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Radix auricularia (Linnæus, 1758)
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Species name:
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Radix auricularia (Linnæus, 1758)
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Taxon name:
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Helix Auricularia Linnæus, 1758
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Originally described in:
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Linnæus, C. 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. - pp. [1-4], 1-824. Holmiæ. (Salvius).
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Distribution:
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Europe except Sicily and Pelopónisos, in Norway up to 69° N, SW and N Asia, introduced to North America
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Diagnosis:
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Shell with upper whorls small and pointed, last whorl inflated, provoking a concave outline of the upper section of the shell, apertural height slightly larger than apertural diameter, margin on upper palatal side almost horizontally, columella twisted at the aperture with strong blunt edge, umbilicus usually closed. Juveniles are strongly pointed and high-spired.
Species can be identified by its length/width ratio, also juveniles. Differs from Radix balthica in the concave outline of the upper part, upper palatal apertural margin is not horizontal in R. balthica.
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Size:
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10-35 x 7-27 mm, usually 14-24 x 12-18 mm
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Biology:
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Lakes with rich vegetation, old river arms and silent stream bays. Up to 25 m deep. Tolerates up to 0.6 % salt, pH tolerance 7-9.9. Usually not in small standing waters, but sometimes successfully introduced into ornamental ponds in gardens and parks. In Switzerland in up to 1800 m, usually in the lowlands, Norway 70 m, in Britain restricted to lowlands. Feeds on overgrown soft substrates, consumes mainly green algae and protozoans.
30-80 oval eggs (1.5 x 1.8 mm) are laid in clutches of 15-30 mm between July and September, fixed at stones and aquatic plants, juveniles hatch after 2-3 weeks, life span 1 year.
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Threatened:
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Not very frequent in Spain. In Zurich lake up to 1 specimen per square meter. Seems to be sensitive against water pollution, may disappear locally in Britain, but no general decline was observed until 1999.
Critically endangered in Tirol (Austria), vulnerable in Niedersachsen/Hamburg, lower concern in Switzerland and Germany.
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Family:
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Lymnaeidae
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Higher group:
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Gastropoda
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Comments:
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Pictures 01-03 do possibly not represent true R. auricularia, but more likely R. balthica.
References: Gassies 1849: 163 (Lymnaea trencaleonis), Moquin-Tandon 1855: 463, Germain 1931: 487, 490 (L. ampla), Clarke 1981: 114, Jungbluth et al. 1989: 58, Falkner 1990: 138, Kruglov & Starobogatov 1993: 85, Vogt et al. 1994: 61, Manganelli et al. 1995: 10, Turner et al. 1998: 106, Kerney 1999: 55, Glöer 2002: 213, Pérez-Quintero et al. 2004, Beckmann 2007: 46 (Mallorca, Menorca), Welter-Schultes 2012: 52 (range map Europe).
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