Antarctolichenia Selbmann, Muggia, Coleine, gen. nov. (Figures 3 and 4)
MycoBank number: MB 839455; Index Fungorum number: IF 839455; Facesoffungi number: FoF;
Etymology: the genus name refers to the geographic origin of the fungus, as it was collected in the Antarctic continent, and to its lifestyle, growing in association with algae, resembling that of a lichen-forming fungus, within endolithic lichen communities. Monotypic genus in the family Phaeococcomycetaceae, order Lichenostigmatales, Arthoniomycetes, and Ascomycota. Endolithic, anamorphic fungus, for which the sexual morph is unknown. Colonies growing rather slowly in vitro and heavily melanized. Thallus composed of yeast-like cells and filamentous hyphae; yeast-like cells with a thick cell wall, heavily melanized, and slightly verrucose in more mature cells, almost hyaline in young stages; filamentous thallus with rectangular cells and more isodiametric cells at the branchings.
Type species: Antarctolichenia onofrii Selbmann and Muggia sp. nov.—MycoBank:MB839456 (Figures 3 and 4).
Holotype: MUT 6552 = MNA-CCFEE 6564 cultured strain, isolated from cryptoendolithically colonized sandstone collected in Helliwell Hills, Antarctica. The culture is preserved in a metabolically inactive state at 150 ◦C. Antarctolichenia onofrii MUT 6552 is the unique identifier of the holotype sheet in the Mycotheca Universitatis Taurinensis (MUT), Department of Life Sciences and Systems Biology, University of Turin.
Etymology: the species is named after the Italian mycologist Silvano Onofri, who collected the rock sample from which the fungus was isolated for the very first time (Antarctic Expedition PNRA 1996/97).
Diagnosis: Strictly rock-inhabiting, endolithic, and asexual fungus. Colonies growing extremely slowly in vitro (reaching about 1 cm in a year), black. A yeast-like and filamentous thallus. Yeast-like isodiametric cells, 5–10 um, with a thick, slightly verrucose cell wall (Figure 4A–G), heavily melanized in more mature cells, and almost hyaline in their young stages (Figure 4B,C,G). Filamentous thallus with rectangular-to-oblong cells, 4–5 5–6 um, with a melanized and slightly verrucose cell wall (Figure 4H–P), branching hyphae, isodiametric cells sometimes present at the branchings (Figure 4K,M), and rarely building an entire hyphae (Figure 4O,P). Occasionally growing together with Stichococcus-like algae (Supplementary Figure S2C) but not forming haustoria-like or more organized mycelium or lichen-like thallus structures.
Distribution: Continental Antarctica, isolated from endolithic lichen-dominated communities in Victoria Land.
Material examined: the examined strains and metadata are reported in Table 1.
Notes: – as reported for other species in the family Phaeococcomycetaceae, Antarctolichenia onofrii displays both yeast-like and mycelial organization, conversely, Phaeococcomyces spp., reproduced by budding. Unlike Lichenostigma, conidiomata and ascomata were not observed in Antarctolichenia. Antarctolichenia onofrii, is also peculiar for its distribution and ecology, occurring exclusively in lichen-dominated endolithic communities in continental Antarctica.
Table 1. Details of the geographic origin and NCBI accession numbers of Antarctolichenia onofrii analyzed in this study. The type strain is highlighted in bold. SVL = southern Victoria Land and NVL = northern Victoria Land. * T = type strain
Figure 3. Colony appearance in the culture of Antarctolichenia onofrii: (A) the isolated strains of MNA-CCFEE6163 and (B) MUT 6552 alone, and (C) the strain MNA-CCFEE6574 grown together with the Stichococcus-like algae. Strains were grown on MEA (17 ◦C, 20 µmol fot·m−2 ·s−1, with a light/dark cycle of 14/10 h). Scale bars: (A) 3 mm; (B) 8 mm; and (C) 6 mm.
Figure 4. Morphological characters of Antarctolichenia onofrii analyzed in the isolated strains MNA- CCFEE5176 (A,B,D,E); MUT 6552 (type strain) (C); MNA-CCFEE6163 (F,G); and MUT 6495 (H–P). Both isodiametric, yeast-like cells with a thick, melanized cell wall (A–G) and filamentous branching hyphae with a thinner cell wall (H–P) are observed. The filamentous hyphae are composed of isodiametric-to-rectangular cells (H–P). Scale bars: (H) 50 µm; (A,B) 20 µm; (C,G,I–O) 10 µm; and (D,E,F,P) 5 µm.
Species