''Malmidea cineracea'' is a little-known 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 Nicaragua.

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 2015 by the lichenologists Othmar Breuss and

Robert Lücking Robert Lücking (born 1964) is a German lichenologist, known for his extensive research on foliicolous lichens (lichens that live on leaves) and his significant contributions to the taxonomy, ecology, and biodiversity of fungi and lichens. He e ...

. 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 first author from a Caribbean lowland

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 ...

in the Indio Maíz Biological Reserve ( San Juan River). The

name A name is a term used for identification by an external observer. They can identify a class or category of things, or a single thing, either uniquely, or within a given context. The entity identified by a name is called its referent. A person ...

of the species, ''cineracea'', translates to "ash-greyish", and alludes to the colour of the margins of 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 cineracea'' grows on bark and has a - texture with a greenish-grey colour, appearing dull on a whitish, fibrous base layer, and is about 150–200

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 ...

thick. The individual range from 70 to 150 μm in diameter, and their cortex, which is colourless, measures 10 to 15 μm thick. The photobiont is , forming spherical or flattened groups of 30 to 60 μm in diameter, and consists of cells 6 to 8 μm in diameter. 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 the lichen has a yellowish hue and does not react to a solution of

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 ...

(K−). The

, or fruiting bodies, 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 range from 0.5 to 1.1 mm in diameter and 0.20 to 0.35 mm in height. They are typically rounded but can be slightly irregular, with a flat that is grey-brown to brown. The margin is smooth, pale brownish grey, distinct but not prominently raised, and about 0.1 mm wide. The is compact, with a hyaline outer layer (10–30 μm) and an inner layer densely encrusted with yellowish-brown , which turn pale greenish-yellow when treated with potassium hydroxide. The is 10–20 μm high and brownish, while the is dark brown to brownish black, 100–150 μm deep, and does not react to potassium hydroxide. 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 ...

is approximately 80 μm high, hyaline, and turns blue when stained with iodine; it contains simple

paraphyses Paraphyses are erect sterile filament-like support structures occurring among the reproductive apparatuses of fungi, ferns, bryophytes and some thallophytes. The singular form of the word is paraphysis. In certain fungi, they are part of the f ...

that are not thickened at the tips. The asci are narrowly (club-shaped), measuring 60–70 by 12–16 μm, with a thickened apical wall but no visible internal structure. There are typically 6 to 8 ascospores per ascus, measuring 12–15 by 6–8 μm,

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 with somewhat pointed ends, and surrounded by a that is 0.5–1.0 μm thick. No

conidiomata Conidiomata (singular: Conidioma) are blister-like fruiting structures produced by a specific type of fungus called a coelomycete. They are formed as a means of dispersing asexual spores call conidia, which they accomplish by creating the blister- ...

have been observed to occur in this species, and

thin-layer chromatography Thin-layer chromatography (TLC) is a chromatography technique that separates components in non-volatile mixtures. It is performed on a TLC plate made up of a non-reactive solid coated with a thin layer of adsorbent material. This is called the sta ...

reveals no substances except for thin bands of

terpenoid The terpenoids, also known as isoprenoids, are a class of naturally occurring organic compound, organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeabl ...

s, likely originating from the bark. Standard chemical spot tests on the thallus and excipulum are all negative.

Similar species

''Malmidea cineracea'' is similar to ''

Malmidea furfurosa ''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 ...

'', but can be distinguished by its pale apothecial margins (as opposed to black in ''M. furfurosa''), an excipulum that contains crystals but no medullary tissue, and a yellowish medulla. '' Malmidea attenboroughii'', which also has a granulose-isidiate thallus, bears a morphological resemblance to ''Malmidea cineracea''. The former species, found in the

Amazon rainforest The Amazon rainforest, also called the Amazon jungle or Amazonia, is a Tropical and subtropical moist broadleaf forests, moist broadleaf tropical rainforest in the Amazon biome that covers most of the Amazon basin of South America. This basin ...

of Bolivia, can be distinguished by its abraded margin, which internally contains yellowish-brown granules that are unreactive when treated with potassium hydroxide (K−).

Habitat and distribution

''Malmidea cineracea'' has been exclusively observed growing on the bark of trees in a lowland

, with its presence limited to Nicaragua. It is one of five ''Malmidea'' species that occur in that country.

References

{{Taxonbar, from=Q25354704 cineracea Lichen species Lichens described in 2015 Lichens of Central America Taxa named by Robert Lücking