# Crocellina

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***Crocellina*** is a [monotypic](/source/Monotypic) fungal [genus](/source/Genus) in the family [Roccellaceae](/source/Roccellaceae).[1] It contains the single species ***Crocellina cinerea***, a [saxicolous](/source/Saxicolous_lichen) (rock-dwelling), [crustose lichen](/source/Crustose_lichen) that is [endemic](/source/Endemism) to [Socotra Island](/source/Socotra_Island) in the Indian Ocean. This cream-coloured [crustose lichen](/source/Crustose_lichen) is distinguished by its unusual three-layered internal structure, featuring a characteristic [saffron](/source/Saffron)-yellow middle band that gives the genus its name. The species was originally described in 1882 and was reclassified into its own genus in 2014 when [molecular](/source/Molecular_phylogenetics) studies revealed it was genetically distinct from closely related lichens.

## Taxonomy

The genus *Crocellina* was [circumscribed](/source/Circumscription_(taxonomy)) in 2014 by Anders Tehler and Damien Ertz to accommodate a distinct [lineage](/source/Lineage_(evolution)) of lichen-forming fungi previously classified under *[Roccellina](/source/Roccellina)*. Its [type](/source/Type_(biology)) and only species, *Crocellina cinerea*, was originally [described](/source/Species_description) as *Dirina cinerea* by [Johannes Müller Argoviensis](/source/Johannes_M%C3%BCller_Argoviensis) in 1882,[2] based on material collected from [Socotra Island](/source/Socotra_Island). It was later transferred to *Roccellina* by Tehler before being reclassified under *Crocellina* once [molecular](/source/Molecular_phylogenetics) data revealed that it did not belong within *Roccellina'*s core group.[3][4]

The defining features that distinguish *Crocellina* from closely related genera include a characteristic three-layered [medulla](/source/Medulla_(lichenology)) with a distinctive saffron-yellow middle layer (the basis for the genus name, from [Latin](/source/Latin) *croceus*), and a brown-tipped composed of vertically arranged [hyphae](/source/Hypha). These features, along with its molecular distinctiveness, support its recognition as a separate genus within the Roccellaceae. Although a sterile, sorediate form had previously been described as *Dirina cinerea* f. *sorediosa*, subsequent research has demonstrated that such asexual forms are the same species ([conspecific](/source/Conspecific)) as their fertile counterparts and do not merit separate taxonomic status.[4]

## Description

*Crocellina* is a [crustose lichen](/source/Crustose_lichen)-forming fungus with a distinctive cream-coloured [thallus](/source/Thallus) that can appear smooth or slightly wrinkled and convex. In well-developed specimens, the internal structure ([medulla](/source/Medulla_(lichenology))) shows a characteristic three-layered pattern: a white upper zone, a saffron-yellow middle band, and a greyish-brown lower layer. The yellow layer is sometimes only present beneath the fruiting structures. The outer surface () consists of vertically aligned [hyphae](/source/Hypha) with brown tips, embedded in a brownish gelatinous substance. Reproductive structures called [soralia](/source/Soralia) are uncommon but, when present, appear as small, rounded patches up to 1 mm in diameter. The lichen's [photosynthetic](/source/Photosynthesis) partner is a [green alga](/source/Green_alga) from the genus *[Trentepohlia](/source/Trentepohlia_(alga))*.[4]

The fungal fruiting bodies ([apothecia](/source/Apothecia)) are disc-shaped and sit directly on the thallus. They are entire, not split or branched, and constricted at the base. A dark, carbon-rich (the supportive tissue below the spore-producing layer) extends downward and merges with the lowest medullary layer. [Ascospores](/source/Ascospore) are clear, spindle-shaped, slightly curved or straight, and measure around 18–21 μm in length by 5–6 μm in width. [Asexual reproductive](/source/Asexual_reproduction) structures ([pycnidia](/source/Pycnidia)) are embedded in the thallus as greyish spots; they produce slender, curved [conidia](/source/Conidia) roughly 9–17 μm long and less than 1 μm wide.[4]

Chemical [spot tests](/source/Spot_test_(lichen)) reveal that the cortex reacts C+ (red), K–, and PD–. The yellow layer in the medulla turns purple in K. [Thin-layer chromatography](/source/Thin-layer_chromatography) has identified several [lichen products](/source/Lichen_product) in *Crocellina*, including [erythrin](/source/Erythrin), [lecanoric acid](/source/Lecanoric_acid), [roccellic acid](/source/Roccellic_acid), and [skyrin](/source/Skyrin).[4]

## References

1. Müller, J. (1882). ["Diagnoses lichenum Socotrensium novorum a participibus expeditionum Prof. Bayley Balfour et Dr. Schweinfurth lectorum"](https://www.biodiversitylibrary.org/page/48711413) [Diagnoses of new Socotran lichens collected by participants of the expeditions of Prof. Bayley Balfour and Dr. Schweinfurth] (in Latin). *Proceedings of the Royal Society of Edinburgh*. **11**: 457–472 [465]

1. Tehler, Anders (1983). "The genera *Dirina* and *Roccellina*". *Nordic Journal of Botany*. **70**: 67. [doi:10.1111/j.1756-1051.1983.tb01473.x](https://doi.org/10.1111/j.1756-1051.1983.tb01473.x)

1. Ertz, Damien; Tehler, Anders; Irestedt, Martin; Frisch, Andreas; Thor, Göran; van den Boom, Pieter (2014). "A large-scale phylogenetic revision of Roccellaceae (Arthoniales) reveals eight new genera". *Fungal Diversity*. **70** (1): 31–53. [doi:10.1007/s13225-014-0286-5](https://doi.org/10.1007/s13225-014-0286-5)

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Adapted from the Wikipedia article [Crocellina](https://en.wikipedia.org/wiki/Crocellina) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Crocellina?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.