Tag Archives: lichens

by | November 11, 2022 · 9:00 am

Friday Fellow: Bristly Beard Lichen

by Piter Kehoma Boll

Lichens form an astonishingly diverse group of algae-associated fungi that are found in all sorts of places over the world. One of the most easily recognizable genera is Usnea, whose species are commonly known as beard lichen. One of the most widespread species across the globe is Usnea hirta, the bristly beard lichen.

A specimen of the bristly beard lichen hanging from a branch in Estonia. Photo by Teodor Agabus.*

Like all species of Usnea, the bristly beard lichen is a fruticose lichen, which means it grows in the shape of a small leafless shrub or coral on the surface of trees. It has a grayish-green or greenish-gray color, and its “branches” are very flexible but not as long as in other species that look more like a beard. It prefers to grow on acid bark, especially branches of conifers such as Pinus, and is not that common in deciduous trees, at least in temperate regions. It likes open sites where it can receive lots of sunlight.

A species of Usnea, likely the bristly beard lichen, growing in Uruguay. Photo by Pablo Balduvino.*

With worldwide distribution, the bristly beard lichen is a relatively heterogeneous species, which led to many problems in its classification, as many regional forms were described as separate species and later revealed to be the same Usnea hirta.

In this specimen from Spain, we can see a large apothecium, a structure that produces spores for sexual reproduction. Photo by Maria José Chesa Marro.*

Like many lichens, the bristly beard lichen can reproduce both sexually and asexually. Sexual reproduction occurs through spore production in apothecia (singular apothecium), cup-shaped structures. When the spores are released in the environment and germinate, they need to find a compatible alga to start a new association or the fungus will not survive. Thus, sexual reproduction is very difficult and asexual reproduction is the most efficient strategy. It consists of forming soralia (singular soralium), small “warts” that grow attached to the branches of the lichen. The soralia are groups of sorecia (singular sorecium), which are small units formed by a piece of alga surrounded by fungal hyphae. As both components of the association are already present, a sorecium can germinate whenever it lands on a suitable surface.

The greener wart-like structures covering most of the branches in this specimen from Latvia are likely soralia, the structures for asexual reproduction. Photo by Davis Birzgalis.*

The bristly beard lichen is very sensitive to air pollution, especially to sulfur dioxide (SO2) and nitrogen compounds. It has also shown the ability to bioaccumulate heavy metals in its tissues. As a result, more recent studies are trying to turn it into a model species for bio-monitoring of air pollution, especially in North America.

Thus, if you find yourself surrounded by trees covered with lots and lots of bristly beard lichens, it is likely that the air where you live is not that bad, at least considering sulfur and nitrogen compounds.

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More lichens:

Friday Fellow: Elegant sunburst lichen (on 15 July 2016)

Friday Fellow: Christmas wreath lichen (on 23 December 2016)

Friday Fellow: Pygmy black lichen (on 13 November 2020)

Friday Fellow: Black wart lichen (on 29 October 2021)

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References:

Clerc, P. (1997). Notes on the genus Usnea Dill. ex Adanson. The Lichenologist, 29(3), 209-215. https://doi.org/10.1006/lich.1996.0075

Fos, S., & Clerc, P. (2000). The lichen genus Usnea on Quercus suber in Iberian cork-oak forests. The lichenologist, 32(1), 67-88. https://doi.org/10.1006/lich.1999.0242

Shrestha, G., Petersen, S. L., & CLAIR, L. L. S. (2012). Predicting the distribution of the air pollution sensitive lichen species Usnea hirta. The Lichenologist, 44(4), 511-521. https://doi.org/10.1017/S0024282912000060

Van Herk, C. M., Mathijssen-Spiekman, E. A. M., & De Zwart, D. (2003). Long distance nitrogen air pollution effects on lichens in Europe. The Lichenologist, 35(4), 347-359. https://doi.org/10.1016/S0024-2829(03)00036-7

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by | October 29, 2021 · 8:00 am

Friday Fellow: Black Wart Lichen

by Piter Kehoma Boll

During their evolution, fungi realized that becoming friends with algae was a successful business, and so this association evolved several times independently, giving rise to a particular type of organism that we call lichen. Three lichens have been presented here previously, the elegant sunburst lichen, the Christmas wreath lichen, and the Pygmy black lichen. And today we have once more a black lichen, Verrucaria nigrescens, or the black wart lichen.

