomycota. Although the family has had its classification chan ...

. The genus has a widespread distribution and contains six species. These lichens are found on bark and wood, occasionally on rocks, or growing on other lichens. The genus was originally proposed as a subdivision of ''

Calicium ''Calicium'' is a genus of leprose lichens. It is in the family Caliciaceae, and has 40 species. The sexual reproduction structures are a mass of loose ascospores that are enclosed by a cup shaped exciple sitting on top of a tiny stalk, having ...

'' by

Erik Acharius Erik Acharius (10 October 1757 – 14 August 1819) was a Swedish botanist who pioneered the Taxonomy (biology), taxonomy of lichens and is known as the "father of lichenology". Acharius was famously the last pupil of Carl Linnaeus. Life Ac ...

in 1808, and promoted to generic status by

Samuel Frederick Gray Samuel Frederick Gray (10 December 1766 – 12 April 1828) was a British botanist, mycologist, and pharmacologist. He was the father of the zoologists John Edward Gray and George Robert Gray. Background He was the son of Samuel Gray, a London Se ...

in 1821.

Description

''Acolium'' is characterized by a

crustose Crustose is a Habit (biology), habit of some types of algae and lichens in which the organism grows tightly appressed to a substrate, forming a biological layer. ''Crustose'' adheres very closely to the Substrate (biology), substrates at all poin ...

thallus that can vary in appearance from a rough, warty surface to a cracked, mosaic-like pattern. The

thallus Thallus (: 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. A thallus usually names the entir ...

can be thick or thin, and its colour ranges from grey to brownish. However, in species that live on other lichens, the thallus is absent. The of these lichens is composed of interwoven

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

e, and they have a photobiont. ''Acolium'' lichens produce

apothecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. As ...

, which are black, and can be either

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

or partially immersed. The is consistently thick, particularly at the base, and has a blackish-brown hue, occasionally displaying a white or grey powdery appearance. The , which is not easily visible, consists of simple, unbranched . Asci develop individually from hyphae with

croziers A crozier or crosier (also known as a paterissa, pastoral staff, or bishop's staff) is a stylized staff that is a symbol of the governing office of a bishop or abbot and is carried by high-ranking prelates of Roman Catholic, Eastern Catholi ...

and are cylindrical in shape. They possess a single functional wall layer and disintegrate early on, releasing spores into a dry, black, powdery mass called a . The of ''Acolium'' lichens have a single

septum In biology, a septum (Latin language, Latin for ''something that encloses''; septa) is a wall, dividing a Body cavity, cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Hum ...

; they have shapes ranging from broadly cylindrical to

ellipsoid An ellipsoid is a surface that can be obtained from a sphere by deforming it by means of directional Scaling (geometry), scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a Surface (mathemat ...

al. They exhibit a slight or pronounced constriction at the septum and have a thick, dark brown wall adorned with unique ornamentation such as irregular cracks, warts, or parallel ridges. The , or , are spherical or slightly flattened, measuring 50–200

μm The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

in diameter, and initially semi-immersed in the thallus. The conidiophores are branched, and the are aseptate and colourless, existing in two types: cylindrical and tapering at one end or ellipsoidal. Chemically, ''Acolium'' lichens contain

pulvinic acid Pulvinic acids are natural chemical pigments found in some lichens, derived biosynthetically from the aromatic amino acids phenylalanine and tyrosine, via dimerization and oxidative ring-cleavage of arylpyruvic acids, a process that also produces ...

derivatives, which are yellow pigments, along with unidentified compounds.

Species

Species Fungorum ''Index Fungorum'' is an international project to index all formal names (Binomial nomenclature, scientific names) in the fungus Kingdom (biology), kingdom. As of 2015, the project is based at the Royal Botanic Gardens, Kew, one of three partn ...

(in the

Catalogue of Life The Catalogue of Life (CoL) is an online database that provides an index of known species of animals, plants, fungi, and microorganisms. It was created in 2001 as a partnership between the global Species 2000 and the American Integrated Taxono ...

) accepts 6 species of ''Acolium''. *'' Acolium chloroconium'' *'' Acolium inquinans'' *'' Acolium karelicum'' *'' Acolium marcianum'' *'' Acolium sessile'' *'' Acolium yunnanense''

References

{{Taxonbar, from=Q4674457 Caliciales Lichen genera Taxa named by Erik Acharius Caliciales genera Taxa described in 1808