The eight conchologically investigated specimens (the holotype and seven paratypes) demonstrate moderate shell variability. Shells are generally smooth, very thin and fragile. Fresh shells or those of living specimens are translucent, older ones adopt a milky white color. The number of whorls are 5–6, SH ranges from 1.41–1.81 mm, SW from 0.93–1.12 mm, AH from 0.44–0.54 mm and AW from 0.38–0.46 mm. The ratio of SH/SW is between 1.34–1.62 and AH/AW between 1.05–1.30. The 2nd whorl is remarkably enlarged possessing a height of 2/3–5/6 the height of the 3rd + 4th whorl. The columellar is only weakly developed (Fig. 3) and no teeth (i.e. parietalis, palatalis or columellaris) are present. The DNA barcode of the holotype, when compared with other DNA barcodes of Zospeum species deposited in BOLD, shows its lowest interspecific genetic distance to Zospeum pretneri Bole, 1960 (5.6 %; BOLD-ID: BARCA120-10). This result is well above the barcoding gap of 3.2 % for Carychiidae, which is suitable to separate between-species (> 3.2 %, interspecific) and within-species genetic diversity (< 3.2 %, intraspecific) in Zospeum (Weigand et al. 2011, 2013).
The single living specimen was found in an unnamed large chamber at 980 m depth (85 m long, 70 m wide) with lots of stones, rocks and sand (Fig. 1, right site). A temporal small stream of running water was present close to the collecting site. Air temperature was between 3.3–3.5 °C (depending on the measurement device), water temperature 5.1 °C and air humidity 100 %. Shells were observed beginning from 800 m depth till the bottom of the cave. Shells were generally found on layers of mud (Fig. 1, left site). The first 200 m of the entrance passage of Lukina Jama are permanently covered by varying levels of snow and ice.
So far, Zospeum tholussum is only known from the Lukina Jama–Trojama cave system. However, this cave system is situated in the distribution range of the morphologically related species Zospeum amoenum (Frauenfeld, 1856), which inhabits caves of the West Balkan of North Slovenia, West Croatia, Bosnia and Herzegovina and South to Montenegro (Bole 1974).Absolon (1916)named but did not describe another morphologically related species -Zospeumtroglobalcanicum. SinceWeigand et al. (2013)revealed thatZospeumspp. with an inferred large distribution range are particularly prone to host additional, morphologically unrecognized species, some of the distribution records forZospeumamoenummay very well refer toZospeumtholussum. Moreover, the intraspecific genetic and conchological variability of the new species should be investigated in greater detail, thus to judge about the taxonomic information content of the diagnostic characters applied within this description.
The preliminary information on the habitat ofZospeumtholussumis in congruence with previous findings forZospeum. Interestingly, the grazing-labyrinth-like structure, in which most of the shells were embedded (Fig. 1, left site), has been already observed during caving expeditions in Northern Spain (Jochum et al. 2012). Finally, the presence of a temporal stream at the collecting site of the living specimen further supports a passive dispersal scenario as suggested byWeigand et al. (2013).
Zospeum tholussum sp. n. is characterized based on a population from the Lukina Jama–Trojama cave system (Velebit Mts., Croatia). A single living specimen occurred at 980 m depth. The species is morphologically related to Zospeum amoenum (Frauenfeld, 1856), but can be readily distinguished from the latter by the presence of a weak columellar fold and its dome-like structured 2nd whorl. DNA barcoding is capable to clearly delineate Zospeum tholussum from other Zospeum spp. as well. (Weigand, 2013)
Zospeum tholussum ist eine sehr kleine, blinde Schneckenart aus der Familie der Zwerghornschnecken (Carychiidae) in der Ordnung der Lungenschnecken (Pulmonata). Sie lebt in absoluter Dunkelheit in 980 m unter der Erdoberfläche im Lukina Jama–Trojama-Höhlensystem im Velebit (Kroatien).
