# Helminthocarpon

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Single-species fungal genus

Helminthocarpon Scientific classification Kingdom: Fungi Division: Ascomycota Class: Arthoniomycetes Order: Arthoniales Family: incertae sedis Genus: Helminthocarpon Fée (1837) Species: H. leprevostii Binomial name Helminthocarpon leprevostii Fée (1837) Synonyms[1] Graphis leprovostii (Fée) Mont. (1845)

***Helminthocarpon*** is a fungal [genus](/source/Genus) of uncertain [familial](/source/Family_(taxonomy)) placement in the order [Arthoniales](/source/Arthoniales).[2][3] It comprises the single species ***Helminthocarpon leprevostii***, a [crustose lichen](/source/Crustose_lichen). This species, which is widespread in [tropical](/source/Tropical) regions of the world, is typically found growing [on tree bark](/source/Corticolous_lichen), and occasionally [on wood](/source/Lignicolous_lichen).

## Taxonomy

*Helminthocarpon* is a [monospecific](/source/Monospecific) genus, containing only the species *Helminthocarpon leprevostii*. First [described](/source/Species_description) by the French botanist [Antoine Laurent Apollinaire Fée](/source/Antoine_Laurent_Apollinaire_F%C3%A9e) in 1837,[4] its [taxonomic](/source/Taxonomy_(biology)) placement has been a subject of debate. Several years after Fée's original description of the species, [Camille Montagne](/source/Camille_Montagne) suggested that the genus *[Graphis](/source/Graphis_(lichen))* would be a more appropriate placement.[5] Originally classified in the family [Graphidaceae](/source/Graphidaceae) due to its [lirellate](/source/Glossary_of_lichen_terms#lirella) (elongated and furrowed) fruiting bodies, studies in the late 20th and early 21st centuries suggested that *Helminthocarpon* may be more closely related to members of the order Arthoniales.[6]

*Helminthocarpon* shares several characteristics with genera in the Arthoniales, particularly *[Cryptothecia](/source/Cryptothecia)*. These include similarities in ascus development, spore structure, and the arrangement of structures surrounding the asci. However, *Helminthocarpon* differs in having a [corticate](/source/Glossary_of_lichen_terms#corticate) thallus (outer fungal layer) and more well-defined fruiting structures compared to *Cryptothecia*. Some researchers have suggested *Helminthocarpon* may represent an evolutionary link between the less structured fruiting bodies of *Cryptothecia* and the more defined ones of other Arthoniales genera.[6]

As of 2013, the exact familial placement of *Helminthocarpon* within the Arthoniales remains unresolved. Further molecular studies are needed to determine whether it belongs in the family Arthoniaceae or Opegraphaceae. The genus is no longer included in major taxonomic outlines of the Graphidaceae.[6]

Two species described from [Meghalaya](/source/Meghalaya) (India) and formerly placed in the genus, *Helminthocarpon album* and *H. cherrapunjiense*,[7] were made [synonymous](/source/Synonym_(taxonomy)) with *[Diorygma radiatum](https://en.wikipedia.org/w/index.php?title=Diorygma_radiatum&action=edit&redlink=1)* in 2009.[8]

## Description

The crustose thallus of *Helminthocarpon leprevostii* is pale beige in colour with a smooth, somewhat shiny surface. Unlike many related lichens in the Arthoniales, *Helminthocarpon* has a cortex, a protective outer layer that gives the thallus its distinctive appearance. The [ascomata](/source/Ascomata) (fruiting bodies) are a defining feature of this species. They appear as short, broad, swollen lirellae – elongated fruiting bodies resembling small beans or furrows. These lirellae are beige to white in colour, similar to the thallus, and develop a wide, irregular central slit as they mature. The internal structure of the lirellae is complex: the sides ([exciple](/source/Glossary_of_lichen_terms#exciple) flanks) are strongly [carbonised](/source/Glossary_of_lichen_terms#carbonised), appearing black, but this carbonisation is concealed beneath a thick thalline layer, giving the outward appearance of pale, swollen structures on the lichen surface.[6]

The internal reproductive components of *Helminthocarpon* are equally distinctive. The [asci](/source/Ascus), or spore-producing cells, develop within a [hamathecium](/source/Glossary_of_lichen_terms#hamathecium) – a structure composed of strongly branched and repeatedly joining threads called [paraphysoids](/source/Glossary_of_lichen_terms#paraphysoids). These paraphysoids form a dense network around individual asci, a characteristic that distinguishes *Helminthocarpon* from many other lichens. The asci themselves are cylindrical to narrowly club-shaped, tapering at the base into a stalk. They have a thick, two-layered wall that reacts differently to [iodine](/source/Iodine)-based [staining](/source/Staining): the outer layer does not stain, while the inner layer turns a pale blue. The [ascospores](/source/Glossary_of_lichen_terms#ascospores) are large (89–165 μm long and 22–62 μm wide), colourless, and [muriform](/source/Glossary_of_lichen_terms#muriform), meaning they are divided by both longitudinal and transverse [septa](/source/Septum) (internal walls). These septa are curved rather than straight, giving the spores a distinctive appearance. Both the [medulla](/source/Medulla_(lichenology)) (the internal layer of the thallus) and the spores show no colour change (are negative) when tested with iodine.[6]