Found across Eurasia and North America, the black wart lichen is a crustose lichen, meaning that it grows on the substrate as a crust, resembling a kind of thick and dry drop of paint, in this case, black paint. Although somehow even in height, the surface of the black wart lichen is rough and crossed by fissures that make it look kind of like a set of tightly arranged warts.

The black wart lichen often looks as if someone dropped some black paint on a rock. Photo by Heikel B..*

Although some lichen species can grow on several substrates, the black wart lichen grows almost exclusively on limestone, eventually appearing on siliceous rocks, but the latter do not seem to be an ideal substrate. But spores cannot move around looking for a better substrate, right? So it is try or die for them.

The color of lichens is often affected by the color of their algal component, but in the black wart lichen the black color is part of the fungal component and the green color of the algae becomes completely masked.

Snails appear to be one of the main grazers of the black wart lichen. Several species have been observed feeding on the lichen’s thallus, sometimes only removing the fungal surface, which exposed the green algal layers beneath it, and sometimes eating the algae as well, exposing the white lower layer of the organism or sometimes even to rock itself by eating the lichen as a whole.

Detail of the black wart lichen’s surface. Photo by Valentin Hamon.*

The preference for limestones makes it very likely to find the black wart lichen growing on human-made structures that are made of limestone or otherwise rich in calcium, such as marble. This may be considered aesthetically unpleasant (which I disagree; a lichen-covered sculpture is very cool) but can also affect the integrity of the structure. Although the black wart lichen is a surface lichen, which means it does not penetrate the substrate with its hyphae, it secrets oxalic acid, which slowly dissolves the rock below it. Studies have also shown that the lichen’s blackness causes a considerable increase in the temperature of the substrate below it, which can make it more susceptible to breakdown. As a result, several techniques have been studied to find effective ways to remove the black wart lichen from surfaces.

On the other hand, a lichen-covered limestone is also protected from the erosion caused by water and, although the lichen increases the rock’s temperature under it when the sun shines on it, lichen-covered rocks have in general a more stable temperature, without strong fluctuations across the day, as the lichen also works as a thermal insulator. It seems, therefore, that we must be careful in judging whether a lichen is indeed harmful to the structure it grows on. Sometimes it will actually protect it.

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References:

Carter, N. E. A., & Viles, H. A. (2003). Experimental investigations into the interactions between moisture, rock surface temperatures and an epilithic lichen cover in the bioprotection of limestone. Building and environment, 38(9-10), 1225-1234. https://doi.org/10.1016/S0360-1323(03)00079-9

Carter, N. E. A., & Viles, H. A. (2004). Lichen hotspots: raised rock temperatures beneath Verrucaria nigrescens on limestone. Geomorphology, 62(1-2), 1-16. https://doi.org/10.1016/j.geomorph.2004.02.001

Fröberg, L., Baur, A., & Baur, B. (1993). Differential herbivore damage to calcicolous lichens by snails. The Lichenologist, 25(1), 83-95.

Osticioli, I., Mascalchi, M., Pinna, D., & Siano, S. (2015). Removal of Verrucaria nigrescens from Carrara marble artefacts using Nd: YAG lasers: comparison among different pulse durations and wavelengths. Applied Physics A, 118(4), 1517-1526. https://doi.org/10.1007/s00339-014-8933-y

Radeka, M., Ranogajec, J., Kiurski, J., Markov, S., & Marinković-Nedučin, R. (2007). Influence of lichen biocorrosion on the quality of ceramic roofing tiles. Journal of the European Ceramic Society, 27(2-3), 1763-1766. https://doi.org/10.1016/j.jeurceramsoc.2006.05.001