Das rechtsgewundene Gehäuse ist 1,41 bis 1,81 mm hoch (n=7), die Breite variiert von 0,93 bis 1,12 mm. Die Mündung ist 0,44 bis 0,54 mm hoch und 0,38 bis 0,46 mm breit. Das Verhältnis Gehäusehöhe zu Gehäusebreite liegt zwischen 1,34 und 1,62, und das Verhältnis Mündungshöhe zu Mündungsbreite zwischen 1,05 und 1,30. Es sind fünf bis sechs Windungen vorhanden. Die zweite Windung ist auffällig vergrößert und weist zwei Drittel bis fünf Sechstel der Höhe der dritten und vierten Windung auf. Die Spindel ist nur schwach entwickelt, die Windung ist ohne Zähne und Falten.
Die Oberfläche ist glatt und glänzend. Die Schale ist sehr dünn und leicht zerbrechlich. Frische Gehäuse oder die Gehäuse von noch lebenden Tieren sind durchscheinend, pigmentlos, nicht mehr frische Gehäuse sind eher milchig-trübe.
Auch der Weichkörper ist glasig-hell, durchscheinend und pigmentlos. Die Fühler sind kegelförmig, Augen fehlen. Nur der Darminhalt ist bräunlich und scheint durch Weichkörper und Schale durch.
Der DNA-Barcode weist die geringste Distanz zu Zospeum pretneri Bole, 1960 auf (etwa 5,6 %), ist jedoch deutlich über dem Wert (3,2 %), der für gewöhnlich ausreicht um Arten der Gattung Zospeum molekulargenetisch zu unterscheiden. In der generellen Gehäuseform erinnert Zospeum tholussum an größere Exemplare von Zospeum amoenum (Frauenfeld, 1856). Zospeum tholussum unterscheidet sich von dieser Art jedoch durch die stark aufgeblasene Form der zweiten Windung. Zospeum amoenum besitzt dagegen eine schwache, aber durchaus vorhandene Spindelfalte. Die genetische p-Distanz des DNA-Barcodes beträgt 11,7 % bis 12,1 %.
Im Lukina Jama–Trojama-Höhlensystem kommt noch eine zweite, bisher nicht beschriebene Zospeum-Art vor. Diese Art unterscheidet sich von Zospeum tholussum durch das Fehlen der typischen, aufgeblähten zweiten Windung, in der generellen Form des Gehäuses, durch einen gut ausgebildeten Mündungszahn und der deutlich kräftigeren Spindelfalte. Da kein lebendes Exemplar gefunden wurde, konnte die Art bisher nicht beschrieben werden.
Das einzige lebende Exemplar wurde in einer großen Höhlenkammer (85 m lang, 70 m weit) in 980 m Tiefe gefunden. In der Höhlenkammer lagen eine große Menge kleinere und größere Gesteinsblöcke und Sand; in der Nähe des Fundpunktes floss ein kleines Rinnsal. Die Lufttemperatur betrug 3,3 bis 3,5 °C, die Wassertemperatur 5,1 °C und die Luftfeuchtigkeit 100 %. Leere Gehäuse wurden schon ab 800 m bis zur 980 m Tiefe in der Höhle gefunden. Die Gehäuse lagen alle auf Schichten von Höhlenton. Die ersten 200 m des Eingangsbereiches des Lukina Jama-Höhlensystem sind das ganze Jahr über in unterschiedlichem Ausmaß mit Schnee und Eis bedeckt. Bisher ist die Art nur aus dem Lukina Jama-Höhlensystem bekannt.
Die Tiere bewegen sich nur wenige Millimeter oder Zentimeter in der Woche. Sie ernähren sich von dem Aufwuchs auf den lehmigen Böden der Höhlen. Die meisten leeren Gehäuse wurden in Labyrinth-ähnlichen Weidestrukturen gefunden. Solche Weidestrukturen wurden auch schon in Höhlen in Nordspanien gefunden, in denen ebenfalls Arten der Gattung Zospeum leben. Die Art verbreitet sich passiv durch fließendes Wasser oder auch durch in Höhlen lebende Tiere.
Das Taxon wurde 2013 von Alexander Weigand in der Zeitschrift Subterranean Biology erstmals beschrieben. Die Art ist bisher nur von der Typlokalität bekannt. Der Artname ist vom lateinischen Wort tholus abgeleitet, das Kuppel oder Dom bedeutet. Der Artname spielt auf die stark aufgeblähte, dom-artige zweite Windung an.
