Arched head shield snail
| Arched head shield snail | ||||||||||||
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Arched head shield snail ( Retusa obtusa ) |
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| Scientific name | ||||||||||||
| Retusa obtusa | ||||||||||||
| ( Montagu , 1803) |
The arched head shield snail ( Retusa obtusa ) from the order of the head shield snail (Cephalaspidea) and the family Retusidae is also known under the name Retusa . Other species in the genus Retusa are the Retusa truncatula and Retusa umbilicata .
distribution
The species is found in the Mediterranean , the Atlantic , the English Channel , the North Sea and the western Baltic Sea . There it lives mainly in sandy and silty soils, where it digs through the sediment just below the surface .
features
The white to cream-colored domed head shield snail has a barrel-shaped shell and a long, slit-shaped mouth that is widened at the bottom. In addition, it is noticeable that the outer lip almost reaches the top of the case and that older surrounds can be clearly seen, albeit little. The snail reaches a height of one centimeter.
Life cycle
The arched head shield snail can live for about a year. It is first male and then female ( protandric hermaphroditism ) with internal fertilization. The mating takes place in the fall. The eggs mature in the mother animal in late autumn and winter and are fertilized by the sperm of the sexual partners stored in the receptaculum seminis . The eggs are laid by spring. In studies in Barry (Wales) , an average of 33 eggs per dam were counted, laid in 1 to 4 clutches. The development is direct, so that finished snails hatch from the egg capsules without a previous swimming larval stage.
food
The species feeds on carrion, plant debris and waders' snails ( Hydrobia ulvae ), which are completely devoured.
literature
- K. Janke, B. Kremer: Dune, Beach and Wadden Sea. Kosmos-Verlag, 1999, ISBN 3-440-07734-9 .
Web links
- Taxonomy: Costello, MJ; Bouchet, P .; Boxshall, G .; Emblow, C .; Vanden Berghe, E. (2004). European Register of Marine Species accessed on November 22, 2006 ( data set ).
Individual evidence
- ^ A b S. Tyrell Smith: The ecology and life history of Retusa obtusa (Montagu) (Gastropoda, Opisthobranchia). In: Canadian Journal of Zoology. 45, 1967, pp. 397-405, doi : 10.1139 / z67-051 .