Vitrea contracta explained

Vitrea contracta, the milky crystal snail, is a species of small, air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Pristilomatidae.^[1]

Description

For terms see gastropod shell.

The 2.2-2.6 mm. shell is colourless translucent and shiny. It is almost smooth with 4-5 whorls, the last whorl width seen from above 1.4-1.6 x of penultimate whorl. The umbilicus is moderately wide, becoming wider at the last whorl.

The coiled, rather small, dextral shell is strongly oblate-conical, almost disc-shaped. When mature, the shell is 1.8 to 3.0 (usually about 2 mm) wide (diameter) and 1.0 to 1.4 mm high. Viewed from its side, the seam is only slightly raised. The shell consists of 4 to 5 whorls, which increase slowly and regularly. The body whorl is relatively narrow. Seen from above, each whorl increases by about 1.4 to 1.6 times the size of the previous whorl. The top of the whorls has a flat curve, so that the seams are also very flat. The outline of the shell is well rounded, its bottom is relatively flat. The aperture has a flattened-elliptical shape in its entire circumference and is obliquely crescent-shaped because of the deep cut of the previous whorl. The outer lip is straight and tapering and not thickened . The umbilicus is deep and broad, becoming wider at the body whorl. All convolutions are visible in the navel.

The epidermis of the shell is colorless and translucent to slightly milky. The surface is very glossy. There are very fine, irregular growth lines and a suggestion of spiral lines.^[2]

Distribution

This species occurs in countries and islands of central and northwestern Europa including:

• Czech Republic
• Ukraine^[3]
• Great Britain
• Ireland
• Iceland
• and sometimes introduced in other areas such as Palestine, California, Washingston (state) and Toronto, Ontario.

These snails live hidden in the litter, in loose soil, at the foot of rocks or among rubble, in meadows with rubble, forests with stones and rubble, but also in cool gorges and swampy alder grooves, even in holes and crevices. In protected biotopes they also remain active in winter. The species occurs in moist to dry habitats on calcareous soils.

References

• Westerlund, C. A. (1871). Fauna molluscorum terrestrium et fluviatilium Sveciae, Norvegiae et Daniae. I. Landmolluskerna. Adolf Bonnier, Stockholm. 1-296
• Wagner, A. J. (1907). Zur Kenntnis der Molluskenfauna Oesterreichs und Ungarns, sowie der angrenzenden Balkanländer. Nachrichtsblatt der Deutschen Malakozoologischen Gesellschaft. 39 (3): 101–115. Frankfurt am Main.
• Pintér, L. (1972). Die Gattung Vitrea Fitzinger, 1833 in den Balkanländern (Gastropoda: Zonitidae). Annales Zoologici, 29 (8): 209–315. Warszawa
• Riedel, A. (1995). Zonitidae sensu lato (Gastropoda, Stylommatophora) der Türkei. Übersicht der Arten. Fragmenta Faunistica, 38 (1): 1-86. Warszawa
• Sysoev, A. V. & Schileyko, A. A. (2009). Land snails and slugs of Russia and adjacent countries. Sofia/Moskva (Pensoft). 312 pp., 142 plates.
• Bank, R. A.; Neubert, E. (2017). Checklist of the land and freshwater Gastropoda of Europe. Last update: July 16, 2017
• Herbert, D.G. (2010). The introduced terrestrial Mollusca of South Africa. SANBI Biodiversity Series, 15: vi + 108 pp. Pretoria.
• Cameron, R. A. D., Teixeira, D., Pokryszko, B., Silva, I. & Groh, K. (2021). An annotated checklist of the extant and Quaternary land molluscs of the Desertas Islands, Madeiran Archipelago. Journal of Conchology. 44(1): 53–70.
• Valovirta, Ilmari, and Risto A. Väisänen. "Multivariate morphological discrimination between Vitrea contracta (Westerlund) and V. crystallina (Müller)(Gastropoda, Zonitidae)." Journal of molluscan studies 52.1 (1986): 62–67.

External links

• Westerlund, C. A. (1902). Malacologische Bemerkungen und Beschreibungen. Nachrichtsblatt der Deutschen Malakozoologischen Gesellschaft. 34 (1/2): 19-26; 34 (3/4): 35-47. Frankfurt am Main
• Westerlund, C. A. (1898). Novum specilegium malacologicum. Neue Binnenconchylien aus der paläarktischen Region. Annuaire du Musée Zoologique de l'Académie Impériale des Sciences de St.-Pétersbourg. 3 (2): 155-183. St.-Petersburg
• Hesse, P. (1882). Eine Reise nach Griechenland. Jahrbücher der Deutschen Malakozoologischen Gesellschaft. 9 (4): 283-336, pl. 12. Frankfurt am Main
• Roth, B. A. R. R. Y., and TIMOTHY A. Pearce. "Vitrea contracta (Westerlund) and other introduced land mollusks in Lynnwood, Washington." The Veliger 27.9 (1984): 92.
• - Forsyth, Robert G. "Distributions of nine new or little-known exotic land snails in British Columbia." Canadian Field-Naturalist 113.4 (1999): 559-568.
• Vitrea contracta at Animalbase taxonomy,short description, distribution, biology,status (threats), images

Notes and References

1. MolluscaBase eds. (2023). MolluscaBase. Vitrea contracta (Westerlund, 1871). Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=1002768 on 2023-06-13
2. [:nl:Kleine kristalslak|nl.wikipedia: de kleine kristalslak]
3. Balashov I. & Gural-Sverlova N. 2012. An annotated checklist of the terrestrial molluscs of Ukraine. Journal of Conchology. 41 (1): 91-109.