Im Jahr 2014 wurde die Art in die Top Ten der neu beschriebenen Arten (des Vorjahres) gewählt. Die Art beeindruckte die Mitglieder der Auswahlkommission durch die Geist-ähnliche Erscheinung, da Gehäuse wie auch Körper ohne Pigmente sind[1]. In den Medien wird diese Top Ten der neubeschriebenen Arten gerne als die skurrilen oder sogar skurrilsten neuen Arten vorgestellt (z. B. der Spiegel[2] oder Focus[3]).
Zospeum tholussum ist eine sehr kleine, blinde Schneckenart aus der Familie der Zwerghornschnecken (Carychiidae) in der Ordnung der Lungenschnecken (Pulmonata). Sie lebt in absoluter Dunkelheit in 980 m unter der Erdoberfläche im Lukina Jama–Trojama-Höhlensystem im Velebit (Kroatien).
Zospeum tholussum or the domed land snail,[2] 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 2 mm (0.08 in) and a shell width of around 1 mm (0.04 in). 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 743 to 1,392 m (2,438 to 4,567 ft) in the Lukina jama–Trojama cave system in Croatia in 2012, 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.[3][4]
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, 2012.[5] 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 1,421 m (4,662 ft), including submerged passages.[6][7] Aside from its great depth, the cave system is also known for its vertical orientation and deep shafts.[8][9][10]
The expedition was primarily to determine the cave system's depth,[11] but the team also collected specimens of animals they encountered.[12] The cave system has two entrances, the Lukina jama and the Trojama caves (jama means "pit" in Croatian). Lukina jama is situated about 37 m (121 ft) lower on the mountain slopes than Trojama.[5] 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 558 m (1,831 ft) from the entrance of Lukina jama (595 m (1,952 ft) if measured from the entrance of Trojama).[6] The cave system is unusual for containing three different microclimatic layers which makes it extremely interesting in terms of biodiversity to scientists.[12] The first 200 m (660 ft) of the cave system's entrance is permanently covered in thick layers of snow and ice and has an average air temperature of 1 °C (34 °F).[5][6] The cave system progressively becomes warmer in deeper areas, with an average air temperature of 2 °C (36 °F) in the middle part and 4 °C (39 °F) at the bottom.[12]
Empty shells of Zospeum tholussum were encountered by the team beginning at a depth of 743 m (2,438 ft) and down to the lake at the bottom of the cave, which is about 1,392 m (4,567 ft) 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.[5] They also recovered a single live specimen of Zospeum tholussum from an unnamed large chamber at a depth of about 980 m (3,220 ft). The chamber was about 65 m (213 ft) long and 70 m (230 ft) 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 3.3 to 3.5 °C (37.9 to 38.3 °F) with an air humidity of 100%. The water temperature of the stream was about 5.1 °C (41.2 °F).[5]
Zospeum tholussum was formally described by the German taxonomist Alexander M. Weigand in 2013, based on the specimens the caving expedition recovered. The specific name is derived from Latin tholus, meaning dome or cupola, referring to the distinctive dome-like shape of the second whorl of the shell. The nine type specimens are currently deposited in the Forschungsinstitut und Naturmuseum Senckenberg in Frankfurt am Main, Germany (museum voucher SMF 341633). The eight empty shells were used as the paratypes by Weigand, one of which was broken open to investigate the central column of the shell, while the single living specimen was designated as the holotype.[5] Zospeum tholussum is classified under the genus Zospeum of the subfamily Carychiinae in the hollow-shelled snail family, Ellobiidae.[13] Although some authors (including Weigand) consider Carychiinae to be a separate family, Carychiidae.[14]
Weigand identified Zospeum tholussum as a new species based on the morphology of the shells, as well as molecular genetic data recovered from the single living specimen. The DNA barcode of the Zospeum tholussum holotype, when compared with other DNA barcodes of Zospeum species, shows its lowest interspecific genetic distance to Zospeum pretneri. This result is well above the barcoding gap of 3.2% for Carychiinae, which is suitable to separate between species (> 3.2%, interspecific) and within species genetic diversity (< 3.2%, intraspecific) in Zospeum.[5] Zospeum tholussum closely resemble Zospeum amoenum morphologically, but can be readily distinguished by the dome-like shape of their second whorls and by the presence of a slight fold in the central column of the shells. They can also be readily separated by means of their DNA barcodes (11.7% to 12.1% genetic p {displaystyle p} 
