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A tale of ants, jays and nettles
If you have gone for a walk through any European pine forest, you probably have spotted some hills between the trees. Have you looked carefully at those hills? If so, you have seen that these constructions are, in fact, ant hills! In the pine forests of Europe the species Formica rufa is responsible for these ant hills. I enjoy sitting in front of the colonies and observing how the ants work. But be careful! If you get too close they will consider you an enemy and will defend the colony! They will respond by spraying formic acid (Fig. 1)…and jays know it. When a member of this bird species, Garrulus glandarius, spots an ant hill, it disturbs the ants on purpose to get a formic acid bath. Why? Because this compound acts as insecticide (you can observe this curious behaviour here).
Figure 1. Formica rufa defending the nest by spraying formic acid2
As you have suspected, the name formic acid comes from the scientific name of the ant, Formica. This is because this chemical compound was isolated for the first time from ants. John Wray, an English naturalist in 1671 wrote in a letter “If with a staff or other instrument you stir a heap of Ants, so as to anger them, they will let fall thereon a liquor”3. So, in search of more information about that liquor, he distilled some ants until he got what he called an acid spirit.
However, Formica ants are not the only living creatures that produce formic acid. Now maybe you are trying to figure out what other insects do. Here you have another example: Stingless bees (genus Oxytrigona)4. But what do you think if I tell you that plants also synthesise it? There is a common (and extremely hated) plant across Europe that does it: nettle!
I have spent most of my life thinking that when someone is stung by a nettle (Urtica dioica) the stinging hairs, called trichomes, were responsible for the pain (I mean, in a physical way). But the fact is that there is a complex chemical response (a wonderful one) behind that unpleasant experience (Fig. 2). When someone brushes against a nettle, the trichomes pierce the skin so the venom is injected. Formic acid is responsible for inducing the pain5. But wait, nettles have a secret strategy: the three neurotransmitters, histamine, acetylcholine and serotonin, cause inflammation and more pain6,7. Finally, to end this wonderful experience, tartaric and oxalic acid are in charge of extending pain duration8.
So, next time you brush against a nettle, think about it. It won’t be less painful, but at least you will be distracted by their wonder
Figure 2. The chemistry of stinging nettles5
Additional information and references
1 https://www.britannica.com/video/180428/nest-ants-formic-acid-jay
2 Warren Photographic. Image Library of Animals in Action
3 Wray, J. (1670). “Extract of a Letter, Written by Mr John Wray to the Publisher January 13. 1670. Concerning Some Un-Common Observations and Experiments Made with an Acid Juyce to be Found in Ants”. Philosophical Transactions of the Royal Society of London, 5(57–68): 2063-2066. doi:10.1098/rstl.1670.0052
4 Roubik, D.W., Smith, B.H. & Carlson, R.G. (1987). Formic acid in caustic cephalic secretions of stingless bee,Oxytrigona (Hymenoptera: Apidae). J Chem Ecol, 13: 1079–1086. https://doi.org/10.1007/BF01020539
5 Dobbin, L. (1920). XI.—On the Presence of Formic Acid in the Stinging Hairs of the Nettle. Proceedings of the Royal Society of Edinburgh, 39: 137-142.
6 Emmelin, N. & Feldberg, W. (1947). The mechanism of the sting of the common nettle (Urtica urens). Journal of Physiology, 106: 440–455.
6 Taskila, K., Saarinan, J.V., Harvima, I.T. & Harvima, R.J. (2000). Histamine and LTC4 in stinging nettle-induced urticaria. Allergy, 55: 680–681.
8 Fu, H.Y., Chen, S.J., Chen, R.F., Ding, W.H., Kuo-Huang, L.L. & Huang, R.N. (2006). Identification of Oxalic Acid and Tartaric Acid as Major Persistent Pain-inducing Toxins in the Stinging Hairs of the Nettle, Urtica thunbergiana, Annals of Botany, 98(1): 57–65. https://doi.org/10.1093/aob/mcl089
9 Compound Interest 2015. https://www.compoundchem.com/2015/06/04/nettles/
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The Pyrenean desman
Is it a rat??? Is it a platypus??? No!!! It’s the Pyrenean desman!
