''Heppia arenacea'' is a species of

terricolous A terricolous lichen is a lichen that grows on the soil as a substrate. An example is some members of the genus ''Peltigera ''Peltigera'' is a genus of approximately 100 species of foliose lichens in the family Peltigeraceae. Commonly known as ...

(ground-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.Lichinaceae The Lichinaceae are a family of ascomycete fungi. Most species are lichenized with cyanobacteria, and have a distribution largely in temperate regions. Taxonomy The family was circumscribed in 1854 by Finnish lichenologist William Nylander. H ...

. Discovered in

Yemen Yemen (; ar, ٱلْيَمَن, al-Yaman), officially the Republic of Yemen,, ) is a country in Western Asia. It is situated on the southern end of the Arabian Peninsula, and borders Saudi Arabia to the Saudi Arabia–Yemen border, north and ...

, it is characterized by its sand-coloured

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 wer ...

and the incorporation of soil particles throughout its vegetative (i.e., non-reproductive) parts. The lichen is found in soil crust communities over

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

and

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

ic rock in desert habitats, as well as in partially sheltered areas between large boulders.

Taxonomy

''Heppia arenacea'' was first formally described by German lichenologist Matthias Schultz in 2005. The

type specimen In biology, a type is a particular wiktionary:en:specimen, 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 a ...

was collected by the author in Wadi Asariah, Jabal Arays (

Abyan Governorate Abyan ( ar, أَبْيَن ) is a governorate of Yemen. The Abyan region was historically part of the Fadhli Sultanate. It was a base to the Aden-Abyan Islamic Army militant group. Its capital is the city of Zinjibar. This governorate is n ...

) at an elevation of approximately ; there it was found growing on exposed soil over

basaltic rock Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

under an '' Anisotes trisulcus'' shrub.

Description

''Heppia arenacea'' has a sand-coloured to pale ochre

, which can sometimes be slightly greyish-white and is somewhat gelatinous when wet. The thallus is , resembling an crust with somewhat angular to roundish measuring 0.6–2.5 mm wide. Microscopically, the lichen's thallus anatomy is , with an upper 20–35

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 ...

thick, comprising cells that are angulate to roundish and small, measuring 3–5 μm wide. The is 75–150 μm thick, consisting of vertical or irregular reticulate

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 or ...

e, with short to elongated cells measuring 7.5–12.5 by 2.5–3 μm. The of ''Heppia arenacea'' is a filamentous cyanobacterium ('' Scytonema''), present as short and contorted filaments or split individual cells. The filament cells are 7.5–12.5 μm wide without a sheath and 10–17.5 μm wide including the sheath. The lichen lacks a lower cortex and medulla. Except for the

hymenium The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some ...

and , abundant soil particles are incorporated in all parts of the thallus and

apothecium An ascocarp, or ascoma (), 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. Ascocarps are ...

Similar species

''Heppia arenacea'' resembles '' Heppia despreauxii'', '' H. conchiloba'', and '' H. solorinoides'' in the presence of an , a distinct upper cortex, and the lack of a lower cortex. However, it is distinguished from other ''Heppia'' species by its unique sand-colored thallus and the incorporation of soil particles in its vegetative parts.

Habitat and distribution

''Heppia arenacea'' is found in soil crust communities situated on

and

ic rock in desert habitats. This lichen has been observed at elevations ranging from and has been recorded in a few distant regions in southern Yemen such as

Djaul plateau Djaul may refer to: *Dyaul Island in the New Ireland chain of Papua New Guinea *Tiang language The Tiang language also known as Djaul is a language spoken in Papua New Guinea.

Ras Fartak Ras or RAS may refer to: Arts and media * RAS Records Real Authentic Sound, a reggae record label * Rundfunk Anstalt Südtirol, a south Tyrolese public broadcasting service * Rás 1, an Icelandic radio station * Rás 2, an Icelandic radio statio ...

