Western oat grain snail

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Western oat grain snail
Western oat grain snail (Chondrina avenacea)

Western oat grain snail ( Chondrina avenacea )

Systematics
Order : Lung snails (pulmonata)
Subordination : Land snails (Stylommatophora)
Superfamily : Pupilloidea
Family : Corn snails (Chondrinidae)
Genre : Chondrina
Type : Western oat grain snail
Scientific name
Chondrina avenacea
( Bruguière , 1792)

The western oat grain snail ( Chondrina avenacea ), also just called oat grain snail , common oat grain snail or just oat grain , is a terrestrial snail from the family of grain snails (Chondrinidae). It lives exclusively on endolithic algae, the surface of limestone rocks including the algae and lichens living in them is scraped off.

features

The right-hand winding case is relatively small; it is 6 to 8 mm high and measures 2.3 to 2.5 mm in thickness. It is cylindrical-conical and has seven to eight turns. The seam is clearly formed, the last turn takes up about a third of the height of the case. The mouth is elliptical, the white edge of the mouth is only slightly expanded and also hardly bent back. The edge of the mouth is relatively thin and interrupted in the parietal region of the mouth. The inside of the muzzle is yellowish to reddish brown in color. Usually eight strong “teeth” protrude into the mouth; three palatal teeth, the upper one being somewhat weaker or missing, an angular tooth located far in front and a parietal tooth located deeper in the mouth and two columellar teeth.

The housing is colored dark gray to reddish brown and shows variable stripes on the largely smooth, non-glossy surface. It can be coarse to fine, and the spacing between the strips also varies greatly. The housing is very often covered by rock dust or lichen remnants.

The animals are hermaphrodites. In the genital apparatus, the spermatic duct (vas deferens) lies close to the penis opening in the atrium, and the penis and spermatic duct are enclosed by a tissue cover. The spermatic duct leaves the tissue after a short distance and penetrates the epiphallus. This is separated from the penis by a strong constriction in the area of ​​the 180 ° loop. There is no blind bag. The penile retactor muscle starts near the bend of the penis / epiphallus. In the female tract, the free fallopian tube (oviduct) is very short, while the vagina is very long. The spermathec is a long tube that attaches to the egg ladder but does not reach the albumin gland. The reservoir (bladder) is elongated, club-shaped, without a diverticulum.

Similar species

When finely ribbed oats screw ( chondrina arcadica ) the last deal is not enlarged. In comparison, this species has evenly and strongly curved turns, and the seams are somewhat deeper. In addition, the shell of the finely ribbed oat grain snail is a little smaller and more conical in shape.

Distribution of the oat grain snail in Europe (according to Welter-Schultes)

Geographical distribution and habitat

The western oat grain snail is widespread in Central Europe, but very scattered and strictly tied to the areas where lime or dolomite is on the surface. It occurs from the Spanish Mediterranean coast (around the height of Valencia ), southern and eastern France, with smaller occurrences in southern Belgium, via Switzerland, southern Germany, Austria, northern Italy to the Czech Republic and isolated in Bulgaria . In Germany, the northernmost deposit is in Thuringia ( Hörselberge near Eisenach).

The western oat grain snail is strictly bound to limestone or dolomite . It inhabits the sunlit sides of rocks and rock faces. The animals are only active in high humidity, rainy weather or on wet surfaces. When dry, they retreat into the housing, but attach the housing firmly to the rock with dried slime. In this way, they can be dragged away when the rock is extracted. They spend extreme drought in the detritus and rock rubble under the rocks. In the mountains it rises to an altitude of 1800 m above sea level. Occasionally the western oat grain snail and the finely ribbed oat grain snail ( Chondrina arcadica ) appear sympatric .

Way of life

The oat grain snail feeds on endolithic lichens, algae and also detritus. With the help of their radula, the animals grate off the top thin layer of rock, including the algae and lichens burrowing in it. They don't eat green, higher plants. The animals are fully grown after about three to five years and reach a maximum age of ten years. Between 1 and 90% of the individuals in a population are aphallic and have no penis, only the female genitals. However, male and female sex cells are produced in the sex glands. However, it is not known whether self-fertilization occurs in these individuals.

