Common boat snail
| Common boat snail | ||||||||||||
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Common barnacle ( Theodoxus fluviatilis ), Philip Henry Gosse : Natural History - Mollusca, London 1854 |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Theodoxus fluviatilis | ||||||||||||
| ( Linnaeus , 1758) |
The Common nerite , river floating worm or dwarf river snail ( Theodoxus fluviatilis ) is an in freshwater and brackish living snail from the family of neritidae (Neritidae) that the superiority of the Neritimorpha is expected. The common barnacle was mollusk of the year 2004.
features
The housing is thick-walled and ear-shaped with a few turns. It is up to 6.5 mm high and up to 10 mm wide. The inner walls are dissolved during growth. The opening is flat: it can be closed with an operculum . The housing is very variable in terms of color and color pattern. Usually the pattern is reticulated; dark red on a light background, or the basic color is dark red with white spots. The spots are often arranged in ribbons. The animal is light yellow with a black head. The tentacles are relatively long and gray. The foot is whitish.
Theodoxus fluviatilis littoralis
Theodoxus fluviatilis dalmatinus
Multiplication
The animals, like all barnacles (Neritidae), are of separate sexes. The male's penis sits inside the right antennae. The female has a vagina for copulation and a second sexual opening for oviposition. After fertilization, the females lay about 1 mm large white egg capsules on stones and other hard grounds over the summer. Of the approximately 30 to 70 eggs in a capsule, only one develops, while the others serve as food eggs. The larval development takes place in the egg capsules, so that finished snails, about 0.5 to 1 mm in size, hatch, depending on the temperature, about 4 to 8 weeks after egg-laying. Here part of the egg capsule is shed along a seam. The animals live to be 2 to 3 years old.
Occurrence, way of life and distribution
The species occurs in almost all of Europe and parts of Asia (Iran, Azerbaijan, Kazakhstan, Turkmenistan) and occasionally in North Africa (Morocco, Algeria, Tunisia, Egypt) in the larger rivers and in brackish water . There are deposits in the Baltic Sea and the Caspian Sea . It is absent in the Alps and in the northern Alpine foothills. The barn snails that live in brackish water are smaller and have thinner snail shells than those that live in fresh water . It is not yet clear whether this is genetically determined, i.e. whether two different subspecies exist.
The common boat snail lives on stones, in brackish water also on seaweed and seaweed and grazes the vegetation consisting of small algae, especially diatoms . In order to be able to digest the cell contents, the snail has to destroy the shell of the diatom by rubbing its radula against the hard substrate.
Danger
The common boat snail is classified as endangered in Germany. In Switzerland it is even threatened with extinction. It is already extinct in the Czech Republic.
Saprobic index
The saprobic index for this species is 1.5.
literature
- Eduard von Martens : The genus Neritina. Systematic Conchylia Cabinet. Nuremberg, 1879. pp. 204ff. No. 106 Neritina fluviatilis L.
- Peter Glöer: The animal world of Germany. Mollusca I Freshwater gastropods of Northern and Central Europe Key to identification, way of life, distribution. 2nd, revised edition. 327 pp., 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
Individual evidence
- ^ Václav Pfleger: Mollusks. 192 pp., Artia Publishing House, Prague 1984.
- ↑ Meyer, Detlef .: Macroscopic biological field methods for assessing the water quality of rivers: with lists of species for beginning and experienced investigators and detailed descriptions and images of the indicator organisms . 4th, unchanged. BUND, Hannover 1990, ISBN 3-9800871-4-X .
Web links
- MollBase
- Working group Mollusks NRW: Molluscs of the year 2004
- Home biotope: racing snails, swimming snails, barn snails or mermaid snails (Neritidae) : river swimming snail, barge snail or dwarf river snail (Theodoxus fluviatilis)
- Fischhaus Zepkow: Family Neritidae - mermaid snails
- Theodoxus fluviatilis inthe IUCN 2013 Red List of Threatened Species . Posted by: Kebapçı, U. & Van Damme, D., 2012. Accessed February 14, 2014.
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