Scientists Describe Two Tiny Glassy Snails Discovered in Northern Spain

March 17, 2015 / Spain, Europe
Researchers on the hunt for Zospeum in cave of Northern Spain

Researchers on the hunt for Zospeum in cave of Northern Spain. Photo by Adrienne Jochum

Two tiny, glassy snails found in 2012 during a 17-cave sampling expedition of Northern Spain have been described.

The international expedition team of scientists included Adrienne Jochum and Alexander Weigand from Germany, Rajko Slapnik and Jana Valentincic from Slovenia, and Carlos Prieto and Benjamín Gómez hailing from Spain who painstakingly searched the moist, muddy cave walls underneath the Basque-Cantabrian Mountains for the tiny creatures.

In a paper published in the open access journal ZooKeys, the cave-dwelling snails, known as Thorn Snails, are described as less than 2 mm (0.07 inch) across, some barely reaching 1 mm (0.03 inch) in shell size. This makes them among the smallest terrestrial snails known.

Their evolution dates back to the Cenozoic Era, ca. 65 million years ago. These transparent, unpigmented snails belong to the genus Zospeum, whose species are all cave dwellers.

The two new species, Zospeum vasconicum and Zospeum zaldivarae, comprise a genus containing about 20 species known to inhabit caves from Northern Spain to the Dinaric Alps of former Yugoslavia. These are the first subterranean Thorn Snail colony discovered in Northern Spain.

Previous research dates from the latter half of the 19th and 20th Centuries and was conducted on shells alone. Live individuals are very rare. Molecular studies published by the first three authors have contributed much to the knowledge of the evolution of these tiny troglobitic snails. The new species belong to the first recorded live Zospeum populations from Spain. Two years ago, Alexander Weigand described the cave-dwelling, Thorn Snail relative of these Spanish species from a plunging 950 meter (3116 foot) deep chasm in the Velebit Mountains of Croatia.

Rotund shells of Zospeum zaldivarae from Cueva de las Paúles.

Rotund shells of Zospeum zaldivarae from Cueva de las Paúles. Photo by Adrienne Jochum

These rare denizens of the dark can only be found alive using a magnifying glass. Knowledge of their subterranean ecology as well as a “gut feeling” of where they might be hanging out is necessary.

The two new species were described using shell criteria in conjunction with molecular investigations.

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