Smooth grass snail
| Smooth grass snail | ||||||||||||
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Smooth grass snail ( Vallonia pulchella ) |
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| Scientific name | ||||||||||||
| Vallonia pulchella | ||||||||||||
| ( OV Müller , 1774) |
The smooth grass snail ( Vallonia pulchella ) is a species of land living snail from the family of grass snails (Valloniidae); the family belongs to the subordination of land snails (Stylommatophora).
features
The thick disk-shaped case is 1 to 1.5 mm high and 2 to 2.75 mm (2 to 2.5 mm) wide. It has 2 3/4 to 3 3/8 well-arched but not shouldered whorls that regularly increase. The thread only rises slightly from the level of the housing. The embryonic casing takes up about 1 1/8 turn. The whorls are moderately arched at the periphery, and when viewed in cross-section they encircle each other strongly. The last turn can rise or fall slightly towards the mouth. The embryonic casing shows a fine shagreen coating . The Teleoconch, on the other hand, only has irregular growth strips. The navel is deep and bowl-shaped.
The muzzle plane is at an angle of about 30 ° from the axis of the housing. The mouth is almost rounded, the points of attachment of the mouth seam to the previous turn are far apart. They are connected to one another by a flat-arched callus indented towards the mouth. The edge of the mouth is bent outwards at approximately a right angle and forms a wide brim. The inside of the mouth is thickened with a thick, white lip. It even steps forward over the mouth level.
The (fresh) housing is faintly translucent with a milky-white cloudiness, but often also clear and transparent. It shines through as a ring-shaped, opaque-white strip. The surface is glossy, the color is yellowish-white to yellowish-gray.
The soft body is milky white. The foot is noticeably rounded at the rear end. The tentacles are comparatively short. In most of the specimens in a population, the male ducts in the hermaphroditic genitalia are reduced ("aphallic"). Only a few specimens still have the male exits and can still copulate. The spermatic duct (vas deferens) branches off very far below from the egg duct (sperm duct). It is comparatively very short and ends in a short, inflated epiphallus. The actual penis is very short, about as long as the epiphallus. At the epiphallus / penis transition, there is a very long penis appendage, which essentially consists of three sections: a thick, heavily inflated basal part that is almost half the length and separated from the penis by a constriction, a short, thin middle part and a club-shaped end part . The retractor muscle divides into two strands and attaches to the penis and epiphallus, close to the penis / epiphallus transition. In the female tract, the free fallopian tube and the vagina are quite short and almost the same length. The stem of the sperm library is comparatively very short and the bladder small.
Similar species
The shell of the smooth grass snail ( Vallonia pulchella ) is significantly smaller than that of the large grass snail ( Vallonia declivis ). The edge of the mouth of the smooth grass snail is much more turned.
Geographical distribution and habitat
The smooth grass snail has a Holarctic distribution. In the west it extends to the Canary Islands , Madeira and the Azores . In Northern Europe it occurs up to 71 ° N. In the south the area extends to North Africa, the Middle East, Iran , Afghanistan and Kashmir . The distribution area has increased significantly through anthropogenic displacement. Today it is also found in Iceland , the Cape Verde Islands , Australia , New Zealand , China , South Africa , Madagascar , Mauritius , Bermuda , Argentina , Brazil , Uruguay , Peru and Guatemala (and probably in other countries as well).
The smooth grass snail prefers open, moist meadows and marshland on calcareous subsoil near flowing waters, more rarely on dry grass or scree, but not in the forest. In Switzerland it rises up to 2000 m. Due to the affinity to more humid meadows near rivers, empty shells can often be found in large numbers in river gullies.
Way of life
The animals reproduce mainly through self-fertilization; Copulations are rare. They lay about 20 eggs individually in the earth or in small crevices. An egg is laid every day under optimal conditions. However, there can be several days in between. The eggs are 0.7 to 0.8 mm in diameter. Under controlled conditions (21–22 ° C) the development takes about 12 days until the hatchlings. In the wild, the young hatched after 15 to 20 days (according to observations in Austria and France). The final size with the formation of the mouth is already reached after two months. The animals begin to lay eggs one week after they have reached adult size. At the end of the egg-laying period, which can last for more than a month, the animals die. Probably two generations are formed a year. In winter, the animals hibernate. In France, the second generation laid eggs between July and September. The animals overwinter as juveniles and reach sexual maturity in spring.
Taxonomy
The taxon was first described by Otto Friedrich Müller in 1774 as Helix pulchella . The smooth grass snail ( Vallonia pulchella ) is de facto the typical species of the genus Vallonia , the formal type species Vallonia rosalia Risso, 1826 a more recent synonym of Vallonia pulchella Müller, 1774. The species is now widely recognized.
Danger
The smooth grass snail is not endangered in Germany.
supporting documents
literature
- Klaus Bogon: Land snails biology, ecology, biotope protection. Natur Verlag, Augsburg 1990, ISBN 3-89440-002-1 (p. 140).
- Rosina Fechter and Gerhard Falkner: molluscs. 287 p., Mosaik-Verlag, Munich 1990 (Steinbach's Nature Guide 10), ISBN 3-570-03414-3 (p. 150)
- Jochen Gerber: Revision of the genus Vallonia Risso 1826 (Mollusca: Gastropoda: Valloniidae). Schriften zur Malakozoologie, 8: 1–227, Cismar, 1996 (p. 48ff.)
- Michael P. Kerney, Robert AD Cameron & Jürgen H. Jungbluth: The land snails of Northern and Central Europe. 384 pp., Paul Parey, Hamburg & Berlin 1983, ISBN 3-490-17918-8 (p. 127)
- Francisco W. Welter-Schultes: European non-marine molluscs, a guide for species identification = identification book for European land and freshwater mollusks. A1-A3 S., 679 S., Q1-Q78 S., Planet Poster Ed., Göttingen 2012, ISBN 3-933922-75-5 , ISBN 978-3-933922-75-5 (p. 207)
Individual evidence
- ↑ a b Vollrath Wiese: The land snails of Germany. 352 p., Quelle & Meyer, Wiebelsheim 2014 ISBN 978-3-494-01551-4 (p. 96/7)
- ^ Folco Giusti, Giuseppe Manganelli: Notulae malacologicae, XXXIII. 'Helix' sororcula Benoit 1859 and its relationships to the genera Vallonia Risso and Planogyra Morse (Pulmonata: Pupilloidea). Archives for Molluscology, 116 (4/6): 157-181, Frankfurt / Main 1986.
- ^ David G. Herbert: The introduced terrestrial Mollusca of South Africa. SANBI Biodiversity series, 15, South African National Biodiversity Institute, Pretoria 2010 ISBN 978-1-919976-56-3 PDF .
- ↑ a b c Alejandra Rumi, Julieta Sánchez, Noelia S. Ferrando: Theba pisana (Müller, 1774) (Gastropoda, Helicidae) and other alien land molluscs species in Argentina. Biological Invasions, 12: 2985-2990, 2010 doi : 10.1007 / s10530-010-9715-x
- ↑ Otto Friedrich Müller: Vermium terrestrium et fluviatilium, seu animalium infusoriorum, helminthicorum, et testaceorum, non marinorum, succincta historia. Volume alterum. SI-XXXVI, 1-214, Heineck & Faber, Copenhagen & Leipzig 1774 Online at www.biodiversitylibrary.org (p. 81/2)
- ↑ Fauna Europaea
