Carychium minimum

Carychium minimum O. F. Müller, 1774
Herald Thorn

  • Carychium minimum O. F. Müller 1774: 125.
  • Additional synonyms and suspected synonyms in the European literature.
Carychium minimum, St John River, New Brunswick.

Identification. Shell obese-fusiform. Spire elongate, with strongly convex sides. Apex bluntly pointed. Whorls ca 4, convex. Sutures rather well-indented. Protoconch smooth. Teleoconch with weak incremental striae initially, regular, colabral striae on last two whorls. Aperture subovate; 1 parietal lamella, continuing internally around columella in a smooth, not undulating curve; 1 smaller lamella at base of columella. Adult lip expanded, a little recurved, thickened on inner side, especially medially on palatal lip. Belly of the last whorl projected beyond the plane of peristome. Chink-like “false umbilicus” against base of last whorl. translucent, colourless when fresh, opaque, and white when dead. Shell to 1.9 mm high (higher than wide).

This species is recognized by its faintly striate, stouter shell, having fewer whorls and a greatly thickened palatal lip which bears a prominent medial denticle. The aperture is relatively larger than in the native Carychium species. The internal lamella is regularly spiral.

Habitat. Floodplains and margins of rivers, under driftwood and dead vegetation in permanently moist places. Found under flowerpots and other objects in a garden centre on Vancouver Island (Forsyth 2004) and in gardens in San Francisco (Roth 1982). At Ithaca, New York, populations were in a seep near a lake and in the riparian zone of a creek (Weigand & Jochum 2010).

In Europe, this species inhabits marshes, edges of swamps, wet woods, floodplain meadows, and dune slacks are the usual habitats (Germain 1931, Kerney 1999), and in the Alps, occurs at elevations up to 1,000 m (Germain 1931).

Global range. Europe. North to Arkhangelsk, south to Crimea and Caucasus; forested southern Urals; east to eastern Kazakhstan (Sysoev & Schileyko 2009); likely introduced to Madeira (Seddon 2008). Introduced to North America; known in the USA from California (Roth 1982), New York (Weigand & Jochum 2010, Forsyth 2015); Massachusetts (Clapp 1912, Winslow 1922), and Pennsylvania (Pearce and Payne 2011). It is likely that it is more widespread in North America than currently known.

Canadian range. Introduced. In British Columbia (Fraser River estuary and south-eastern Vancouver Island), Ontario (Grand River, Brant County; Port Whitby, Durham Region), and New Brunswick (Mactaquac Lake, a broadening of the Saint John River) (Forsyth 2015, unpubl. data).

Although only known in southern Ontario from stream drift, it is almost certainly naturalized there. An early literature record exists for C. minimum at Hamilton, Ontario (Hanham 1889), but as this species was absent from a later list by the same author (Hanham 1890), and it is possible that was not this species.

Etymology. Latin, minimum, “least” or “smallest”.

Remarks. In much of the older European literature, C. minimum and C. tridentatum were not distinguished from each other, or with the latter treated as a variety of the former; Watson & Verdcourt (1953) reviewed the history the use of these names.

Weigand et al. (2010) used DNA barcoding to confirm these species as distinct. In another study, Weigandet al. (2012) investigated the population structure of C. minimum andfound in Europe four distinct genetically isolated, phylogenetic units which are likely explained by refugial areas during glacial periods; an eastern North America population was found to belong to the Central–Western Europe group.

  • Clapp W (1912) Carychium minimum Mull. The Nautilus 26: 24.
  • Forsyth RG (2015) First record of Carychium minimum (Müller, 1774 in New Brunswick, Canada (Mollusca: Gastropoda: Ellobioidea). Check List 11: 1511.
  • Müller OF (1774) Vermium terrestrium et fluviatilium, seu animalium Infusorium, Helminthicorum, et Testaceorum, non marinorum, succincta historia. Volumen alterum: Testacea. Heineck & Faber, Havniæ & Lipsia, xxxvi + 214 + [x] pp.
  • Pearce TA, Payne SL (2011) European Carychium land snails in Pennsylvania. Tentacle 19: 13.
  • Roth B (1982) European land mollusks in the San Francisco Bay area, California: Carychium minimum Müller and the Arion hortensis complex. The Veliger 24: 342–344.
  • Seddon MB (2008) The landsnails of Madeira. An illustrated compendium of the land snails and slugs of the Madeiran archipelago. Studies in Biodiversity and Systematics of Terrestrial Organisms from the National Museum of Wales, Biotir Reports 2: i–viii + 1–204.
  • Sysoev A, Schileyko A (2009) Land snails and slugs of Russia and adjacent countries. Pensoft, Sofia, Bulgaria, 212 pp. + 142 pl.
  • Weigand AM, Jochum A (2016) Mollusca, Gastropoda, Ellobioidea, Carychium minimum O.F. Müller, 1774: filling gaps. New population record for the state of New York, northeastern United States. Check List 6: 517–518.
  • Winslow ML (1922) Notes on the internal lamellae of Carychium. Occasional Papers of the Museum of Zoology, University of Michigan 128: 1–17.