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Lendemeriella exsecuta
Lendemeriella exsecuta is a species of saxicolous (rock-dwelling) crustose lichen in the family Teloschistaceae.[2] TaxonomyThe species was first described in 1880 by the Finnish lichenologist William Nylander, who classified it as a member of the genus Lecanora.[3] After having been shuffled to various genera in its taxonomic history,[1] Sergey Kondratyuk transferred it to the genus Lendemeriella in 2020.[4] DescriptionLendemeriella exsecuta is a crustose lichen, meaning it grows as a thin, crust-like layer tightly attached to its substrate. The main body (thallus) appears grey, occasionally dark grey or off-white, and forms a continuous surface that may develop small cracks creating distinct segments called areoles. These areoles measure 0.5–1 mm across and may appear slightly pinched at their base.[5] The reproductive structures (apothecia) are small disc-like organs measuring 0.2–0.7 mm in diameter. These sit directly on the surface without a stalk and display considerable colour variation – from brownish-yellow to orange-brown, eventually becoming completely black. The discs are surrounded by a raised rim (proper margin) that ranges from black to olive in colour and may eventually become less prominent as the disc becomes more convex.[5] When viewed under a microscope, the internal structure reveals several distinct layers. The spore-producing layer (hymenium) is colourless and 65–90 micrometres (μm) tall, occasionally reaching 135 μm. It contains cylindrical spore sacs (asci), each producing eight two-celled spores. These transparent spores are ellipsoid in shape, measuring roughly 12–16.5 by 6–7.5 μm, with a distinctive thickened area at their centre.[5] The lichen contains various chemical compounds, including several pigments that give it its characteristic appearance. When tested with common chemical spot tests, the thallus is K−, C−, and P−. However, the apothecia are K± (red). The lichen's chemistry includes several secondary metabolites such as parietin, emodin, and fragilin, along with a unique substance that remains unidentified. Like most lichens, it contains photosynthetic green algal cells (chlorococcoid photobiont) that provide energy through photosynthesis.[5] Habitat and distributionLendemeriella exsecuta primarily inhabits Arctic and alpine environments, where it grows on silica-rich rocks that have a basic (non-acidic) chemistry. This lichen shows a preference for sheltered locations protected from strong winds, particularly in areas around and above the treeline where conditions are humid. While it is believed to have a circumpolar distribution – occurring in a band around the Earth's polar regions – it is particularly well-documented in the Alps mountain range of Europe.[5] In the Antarctic, it has been documented from the South Shetland Islands and the Antarctic Peninsula, where it often grows alongside Umbilicaria decussata and Usnea sphacelata.[6] Placopsis antarctica is another typical associate.[7] References
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