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Carychium minimum Müller, 1774
Herald Thorn
Family: Ellobiidae
Species account author: Robert Forsyth.
Introduction to the Land Snails of BC

Photograph

© Robert Forsyth     (Photo ID #6397)

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Distribution of Carychium minimum in British Columbia in British Columbia

Species Information

Diagnosis Among species of Carychium in BC, Carychium minimum is recognized by the combination of its stout, faintly striate shell, fewer whorls, and a thickened palatal lip that bears a prominent medial denticle. The internal lamella is evenly spiral.

Shell Minute (Maximum mature height: 1.6–2.0 mm × width: 0.8–1.0 mm); growth determinate; ovate-fusiform, thin-shelled; translucent. Whorls: ca 3⅔ – 4¾; evenly increasing in width; spire whorls convex. Spire: elongate; sides convex; apex bluntly rounded. Suture: deep. Last whorl: not descending to the peristome; constriction of whorl behind the baso-palatal lip almost non-existent; no crest. Periphery: rounded. Protoconch: smooth. Teleoconch sculpture: numerous, fine colabral striae (almost riblet-like), often crossed by weak, poorly defined spiral striae. Periostracum: inconspicuous. Umbilicus: absent or nearly closed. Aperture: subovate; ca 2/5 of total shell height. Peristome: incomplete. Apertural dentition: 1 (larger) parietal lamella that continues internally around columella a smooth curve; 1 small lamella at base of columella; 1 medial denticle (or well-developed swelling) on palatal lip. Palatal lip: slightly expanded, strongly callused on inside, edge thin, recurved. Peristome, viewed from side: sinuous; belly of last whorl not projecting beyond the plane of peristome. Parietal callus: glazed, transparent, inconspicuous. Colour: colourless or white; with a silken sheen.

In Europe shells are somewhat variable in their slenderness, and some approach the form of another species, Carychium tridentatum from which they are usually told apart by the structure of the internal parietal lamella. Variation in the relatively few shells found in BC has not been assessed.

Animal

Body unpigmented, white, having black eye spots behind the bases of a single pair of cylindrical tentacles (Adam 1960, Roth 1982). Foot not divided into two longitudinal sections as is typical for many marine ellobiids (Watson and Verdcourt 1953).

Biology


The biology of this species is little known, but is expected to be similar to that of Carychium tridentatum.

Habitat


In permanently moist places; very hygrophilic. In Europe, this species lives in marshes, edges of swamps, in wet woods, on flood-plain meadows, and in dune slacks (Germain 1931, Kerney 1999), and lives in leaf litter, on sticks, in vegetation, etc. It occurs at elevations up to 1,100 m in the Alps (Germain 1931).

In North America it is known from synanthropic habitats, including gardens (Roth 1982) and nurseries and greenhouses, where it has been found under pots (Grimm et al. 2010), and more natural habitats. At Ithaca, New York, C. minimum has now been found to be naturalized; populations were discovered at a seep near a lake and in the riparian zone of a creek (Weigand and Jochum 2010).

Distribution


Global range

Native to Europe; north to Arkhangelsk, south to Crimea and Caucasus; forested south Urals; east to eastern Kazakhstan (Sysoev and Schileyko 2009); likely introduced to Madeira (Seddon 2008). Introduced to North America, including to Canada (BC, Ontario), where records are few and scattered. In the United States, this species is known from San Francisco and Alameda counties, California (Roth 1982, Roth and Sadeghian 2003), from drift of the Tioughnioga River, Cortland Co., New York (leg. F.W. Schueler, RGF collection), and naturalized at Ithaca, New York (Weigand and Jochum 2010). This species was recorded from Quincy, Massachusetts (Clapp 1912, Winslow 1922, Pilsbry 1948) but it was subsequently re-identified as another species, C. tridentatum (Roth 1982). Carychium minimum is likely more widespread in North America, and almost certainly in the northeastern U.S than currently known.

BC range

First found in a retail nursery at Cobble Hill on southern Vancouver Island in 2001 (RBCM coll., Forsyth 2004, Forsyth et al. 2008), this species may not yet be established in British Columbia (Grimm et al. 2010); no other records are known from BC and this location has not be revisited to confirm the persistence of the population.

Notes


Etymology

Genus name derived from the Greek, karyx, "a herald", signifying the ancient use of a shell as a trumpet; the gender is neuter. Species name, Latin, "minimus", meaning "least" or “smallest”.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)		COSEWIC
ExoticSNAExoticNot Listed



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