Taxonomy

The taxon was described in 1792 by Jean-Guillaume Bruguière in the form of Bulimus avenaceus . The species is generally accepted as a valid taxon. The species is currently divided into six subspecies:

  • Chondrina avenacea avenacea (Bruguière, 1792)
  • Chondrina avenacea istriana Ehrmann , 1931, Slovenia
  • Chondrina avenacea latilabris (Stossich, 1895), Northern Italy
  • Chondrina avenacea lepta (Westerlund, 1887), Slovenia
  • Chondrina avenacea lessinica (Adami, 1885), Northern Italy
  • Chondrina avenacea veneta H. Nordsieck, 1962, Veneto

Danger

According to Vollrath Wiese, the extent of the risk is unknown. The species is not endangered over the entire range.

literature

  • Ewald Frömming: Biology of the Central European Landgastropods. 404 p., Duncker & Humblot, Berlin 1954
  • Edmund Gittenberger: Contributions to the knowledge of the pupillacea: III. Chondrininae. Zoologische Verhandelingen, 127 (1): 3-267, 1973 ISSN  0024-1652 PDF .
  • Michael P. Kerney, RAD Cameron, Jürgen H. Jungbluth: The land snails of Northern and Central Europe. 384 pp., Paul Parey, Hamburg & Berlin 1983, ISBN 3-490-17918-8 , pp. 114/15

Individual evidence

  1. ↑ Jürgen H. Jungbluth and Dietrich von Knorre: Trivial names of land and freshwater mollusks in Germany (Gastropoda et Bivalvia). Mollusca, 26 (1): 105-156, Dresden 2008 ISSN  1864-5127 , p. 117 (as Chondrina arcadica clienta ).
  2. ↑ Klaus Bogon: Landschnecken biology, ecology, biotope protection. 404 p., Natur Verlag, Augsburg 1990, ISBN 3-89440-002-1 , p. 128/29.
  3. ↑ Peter Reischütz: Mollusks (snails and mussels) Vorarlberg. Species list and proposal for a red list. News sheet of the First Vorarlberg Malacological Society, 1: 4-10, 1993 PDF
  4. ↑ Alexandru V. Grossu: Gastropoda Romaniae 2 Subclasa Pulmonata I Ordo Basommatophora II Ordo Stylommatophora Suprafamiliile: Succineacea, Cochlicopacea, Pupillacea. 443 S., Bucharest 1987, pp. 330-336.
  5. ^ 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., Göttingen, Planet Poster Ed., 2012 ISBN 3-933922-75-5 , ISBN 978-3-933922-75-5 (S. 160)
  6. ↑ Valerio Ketmaier, Folco Giusti and Adalgisa Caccone: Molecular phylogeny and historical biogeography of the land snail genus Solatopupa (Pulmonata) in the peri-Tyrrhenian area. Molecular Phylogenetics and Evolution, 39: 439-451, 2006 doi : 10.1016 / j.ympev.2005.12.008
  7. ↑ a b Species summary for Chondrina avenacea . In: Animal Base. Uni Göttingen, June 25, 2009, accessed June 8, 2010 .
  8. ^ Jean-Guillaume Bruguière: Encyclopédie méthodique. Histoire naturelle des vers. Tome premier. [ABE-CON]. SI-XVIII (= 1-18), pp. 1-757, Panckoucke, Paris, 1792 Online at Biodiversity Heritage Library , p. 355.
  9. ↑ a b Fauna Europaea: Chondrina avenacea (Bruguiere 1792)
  10. ↑ a b MolluscaBase: Chondrina avenacea (Bruguière, 1792)
  11. ^ Vollrath Wiese: The land snails of Germany. 352 pp., Quelle & Meyer, Wiebelsheim 2014, ISBN 978-3-494-01551-4 (p. 88)
  12. ↑ Chondrina avenacea in the IUCN Red List of Threatened Species 2013.1. Posted by: Pall-Gergely, B., 2011. Retrieved July 8, 2018.