Arctomia
| Arctomia | |
|---|---|
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Lecanoromycetes |
| Order: | Baeomycetales |
| Family: | Arctomiaceae |
| Genus: | Th.Fr. (1861) |
| Type species | |
| Arctomia delicatula Th.Fr. (1861)
| |
| Species | |
|
A. delicatula | |
| Synonyms[1] | |
| |
Arctomia is a genus of lichen-forming fungi in the family Arctomiaceae.[2] The genus was originally circumscribed by Theodor Magnus Fries in 1861. Arctomia has a circumpolar distribution.[3]
Description
Arctomia grows as a thin crust that can look either granular or like a miniature patchwork of tiny leaf-like scales. When dry the surface is reddish-brown to nearly black and, unlike some gelatinous lichens, it does not swell appreciably after rain. The edge of a colony is indefinite and may develop small lobes, but the whole thallus remains low-lying. A single-cell-thick cortex—essentially a skin of brown fungal cells—covers the surface, and the lichen never produces the powdery outgrowths (isidia) or soralia seen in many other genera. Sandwiched between the fungal threads are clusters of cyanobacteria of the genus Nostoc; its cells, about 5–7 micrometres (μm) across, sit in a clear jelly that gives the thallus a slightly glossy, rubbery feel when moist.[4]
Sexual reproduction takes place in minute disc-shaped fruit bodies (apothecia) that originate as tiny bumps inside the lobes and become more or less stalkless on maturity. These discs are flat to gently domed and merge smoothly with the surrounding thallus rather than being ringed by a distinct margin. Inside, slender branched filaments (paraphyses) stand among the spore sacs; their tips broaden slightly and carry a brown pigment. Each ascus belongs to the Trapelia-type: it shows a thickened apex (the tholus) that stays colourless in iodine staining, while the surrounding gelatinous sheath stains blue, and it usually contains eight ascospores. The spores themselves are long, spindle-shaped and divided by many cross-walls (septa)—features that help them survive dispersal. Asexual reproduction occurs in embedded pycnidia that release tiny, rod-shaped conidia, and standard chemical spot tests detect no secondary metabolites in the thallus.[4]
Species
As of June 2025, Species Fungorum (in the Catalogue of Life) accept four species of Arctomia:[5]
- Arctomia delicatula Th.Fr. (1861)
- Arctomia papuanorum (Degel.) Otálora & Wedin (2013)
- Arctomia teretiuscula P.M.Jørg. (2003)[3] – China
- Arctomia uviformis (Hue) Otálora & Wedin (2013)
Molecular phylogenetics evidence revealed inappropriate classifications for two species once placed in this genus, A. insignis (P.M.Jørg. & Tønsberg) Ertz and A. borbonica Magain & Sérus.; they were formally transferred to the genus Gabura in 2020. Arctomia fascicularis (L.) Otálora & Wedin (2013) was confirmed to belong to Gabura,[6] a generic placement originally proposed by Per Magnus Jørgensen in 2014.[7]
References
- ^ "Synonymy: Arctomia Th. Fr., Nova Acta R. Soc. Scient. upsal., Ser. 3 3: 387 (1861) [1860]". Species Fungorum. Retrieved 24 February 2022.
- ^ Wijayawardene, Nalin; Hyde, Kevin; Al-Ani, Laith Khalil Tawfeeq; Somayeh, Dolatabadi; Stadler, Marc; Haelewaters, Danny; et al. (2020). "Outline of Fungi and fungus-like taxa". Mycosphere. 11: 1060–1456. doi:10.5943/mycosphere/11/1/8. hdl:10481/61998.
- ^ a b Jørgensen, P.M. (2003). "A new species of Arctomia from Sichuan Province, China". The Lichenologist. 35 (4): 287–289. Bibcode:2003ThLic..35..287J. doi:10.1016/s0024-2829(03)00053-7.
- ^ a b Cannon, P.; Coppins, B.; Sanderson, N.; Simkin, J. (2025). Arctomiales: Arctomiaceae, including Arctomia, Gabura and Gregorella (PDF). Revisions of British and Irish Lichens. Vol. 56. pp. 2–3.
- ^ "Arctomia". Catalogue of Life. Species 2000: Leiden, the Netherlands. Retrieved 16 June 2025.
- ^ Magain, Nicolas; Spribille, Toby; DiMeglio, Joseph; Nelson, Peter R.; Miadlikowska, Jolanta; Sérusiaux, Emmanuël (2020). "Phylogenetic evidence for an expanded circumscription of Gabura (Arctomiaceae)". The Lichenologist. 52 (1): 3–15. Bibcode:2020ThLic..52....3M. doi:10.1017/s0024282919000471. hdl:2268/245664.
- ^ Jørgensen, Per M. (2014). "Taxonomy and nomenclature of Collema fasciculare (L.) G. H. Weber". The Lichenologist. 46 (4): 594. Bibcode:2014ThLic..46..594J. doi:10.1017/s0024282914000140.