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Abbreviations used: W: Width (of shell); H: Height; N: Number of whorls.
Explanation of
shell characters as means of identification.
 Cheese snail (Helicodonta obvoluta) with a shell full of hairs. [RN]
Gallery picture. |
In the Vienna woods, the cheese snail (Helicodonta obvoluta) is a snail often encountered. Its shell, characteristically formed, the spire not ascending, but depressed, gave this snail its name, as it reminds the onlooker of a round loaf of cheese. With its size a little bit smaller than a banded snail, it is also easily recognized in nature with the bare eye.
Size: B: 11 - 15 mm; H: 5 - 7 mm; N: 5 - 6.
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Apart from the form of a cheese snail's shell as such, the form of the shell's aperture or shell mouth is striking: It is triangular, and because of the bulging lip appears to be even more peculiar. The shell spire's whorls are coiled tightly, like a belt, which gave the snail its name in some other languages, like in German: Riemenschnecke, the belt snail.
 Cheese snail (Helicodonta obvoluta) with a shell full of hairs not exclusively used as a means for camouflage. [RN] |
Especially among juvenile animals, the shell with its irregularly striped surface is covered with hairs a millimetre long. Among older specimens usually only the scars remain in the shell surface. Apart from their main role of improving control over humidity and adhesion to the wet leaves of the snails' food plants, one task of those hairs seems to be camouflage, as they keep dirt to the shell and so disguise the shell from its environment.
Pfenninger,
M. et al.: "Why
do snails have hairs? A Bayesian inference of character evolution".
During phases of dormancy and during winter, the cheese snail closes its shell aperture with a chalky white lid called an epiphragma (also see: The Roman snail in hibernation).
Helicodonta obvoluta lives in forests under dead leaves, on fallen logs and between stones. While it is usually found on limestone ground, it is not necessarily restricted to limestone.
 Cheese snail (on the right) and a juvenile keelback slug (Limax cinereoniger). [RN] |
The cheese snail occurs in vast parts of Europe: From the Pyrenees, its distribution areas stretches through south and middle France as far as Belgium and the Limburg province in the southern Netherlands. Through the German low mountain ranges, Helicodonta obvoluta occurs as far east as the inner western Carpathians; as already mentioned, in the Vienna woods (the low mountain ranges west and south-west of Vienna), it is among the more common species.
In the south, the cheese snail's distribution area stretches over the Alps though Tuscany and the north-eastern Balkan Peninsula. As a relic of a postglacial warm period, it also lives isolated in south-eastern England (in the South Downs) and Schleswig Holstein in North Germany.
Systematics:
There is still argument about into which order to put the cheese snails, as a family (Helicodontidae) or a subfamily (Helicodontinae), which would then belong to the bush snails (Hygromiidae, Helicoidea superfamily). While Clecom states the Helicodontidae as a family, Mollbase favours the Helicodontinae as a subfamily.
Literature:
Links:
Complete species list for the UK and Ireland
Source:
Clecom,
as of June 2008)
Helicodontidae Kobelt, 1904
Helicodontinae Kobelt, 1904
Helicodonta A. Férussac, 1821
Helicodonta obvoluta obvoluta (O.F. Müller, 1774)
