Citizen scientists from three continents help discover a new, giant slug from Europe

You might think that Europe is so well studied that no large animals remain undiscovered. Yet today, a new species of giant keelback slug from Montenegro was announced in the open-access Biodiversity Data Journal. The animal, as big as a medium-sized carrot, was discovered on a citizen-science expedition and jointly described by its participants.

The international team of citizen scientists from Italy, the Netherlands, Serbia, South Africa, and the United States found the slug in July 2019 while exploring the spectacular Tara Canyon, Europe's deepest gorge, on inflatable rafts. The brownish-grey animals, with a sharp ridge along the back, and 20 cm in length when fully stretched, were hiding under rocky overhangs in the narrowest part of the ravine.

At first, the newly discovered slugs seemed superficially indistinguishable from the ash-black keelback slug (Limax cinereoniger), which also lives in the Tara Canyon. The team had to use a portable DNA lab to work out that there is a 10% difference between the two slugs in the so-called DNA barcode. Moreover, when they dissected a few of them, they found differences in the reproductive organs as well. This was enough to decide that a new species had been discovered, and they named it Limax pseudocinereoniger to indicate its similarity to L. cinereoniger.

The field trip was run by Taxon Expeditions, which organises real scientific expeditions for the general public, with the aim to make scientific discoveries. Rick de Vries, a web editor and illustrator from Amsterdam who found the first specimen of L. pseudocinereoniger, says: “It's an incredible thrill to hold an animal in your hands and to know that it is still unknown to science”.

Zoologist Iva Njunjić, one of the authors of the paper, thinks that more unknown species are likely to be found in Tara Canyon and the Durmitor National Park, of which it is part. “Using a combination of DNA analysis and anatomy will probably reveal more species that are identical on the outside but actually belong to different species,” she says.

In 2023, Taxon Expeditions plans to take a new team of citizen scientists to Montenegro with a mission to discover new species and document the hidden biodiversity.

Taxon Expeditions was founded by Iva Njunjić and Menno Schilthuizen of Naturalis Biodiversity Center and specialises in 'taxonomy tourism' trips in Brunei, Italy, Montenegro, Panama, and the Netherlands.

Original source:

Schilthuizen M, Thompson CG, de Vries R, van Peursen ADP, Paterno M, Maestri S, Marcolongo L, Esposti CD, Delledonne M, Njunjić I (2022) A new giant keelback slug of the genus Limax from the Balkans, described by citizen scientists. Biodiversity Data Journal 10: e69685. https://doi.org/10.3897/BDJ.10.e69685