Jabal Arays Jabal, Jabel, Jebel or Jibal may refer to: People * Jabal (name), a male Arabic given name * Jabal (Bible), mentioned in the Hebrew Bible Places In Arabic, ''jabal'' or ''jebel'' (spelling variants of the same word) means 'mountain'. * Dzhebel, ...

Wadi Raiwa Wadi ( ar, وَادِي, wādī), alternatively ''wād'' ( ar, وَاد), North African Arabic Oued, is the Arabic term traditionally referring to a valley. In some instances, it may refer to a wet (ephemeral) riverbed that contains water onl ...

, as well as on

Socotra Socotra or Soqotra (; ar, سُقُطْرَىٰ ; so, Suqadara) is an island of the Republic of Yemen in the Indian Ocean, under the ''de facto'' control of the UAE-backed Southern Transitional Council, a secessionist participant in Yemen’s ...

. The author suggests that the lichen may also be present in comparable habitats in

Oman Oman ( ; ar, عُمَان ' ), officially the Sultanate of Oman ( ar, سلْطنةُ عُمان ), is an Arabian country located in southwestern Asia. It is situated on the southeastern coast of the Arabian Peninsula, and spans the mouth of t ...

Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in Western Asia. It covers the bulk of the Arabian Peninsula, and has a land area of about , making it the fifth-largest country in Asia, the second-largest in the A ...

Eritrea Eritrea ( ; ti, ኤርትራ, Ertra, ; ar, إرتريا, ʾIritriyā), officially the State of Eritrea, is a country in the Horn of Africa region of Eastern Africa, with its capital and largest city at Asmara. It is bordered by Ethiopia ...

, and

Somalia Somalia, , Osmanya script: 𐒈𐒝𐒑𐒛𐒐𐒘𐒕𐒖; ar, الصومال, aṣ-Ṣūmāl officially the Federal Republic of SomaliaThe ''Federal Republic of Somalia'' is the country's name per Article 1 of thProvisional Constituti ...

. Typically, ''Heppia arenacea'' is found alongside free-living

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

('' Scytonema''), riccioid and marchantioid liverworts, and various soil lichens, including ''

Collema coccophorum ''Collema coccophorum'' is a cyanolichen also known as soil pulp lichen or jelly lichen. It can be found in many areas of the world, including North America, Eastern Europe and Norway, Australia, and South America. It has also been recorded in ...

''., ''

Psora decipiens ''Psora'' is a genus of lichen-forming fungi in the family Psoraceae. Members of the genus are commonly called fishscale lichens. Lichens in the genus ''Psora'' are known to have a squamulose thallus and anthraquinones in the hymenium. Specie ...

'', ''

Placidium ''Placidium'' is a genus of crustose lichen, crustose to squamulose lichen, squamulose to almost foliose lichen, foliose lichens. The genus is in the family Verrucariaceae. Most members grow on soil (are terricolous), but some grow on rock (saxi ...

'' spp., ''

Toninia ''Toninia'' is a genus of lichen-forming fungi in the family Ramalinaceae. The genus was circumscribed by Abramo Bartolommeo Massalongo Abramo Bartolommeo Massalongo (13 May 1824 – 25 May 1860) was an Italian paleobotanist and lichenologist ...

'' spp., ''

Heppia ''Heppia'' is a genus of olive, brownish, gray, or blackish squamulose, crustose, or peltate like lichens.Lichen Flora of the Greater Sonoran Desert Region. Vol 1, Nash, T.H., Ryan, B.D., Gries, C., Bugartz, F., (eds.) 2001/ref> ''Heppia'' was onc ...

'' spp., ''

Peltula ''Peltula'' is a genus of small dark brown to olive or dark gray squamulose lichens that can be saxicolous (grow on rock)) or terricolous (grow on soil). Members of the genus are commonly called rock-olive lichens.Field Guide to California Lichen ...

'' spp., and '' Gloeoheppia turgida''.

References

{{Taxonbar, from=Q17387121 Lichinomycetes Lichen species Lichens described in 2005 Lichens of Western Asia