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by | November 13, 2020 · 8:00 am

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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by | May 28, 2019 · 8:44 pm

Looking like lichens: leaves disguised as tree trunks to avoid being eaten

by Piter Kehoma Boll

We are all familiar with animals of many species that developed interesting mechanisms to avoid being eaten. This includes, for example, animals that look like plant parts:

The famous giant leaf insect, Phyllium giganteum. Photo by Bernard Dupont.**

and animals that merge with the background:

An East African jackal, Canis mesomelas, in the Savanna. Can you spot it? Photo by Nevit Dilmen.***

There are also animals that look like other, unpalatable or dangerous, animals, in order to push predators away:

The edible viceroy butterfly Limenitis archippus (top) mimicks the poisonous monarch butterfly Danaus plexippus (bottom). Credits to Wikimedia user DRosenbach. Photos by D. Gordon E. Robertson and Derek Ramsey.***

But we rarely think that plants also use this sort of mechanisms to avoid being eaten. There are, however, some recorded cases of similar behaviors in plants. One case is that of the plant Corydalis benecincta, whose leaves commonly have the brownish color of the surrounding rocks:

The leaves of Corydalis benecincta look like the rocks found in its natural habitat. Photo by Yang Niu.

Recently, a study on plants of the genus Amorphophallus found another interesting case of mimicry. This genus, which includes the famous titan arum, usually develops a single large leaf that in some species can attain the size of a small tree or shrub. Such a gigantic leaf seems to be a perfect meal for some herbivores but, to avoid them, many species of this genus developed a series of marks along the petiole of their leaf that look like lichens or cyanobacteria.

Cyanobacteria-like marks on the petiole of Amorphophallus gigas (A); Cyanobacteria-like plus lichen-like marks also on A. gigas (B); And lichen-like marks on A. hewittii (C) and A. dactylifer (D). Extracted from Claudel et al. (2019).

With this mimicry, the petioles, which are quite tender, end up looking like a hard and old trunk that does not look that interesting as a meal for most herbivores. The lichen marks are so well represented that they can even be associated with real lichen genera. For example, the marks seen on the figures B and C above look like lichens of the genus Cryptothecia.

Lichen of the species Cryptothecia striata, which seems to be mimicked by the marks in Amorphophallus gigas and A. hewittii. Photo by Jason Hollinger.*

How and why this marks evolved across Amorphophallus species is still not well understood. Despite the hypothesis that they help the plant mimic a tree trunk, some species with small leaves also have those marks, while some with large leaves do not have any marks or have them in simpler patterns. The titan arum Amorphophallus titanum is a good example of the latter:

Amorphophallus titanum is the largest species of Amorphophallus but displays a considerably simple lichen-like pattern. Photo by flickr user Björn S.**

For a long time, plants were regarded as less dynamic organisms than animals, but in recent years our knowledge about them is increasing and showing that they are actually very versatile creatures that developed similar creative and complex strategies.

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Reference:

Claudel C, Lev-Yadun S, Hetterscheid W, & Schultz M 2019. Mimicry of lichens and cyanobacteria on tree-sized Amorphophallus petioles results in their masquerade as inedible tree trunks. Bot J Linn Soc 190: 192–214.

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**Creative Commons License This work is licensed under a Creative Commons Attribution-Share Alike 2.0 Generic License.

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by | December 23, 2016 · 8:00 am

Friday Fellow: Christmas Wreath Lichen

ResearchBlogging.orgby Piter Kehoma Boll

Celebrating Christmas (or whatever you call this time of the year), today’s Friday Fellow is another lichen. And the reason I chose it is because it is known as Christmas wreath lichen due to its red and green color.

Cryptothecia rubrocinta growing on Patagonula americana in Argentina. Photo by Wikimedia user Millifolium.*

Cryptothecia rubrocicnta growing on Patagonula americana in Argentina. Photo by Wikimedia user Millifolium.*

Scientifically known as Cryptothecia rubrocincta, the Christmas wreath lichen is found throughout the Americas, from the United States to Argentina, and usually grows on shady tree trunks. In mature specimens, three different color zones can be seen, a central grayish-green zone, an intermediate white zone, and an external red rim. The central zone is usually covered by red nodules which in some cases may hinder the visibility of the grayish-green color.

