Arthopyrenia

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Arthopyrenia
Arthopyrenia fallaciosa
Scientific classification Edit this classification
Kingdom: Fungi
Division: Ascomycota
Class: Dothideomycetes
Order: Trypetheliales
Family: Trypetheliaceae
Genus: Arthopyrenia
A.Massal. (1852)
Type species
Arthopyrenia cerasi
(Schrad.) A.Massal. (1852)
Species

See text

Synonyms[1]
List
  • Verrucaria * Leiophloea Ach. (1803)
  • Leiophloea (Ach.) Gray (1821)
  • Pyrenyllium Clem. (1909)
  • Cyrtidium Vain. (1921)
  • Mycarthopyrenia Keissl. (1921)
  • Mesopyrenia M.Choisy (1931)
  • Ciferriolichen Tomas. (1952)
  • Jattaeolichen Tomas. & Cif. (1952)
  • Arthopyreniomyces Cif. & Tomas. (1953)
  • Giacominia Cif. & Tomas. (1953)
  • Jattaeomyces Cif. & Tomas. (1953)
  • Mycoarthopyrenia Cif. & Tomas. (1953)
  • Mycociferria Tomas. (1953)

Arthopyrenia is a genus of fungi in the family Trypetheliaceae.[2] It was formerly classified in the eponymic family Arthopyreniaceae, but molecular phylogenetics studies showed that the type species, Arthopyrenia cerasi, was a member of the Trypetheliaceae.[3] Arthopyrenia fungi typically form inconspicuous films embedded within tree bark and produce tiny, flask-shaped fruiting bodies covered by dark, shield-like caps. The genus includes both lichen-forming species (those that partner with algae) and non-lichenized species, with about 100 currently recognized species found primarily on bark and wood substrates.

Description

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Arthopyrenia forms an immersed thallus, essentially a film sunk into the outer bark, which is usually inconspicuous or only slightly paler than the surrounding tissue and spreads in a diffuse patch. It is not lichenised (i.e. it lacks a visible partnership with algae). The sexual fruit bodies are perithecia (flask-shaped structures with a minute pore), circular to elliptical in surface view. They are covered by a dark, often laterally spreading, clypeate involucrellum—a shield-like cap made of compacted fungal hyphae intermingled with bark cells—and surrounded internally by a thin, usually colourless exciple (the fruit-body wall). The hyphae are dark brown and react K+ (greenish) in potassium hydroxide. The tissue between and above the asci (the hamathecium) consists of robust, thick-walled pseudoparaphyses—sterile threads that are sparsely branched, occasionally connected to one another (anastomosing), and only distantly partitioned by cross-walls; the gelatinous matrix of the hymenium is iodine-negative (I–).[4]

The asci are fissitunicate, meaning they have two functional wall layers that separate during spore release; they are roughly cylindrical, with an apical ocular chamber (a small, frequently conical cap-like apparatus), and do not stain in iodine (I–). Each ascus bears eight spores. The ascospores are clavate to cylindric-clavate (club-shaped to narrowly club-shaped), with one or three cross-walls (septae) and a strong narrowing at each septum; they are colourless and smooth when young, sometimes becoming faintly brown and minutely warted in old age. A broad, persistent gelatinous sheath surrounds each spore, a feature that can aid recognition in section.[4]

Asexual reproduction occurs in pycnidia—minute, blackish, flask-like structures whose walls contain the same dark pigment as the perithecial involucrellum. The conidiogenous cells (which produce the asexual spores) are variably shaped—cylindrical, flask-shaped (lageniform), or nearly spherical—and often proliferate percurrently, extending through the old opening to make a new one like the telescoping of a pen. The resulting conidia are colourless, cylindrical to bacilliform (rod-like), and either lack septae or have three; some species produce two distinct asexual spore types (two anamorphs). No secondary metabolites are detected by thin-layer chromatography.[4]

Description

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Arthopyrenia includes both lichenised and saprobic species. Where lichenised, the photobiont is a trentepohlioid alga; in other species no photobiont is present. The thallus is usually crustose and largely immersed in the bark or wood, but in some taxa it is reduced to a thin, byssoid (cottony) cover formed by a black subiculum (a superficial mat of hyphae), and it can also be absent.[5]

The sexual structures are perithecial ascomata that appear circular to ellipsoid in surface view. A dark-brown, clypeate (shield-like) involucrellum overlies the fruiting body and is composed of compressed fungal hyphae mixed with host bark cells. The true ascomatal wall is black and becomes discontinuous beneath the hamathecium. A thin, usually colourless exciple surrounds the central cavity. The hamathecium comprises branched, anastomosing, sometimes bead-like pseudoparaphyses that are typically non-amyloid; in some species these elements partly dissolve, and the remaining material may stain amyloid. Periphysoids are also present around the ostiole.[5]

The asci are bitunicate (double-walled), pyriform to clavate, with an apical tholus; they are non-amyloid and contain eight ascospores. The ascospores are usually hyaline (becoming brownish with age in some species), pyriform to clavate, and 1–3-septate with true septa (eusepta); walls may bear minute wart-like ornamentation. Reported spore dimensions are about 4–16 × 12–50 μm. Asexual reproduction occurs in blackish pycnidia producing conidia that are simple or 1–3-septate, variously oblong, ovoid, bacilliform, or thread-like. No lichen secondary metabolites are known from the genus.[5]

Species

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Arthopyrenia cerasi

As of October 2025, Species Fungorum (in the Catalogue of Life) accepts 99 species of Arthopyrenia:[2]

See also

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References

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