Roccella (lichen)

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Roccella
Roccella fuciformis
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Arthoniomycetes
Order: Arthoniales
Family: Roccellaceae
Genus: Roccella
DC. (1805)
Type species
Roccella fuciformis
(L.) DC. (1805)
Synonyms[1]

Roccella is a genus of 23 species of lichens in the family Roccellaceae.[2] The genus was circumscribed by Swiss botanist Augustin Pyramus de Candolle in 1805, with Roccella fuciformis as the type species.[3]

Description

Roccella presents a fruticose (shrub-like), thallus that is either erect or pendulous (hanging) with sparse dichotomous branching. The main and terminal branches, varying in shape from flattened to rounded (terete), typically measure 2 to 5 mm (up to 10 mm) in thickness and 5 to 15 cm in length. These branches has colours ranging from creamy white-greyish to greyish-brown and have surfaces that are either smooth or wrinkled, with some being sparsely pruinose (powdery) or lacking pruina (epruinose). Soredia, reproductive propagules for asexual reproduction, are present in many species within the genus.[4]

The cortex of Roccella lichens is made of hyphae that are arranged in an anticlinal manner and are about 40 to 70 µm thick. The medulla (the inner layer) is loosely structured above, having a byssoid (fibrous) or chalky texture, and below it becomes plectenchymatous (tightly packed cells) near the basal plate (holdfast) area, often showing a (yellowish) brown colouration. These lichens primarily associate with the photobiont Trentepohlia, with no secondary photobiont present. They attach to surfaces using holdfasts, including a hypomedulla which usually appears brown to dark brown, sometimes with a yellowish tinge.[4]

The ascomata (spore-producing structures) of Roccella are in the form of apothecia, lateral, and circular in outline. They can be either immersed in the thallus or sessile with a constricted base and can reach up to 2.5 mm in diameter. The disc of the apothecia is exposed, white, and features a rimose, pruinose layer. The exciple (the outer layer of the ascomata) initially contains algae and a cortex, but over time, the algae may be displaced, and the cortex eroded. The proper exciple forms a thin parathecium and is sometimes inconspicuous.[4]

The epithecium (upper layer of the ascomata) is about 40 to 50 µm high, brown, with intertwined paraphysoids (supporting structures in the hymenium) that are sparsely branched. The hymenium (spore-bearing layer) itself is 70 to 90 µm high. Paraphysoids within the hymenium are sparsely branched, hyaline (translucent), and measure 1 to 2 µm in diameter. The hypothecium (layer beneath the hymenium) is distinct, dark brown, carbonaceous, and does not extend into the medulla. The asci (spore-bearing cells) are clavate (club-shaped), measuring 60 to 85 by 12 to 14 µm. Ascospores are fusiform (spindle-shaped), curved, smooth, contains three septa (internal partitions), and are hyaline.[4]

Conidiomata (asexual reproductive structures) are pycnidial (flask-shaped), solitary, immersed in the thallus, and black, measuring about 0.1 mm in diameter. The conidia (asexual spores) are filiform (thread-like), curved, measuring 16 to 21 by less than 1 µm. In terms of chemistry, Roccella lichens contain orcinol and β-orcinol depsides, as well as aliphatic acids. Roccella lichens grow on rock or on bark.[4]

Species

References

  1. ^ "Synonymy: Roccella DC". Species Fungorum. Retrieved 26 December 2020.
  2. ^ Wijayawardene, Nalin; Hyde, Kevin; Al-Ani, LKT; Dolatabadi, S; 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.
  3. ^ de Candolle, Augustin Pyramus (1805). Flore française (in French). Vol. 2. Paris: Chez H. Agasse. p. 334.
  4. ^ a b c d e Tehler, Anders (2011). "Roccella, the Sonoran species reviewed". In Bates, Scott T.; Bungartz, Frank; Lücking, Robert; Herrea-Campos, Maria A.; Zambrano, Angel (eds.). Biomonitoring, Ecology, and Systematics of Lichens. Festschrift Thomas H. Nash III. Bibliotheca Lichenologica. Vol. 106. Stuttgart: J. Cramer in der Gebr. Borntraeger Verlagsbuchhandlung. pp. 309–318. ISBN 978-3-443-58085-8.
  5. ^ Tehler, Anders; Irestedt, Martin; Bungartz, Frank; Wedin, Mats (2009). "Evolution and reproduction modes in the Roccella galapagoensis aggregate (Roccellaceae, Arthoniales)". Taxon. 58 (2): 436–456. doi:10.1002/tax.582010.
  6. ^ Tehler, Anders; Irestedt, Martin; Wedin, Mats; Ertz, Damien (2009). "Origin, evolution and taxonomy of American Roccella (Roccellaceae, Ascomycetes)". Systematics and Biodiversity. 7 (3): 301–317. doi:10.1017/S1477200009990065.
  7. ^ a b c d Follmann, G.; Werner, B. (2000). "New saxicolous Roccella species from Galapagos and reflections on the evolution of the Roccellaceae (Arthoniales) on the "Enchanted Islands"". Bibliotheca Lichenologica. 75: 1–18.
  8. ^ Aptroot, A.; Schumm, F. (2011). Fruticose Roccellaceae, an anatomical-microscopical atlas and guide with a worldwide key and further notes on some crustose Roccellaceae or similar lichens. Books on Demand. p. 234. ISBN 978-3000336898.
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