The red color is caused by a combination of a quinone, called cheidectonic acid, and beta-carotene, which together protect the organism from radiation and provides DNA repair.

Apparently, this lichen only reproduces asexually, thus not forming any sexual structures. For that reason, it was thought for some time that it could be a basidiomycete fungus, although most lichens are formed by ascomycete fungi. Nowadays, however, we know that it is actually an ascomycete. DNA extraction is difficult, though, because several microscopic fungi live inside the lichen, thus somewhat making it a very complex organism formed by several interconnected species.

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References:

Elfie Stocker-Wörgötter (2010). Stress and Developmental Strategies in Lichens Symbioses and Stress, 525-546 DOI: 10.1007/978-90-481-9449-0_27

Wikipedia. Cryptothecia rubrocincta. Available at <https://en.wikipedia.org/wiki/Cryptothecia_rubrocincta&gt;. Access on December 16, 2016.

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by | July 20, 2016 · 2:40 pm

New Species: July 11 to July 20

by Piter Kehoma Boll

Here is a list of species described from July 11 to July 20. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa, International Journal of Systematic and Evolutionary Microbiology, and Systematic and Applied Microbiology, as well as journals restricted to certain taxa.

Pseudoechthistatus sinicus(top) and P. pufujiae are two of the more than 40 new species of beetles described in the last 10 days.

Pseudoechthistatus sinicus (top) and P. pufujiae (bottom) are two of the 40 new species of beetles described in the last 10 days.

Archaea

Bacteria

SARs

Plants

Excavates

Fungi

Sponges

Flatworms

Annelids

Mollusks

Roundworms

Arachnids

Myriapods

Crustaceans

Hexapods

Cartilaginous fishes

Ray-finned fishes

Reptiles

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by | July 15, 2016 · 8:00 am

Friday Fellow: Elegant sunburst lichen

by Piter Kehoma Boll

Bipolar and Alpine in distribution, occurring in both Arctic and Antarctic regions, as well as on the Alps and nearby temperate areas, the elegant sunburst lichen (Xanthoria elegans) is a beautiful and interesting creature. As all lichens, it is formed by a fungus associated with an alga.

An elegant sunburst lichen growing on a rock in the Alps. Photo by flickr user Björn S...*

An elegant sunburst lichen growing on a rock in the Alps. Photo by flickr user Björn S…*

The elegant sunburst lichen grows on rocks and usually has a circular form and a red or orange color. Growing very slowly, at a rate of about 0.5 mm per year, they are useful to estimate the age of a rock face by a technique called lichenometry. By knowing the growth rate of a lichen, one can assume the lichen’s age by its diameter and so determine the minimal time that the rock has ben exposed, as a lichen cannot grow on a rock if it is not there yet, right? This growth rate is not that regular among all populations. Lichens growing closer to the poles usually grow quickly because they seem to have higher metabolic rates to help them survive in the colder climates.

Beside its use to determine the age of a rock surface, the elegant sunburst lichen is a model organism in experiments related to resistance to the extreme environments of outer space. It has showed the ability to survive and recover from exposures to vacuum, UV radiation, cosmic rays and varying temperatures for as long as 18 months!

Maybe when we finally reach a new inhabitable planet, we will find out that the elegant sunburst lichen had arrived centuries before us!

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References:

Murtagh, G. J.; Dyer, P. S.; Furneaux, P. A.; Critteden, P. D. 2002. Molecular and physiological diversity in the bipolar lichen-forming fungus Xanthoria elegans. Mycological Research, 106(11): 1277–1286. DOI: 10.1017/S0953756202006615

Wikipedia. Xanthoria elegans. Available at: < https://en.wikipedia.org/wiki/Xanthoria_elegans >. Access on June 30, 2016.

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