Squat trough clam

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Squat trough clam
Squat trough clam (Spisula subtruncata)

Squat trough clam ( Spisula subtruncata )

Systematics
Superordinate : Imparidentia
Order :
Superfamily : Mactroidea
Family : Trough clams (Mactridae)
Genre : Spisula
Type : Squat trough clam
Scientific name
Spisula subtruncata
( da Costa , 1778)

The squat trough clam ( Spisula subtruncata ) is a species of clam from the family of trough clams (Mactridae) that is widespread in the North Atlantic .

features

The same-folding, not gaping, clearly inflated housing is up to 26 millimeters long.

It is rounded-triangular in outline and only slightly unequal. The prosogyren vertebrae sit almost in the middle to slightly in front of the midline, based on the length of the shell. However, there are several forms that differ slightly from the general form. The length to width ratio therefore varies from about 1.1 to 1.3. The anterior dorsal margin is shorter than the posterior dorsal margin. The posterior dorsal margin drops off somewhat more steeply than the anterior dorsal margin. The rear end is slightly elongated and truncated at an angle, or almost pointed or very tightly rounded. The front edge is well rounded. The lunula is heart-shaped and clearly demarcated. The elongated and comparatively wide area is flat-concave and doubly bordered by low lines emanating from the vertebra. The external, dark brown ligament behind the vertebra is very small and thin. The internal part sits in a triangular pit. The lock has two cardinal teeth in the right flap and two anterior and posterior lateral teeth, one above the other. In the left flap there are three cardinal teeth, of which the two front teeth form an inverted V-shaped extension that protrudes beyond the actual lock plate. The third posterior cardinal tooth is small and fragile and therefore often broken off. There are also anterior and posterior lateral teeth. The upper and lower surfaces of the lateral teeth in the left valve are notched. The inner sides of the four lateral teeth are notched in the right flap. The surface line is indented, but the bay does not reach the rear end of the chondrophor .

The whitish to cream-colored skin is thick-walled and very firm. The ornamentation consists of concentric lines and pits. The growth stages are clearly pronounced. The inside edge of the case is smooth. The inside of the bowl is glossy white. The thin periostracum is gray-brown to light brown.

The edge of the coat is serrated. The siphons are short and grown together over their entire length. The openings are filled with fringe-like, yellow or red filaments. The yellowish foot is comparatively slim.

Geographical distribution, habitat and way of life

The species is distributed from Norway along the coasts of the Eastern Atlantic to Senegal . It also penetrates the tributaries of the North Sea, Baltic Sea, Mediterranean and Black Sea, and has also been found in the coastal waters of the Canary Islands .

The squat trough clam lives shallowly buried in fine to muddy sand from the intertidal zone to a depth of around 200 meters. It prefers areas with a high intake of organic matter. With the help of its very agile foot, it can move quickly if it is threatened or disturbed by a predator.

Taxonomy

The species was established by da Costa in 1778 under the original binomial Trigonella subtruncata . It is now generally accepted as belonging to the genus Spisula Gray, 1837. Fritz Nordsieck excludes three varieties:

  • var. striata Brown: larger, bloated (thick) and stocky, rounded-triangular in outline, almost equilateral, and coarser ornamentation.
  • var. inaequalis Jeffreys: the shells are larger, the shell thicker and relatively high, the length / width ratio is low.
  • var. tenuis Jeffreys: the cases are very large, the shell thin, crooked or the vertebra is clearly in front of the center, the surface is smooth or irregularly striped

supporting documents

literature

  • 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 p., Gustav Fischer Verlag, Stuttgart 1969 (p. 142)
  • Guido Poppe. Yoshihiro Goto: European Seashells Volume 2 (Scaphopoda, Bivalvia, Cephalopoda) . 221 pp., Verlag Christa Hemmen, Wiesbaden 1993 (2000 unc. Reprint), ISBN 3925919104 (p. 103)
  • Rainer Willmann: Mussels of the North and Baltic Seas. 310 p., Neumann-Neudamm, Melsungen 1989 ISBN 3-7888-0555-2 (p. 150)

On-line

Individual evidence

  1. ^ Emanuel Mendez da Costa: Historia naturalis testaceorum Britanniæ, or, the British conchology; containing the descriptions and other particulars of natural history of the shells of Great Britain and Ireland: illustrated with figures. In English and French. - Historia naturalis testaceorum Britanniæ, ou, la conchologie Britannique; contenant les descriptions & autres particularités d'histoire naturelle des coquilles de la Grande Bretagne & de l'Irlande: avec figures en taille douce. En anglois & françois. SI-XII, 1-254, London, Millan, White, Emsley & Robson, 1778 Online at www.biodiversitylibrary.org (p. 198/9)
  2. ↑ MolluscaBase: Spisula subtruncata (da Costa, 1778)

Web links

Commons : Squat clam ( Spisula subtruncata )  - Collection of images, videos and audio files