''Cetradonia'' is a

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 ...

genus in the family

Cladoniaceae The Cladoniaceae are a family of lichen-forming fungi in the order Lecanorales, comprising about 560 species distributed amongst 18 genera. This family is one of the largest among lichen-forming fungi and is globally distributed, from Arctic t ...

. A

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

genus, ''Cetradonia'' contains the single species ''Cetradonia linearis'' (formerly known as ''Cladonia linearis'' and as ''Gymnoderma lineare''). The genus was

circumscribed In geometry, a circumscribed circle for a set of points is a circle passing through each of them. Such a circle is said to ''circumscribe'' the points or a polygon formed from them; such a polygon is said to be ''inscribed'' in the circle. * Circum ...

in 2002 by Jiang-Chun Wei and

Teuvo Ahti Teuvo "Ted" Tapio Ahti (born 14 June 1934) is a Finnish botanist and lichenologist who has made significant contributions to the taxonomy and biogeography of lichens. Known particularly for his work on the lichen family Cladoniaceae, he has h ...

. The genus was once placed in the family Cetradoniaceae (created in 2002) until that family was subsumed into the Cladoniaceae in 2006. ''Cetradonia linearis'', commonly known as the rock gnome lichen, is a

squamulose lichen A squamulose lichen is a lichen that is composed of small, often overlapping "scales" called . If they are raised from the substrate and appear leafy, the lichen may appear to be a foliose lichen, but the underside does not have a "skin" (cortex), ...

found in the higher elevations of the southern

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

. Populations are only known to exist in

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

South Carolina South Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders North Carolina to the north and northeast, the Atlantic Ocean to the southeast, and Georgia (U.S. state), Georg ...

and

Tennessee Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina t ...

. The lichen occurs only in frequent fog, or in deep river gorges. Because of its specialized habitat requirements and heavy collection for scientific purposes, the lichen has been listed as an

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

since January 18, 1995. It is only one of two lichens on the endangered species list, the other being the Florida perforate cladonia.USFWS
Rock Gnome Lichen.
Asheville Field Office.

Description

Genus ''Cetradonia'' features a

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 ...

that is enduring and well-formed, typically aggregating into clumps. These thalli are characterized by their almost cylindrical base stalks that evolve into linear, flattened, and strap-like . These lobes are somewhat upright, ranging from unbranched to minimally branched, and have a texture. They measure between in length and 0.5 to 1 mm in width, often connecting at the base through horizontal structures known as

rhizomorph Mycelial cords are linear aggregations of parallel-oriented hyphae. The mature cords are composed of wide, empty vessel hyphae surrounded by narrower sheathing hyphae. Cords may look similar to plant roots, and also frequently have similar functi ...

s. The upper surface of the thallus is densely covered by a cortex, with colors from greyish green to pale yellowish brown or olive-green, enclosing a cartilaginous core. In contrast, the lower surface has a thinner cortex, lacks , though it may show transverse wrinkling towards the lower end and has furrows and pits near the tips, transitioning in color from white or cream at the tip to black towards the base. Podetia, which are small stalked structures, emerge predominantly from the upper section of the thallus's lower surface, often near the tip, and have a dirty white hue. These structures can range from 0.3 to 2 mm in height, are covered by a , solid in form, and may or may not contain algae. The reproductive structures, known as

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

, host clusters of hymenial that can expand up to 2 mm across, with individual discs varying from 0.1 to 1 mm in diameter. These discs are flat to spherical in shape and dark brown to black in color, occasionally stacking atop one another in a manner similar to ''

Cladia aggregata ''Cladia'' is a genus of lichen-forming fungi in the family Cladoniaceae. ''Cladia'' species have a crustose lichen, crustose or (scaly) primary thallus and a fruticose lichen, fruticose, secondary thallus, often referred to as pseudopodetium. T ...

''. The asci, or spore-bearing structures, are slender, with stalks that can extend up to 2 mm;

conidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...

(asexual spores) have not been observed to occur in this species. In terms of chemical composition, ''Cetradonia'' contains

atranorin Atranorin is a chemical substance produced by some species of lichen. It is a secondary metabolite belonging to a group of compounds known as depsides. Atranorin has analgesic, anti-inflammatory, antibacterial, antifungal, cytotoxic, antioxidant, ...

and lichesterinic acids.

References

External links

Photograph of Rock gnome lichen
*USFWS
Rock Gnome Lichen Recovery Plan.
September 1997. {{Taxonbar, from=Q5065690 Cladoniaceae Lichen genera Monotypic Lecanorales genera Taxa described in 2002 Taxa named by Teuvo Ahti

Description

See also

References

External links