Leptogium antarcticum
Leptogium antarcticum is a small, dark jelly lichen in the family Collemataceae described in 2018 from the maritime Antarctic. The thallus forms tight, upward‑tilted with a roughened, warted surface; the underside bears felted, beard‑like hairs that help it grip its substrate. When fertile it develops apothecia whose rims often show neat circular ridges. At present it is confirmed only from King George Island in the South Shetland Islands.
Taxonomy
The species was described as new to science in 2018 by Mayara Camila Scur, Aline Pedroso Lorenz‑Lemke and Marcos Junji Kitaura in a revision of Antarctic Leptogium. The holotype was collected on mosses near the Comandante Ferraz Antarctic Station at 24 m elevation, and is deposited in the herbarium of the Federal University of Mato Grosso do Sul. The epithet antarcticum refers plainly to the region in which it occurs.The authors used an integrative approach: diagnostic morphology was combined with DNA sequence data from the fungal ITS and mitochondrial small‑subunit markers to delimit species. In Bayesian and maximum‑likelihood analysis, L. antarcticum falls within Leptogium "clade B"; mtSSU data placed it near L. biloculare, L. crispatellum and L. rivulare. The analyses clearly separated L. antarcticum from the other Antarctic species treated in the study, including the superficially similar L. puberulum and L. marcellii.
Description
The thallus is foliose, about 2.5 cm across and 85–125 micrometres thick, appearing grey‑brown to black. Its narrow are tightly crowded and tend to tilt upwards. The surface bears small tooth‑like and wart‑like outgrowths, giving a granular feel at the margins; by contrast, it lacks isidia and true, which are common in some related species. In practical terms, this means the species spreads and protects itself without the tiny, easily broken "cloning pegs" seen in several other Leptogium.Below, the lichen anchors itself by pale, beard‑like hairs—short, agglutinated bundles that create a felted lower surface. Internally, the medulla houses cyanobacteria, which explains the "jelly lichen" label: when wet, the gelatinous matrix swells and the thallus softens. The fungal hyphae in the medulla include short columns of threads set at about 65° to the surface; this columnar arrangement is a reliable microscopic marker for the species.
Fruiting bodies, when present, are, up to 3.0 mm in diameter, with a plane to shallowly cupped disc. The rim is usually smooth to finely toothed and is often marked by circular ridges, which is a recognisable field clue. Spores are spindle‑shaped, 20–25 × 10–15 μm, with several internal walls. Tiny asexual structures are rare; their conidia are about 2.5 × 1.0 μm.
Habitat and distribution
As of its original publication, Leptogium antarcticum was confirmed only from King George Island, where the type material was collected on mosses close to sea level. The species grows in the maritime Antarctic setting that favours many Leptogium: cool, wet, and often stony ground where meltwater and persistent moisture are common.Field workers may encounter L. antarcticum mixed with other dark Leptogium. The combination of a crowded, upward‑facing lobed thallus, a distinctly hairy lower surface, absence of isidia or true lobules, and apothecial rims with circular ridges separates it from co‑occurring species such as L. puberulum and L. marcellii. L. antarcticum is one of seven Leptogium species recorded from the Antarctic.