# Thelenella

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***Thelenella*** is a [genus](/source/Genus) of [lichen](/source/Lichen)-forming [fungi](/source/Fungi) in the family [Thelenellaceae](/source/Thelenellaceae).[1][2] These inconspicuous lichens form thin, crust-like growths that are tightly attached to their [substrates](/source/Substrate_(biology)) and appear as dull whitish, pale grey, or light brown patches. Species of *Thelenella* are commonly found in damp, shaded environments where they grow on tree bark, living leaves, moss cushions, rock faces, and moss-rich soil. The genus is distinguished by its thick-walled [fruiting bodies](/source/Fruiting_bodies) that are mostly embedded within the lichen crust and contain multicellular [spores](/source/Spore) with multiple [cross-walls](/source/Septum).

## Taxonomy

The genus was [circumscribed](/source/Circumscription_(taxonomy)) by the Finnish lichenologist [William Nylander](/source/William_Nylander_(botanist)) in 1855, with *[Thelenella modesta](/source/Thelenella_modesta)* assigned as the [type species](/source/Type_species). In his original description, Nylander characterised *Thelenella* by its pore-like [fruiting bodies](/source/Fruiting_bodies) with an immersed [perithecium](/source/Perithecium) that was either uncoloured or only superficially pale. He noted that the [spores](/source/Spore) were somewhat large, oblong, and multicellular, whilst the gelatinous [hymenium](/source/Hymenium) remained entirely colourless. Nylander distinguished the genus as [morphologically](/source/Morphology_(biology)) distinct, noting that the fruiting bodies were quite different from those of *[Verrucaria](/source/Verrucaria)*.[3]

## Description

*Thelenella* forms an inconspicuous, crust‑like [thallus](/source/Thallus) that lies tightly attached to its [substrate](/source/Substrate_(biology)) and ranges from thin, membranous patches to cracked or warted crusts in dull whitish, pale grey, or light brown tones. The [photosynthetic](/source/Photosynthesis) partner is a minute, spherical [green alga](/source/Green_alga) of the type, evenly distributed through the fungal tissue.[4]

[Sexual reproduction](/source/Sexual_reproduction) takes place in thick‑walled [perithecia](/source/Perithecia) that are mostly immersed in the thallus. Their outer wall () is built of long, narrow cells arranged either lengthwise or in a tangled mesh; the pigment is evenly spread through this wall or diffused in a surrounding gel, never appearing grainy under high magnification. A second, darker protective layer () is rarely developed. Inside, the hymenial gel shows no reaction to iodine (I–, K/I–). Delicate, thread‑like branch and fuse, especially near their bases and tips, but they may be absent around the apical pore. The [asci](/source/Ascus) are , meaning they have two functional wall layers: a thin inner and a thicker outer one; they usually carry no iodine‑positive structures and contain two to eight [ascospores](/source/Ascospore). The spores themselves are colourless to slightly brown, with multiple [cross‑walls](/source/Septum) that give them a somewhat to strongly muriform appearance; their outer wall is only marginally thicker than the septa.[4]

[Asexual](/source/Asexual_reproduction) propagation is achieved by *[Roccella](/source/Roccella_(lichen))*‑type [pycnidia](/source/Pycnidia) embedded in the thallus, which release colourless, rod‑shaped [conidia](/source/Conidia) lacking internal septa. No [secondary metabolites](/source/Secondary_metabolite) ([lichen products](/source/Lichen_product)) have been detected in *Thelenella* species by [thin-layer chromatography](/source/Thin-layer_chromatography).[4]

## Ecology

Species of *Thelenella* occupy a wide range of damp, shaded [substrates](/source/Substrate_(biology)). They most often grow directly on tree bark ([corticolous](/source/Corticolous_lichen)) but can also [colonise](/source/Colonisation_(biology)) living leaves ([foliicolous](/source/Foliicolous_lichen)), bryophyte cushions on foliage ([bryophilous](/source/Bryophilous_lichen)), shaded rock faces ([saxicolous](/source/Saxicolous_lichen)), and patches of moss-rich soil ([terricolous](/source/Terricolous_lichen)).[4]

## Species

As of July 2025, [Species Fungorum](/source/Species_Fungorum) (in the [Catalogue of Life](/source/Catalogue_of_Life)) accepts 22 species of *Thelenella*.[2]

- *[Thelenella brasiliensis](/source/Thelenella_brasiliensis)* [5]
- *[Thelenella calcicola](/source/Thelenella_calcicola)* [6]
- *[Thelenella cinerascens](/source/Thelenella_cinerascens)* [7]
- *[Thelenella fugiens](/source/Thelenella_fugiens)* [7]
- *[Thelenella fusispora](/source/Thelenella_fusispora)* [8] – Tanzania
- *[Thelenella geminipara](/source/Thelenella_geminipara)* [7]
- *[Thelenella haradae](/source/Thelenella_haradae)* [9] – South Korea
- *[Thelenella humilis](/source/Thelenella_humilis)* [7]
- *[Thelenella indica](/source/Thelenella_indica)* [10] – India
- *[Thelenella inductula](/source/Thelenella_inductula)* [8]
- *[Thelenella justii](/source/Thelenella_justii)*
- *[Thelenella kerguelena](/source/Thelenella_kerguelena)* [8]
- *[Thelenella larbalestieri](/source/Thelenella_larbalestieri)*
- *[Thelenella lateralis](/source/Thelenella_lateralis)* [11]
- *[Thelenella luridella](/source/Thelenella_luridella)* [8]
- *[Thelenella luzonensis](/source/Thelenella_luzonensis)*
- *[Thelenella marginata](/source/Thelenella_marginata)* [8]
- *[Thelenella mawsonii](/source/Thelenella_mawsonii)* [12]
- *[Thelenella melanospora](/source/Thelenella_melanospora)* [13]
- *[Thelenella modesta](/source/Thelenella_modesta)* [14]
- *[Thelenella monospora](/source/Thelenella_monospora)* [15] – Brazil
- *[Thelenella muscorum](/source/Thelenella_muscorum)*
- *[Thelenella nubifera](/source/Thelenella_nubifera)* [6]
- *[Thelenella philippina](/source/Thelenella_philippina)*
- *[Thelenella rappii](/source/Thelenella_rappii)* [7]
- *[Thelenella sampaiana](/source/Thelenella_sampaiana)*
- *[Thelenella sastreana](/source/Thelenella_sastreana)* [7]
- *[Thelenella sychnogonioides](/source/Thelenella_sychnogonioides)* [7]
- *[Thelenella tasmanica](/source/Thelenella_tasmanica)* [12]
- *[Thelenella vezdae](/source/Thelenella_vezdae)*
- *[Thelenella weberi](/source/Thelenella_weberi)* [8]

