''Malmidea albomarginata'' is a species of

corticolous This glossary of mycology is a list of definitions of terms and concepts relevant to mycology, the study of fungi. Terms in common with other fields, if repeated here, generally focus on their mycology-specific meaning. Related terms can be found ...

(bark-dwelling),

crustose lichen Crustose lichens are lichens that form a crust which strongly adheres to the Substrate (biology), substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. The basic structure of crustose lichen ...

in the family

Malmideaceae Malmideaceae is a family of crustose and corticolous lichens in the order Lecanorales. It contains eight genera and about 70 species. Taxonomy Malmideaceae was created in 2011 to accommodate a group of species, formerly placed in genus '' Malc ...

. It is found in Venezuela.

Taxonomy

The lichen was

formally described A species description is a formal scientific description of a newly encountered species, typically articulated through a scientific publication. Its purpose is to provide a clear description of a new species of organism and explain how it differ ...

as a new species in 2021 by the lichenologists

Klaus Kalb Klaus Kalb (born 1942) is a German lichenologist and an authority on tropical lichens. Born in Nuremberg, he studied at the University of Erlangen–Nuremberg before pursuing a career that significantly advanced the field of lichenology, parti ...

and Jesús Maldonado. The

type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

was collected by the authors from the

Cerro El Volcán Cerro El Volcán (sometimes written as "El Picacho Volcano") is the highest peak in El Hatillo Municipality, which is part of the metropolitan area of the Metropolitan District of Caracas in northern Venezuela, South America South Americ ...

( Miranda) at an elevation of ; there it was found growing in a disturbed tropical mountain

rainforest Rainforests are forests characterized by a closed and continuous tree Canopy (biology), canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforests can be generally classified as tropi ...

. The

species epithet Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In Taxonomy (biology), taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany) ...

''albomarginata'' alludes to the distinctive white margins that characterise its

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 ...

Description

''Malmidea albomarginata'' is a

with a continuous

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 ...

measuring 200–300

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 thickness. The thallus surface is initially , with being scarce and unevenly distributed, each measuring 0.1–0.3 mm in height and 0.15–0.3 mm in width. Over time, the thallus becomes dull and transforms from grey or greenish-grey to a coralloid texture as it ages. This species lacks

soralia Soredia are common reproductive structures of lichens. Lichens reproduce asexually by employing simple fragmentation and production of soredia and isidia. Soredia are powdery propagules composed of fungal hyphae wrapped around cyanobacteria or g ...

and

isidia An isidium (plural: isidia) is a tiny, wart- or finger-like outgrowth on the thallus surface of certain lichen species. It is one of two principal types of vegetative reproduction, vegetative reproductive structures in lichens, the other being ...

. The

medulla Medulla (Latin for "marrow") 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 ...

of both the verrucae and thallus is white to faintly yellow, reacting K+ (orange to reddish) when tested with

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which utili ...

, but without a reaction to the P

spot test Spot analysis, spot test analysis, or a spot test is a chemical test, a simple and efficient technique where analytic assays are executed in only one, or a few drops, of a chemical solution, preferably in a great piece of filter paper, without usin ...

. The is , with cells around 6–8 μm in diameter.

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 ...

in ''Malmidea albomarginata'' are

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 ...

and rounded, ranging from 0.8–1.8 mm in diameter and 0.2–0.3 mm in height. The apothecial are flat to slightly convex, with colours varying from

ochre Ochre ( ; , ), iron ochre, or ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colou ...

to light greyish-brown. The is of the ''granifera'' type, , thin, and white. The is

hyaline A hyaline substance is one with a glassy appearance. The word is derived from , and . Histopathology Hyaline cartilage is named after its glassy appearance on fresh gross pathology. On light microscopy of H&E stained slides, the extracellula ...

, while the medullary excipulum is whitish to slightly yellowish, filled with opaque, greyish to yellowish that partially dissolve in KOH, producing a K+ (orange-red) efflux. The is about 25 μm high and hyaline to light brown, while the centrally located is 100–150 μm high, narrowing towards the margin and dark brown, showing no reaction to K tests. The is indistinct, and 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 oth ...

measures 75–90 μm in height, being hyaline. Asci are sized 65–80 μm by 12–18 μm, containing 6–8 non-

septate In biology, a septum (Latin for ''something that encloses''; 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 * Interatrial se ...

, ,

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 ...

ascospores per ascus, measuring (10–)14 by 6–9 μm, with a of 1.5–2 μm. Chemically, ''Malmidea albomarginata'' primarily 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, ...

, alongside several unidentified xantholepinones. It is distinguished from similar species like ''

Malmidea attenboroughii ''Malmidea attenboroughii'' is a species of corticolous (bark-dwelling), crustose lichen in the family Malmideaceae. It is known to occur from a single location in the Amazon rainforest of Bolivia. Taxonomy The lichen was formally described in 2 ...

'' by differences in apothecia size and the presence of

. In comparison with ''

Malmidea aurigera ''Malmidea'' is a genus of crustose lichens and the type genus of the family Malmideaceae. It was established in 2011 to contain a phylogenetically distinct group of species formerly placed in the genus '' Malcolmiella''. The crust-like thallus o ...

'' and '' Malmidea piperina'', ''Malmidea albomarginata'' features larger apothecia, a paler apothecial disc, and warts that become coralloid granular.

References

{{Taxonbar, from=Q123983198 albomarginata Lichen species Lichens described in 2021 Lichens of Venezuela Taxa named by Klaus Kalb