Thick-shelled trough clam
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Thick-shelled trough clam ( Spisula solida (Linné, 1758)) |
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| Spisula solida | ||||||||||||
| ( Linnaeus , 1758) |
The thick-shelled trough mussel (lat. Spisula solida ), also called thick trough mussel or solid trough mussel , is a type of mussel from the family of trough mussels (Mactridae) that is widespread in the North Atlantic . Their stocks were fished in the North Sea from 1992 to 1996, but as a result their populations declined so much that further economic use is no longer possible.
features
The equally-folded, strongly flared (thick), non-gaping case is up to 4.5 cm long (according to other information up to 5.5 cm (Poppe & Goto)). It is roughly triangular in outline. The vertebra sits approximately in the middle of the length of the case or only slightly in front of the middle, i.e. H. the housing is almost equilateral. The dark brown ligament is divided into two parts; the outer ligament lies behind the vertebra and is short and narrow. The inner ligament is very distinct and lies below and behind the vertebra; it is attached to a special shell process ("chondrophor"). The lock has two separate main teeth on the right flap and two anterior and posterior teeth. The left valve has three main teeth and a posterior and an anterior posterior tooth. The two front main teeth have grown together to form an inverted V-shaped structure. The third posterior main tooth is thin, fragile, and often broken off. The upper and lower surfaces of the lateral teeth in the left valve are notched. The inner sides of the lateral teeth are notched in the right flap. The edge of the mantle is indented, but does not reach the rear end of the chondrophor.
The whitish shell is relatively thick and tight, hence the Latin name of the species solida = solid. The surface has concentric strips of growth. The inner edge of the case is smooth. The periostracum is a very thin, light brown coating.
Geographical distribution, habitat and way of life
The range of the thick-shelled trough clam extends in the eastern and northern Atlantic from Iceland and northern Norway to Mauritania . It is also found in the North Sea and the Mediterranean .
The thick-shelled trough clam lives buried in sandy soils from 15 to 160 m depth. The main occurrence in the North Sea is 15 to 40 m deep. In summer it lives close to the sediment surface, in winter it digs deeper into the sea floor. It lives from animal and vegetable suspended matter. The spawning season extends (in the North Sea) from May to July. During these months, eggs and sperm are released into the open water several times, where fertilization can then take place. The animals are sexually mature at the age of about two years and a size of about three centimeters. As a rule, they live to be no more than six years old.
Economical meaning
In 1992, fishing for the fixed trough mussel began in Schleswig-Holstein . In 1995 the amount fished was 6,300 tons, but in January 1996, after a severe winter, fishing had to be stopped as it was unprofitable. Since then there have been no more fishable stocks of the hard trough clam in the North Sea. It is still widespread on sandy soils, but in low population densities (less than 5 individuals per m²).
Taxonomy
The species was already described by Carl von Linné in 1758 as Cardium solidum . It is the type species of the genus Spisula Gray, 1837.
supporting documents
literature
- Rosina Fechter and Gerhard Falkner: molluscs. 287 pp., Mosaik-Verlag, Munich 1990 (Steinbach's Nature Guide 10) ISBN 3-570-03414-3
- 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
- Guido Poppe and Yoshihiro Goto: European Seashells Volume 2 (Scaphopoda, Bivalvia, Cephalopoda) . 221 pp., Verlag Christa Hemmen, Wiesbaden 1993 (2000 unc. Reprint), ISBN 3925919104
- Rainer Willmann: Mussels of the North and Baltic Seas. Neumann-Neudamm, Melsungen 1989, ISBN 3-7888-0555-2
On-line
Individual evidence
- ↑ Hein v. Westernhagen: How endangered is the trough clam Spisula solida? ( Memento of the original from December 17, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF file; 33 kB)
- ↑ Jennifer Dannheim: On the biology of Ensis directus and Spisula solida (Mollusca: Bivalvia) in the coastal waters of the eastern North Sea. Diploma thesis Institute for Oceanography, University of Kiel 2002 ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ^ Carl von Linné: Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Pp. 1-824, Holmia / Stockholm, Salvius, 1758. Online at www.biodiversitylibrary.org (p. 681).
- ↑ MolluscaBase: Spisula solida (Linnaeus, 1758)
