Vitrea contracta (Westerlund, 1871)

• Zonites (Vitrea) crystallina var. contracta Westerlund 1871: 56.
• Many older synonyms in the European literature.

Identification. Shell subdiscoidal. Spire very low, conic. Whorls c. 4–4½, slowly enlarging, tightly coiled. Periphery rounded, above middle; whorls shouldered. Suture moderately indented, bordered by a ‘false suture’. Protoconch smooth. Teleoconch smoothish, with weak incremental lines, stronger on upper surface of whorls near suture. Aperture, narrowly lunate, edentulous. No barriers inside whorls. Lip thin, simple. Umbilicus narrow, deep, c. 1/7 of shell width. Shell transparent or translucent, glassy, colourless or milky white, becoming white and opaque when weathered. Shell width to 2.6 mm.

Animal pale tan to ivory-white; ocular tentacles translucent, with black eye spots (Roth 1977).

Comparison. The tightly coiled shell of V. contracta resembles some species of Pristiloma but the shells of these are darker coloured, variously brown.

Habitat. In BC, V. contracta has been found in urban parks and gardens, and on waste ground, living under ivy and other vegetation, in leaf litter, and under rocks, concrete, boards, and woody debris.

In Toronto, it has been found in a wooded, urban ravine. Snails generally are found under wood, stones, and debris, in leaf litter, and in ivy and other vegetation. In Britain other, more natural, habitats are occupied, including grasslands, woodlands, around cliffs, in caves, talus slopes and stone walls (Kerney 1999). This species is often associated with dry areas having limestone (Kerney 1999), but in BC it is not especially associated with calcareous soils but rather with synanthropic habitats (Grimm et al. 2010). On a calcareous down in England, fresh shells were found below the surface, suggesting that this snail also occupies voids in soil (Carter 1990).

Biology. It is omnivorous (Smith 1992).

Geographic range. Vitrea contracta is introduced to BC, where it is known to occur along the east coast of Vancouver Island north to at least Nanaimo, in the Gulf Islands, in Metro Vancouver and the Fraser Valley east to Abbotsford and near Chilliwack, Kamloops, and on Haida Gwaii (Forsyth 1999, 2004b, unpublished data). This introduced species was first reported from BC by Forsyth (1999).

Elsewhere in Canada V. contracta has been reported Toronto, Ontario (Grimm et al. 2010). In the USA, this species is known from San Francisco, California (Roth 1977; Roth & Sadeghian 2003) and Lynden, Washington (Roth & Pearce 1984). It also has been introduced to Colombia (Hausdorf 2002) and the state of Victoria, Australia (Smith 1992).

Vitrea contracta is native to the Western Palaearctic and is widespread in Europe: Iceland and coastal regions of Scandinavia south to the Iberian Peninsula and all around the Mediterranean, including North Africa, Greece (Riedel 1992) and Turkey (Schütt 2005), and east to the Baltic States, Crimea and central Ukraine, and the Caucasus (Sysoev & Schileyko 2009).

Etymology. Vitrea: vitreus (Latin), glassy; the gender is feminine. Contractus (Latin): narrowed; likely in reference to the aperture.

Remarks. Some authors divide the genus Vitrea into subgenera and place V. contracta in the subgenus Crystallus R.T. Lowe, 1855 (e.g. Falkner et al. 2002; Roth and Sadeghian 2003; Schileyko 2003). However, no subgenera are used here following Riedel (1992) who reversed his earlier acceptance of subgenera based on the internal structure of the penis (Riedel 1980).

In some older European literature, V. contracta had not always been distinguished from a similar appearing species, Vitrea crystallina (O.F. Müller, 1774) and treated as a variety of the latter (Kuiper 1964). However, this is not the case, and the two taxa are distinct species. Valovirta & Väisänen (1986) provided additional means to morphologically distinguish these species.

