The Lukina Jama–Trojama is the deepest cave system in Croatia. It is well known for its vertical shape, long pits and great depth of about 1.4 km.
The new species, named Zospeum tholussum, is a tiny and fragile snail with a beautifully shaped dome-like semi-transparent shell.
Dr Weigand found only one living specimen of Zospeum tholussum in an unnamed large chamber at the remarkable depth of 980 m.
“The single living specimen was found in an unnamed large chamber with lots of stones, rocks and sand. A temporal small stream of running water was present close to the collecting site. Air temperature was between 3.3 – 3.5 degrees Celsius, water temperature 5.1 degrees Celsius and air humidity 100 per cent. Shells were observed beginning from 800 m depth till the bottom of the cave. Shells were generally found on layers of mud,” Dr Weigand wrote in a paper published in the open-access journal Subterranean Biology.
All known species from the cave-dwelling genus Zospeum possess a limited ability to move. Their preference of a muddy habitat and the fact that they are usually located near the drainage system of the cave, in a close proximity to running water, however suggest that these animals are not exactly immobile. Scientists hypothesize that dispersal is achieved through passive transportation via water or larger mammals.