- Helix costata O.F. Müller 1774 in 1773–1774: 31.
Identification. Shell subdiscoidal, with spire slightly elevated. Whorls few, c. 3¼–3½. Periphery rounded. Aperture subrotund. Adult lip thickened within by an opaque rib-like callus, expanded and flat-faced. Umbilicus c. 1/3 of shell width. Protoconch usually with indistinct spiral threads (periostracal). Teleoconch with prominent mostly periostracal colabral ribs, c. 28–41 on last whorl; microscopic incremental striae. Shell with a silky sheen, greyish white. Width to c. 2.7 mm (wider than high).
Animal milky white with dark eyespots.
Comparison. This species closely resembles other ribbed Vallonia. From V. gracilicosta, it is distinguished by the fewer colabral ribs, which are, thus, more widely spaced, and the presence of weak spiral threads on the protoconch.
Habitat. In BC, V. costata is known from gardens and open anthropogenic habitats. Generally, it occurs in open, usually rather xeric, anthropogenic habitats, such as lawns, waste ground, roadsides, meadows, and unkempt gardens. It is a calciphile and is frequently associated with concrete structures and limestone in some area. Underneath rocks, debris, boards, dead wood, and vegetation.
Biology. Animals predominantly reproduce by self-fertilization several times during their lives, producing eggs are ellipsoid (mean length 0.69 mm), heavily calcified, and laid singly (Kuźnik-Kowalska & Proćków 2016). Under laboratory conditions, snails lived for c. 1–2⅓ years. During this time, shell growth is initially rapid, then slower, with the mature, thickened lip being completed 120 days on average after hatching, but in as few as 42 days (Kuźnik-Kowalska & Proćków 2016).
Geographic range. Introduced to BC and known only from Kamloops (Forsyth & Nicolai 2019), although it could be expected elsewhere but may be mistaken for another species. Elsewhere in Canada, V. costata is known from Alberta (rare) and southern Manitoba through southern Ontario and southern Quebec (common). There are a few records from New Brunswick. The Central Canadian and US populations may represent early introductions (Gerber 1996), and the remote and peripheral occurrences are almost certainly introduced. Indeed, it is possible that North American populations are entirely introduced (Nicolai & Forsyth 2019).
Widespread in Europe north to Scandinavia, south to North Africa, and scattered records east to Lake Baikal, Siberia (Gerber 1996); also reported from Israel, South Africa, and Australia (Gerber 1996).
Etymology. Vallonia: named after either for the Roman goddess of valleys, Vallonia (Pilsbry 1948), or perhaps after the town of Vallon, Ardèche, south-central France (Kennard & Woodward 1926); the gender is feminine. Costatus (Latin), ribbed.
References
- Gerber J (1996) Revision der Gattung Vallonia Risso 1826 (Mollusca: Gastropoda: Valloniidae). Schriften zur Malakozoologie aus dem Haus der Natur—Cismar 8: 1–227.
- Kennard AS, Woodward BB (1926) Synonymy of the British non-marine Mollusca (Recent and post-Tertiary). British Museum (Natural History), London, United Kingdom, xxiv + 447 pp. https://doi.org/10.5962/bhl.title.8325
- Kuźnik-Kowalska E, Proćków M (2016) Reproductive biology and growth of two Vallonia species in laboratory conditions (Gastropoda: Eupulmonata: Valloniidae). Folia Malacologica 24: 265-273. https://doi.org/10.12657/folmal.024.022
- Müller OF (1774) Vermium terrestrivm et fluviatilium, seu animalium infusorium, helminthicorum, et testaceorum, non marinorum, succincta historia. Volumen alterum: testacea. Heineck & Faber, Havniæ & Lipsiæ, xxxvi + 214 + [x] pp. https://doi.org/10.5962/bhl.title.46299
- Nicolai A, Forsyth RG (2019) First record of Vallonia costata (O.F. Müller, 1774) (Gastropoda, Eupulmonata, Valloniidae) from British Columbia, Canada, confirmed by partial-COI gene sequence. Check List 15: 287–293. https://doi.org/10.15560/15.2.287
- Pilsbry HA (1948) Land Mollusca of North America (north of Mexico), vol. II, part 2. The Academy of Natural Sciences of Philadelphia, Monographs 3: i–xlvii + 521–1113.