Verrucaria difficilis
From Wikipedia, the free encyclopedia
| Verrucaria difficilis | |
|---|---|
 | |
| Image of holotype specimen; scale bar = 1 mm | |
Scientific classification  | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Eurotiomycetes |
| Order: | Verrucariales |
| Family: | Verrucariaceae |
| Genus: | Verrucaria |
| Species: | V. difficilis |
| Binomial name | |
| Verrucaria difficilis Pykälä & Myllys (2020) | |
 Holotype: Varsinais-Suomi, Finland | |
Verrucaria difficilis is a species of saxicolous (rock-dwelling) crustose lichen in the family Verrucariaceae.[1] It is found in Finland.
Verrucaria difficilis was described as new to science in 2020 by the Finnish lichenologists Juha Pykälä, Annina Kantelinen and Leena Myllys. It belongs to the "Verrucaria subtilis complex", a group of closely related species within the genus Verrucaria. This complex is characterised by large spores, perithecia (fruiting bodies) that leave pits in the rock substrate, and a pale, thin thallus (lichen body). The species epithet difficilis, meaning difficult in Latin, alludes to the challenges in distinguishing this species from its close relatives based on morphology alone. Despite its morphological similarities to other members of the complex, V. difficilis can be identified through DNA analysis of the internal transcribed spacer region, showing a genetic divergence of 1.7–2.6% from its closest relatives.[2]
Description
Verrucaria difficilis forms an inconspicuous, white or grey crust (thallus) on calcareous rock surfaces. The thallus can be endolithic (growing within the rock) or thinly epilithic (growing on the surface), and is often continuous or irregularly cracked.[2]
The perithecia are small to medium-sized (0.18–0.36 mm in diameter) and partially immersed in the rock substrate, typically leaving shallow pits. A distinguishing feature of V. difficilis is its involucrellum, an outer layer covering the perithecium, which often extends to cover half or more of the perithecium's height.[2]
The spores of V. difficilis are relatively large, measuring 23–34 μm long and 10–13 μm wide. They are non-septate (lacking internal divisions) and enclosed in a thin perispore.[2]