Known by the scientific society as Galemys pyrenaicus, this little and ―it has to be said― weird animal, belongs to the Talpidae family (that is, the mole family). Now, prepare yourself because I’m going to introduce you to one of my favourite words: Eulipotyphla. It sounds funny, doesn’t it? The term Eulipotyphla refers to a group of mammals that underwent a rapid diversification just after the Cretaceous-Paleogene boundary1 and includes members of the Talpidae family along with hedgehogs, shrews and solenodons (Fig. 1).This species can be found in non-polluted mountain rivers in the northern half of the Iberian Peninsula. Nowadays, this species is endangered because of habitat loss and fragmentation, presence of pollutants and predation by non-native invasive species. Desmans are small semi-aquatic animals with a furry compact body, long tail, and peculiar flat trunk-like nose (Fig. 2). They show nocturnal habits and prey on aquatic invertebrates. Little is known about its ecology and behaviour. Due to the nocturnal habits and its habitat requirements, they are extremely difficult to spot. For this reason, any evidence about them is considered a treasure. I am going to be clear here, when a researcher finds a desman’s poo, feels like the luckiest human in the entire world. I will tell you why: DNA can be extracted from excrements to obtain very valuable information. Researchers have employed this methodology to reveal the presence of this animal in different areas2, but also to obtain information about its diet3.
Figure 1. Diversification of Eulipotyphla1
Figure 2. Artist impression of Galemys pyrenaicus4.
Now, I will reveal a little secret, I have experienced that poo-happiness. One of my best friends is a researcher who studies genetic material from insectivorous animals. I had the chance to go with him during one of his field campaigns. On that expedition, we had to walk upstream in the water with lanterns, carefully inspecting each space behind the rocks and waterfalls in search of desmans’ excrements. Our mission was successful, we found excrements of different aquatic animals. He taught me how to differentiate between them based on the consistency, colour and composition (so yummy, I know). One of those little excrements seemed to belong to our peculiar friend, so we put the sample into an Eppendorf tube and added alcohol to preserve it. Could this sample belong to a Pyrenean desman? We didn’t know yet, but, at that moment, I felt extremely (and weirdly) proud of carrying such a valuable sample in one of my pockets. The sample is now in his laboratory, waiting to be examined. After the genetic test, my friend will be able to disclose if we achieved our mission to get close to one of the rarest extant animals in Europe.
Additional information and references
1 Jun J. Sato, Tessa M. Bradford, Kyle N. Armstrong, Stephen C. Donnellan, Lazaro M. Echenique-Diaz, Gerardo Begué-Quiala, Jorgelino Gámez-Díez, Nobuyuki Yamaguchig, Son Truong Nguyen, Masaki Kita, Satoshi D. Ohdachi. Post K-Pg diversification of the mammalian order Eulipotyphla as suggested by phylogenomic analyses of ultra-conserved elements. Molecular Phylogenetics and Evolution. 2019, 141: 1-14.
2 Pere Aymerich, Francesca Casadesús, Joaquim Gosálbez. Distribució de Galemys pyrenaicus (Insectivora, Talpidae) a Catalunya. Orsis. 2001, 16: 93-110.
3 François Gillet, Marie-Laure Tiouchichine, Maxime Galan, Frédéric Blanc, Mélanie Némoz, Stéphane Aulagnier, Johan R. Michaux. A new method to identify the endangered Pyrenean desman (Galemys pyrenaicus) and to study its diet, using next generation sequencing from faeces. Mammalian Biology. 2015, 50: 205-209.
4 Enciclopedia Virtual de los Vertebrados Españoles. Galemys pyrenaicus.( in Spanish) Museo Nacional de Ciencias Naturales http://www.vertebradosibericos.org/mamiferos/galpyr.html
– Escoda, L, Castresana, J. The genome of the Pyrenean desman and the effects of bottlenecks and inbreeding on the genomic landscape of an endangered species. Evol Appl. 2021; 14: 1898–1913. https://doi.org/10.1111/eva.13249
– Desmán (Galemys pyrenaicus) en la Península Ibérica (in Spanish). Ministerio para la Transición Ecológica y el Reto Demográfico. https://www.miteco.gob.es/es/biodiversidad/temas/conservacion-de-especies-amenazadas/vertebrados/desman_peninsula_iberica.html
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