Lukina jama–Trojama also contains a second yet undescribed species of Zospeum, also recovered by the 2012 expedition. It can be distinguished from Zospeum tholussum by its general shell shape, a more prominent fold in the shell central column, the absence of the dome-like structure on the second whorl, and the presence of a tooth. However, no living specimens of this species were recovered, so DNA barcodes could not be obtained to determine its exact taxonomic relationship with Zospeum tholussum.[5]
Zospeum tholussum are microscopic snails (microgastropods), with a shell height of only about 1.41 to 1.81 mm (0.056 to 0.071 in) and a shell width of about 0.93 to 1.12 mm (0.037 to 0.044 in). The shell height to width ratio is between 1.34 and 1.62. They possess about five to six whorls. The second whorl is distinctive for being greatly enlarged and dome-like in shape, with a height of about 2⁄3 to 5⁄6 of the heights of the third and fourth whorls combined.[5]
The opening of the shell (aperture) is about 0.44 to 0.54 mm (0.017 to 0.021 in) in height and 0.38 to 0.46 mm (0.015 to 0.018 in) in width, with an aperture height to width ratio between 1.05 and 1.30. It is devoid of teeth. The central column of the shell (the columella) possesses a weakly developed columellar fold.[5] The shells of the collected specimens of Zospeum tholussum have a moderately variable morphology between individuals in the species. They are typically very thin and fragile with a smooth surface. Fresh shells or those of living specimens are translucent, while older ones are more opaque, with a milky white color.[5]
Like all members of the genus Zospeum, Zospeum tholussum are completely blind. Because of this and their lack of pigmentation, they are considered to be true cave-dwelling organisms (eutroglobionts).[11] Very little is known about their biology, but members of the genus Zospeum are known to prefer muddy to permanently wet subterranean microhabitats. They are generally found along the drainage systems of caves.[5]
Due to their tiny shell sizes,[14] Zospeum species are extremely slow-moving snails. In a week's time, they may only move a few millimeters or centimeters while grazing, usually in small circles around a given point.[12] Because of their proximity to bodies of water and their preference for habitats with a mud substrate, Weigand and colleagues (2013) have proposed that the primary mode of dispersal of Zospeum species may be passive, either by being carried along in running water or through the activities of larger animals like cave bats or crickets.[5][14]
Zospeum tholussum are currently only known from the Lukina jama–Trojama cave system of Croatia. Its distribution range is within the larger distribution range of the morphologically similar Zospeum amoenum (which is found in caves in the Western Balkans in northern Slovenia, western Croatia, Bosnia and Herzegovina, and Montenegro).[5] Since Zospeum species with large inferred distribution ranges are known to actually also contain morphologically similar and unrecognized cryptic species, Weigand postulated that some early records of Zospeum amoenum may have actually been specimens of Zospeum tholussum.[5]
Zospeum tholussum or the domed land snail, 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 2 mm (0.08 in) and a shell width of around 1 mm (0.04 in). 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 743 to 1,392 m (2,438 to 4,567 ft) in the Lukina jama–Trojama cave system in Croatia in 2012, 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.
Zospeum tholussum es una especie de molusco gasterópodo de la familia Ellobiidae, conocido vulgarmente como caracol fantasma.[3]
Los investigadores en Croacia únicamente hallaron un ejemplar vivo durante su expedición por el sistema de cuevas Lukina Jama, a una profundidad de 980 m encontraron el diminuto caracol en una cámara llena de rocas y arena por la que cruza un pequeño arroyo. Tomaron conchas vacías de siete caracoles para analizar.
