American razor clam
| American razor clam | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
American razor clam ( Ensis directus ) with a living soft body in the shells |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Ensis directus | ||||||||||||
| ( Conrad , 1843) |
The American razor clam ( Ensis directus ), also known as the American razor clam or straight razor clam , is a species of clam originating from the United States (east coast) that has spread along the southern North Sea coast of Europe since 1976. It is often referred to unspecifically as a razor clam. This name is also used for the sword-shaped scabbard .
features
The American razor clam has a very long, narrow, equilateral housing , the upper and lower edges of which are almost parallel. They are up to 17 cm long in the North Sea and up to 25 cm in North America. It is up to 2.5 cm high. The quotient of the housing length to the housing height is 5 to 7. The front and rear ends are rounded flat. It is very unequal, the vertebra is close to the anterior end, but is not very clearly developed. The front and rear ends cannot be closed completely, they constantly gape. At the front end the muscular foot emerges, at the rear end the relatively short siphons . The ligament lies on the outside as a long, narrow brown to black band behind the vertebrae. The lock has an elongated cardinal tooth and a horizontal, elongated lateral tooth in the right flap. In the left valve there are two cardinal teeth and two rear, elongated cardinal teeth, one above the other. The jacket bay is S-shaped. There are two sphincters. The anterior sphincter is elongated, the posterior small.
The shell is comparatively thin and brittle. The outside of the housing is smooth except for growth lines and growth interruptions (coarser lines). The color of the housing is divided diagonally from the vertebra (front) to the lower edge of the rear end. The upper diagonal field is relatively uniformly reddish to gray, the lower diagonal field is brownish. The periostracum is greenish to dark brown. Inside the shell is whitish with cream-colored spots. The inside edge of the housing is smooth.
Similar species
The Ensis species found in the North Atlantic are all quite similar. They differ somewhat in the length / height quotient and in the color of the housing as well as in internal features.
Geographical distribution, habitat and way of life
The species occurs in its original range on the west coast of the Atlantic from Labrador to South Carolina , possibly to Florida . In 1979 young animals were detected for the first time in the German Bight near the lightship "Elbe I". Presumably, larvae were carried off into the German Bight by ships with ballast water. It already occurs en masse on the southern North Sea coast from southern Norway to the English and French Channel coasts. It has already penetrated into the western Baltic Sea.
Sand and silt soils are preferred, where the mussels live vertically with the rear end up in deep tubes. They are usually located just below the surface and filter the water for food there, but in case of danger they can withdraw very quickly with the help of their feet into the depths of their tubes. They occur between 3 and 18 m, more rarely in over 20 m water depth. In densely populated areas, over 400 specimens can live on one square meter. The animals grow relatively quickly and are sexually mature after about 1 year. They can be up to 5 years old. Propagation takes place via planktonic Veliger larvae.
Despite the very high density of individuals and rapid growth in the German Wadden Sea, no relevant interspecific competition has become known. The native Ensis species live in the deeper sediment.
Taxonomy
The American razor clam is alternately referred to in the literature as Ensis directus (Conrad, 1843) or Ensis americanus (Gould, 1870). The former name has priority. Timothy Abbott Conrad published it in 1843 as Solen directus in the first volume of the Proceedings of the Academy of Natural Sciences of Philadelphia . The species is now generally recognized as belonging to the genus Ensis Schumacher, 1817.
supporting documents
literature
- S. Peter Dance, Rudo von Cosel (arrangement of the German edition): The great book of sea shells. 304 p., Verlag Eugen Ulmer, Stuttgart, 1977 ISBN 3-8001-7000-0 (p. 254)
- Fritz Gosselck, Alexander Darr, Jürgen HJ Jungbluth, Michael Zettler: common names for mollusks of the sea and brackish water in Germany. Mollusca, 27 (1): 3-32, 2009 PDF
- Fritz Nordsieck : The European sea shells (Bivalvia). From the Arctic Ocean to Cape Verde, the Mediterranean Sea and the Black Sea. 256 pages, Gustav Fischer Verlag, Stuttgart 1969
- Guido Poppe. Yoshihiro Goto: European Seashells Volume 2 (Scaphopoda, Bivalvia, Cephalopoda) . 221 pp., Verlag Christa Hemmen, Wiesbaden 1993 (2000 unc. Reprint), ISBN 3925919104 (p. 105)
- Rainer Willmann: Mussels of the North and Baltic Seas. 310 p., Neumann-Neudamm, Melsungen 1989 ISBN 3-7888-0555-2 (p. 169/70)
- Paul Chambers (with figures from George Sowerby): British Seashells: A Guide for Collectors and Beachcombers. 233 pp. Remember When, Barnsley Yorkshire, 2009 ISBN 978-1-84468-051-1 (p. 165)
On-line
- Marine Bivalve Shells of the British Isles: Ensis directus (Conrad, 1843) (site of the National Museum Wales, Department of Natural Sciences, Cardiff)
- Marine Species Identification Portal: Ensis directus (Conrad, 1843)
Individual evidence
- ↑ Stefan Nehring, Heiko Leuchs: Neozoa (macrozoobenthos) on the German North Sea coast: An overview. Federal Institute for Hydrology, Report BfG-1200 ( Memento of the original of October 13, 2007 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , Koblenz 1999, p. 47.
- ↑ Timothy Abbott Conrad: Descriptions of nineteen species of Tertiary fossils of Virginia and North Carolina. Proceedings of the Academy of Natural Sciences of Philadelphia, 1: 323-329, Philadelphia 1843 (1844?) Online at www.biodiversitylibrary.org (p. 325)
- ↑ MolluscaBase: Ensis directus (Conrad, 1843)
annotation
- ↑ The naming of the horizontal teeth is not uniform in the literature. In some publications they are referred to as main / cardinal teeth, in other publications as side / lateral teeth.
