Big grass snail
| Big grass snail | ||||||||||||
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Great grass snail ( Vallonia declivis ) |
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| Scientific name | ||||||||||||
| Vallonia declivis | ||||||||||||
| Sterki , 1893 |
The great grass snail ( Vallonia declivis ) is a species of snail from the family of grass snails (Valloniidae) that lives on land ; the family belongs to the subordination of land snails (Stylommatophora).
features
The shell of the great grass snail is 2.34 to 3.15 mm wide and 1.24 to 1.93 mm high. It has 3 1/8 to 3 7/8 well arched turns, 1/8 turns are taken up by the embryonic housing. The shape of the housing is somewhat variable, from almost disk-shaped with a flat conical apex that is lifted out over the last turn to a pressed spherical shape with a dome-shaped apex. The turns increase moderately and evenly, only the last turn falls in a straight line just before the mouth, little to moderately far. The turns are slightly curved and separated from each other by shallow seams. For this, the dealings encompass comparatively strong. The umbilicus is open and takes up more than a quarter of the largest housing diameter. The approximately round mouth is comparatively slightly inclined (approx. 30 °) in relation to the winding axis. The two attachment points of the edge of the mouth are connected by a thin callus, which is flat towards the inside of the housing. The edge of the mouth is not bent outwards near the upper point of attachment to the previous turn, outside and below it is only slightly bent outwards. The inside of the mouth is reinforced with a ring-shaped, usually only moderately strong, white lip. If it is stronger, bead-like, it can also protrude over the level of the mouth. The embryonic casing has a very fine chagrin structure that is only visible under the microscope. The Teleoconch has no ribs, but only clear, sharp and usually very regular growth strips. In front of the mouth every second or third strip of growth is reinforced like ribs. The housing is tinted yellow and milky-whitish, slightly transparent. The lip hardly shines through to the outside.
Similar species
The shell of the great grass snail is significantly larger than that of the other species of the genus Vallonia that occur in Central Europe . Vallonia pulchella and the fossil species Vallonia lepida are quite similar . Both types differ, however, in the strongly turned-up mouth seam.
Geographical distribution and habitat
The distribution area extends, albeit very scattered, over the river plains in Germany, here particularly with a focus in southern Germany, Switzerland (Swiss Jura), Austria, Alsace, the Czech Republic and Poland. The northernmost occurrence was in southern Lower Saxony. In Switzerland it rises to 1,400 m above sea level. The often-reported occurrence in Slovakia has recently been revised. The alleged occurrence in the Canton of Zurich (Switzerland) is based on an incorrect determination. However, research in southern Germany in the 1990s revealed that it has been extinguished there in most of the earlier distribution areas.
The great grass snail prefers moist, open meadows near running waters. Therefore, the housings are often found in river gullies. It is also rarely found in vineyards and reed beds.
Taxonomy
The taxon was introduced into scientific literature by Victor Sterki in 1893. In the older literature the species was often wrongly described as Vallonia adela (Westerlund, 1875). Helix adela Westerlund, 1875 is, however, a more recent synonym of the smooth grass snail ( Vallonia pulchella ). The species is generally recognized as an independent species.
Danger
The current range of the great grass snail is only very poorly known. In the last hundred years it has lost a large part of its previous range or has become very rare in this area. While it used to be quite common in the valleys of the Swabian Alb, in the upper Neckar valley and in the upper Danube valley, Jochen Gerber did not succeed in finding a single live animal in these regions in the early 1990s. In 1997 Günter Schmid found some fresh housings in genists from the Neckar and Danube, which suggest that the species has not yet died out there. Only in the Bavarian Danube Valley near Weltenburg and Deggendorf were two (!) Finds made by Jochen Gerber. The species is therefore classified as critically endangered in Germany. In contrast, the species is classified by the International Union for Conservation of Nature and Natural Resources (IUCN) as “only“ potentially endangered. ”More recent studies on the population of the great grass snail are not available.
supporting documents
literature
- Michael P. Kerney, Robert AD Cameron & Jürgen H. Jungbluth: The land snails of Northern and Central Europe. 384 p., Paul Parey, Hamburg & Berlin 1983, ISBN 3-490-17918-8 (p. 130/1)
- Jochen Gerber: Revision of the genus Vallonia Risso 1826 (Mollusca: Gastropoda: Valloniidae). Schriften zur Malakozoologie, 8: 1-227, Cismar, 1996 (pp. 78-84).
- Francisco W. Welter-Schultes: European non-marine molluscs, a guide for species identification = identification book for European land and freshwater mollusks. A1-A3 p., 679 p., Q1-Q78 p., Planet Poster Ed., Göttingen 2012, ISBN 3-933922-75-5 , ISBN 978-3-933922-75-5 (p. 206)
Individual evidence
- ↑ Tomáš Čejka, Libor Dvorřák, Michal Horsák, Jozef Šteffek: Checklist of the Molluscs (Mollusca) of the Slovak Republic. Folia Malacologica, 15 (2): 49-58: Poznan 2007 PDF
- ↑ Hans Turner: The molluscs (Mollusca) of the canton of Zurich: species inventory and endangerment. Quarterly journal of the Natural Research Society in Zurich, 136 (3): 163-181, Zurich 1991 ( PDF
- ^ Victor Sterki: Genus Vallonia Risso. in: Pilsbry, HA: Manual of conchology; structural and systematic. With illustrations of the species. Second series: Pulmonata. Volume III, p. 169-170, Vol. VIII [= 8]. Helicidæ. Pp. 247-261, pl. 32, 33, 43, 56, Philadelphia 1893 Online at www.biodiversitylibrary.org (p. 251).
- ^ Carl Agardh Westerlund: Miscellings. Malakozoologische Blätter, 22: 57-61, Frankfurt / M. 1875. Online at www.biodiversitylibrary.org (p. 57)
- ↑ Fauna Europaea: Vallonia declivis Sterki 1893
- ^ David Geyer: Contributions to the mollusc fauna of Swabia II. Vallonia. Annual books of the Association for Patriotic Natural History in Württemberg, 64: 305-330, Stuttgart 1908. Online at www.biodiversitylibrary.org (p. 326-327 as Vallonia adela )
- ↑ Manfred Colling, Gerhard Falkner, Klaus Groh, Jürgen H. Jungbluth, Matthias Klemm, Hans-Jörg Niederhöfer, Wolfgang Rähle, Günter Schmid: Red List and Species Directory of Snails and Mussels in Baden-Württemberg. State Institute for the Environment, Measurements and Nature Conservation Baden-Württemberg PDF
- ^ Vollrath Wiese: The land snails of Germany. 352 pp., Quelle & Meyer, Wiebelsheim 2014 ISBN 978-3-494-01551-4 (p. 100)
- ↑ The IUCN Red List of Threatened Species: Vallonia declivis