La investigación taxonómica distinguió once morfoespecies del taxón micro gasterópodos Zospeum Bourguignat.[4]
Mide 1 mm de ancho. Su caparazón es traslúcido y tiene forma de espiral. Se adapta a la oscuridad. Ha perdido la orientación visual. Tienen poca movilidad y se piensa que se desplazan sobre la corriente o encima de mamíferos más grandes.[2]
Se alimentan de los microorganismos de rocas, lodo y madera.[cita requerida]
Vistas Zospeum tholussum
Holotipo y Paratipo
Especies Zospeum
Datos: Q14935984
Multimedia:
Especies: Zospeum tholussum
Zospeum tholussum es una especie de molusco gasterópodo de la familia Ellobiidae, conocido vulgarmente como caracol fantasma.
Los investigadores en Croacia únicamente hallaron un ejemplar vivo durante su expedición por el sistema de cuevas Lukina Jama, a una profundidad de 980 m encontraron el diminuto caracol en una cámara llena de rocas y arena por la que cruza un pequeño arroyo. Tomaron conchas vacías de siete caracoles para analizar.
La investigación taxonómica distinguió once morfoespecies del taxón micro gasterópodos Zospeum Bourguignat.
Zospeum tholussum est une espèce d'escargot terrestre à respiration aérienne de type mollusque pulmoné (Pulmonata) du genre Zospeum. Ce gastéropode appartient à la famille Ellobiidae. Cette espèce de petite taille vit essentiellement dans des grottes.
La coquille des Zospeum tholussum est très petite (1 à 2,5 mm de hauteur et 0,8 à 1,5 mm de large) et mince. Les Zospeum tholussum vivants ont une coquille transparente qui reçoit une couleur blanc laiteux après la mort.
Le Zospeum tholussum a été découvert, en 2010, dans la grotte de Lukina Jama–Trojama située en Croatie dans le Parc national de Sjeverni Velebit à une profondeur de 743 mètres à 1 392 mètres dans le massif de Velebit.
Le Zospeum tholussum a été décrit comme une nouvelle espèce, en 2013, par le taxonomiste Alexander Weigand. La dénomination de cette espèce vient du latin "tholus" qui signifie "dôme" ou "coupole", se référant à la forme de dôme distinctif de la deuxième spire de la coquille. Neuf spécimens ont été déposés au muséum Senckenberg à Francfort-sur-le-Main en Allemagne. Huit d'entre eux n'étaient plus que des coquilles vides et furent étudiés par Alexander Weigand qui conclut à un nouveau paratype. L'un d'entre eux était brisé ce qui a permis au taxonomiste d'étudier la colonne centrale. Le neuvième spécimen était vivant et fut choisi comme holotype.
Zospeum tholussum est une espèce d'escargot terrestre à respiration aérienne de type mollusque pulmoné (Pulmonata) du genre Zospeum. Ce gastéropode appartient à la famille Ellobiidae. Cette espèce de petite taille vit essentiellement dans des grottes.
Zospeum tholussum adalah spesies siput darat yang hidup di gua dan tergolong dalam famili Ellobiidae. Siput ini sangat kecil; panjang cangkangnya lebih rendah dari 2 mm (0,08 in) dan lebarnya sekitar 1 mm (0,04 in). Spesies ini buta dan memiliki cangkang yang tembus cahaya dengan lima hingga enam gelungan. Hewan ini juga sangat lambat dan mungkin tersebar lewat transportasi pasif seperti aliran air atau hewan besar.
Zospeum tholussum ditemukan di kedalaman 743 hingga 1.392 m (2.438 hingga 4.567 kaki) di gua Lukina jama–Trojama, Kroasia, pada tahun 2012 selama ekspedisi di gua. Hewan ini secara resmi dideskripsikan sebagai spesies baru oleh taksonom Dr. Alexander M. Weigand pada tahun 2013.
