Danube barn snail
| Danube barn snail | ||||||||||||
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Danube barnacle ( Theodoxus danubialis ) |
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| Theodoxus danubialis | ||||||||||||
| ( C. Pfeiffer , 1828) |
The Danube barge snail ( Theodoxus danubialis ) is a freshwater snail from the family of barge snails (Neritidae), which belongs to the superior order of the Neritimorpha .
features
The Danube barge snail has a 9 to 13 mm large, strongly flattened housing with 2.5 to 3 turns. The top has a characteristic dark zigzag pattern on a light background. The width of the zigzag lines is variable. Occasionally there are also almost black specimens. The mouth is rounded to slightly elliptical. The lid ( operculum ) is light yellow and has a plate-like pin. The edge is brownish and somewhat thickened. The soft body is light with a broad foot. The antennae are long and pointed; the eyes are at the base.
Way of life and occurrence
The Danube barge snail is a freshwater snail that needs clean, oxygen-rich flowing water. It lives on stony ground and is therefore dependent on running water, as the current keeps the gravel free of sludge deposits. It feeds mainly on diatoms . Small residual populations of this species live in the Lower Bavarian Danube . For the free flowing Danube between Straubing and Vilshofen, individual finds of snail shells from more recent times are known in the area of the mouth of the Isar . In Austria it is already considered lost in the main Danube. But it still occurs in the tributaries of the Danube. In Hungary there are even larger populations in various rivers.
Reproduction
The Danube barge snail is separate from the sexes. The females attach the egg capsules, which contain around 30 to 70 eggs, to a hard substrate, often even to the housings of conspecifics. However, only one egg develops within the egg capsules; the remaining eggs function as food eggs, which are eaten by the developing young animal in the egg capsule. The development time is four to eight weeks. Then a finished young animal hatches from the egg capsule.
Systematics and nomenclature
There is both the spelling Donau- Kahnschnecke and Donaukahnschnecke ; however, the notation recommended by Jungbluth and Knorre is Donau-Kahnschnecke. The species was first scientifically described in 1828 by Carl Jonas Pfeiffer under the name Nerita danubialis . Today the species is divided into three subspecies: the nominate subspecies Theodoxus danubialis danubialis (C. Pfeiffer, 1828), Theodoxus danubialis stragulatus (C. Pfeiffer, 1828) and Theodoxus danubialis cantianus (Kennard & Woodward, 1924).
Danger
The species is considered critically endangered in Germany, Austria and Switzerland ( Red List 1). It is endangered in Slovenia.
Others
The Latin name Theodoxus danubialis means something like "God's gift to the Danube" or "The praise of God in the Danube". The conspicuous shells of the Danube barge snail played an important role in the early cultures on the Danube as jewelry and grave goods. Original snail shells can be found, for example, in the exhibition of the Natural History Collection of the Humboldt University in Berlin and in Weltenburg Abbey . Today the patterned snail shell has become a symbol for the resistance against the expansion of the Danube in Lower Bavaria.
literature
- Carl Jonas Pfeiffer : Natural history of German land and freshwater mollusks. Third division . Pp. 1-6, 1-84, plates 1-8. Landes-Industrie-Comptoir, Weimar 1828. p. 48: Nerita danubialis, the Danube swimming snail .
- Peter Glöer: The animal world of Germany. Mollusca I Freshwater gastropods of Northern and Central Europe Key to identification, way of life, distribution. 2. rework. Ed., 327 pages, ConchBooks, Hackenheim 2002 ISBN 3-925919-60-0
- Rosina Fechter and Gerhard Falkner: molluscs. 287 pp., Mosaik-Verlag, Munich 1990 (Steinbach's Nature Guide 10) ISBN 3-570-03414-3
- Jürgen H. Jungbluth and Dietrich von Knore: Trivial names of land and freshwater mollusks in Germany (Gastropoda et Bivalvia). Mollusca, 26 (1): 105-156, Dresden 2008 ISSN 1864-5127 PDF
Web links
Individual evidence
- ^ Gerhard Falkner et al .: Red List of Endangered Snails and Mussels (Mollusca) Bavaria. Bavarian State Office for the Environment, 2003, accessed on August 22, 2019 .
- ↑ Snails (Gastropoda). Retrieved May 23, 2020 .