It has a translucent shell, lives in complete darkness and crawls only a few millimeters a week.
This is how scientists describe a new species of snail discovered more than 3,000 feet underground in Croatia’s Lukina Jama–Trojama cave, according to the Press Trust of India. The findings, published in the journal Subterranean Biology, describe how the tiny, fragile snail lives in one of the deepest cave systems in the world.
"They only creep a few millimeters or centimeters a week, and mainly in circles, grazing at one point where they live," taxonomist Alexander Weigand at Goethe-University in Frankfurt, Germany said.
The new snail species, Zospeum tholussum, was found by a team of cavers and biologists from the Croatian Biospeleological Society. While on an expedition to determine the cave’s depth, they collected animal specimens including one of the previously unidentified snails along with eight of its empty shells.
“The single living specimen was found in an unnamed large chamber with lots of stones, rocks and sand,” Weigand wrote. “Shells were observed beginning from 800 meters depth till the bottom of the cave.”
The snail has no eyes or pigmentation on its shell and is considered to be a true eutroglobiont or cave-dweller.
Unlike other snails belonging to the same genus Zospeum, which have limited mobility, the new snails show signs they know how to get around. Since the species was found in a muddy habitat, close to the cave’s drainage system, scientists suspect they move about the cave from running water and by hopping a ride on larger mammals.
The new species also has a “weak columellar fold,” a “dome-like structured second whorl” along with unique DNA to distinguish itself from one of its closest relatives, Zospeum amoenum, according to the study’s findings.
The Lukina Jama–Trojama is the deepest cave system in Croatia with a depth of 4,566 feet. The cave has three microclimatic layers making it fertile ground for scientists to discover new species.