Pada 22 Mei 2014, International Institute for Species Exploration menyatakan siput ini sebagai salah satu dari "Sepuluh Besar Spesies Baru Tahun 2014" dari antara spesies-spesies yang ditemukan pada tahun 2013. Alasannya adalah karena habitatnya di dalam gua yang gelap dan terletak 900 meter di bawah permukaan. Siput ini juga tidak memiliki mata dan cangkangnya yang transparan membuatnya tampak seperti hantu.[1][2]
Zospeum tholussum adalah spesies siput darat yang hidup di gua dan tergolong dalam famili Ellobiidae. Siput ini sangat kecil; panjang cangkangnya lebih rendah dari 2 mm (0,08 in) dan lebarnya sekitar 1 mm (0,04 in). Spesies ini buta dan memiliki cangkang yang tembus cahaya dengan lima hingga enam gelungan. Hewan ini juga sangat lambat dan mungkin tersebar lewat transportasi pasif seperti aliran air atau hewan besar.
Zospeum tholussum ditemukan di kedalaman 743 hingga 1.392 m (2.438 hingga 4.567 kaki) di gua Lukina jama–Trojama, Kroasia, pada tahun 2012 selama ekspedisi di gua. Hewan ini secara resmi dideskripsikan sebagai spesies baru oleh taksonom Dr. Alexander M. Weigand pada tahun 2013.
Pada 22 Mei 2014, International Institute for Species Exploration menyatakan siput ini sebagai salah satu dari "Sepuluh Besar Spesies Baru Tahun 2014" dari antara spesies-spesies yang ditemukan pada tahun 2013. Alasannya adalah karena habitatnya di dalam gua yang gelap dan terletak 900 meter di bawah permukaan. Siput ini juga tidak memiliki mata dan cangkangnya yang transparan membuatnya tampak seperti hantu.
Zospeum tholussum is een slakkensoort uit de familie van de Ellobiidae.
Het dier leeft in complete duisternis in grotten 900 meter onder het oppervlak van Kroatië. De slak is twee millimeter groot en heeft geen ogen. Het slakkenhuis bevat geen pigment.
Het dier is een van de langzaamste slakkensoorten en legt hooguit enkele centimeters per week af.[1]
Bronnen, noten en/of referentiesZospeum tholussum é uma espécie de caracol terrestre oriundo de cavernas, um Pulmonado da família Ellobiidae. É uma espécie muito pequena com uma concha de até 2mm de altura, e uma largura a cerca de 1mm. São completamente cegos e possuem conchas translúcidas, com 5 ou 6 espirais. A segunda espiral de suas conchas tem uma forma de domo. São extremamente lentos, podendo depender de transporte passivo através de grandes animais aquáticos ou água corrente . O Zospeum tholussum foi descoberto em 2012 na caverna Lukina jama no sistema Trojama, entre profundidades de 743 a 1.392 m na Croácia, durante uma expedição de espeleologia. Foi formalmente descrito como uma nova espécie em 2013 pelo taxonomista Dr. Alexander M. Weigand. Em 22 de maio de 2014 o (IISE) declarou o caracol como sendo uma das 10 novas espécies de 2014, entre espécies descobertas em 2013. A razão à sua seleção é o seu habitat, que se encontra em completa escuridão dentro de uma caverna a cerca de 900 metros abaixo da superfície.
Zospeum tholussum é uma espécie de caracol terrestre oriundo de cavernas, um Pulmonado da família Ellobiidae. É uma espécie muito pequena com uma concha de até 2mm de altura, e uma largura a cerca de 1mm. São completamente cegos e possuem conchas translúcidas, com 5 ou 6 espirais. A segunda espiral de suas conchas tem uma forma de domo. São extremamente lentos, podendo depender de transporte passivo através de grandes animais aquáticos ou água corrente . O Zospeum tholussum foi descoberto em 2012 na caverna Lukina jama no sistema Trojama, entre profundidades de 743 a 1.392 m na Croácia, durante uma expedição de espeleologia. Foi formalmente descrito como uma nova espécie em 2013 pelo taxonomista Dr. Alexander M. Weigand. Em 22 de maio de 2014 o (IISE) declarou o caracol como sendo uma das 10 novas espécies de 2014, entre espécies descobertas em 2013. A razão à sua seleção é o seu habitat, que se encontra em completa escuridão dentro de uma caverna a cerca de 900 metros abaixo da superfície.
