Friday Fellow: Pygmy Black Lichen

by Piter Kehoma Boll

We all know lichens, those crusty fungi that grow associated with algae on trees or rocks, but lichens form such a diverse group that they can be found in all types of environments, including the sea, for example.

Today’s species, Lichina pygmaea, which I decided to call the pygmy black lichen, is one of those marine species. Found at the intertidal zone of rocky shores in Europe, the pygmy black lichen forms conspicuous black tufts that sometimes grow to form extensive black mats on the rocks.

Pygmy black lichen growing among barnacles and fighting for a place with brown and green algae. Photo by iNaturalist user zaca.**

If you look it closely, you will notice that the body of the pygmy black lichen consists of a somehow flattened and branched thallus with rounded tips, being more gelatinous than its terrestrial counterparts. The tips often bear fruiting bodies, which form small round structures.

Reaching about 1 cm in height at maximum, the pygmy black lichen looks somehow like a small red alga, and is, in fact, often confused with some similar red algae, such as Catenella caespitosa, but this alga is dark purple instead of black.

Catenella caespitosa, a red alga that make be mistaken for the pygmy black lichen at first glance and vice versa. Photo by Pierre Corbrion.*

The pygmy black lichen is a so-called cyanolichen, a lichen that has cyanobacteria as associated algae instead of green algae like most terrestrial lichens. In fact, it is not closely related to the more familiar lichens, belonging to a different lineage of fungi that lichenized independently. Its physiology, however, is surprisingly similar to that of terrestrial lichens, which is likely because it spends about half of its life outside the water during the low tide, being exposed to harsh conditions like most intertidal sessile species.

A large mat of the pygmy black lichen. Credits to Pierre Corbrion.*

Lab studies have isolated important compounds of the pygmy black lichen, including pygmaniline, an antioxidant, and pygmeine, an antitumor agent, which can lead to the development of novel anticancer drugs. However, the pygmy black lichen seems to have a very slow growth like most lichens and it has difficulties competing with other intertidal species for space, thus the exploitation of this resource needs to be conducted carefully.

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References:

Mahajan N, Chadda R, Calabro K, Solanki H, O’Connell E, Murphy PV, Thomas OP (2017) Isolation and synthesis of pygmanilines, phenylurea derivatives from the Northeastern Atlantic lichen Lichina pygmaea. Tetrahedron Letters, 58(12), 1237-1239. https://doi.org/10.1016/j.tetlet.2017.02.037

Prieto A, Leal JA, Bernabé M, Hawksworth DL (2008) A polysaccharide from Lichina pygmaea and L. confinis supports the recognition of Lichinomycetes. mycological research, 112(3), 381-388. https://doi.org/10.1016/j.mycres.2007.10.013

Raven JA, Johnston AM, Handley LL, McInrot SG (1990) Transport and assimilation of inorganic carbon by Lichina pygmaea under emersed and submersed conditions. New Phytologist, 114(3), 407-417. https://doi.org/10.1111/j.1469-8137.1990.tb00408.x

Roullier C, Chollet-Krugler M, Van de Weghe P, Lohézic-Le Devehat F, Boustie J (2010) A novel aryl-hydrazide from the marine lichen Lichina pygmaea: Isolation, synthesis of derivatives, and cytotoxicity assays. Bioorganic & medicinal chemistry letters, 20(15), 4582-4586. https://doi.org/10.1016/j.bmcl.2010.06.013

Tyler-Walters H (2002) Lichina pygmaea Black lichen. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 12-11-2020]. Available from: https://www.marlin.ac.uk/species/detail/1803

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* This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

** This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.