|
Planorbarius corneus (Linnæus, 1758)
|
|
Species name:
|
Planorbarius corneus (Linnæus, 1758)
|
|
|
Taxon name:
|
Helix cornea Linnæus, 1758
|
|
Originally described in:
|
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).
|
|
Distribution:
|
Europe and W Asia (probably not native in Ireland and Scotland, not present in N Scotland, up to 64° N in Finland, rare in S Norway, more frequent in S Sweden), scattered distribution, often artificially introduced
|
|
Diagnosis:
|
Shell large, light yellowish with brown, reddish or greenish periostracum, radially and spirally weakly striated, upper side weakly and lower side deeply depressed, 3-4.5 rounded whorls, last whorl predominating.
Animal brown or reddish.
|
|
Size:
|
10-17 x 22-40 mm
|
|
Biology:
|
Silent waters in lowlands with rich vegetation, standing or slowly moving, tolerates periodical droughts and anaerobic bottoms, temperature optimum 19-20°C, perfers pH around 6-9. Poor powers of passive dispersal, but frequently introduced to artificial ponds. Feeds mainly or exclusively on detritus. Often released from aquaria, but does not survive permanently in highlands. In Switzerland in up to 800 m altitude, in Austria 500 m, Erzgebirge (Germany/Czech Rep.) 750 m.
Reproduction in spring and autumn at water temperatures above 15°C, eggs (diameter 1.2-1.7 mm) are laid in mostly elongate capsules of 8-15 mm width, each strain containing 12-40 eggs, fixed to aquatic plants, embryos are reddish with transparent shells, juveniles hatch after 14-16 days, life span up to 3 years. Self-fertilization is possible, one single released animal can establish a stable population, but only 5 % of the juveniles in self-fertilized eggs will hatch.
|
|
Threatened:
|
Extending its range in Britain, frequent in SE and central England.
Endangered in Tirol, vulnerable (but not autochthonous) in Switzerland and Austria, and in Niedersachsen.
|
|
Family:
|
Planorbidae
|
|
Higher group:
|
Gastropoda
|
|
Comments:
|
References: Moquin-Tandon 1855: 445, Germain 1931: 518, Jungbluth et al. 1989: 77, Falkner 1990: 132, Manganelli et al. 1995: 11, Turner et al. 1998: 134, Kerney 1999: 70, Glöer 2002: 244, www.naturamediterraneo.com (2007), Welter-Schultes 2012: 67 (range map Europe).
|
