''Porpidia seakensis'' is a species of crustose lichen in the family Lecideaceae. It is an endolithic species, meaning it grows inside the rocks, between the grains. Found only in Alaska, it was formally described as a new species in 2020 by British lichenologist Alan Fryday. The type specimen was collected in the Hoonah-Angoon Census Area, in Glacier Bay National Park. Here it was discovered growing on granitic rock in a woodland. The lichen is only known from this area, although it is locally common. Its preferred habitat is

siliceous rock Siliceous rocks are sedimentary rocks that have silica (SiO2) as the principal constituent. The most common siliceous rock is chert; other types include diatomite. They commonly form from silica-secreting organisms such as radiolarians, diatoms, or ...

s and boulders in wooded areas that are open and well lit. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''seakensis'' uses the letters "seak" to refer to a standard abbreviation for southeast Alaska ("SE AK"). The lichen appears as a thin, whitish stain on the rock surface. It produce lecideine apothecia that are typically 0.4–0.8 mm across with a reddish-brown disc. The hypothecium (an area of

hyaline A hyaline substance is one with a glassy appearance. The word is derived from el, ὑάλινος, translit=hyálinos, lit=transparent, and el, ὕαλος, translit=hýalos, lit=crystal, glass, label=none. Histopathology Hyaline cartilage is ...

to pigmented tissue below 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 ...

) measures 100

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 and is dark brown. The

asci ASCI or Asci may refer to: * Advertising Standards Council of India * Asci, the plural of ascus, in fungal anatomy * Accelerated Strategic Computing Initiative * American Society for Clinical Investigation * Argus Sour Crude Index * Association of ...

are cylindrical to somewhat club-shaped, measuring 80–95 by 15–20 μm. They produce ascospores that are

ellipsoid An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a surface that may be defined as the ...

, hyaline, unornamented, with dimensions ranging between 17.0–24.0 by 2.3–9.2 μm. ''Porpidia seakensis'' contains the

secondary compound Secondary metabolites, also called specialised metabolites, toxins, secondary products, or natural products, are organic compounds produced by any lifeform, e.g. bacteria, fungi, animals, or plants, which are not directly involved in the norma ...

stictic acid Stictic acid is an aromatic organic compound, a product of secondary metabolism in some species of lichens. Stictic acid is the subject of preliminary biomedical research. Stictic acid has cytotoxic and apoptotic effects ''in vitro''. Computation ...

. In terms of positive standard spot test reactions, the thallus turns yellow with the application of potassium hydroxide solution (K+), and orange with an ethanolic solution of

para-phenylenediamine ''p''-Phenylenediamine (PPD) is an organic compound with the formula C6H4(NH2)2. This derivative of aniline is a white solid, but samples can darken due to air oxidation. It is mainly used as a component of engineering polymers and composites lik ...

(PD+).

References

{{Taxonbar, from=Q108283234 Lecideales Lichen species Lichens described in 2020 Lichens of Subarctic America Taxa named by Alan Fryday