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''Zospeum tholussum'' is a cave-dwelling species of air-breathing land snails in the family Ellobiidae. It is a very small species with a shell height of less than and a shell width of around . ''Z. tholussum'' individuals are completely blind and possess translucent shells with five to six whorls. The second whorl of their shells has a characteristic dome-like shape. They are also extremely slow-moving and may depend on passive transportation through running water or larger animals for dispersal. ''Zospeum tholussum'' was discovered at depths of in the Lukina jama–Trojama cave system in Croatia in 2010 during a caving expedition. It was formally described as a new species in 2013 by the taxonomist Dr. Alexander M. Weigand. On 22 May 2014 International Institute for Species Exploration declared the snail as one of the "Top 10 New Species of 2014" among species discovered in 2013. The reason for its selection is its habitat in complete darkness of a cave some 900 meters below the surface. It lacks eyes and its shell is transparent giving it a ghost-like appearance.〔(【引用サイトリンク】url=http://www.esf.edu/top10/08.htm )〕 ==Discovery== Specimens of ''Zospeum tholussum'' were recovered by a team of cavers and biologists of the Croatian Biospeleological Society (Hrvatsko Biospeleološko Društvo or HBSD) from the Lukina jama–Trojama cave system in the Velebit mountains of Croatia, during an expedition from July 29 to August 8, 2010. The cave system is the deepest in Croatia and one of the top twenty deepest caves in the world at a total measured depth of , including submerged passages. Aside from its great depth, the cave system is also known for its vertical orientation and deep shafts. The expedition was primarily to determine the cave system's depth, but the team also collected specimens of animals they encountered. The cave system has two entrances, the Lukina jama and the Trojama caves (''jama'' means "pit" in Croatian). Lukina jama is situated about lower on the mountain slopes than Trojama.〔 It was named after the caver Ozren Lukic, who was killed in the Velebit mountains while serving as a Croatian soldier in the Croatian War of Independence. Lukina jama and Trojama are connected to each other underground at a depth of from the entrance of Lukina jama ( if measured from the entrance of Trojama).〔 The cave system is unusual for containing three different microclimatic layers which makes it extremely interesting in terms of biodiversity to scientists.〔 The first of the cave system's entrance is permanently covered in thick layers of snow and ice and has an average air temperature of .〔〔 The cave system progressively becomes warmer in deeper areas, with an average air temperature of in the middle part and at the bottom.〔 Empty shells of ''Zospeum tholussum'' were encountered by the team beginning at a depth of and down to the lake at the bottom of the cave, which is about beneath the Trojama cave entrance. The shells were usually found embedded in layers of mud, with an appearance described as a "grazing-labyrinth-like" structure. The team collected eight empty shells over a period of several days.〔 They also recovered a single live specimen of ''Zospeum tholussum'' from an unnamed large chamber at a depth of about . The chamber was about long and wide. The chamber substrate was composed mainly of rocks and sand. A small temporal stream was also present near the area. The air temperature in the chamber was about with an air humidity of 100%. The water temperature of the stream was about .〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Zospeum tholussum」の詳細全文を読む スポンサード リンク
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