References

• Carter S (1990) The distribution of the land snail Vitrea contracta (Westerlund) in a calcareous soil on Martin Down, Hampshire, England. Circaea 7: 91–93.
• Falkner G, Ripken TEJ, Falkner M (2002) Mollusques continentaux de France. Liste de Référence annotée et Bibliographie. Patrimoines naturels 52: 1–350.
• Forsyth RG (1999) Distributions of nine new or little-known exotic land snails in British Columbia. The Canadian Field-Naturalist 113: 559–568. https://doi.org/10.5962/p.358656
• Forsyth RG (2004) Land Snails of British Columbia. Royal BC Museum, Victoria, BC, Canada, iv, 188 pp.
• Grimm FW, Forsyth RG, Schueler FW, Karstad A (2009 [2010]) Identifying Land Snails and Slugs in Canada: Introduced Species and Native Genera. Canadian Food Inspection Agency, Ottawa, Ontario, Canada, iv + 168 pp.
• Hausdorf B (2002) Introduced land snails and slugs in Colombia. Journal of Molluscan Studies 68: 127–131. https://doi.org/10.1093/mollus/68.2.127
• Kerney M (1999) Atlas of the land and freshwater molluscs of Britain and Ireland. Harley Books, Colchester, United Kingdom, 264 pp.
• Kuiper JGJ (1964) On Vitrea contracta (Westerlund). Journal of Conchology 25: 276–278. https://doi.org/10.5962/p.407435
• Riedel A (1980) Genera Zonitidarum. Diagnosen supraspezifischer Taxa der Familie Zonitidae (Gastropoda, Stylommatophora). Dr. W. Backhuys, Rotterdam, The Netherlands, 197 pp.
• Riedel A (1992) The Zonitidae (sensu lato) (Gastropoda, Pulmonata) of Greece. Hellenic Zoological Society, Athens viii + 194 pp.
• Roth B (1977) Vitrea contracta (Westerlund) (Mollusca: Pulmonata) in the San Francisco Bay area. The Veliger 19: 429–430. https://www.biodiversitylibrary.org/page/42409646
• Roth B, Pearce TA (1984) Vitrea contracta (Westerlund) and other introduced land mollusks in Lynnwood, Washington. The Veliger 27: 90–92. https://www.biodiversitylibrary.org/page/42481134
• Roth B, Sadeghian PS (2003) Checklist of the land snails and slugs of California. Santa Barbara Museum of Natural History Contributions in Science 3: 1–81.
• Schileyko AA (2003) Treatise on Recent terrestrial pulmonate molluscs. Part 10: Ariophantidae, Ostracolethidae, Ryssotidae, Milacidae, Dyakiidae, Staffordiidae, Gastrodontidae, Zonitidae, Daudebardiidae, Parmacellidae. Ruthenica Supplement 2: [2] + 1309–1466.
• Schütt H (2005) Turkish Land Snails, 4th ed. Verlag Natur & Wissenschaft, Solingen, Germany, 559 pp.
• Smith BJ (1992) Non-marine Mollusca. In: Houston WWK (Ed.) Zoological Catalogue of Australia. Volume 8. AGPS, Canberra, xii + 405 pp.
• Sysoev A, Schileyko A (2009) Land snails and slugs of Russia and adjacent countries. Pensoft, Sofia, Bulgaria, 212 pp. + 142 pls.
• Valovirta I, Väisänen RA (1986) Multivariate morphological discrimination between Vitrea contracta (Westerlund) and V. crystallina (Müller) (Gastropoda, Zonitidae). Journal of Molluscan Studies 52: 62–67. https://doi.org/10.1093/mollus/52.1.62
• Westerlund CA (1871) Fauna molluscorum terrestrium et fluviatilium Sveciæ, Norvegiæ et Daniæ. Sveriges, Norges och Danmarks land- och sötvatten-mollusker. Adolf Bonnier, Stockholm, 256 pp. https://doi.org/10.5962/bhl.title.13242