## References

1. Wijayawardene, N.N.; Hyde, K.D.; Dai, D.Q.; Sánchez-García, M.; Goto, B.T.; Saxena, R.K. et al. (2022). ["Outline of Fungi and fungus-like taxa – 2021"](https://www.researchgate.net/publication/358798332). *Mycosphere*. **13** (1): 53–453. [doi:10.5943/mycosphere/13/1/2](https://doi.org/10.5943/mycosphere/13/1/2). [hdl:10481/76378](https://hdl.handle.net/10481/76378)

1. Nylander, W. (1855). ["Essai d'une nouvelle classification des lichens (second mémoire)"](https://www.biodiversitylibrary.org/page/3862224) (in French). *Mémoires de la Société Impériale des Sciences Naturelles de Cherbourg*. **3**: 161–202 [193]

1. Orange, A. & Cannon, P. (2021). [*Ostropales: Thelenellaceae, including the genus*Thelenella'](https://britishlichensociety.org.uk/sites/default/files/Thelenellaceae.pdf)**. Vol. 8. Revisions of British and Irish Lichens. pp. 1–4.**

1. Vainio, E.A. (1896). "Lichenes Antillarum a W.R. Elliott collecti" (in Latin). *The Journal of Botany, British and Foreign*. **34**: 292–297.

1. Morse, C.A. (2016). ["Two new species of *Thelenella* and new reports from the Great Plains of central North America, with a world-wide key to the genus"](https://www.biodiversitylibrary.org/part/386097). *Opuscula Philolichenum*. **15**: 22–36. [doi:10.5962/p.386097](https://doi.org/10.5962/p.386097)

1. Harris, Richard C. (1995). [*More Florida Lichens, Including the 10-cent Tour of the Pyrenolichens*](https://nhm2.uio.no/botanisk/lav/RLL/PDF1/R7816.pdf). Bronx, New York: New York Botanical Garden.

1. Mayrhofer, H. (1987). "Monographie der Flechtengattung Thelenella" [Monograph of the lichen genus *Thelenella*]. *Bibliotheca Lichenologica*. **26**: 1–106.

1. Halda, J.P. & Hur, J.S. (2016). "*Thelenella haradae* sp. nov., a saxicolous lichen from South Korea". *Mycotaxon*. **131** (4): 805–809. [doi:10.5248/131.805](https://doi.org/10.5248/131.805)

1. Pinokiyo; Singh; K.P.; A. (2006). ["New species and new record of foliicolous lichenized fungi from Sikkim (India)"](https://www.researchgate.net/publication/292638688). *Mycotaxon*. **97**: 57–61.

1. Aptroot, Andre; Andrade, Dannyelly Santos; Mendonça, Cléverton; Lima, Edvaneide Leandro de; Cáceres, Marcela Eugenia da Silva (2015). ["Ten new species of corticolous pyrenocarpous lichens from NE Brazil"](http://publication.plazi.org/id/8038FFA0FFA95B64531502262269827C). *Phytotaxa*. **197** (3): 197–206. [Bibcode:2015Phytx.197..197A](https://ui.adsabs.harvard.edu/abs/2015Phytx.197..197A). [doi:10.11646/phytotaxa.197.3.3](https://doi.org/10.11646/phytotaxa.197.3.3)

1. Mayrhofer, H. & McCarthy, P.M. (1991). "Notes on the lichenized ascomycete genus *Thelenella* Nyl. in Australia, southern Africa and on the islands of the Subantarctic and Antarctic". *Muelleria*. **7** (3): 333–341. [doi:10.5962/p.198515](https://doi.org/10.5962/p.198515)

1. Etayo, J. & Mayrhofer, H. (2003). "*Thelenella melanospora* (Thelenellaceae, lichenized Ascomycetes), a new species from the Mediterranean region". *Nova Hedwigia*. **77** (1–2): 109–114. [Bibcode:2003NovaH..77..109E](https://ui.adsabs.harvard.edu/abs/2003NovaH..77..109E). [doi:10.1127/0029-5035/2003/0077-0109](https://doi.org/10.1127/0029-5035/2003/0077-0109)

1. Nylander, W. (1855). "Essai d'une nouvelle classification des lichens, (second mémoire)" [Essay on a new classification of lichens, (second memoir)] (in Latin). *Mémoires de la Société Impériale des Sciences Naturelles de Cherbourg*. **3**: 161–202 [193]

1. Cáceres, Marcela Eugenia da Silva & Aptroot, André (2016). "First inventory of lichens from the Brazilian Amazon in Amapá State". *The Bryologist*. **119** (3): 250–265. [doi:10.1639/0007-2745-119.3.250](https://doi.org/10.1639/0007-2745-119.3.250)

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