## Habitat and distribution

*Helminthocarpon leprevostii* has a [pantropical](/source/Pantropical) distribution, meaning it is found in tropical regions around the world. The species has been recorded in various locations, including the [Galápagos Islands](/source/Gal%C3%A1pagos_Islands), where it was newly reported in 2013. In terms of habitat preferences, *H. leprevostii* is primarily [corticolous](/source/Corticolous_lichen), growing on the bark of trees. It shows a particular affinity for native and [endemic](/source/Endemic) tree species in its habitats. In the Galápagos, it has been frequently observed on the bark of *[Bursera graveolens](/source/Bursera_graveolens)*, *[Pisonia floribunda](https://en.wikipedia.org/w/index.php?title=Pisonia_floribunda&action=edit&redlink=1)*, and *[Cordia lutea](/source/Cordia_lutea)*. While primarily bark-dwelling, the species has also been occasionally found growing on wood, demonstrating some versatility in its [substrate](/source/Glossary_of_lichen_terms#substrate) choices.[6]

*Helminthocarpon leprevostii* appears to favour specific ecological zones within its range. In the Galápagos, it is moderately common throughout the dry zone and lower transition zone of the islands. This suggests a tolerance for, or perhaps preference for, somewhat arid conditions. The lichen tends to grow in semi-shaded to shaded environments that offer some degree of shelter. However, it has also been observed in moderately sunny and exposed sites, indicating a certain adaptability to light conditions. This habitat flexibility may contribute to its widespread distribution in tropical regions.[6]

## References

1. **[^](#cite_ref-Species_Fungorum_synonymy_1-0)** ["Synonymy. Current Name: *Helminthocarpon leprevostii* Fée, Essai Crypt. Exot., Suppl. Révis. (Paris): 156 (1837)"](https://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=386712). [Species Fungorum](/source/Species_Fungorum). Retrieved 18 September 2024.

1. **[^](#cite_ref-CoL_2-0)** ["*Helminthocarpon*"](https://www.catalogueoflife.org/data/taxon/637DX). *[Catalogue of Life](/source/Catalogue_of_Life)*. [Species 2000](/source/Species_2000): Leiden, the Netherlands. Retrieved 18 September 2024.

1. **[^](#cite_ref-Wijayawardene_et_al._2022_3-0)** 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](/source/Doi_(identifier)):[10.5943/mycosphere/13/1/2](https://doi.org/10.5943%2Fmycosphere%2F13%2F1%2F2). [hdl](/source/Hdl_(identifier)):[1854/LU-8754813](https://hdl.handle.net/1854%2FLU-8754813).

1. **[^](#cite_ref-Fée_1837_4-0)** Fée, A.L.A. (1837). *Essai sur les Cryptogames des Écorces Exotiques Officinales. Deuxième Partie, Supplément et Révision* [*Essay on the Cryptogams of Exotic Medicinal Barks. Part Two, Supplement and Revision*] (in French). p. 156.

1. **[^](#cite_ref-Montagne_1845_5-0)** Montagne, C. (1842). *Histoire physique, politique et naturelle de l'Ile de Cuba. Botanique, Plantes cellulaires* (in French). pp. 176, t. 35:11.

1. ^ [***a***](#cite_ref-Bungartz_et_al._2013_6-0) [***b***](#cite_ref-Bungartz_et_al._2013_6-1) [***c***](#cite_ref-Bungartz_et_al._2013_6-2) [***d***](#cite_ref-Bungartz_et_al._2013_6-3) [***e***](#cite_ref-Bungartz_et_al._2013_6-4) [***f***](#cite_ref-Bungartz_et_al._2013_6-5) [***g***](#cite_ref-Bungartz_et_al._2013_6-6) Bungartz, Frank; Dután-Patiño, Valeria Leonor; Elix, John A. (2013). "The lichen genera *Cryptothecia*, *Herpothallon* and *Helminthocarpon* (Arthoniales) in the Galapagos Islands, Ecuador". *The Lichenologist*. **45** (6): 739–762. [doi](/source/Doi_(identifier)):[10.1017/S0024282913000522](https://doi.org/10.1017%2FS0024282913000522).

1. **[^](#cite_ref-Awasthi_&_Singh_1977_7-0)** Awasthi, D.D.; Singh, S.R. (1977). "Five new taxa of saxicolous lichens from Meghalaya, India". *Norwegian Journal of Botany*. **24**: 1–8.

1. **[^](#cite_ref-Singh_&_Swarnalatha_2009_8-0)** Singh, K.; Swarnalatha, G. (2009). "Some new combinations in lichen family Graphidaceae". *Indian Journal of Forestry*. **32** (1): 179–180. [doi](/source/Doi_(identifier)):[10.54207/bsmps1000-2009-R0M857](https://doi.org/10.54207%2Fbsmps1000-2009-R0M857).

Taxon identifiers Helminthocarpon Wikidata: Q21213565 Wikispecies: Helminthocarpon AusLichen: 30021788 CoL: 637DX GBIF: 3269571 iNaturalist: 175742 IndexFungorum: 2259 IRMNG: 1068501 MycoBank: 2259 Open Tree of Life: 4929262 PLANTS: HELMI SpeciesFungorum: 2259 Helminthocarpon leprevostii Wikidata: Q21267604 Wikispecies: Helminthocarpon leprevostii CoL: 3KFZ5 EoL: 6549397 GBIF: 5474338 iNaturalist: 221057 IndexFungorum: 386712 MycoBank: 386712 NatureServe: 2.127241 Open Tree of Life: 4929277 PLANTS: HELE7 SpeciesFungorum: 386712

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