Triangular cockle
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Triangular cockle ( Parvicardium exiguum ) |
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| Scientific name | ||||||||||||
| Parvicardium exiguum | ||||||||||||
| ( Gmelin , 1791) |
The triangular cockle ( Parvicardium exiguum ), also known as the small cockle , is a type of mussel from the cockle family (Cardiidae) in the order Cardiida .
features
The equally flared, clearly inflated housing is obliquely rounded and triangular and is up to 2 cm (1.3 cm) long. Especially the juvenile housings are clearly unequal-sided, with adult housings this is less pronounced. The vortices are well in front of the middle of the length of the case. The anterior dorsal margin is very short, sloping sharply and is slightly concave. The posterior dorsal margin is slightly longer, sloping sharply towards the posterior end, but is almost straight. The transition from the dorsal margin to the anterior margin is slightly (rounded) angled. The transitions from the front edge to the ventral edge and from the rear dorsal edge to the rear edge are tightly rounded. The transition from the rear end to the ventral edge, on the other hand, is broadly rounded and not clearly set off. The ventral margin is only slightly convex. The inner edge of the two flaps is notched to match the ribs and spaces, the ribs form furrows on the inside. However, in adult shells, the furrows do not extend to the vertebra. The lunula is egg-shaped and smooth. The ligament lies internally on a short nymph. The lock is not very strong. In the right valve there are two anterior lateral teeth and one posterior lateral tooth as well as two cardinal teeth. In the left flap there are anterior, posterior and two cardinal teeth. The surface line is not indented.
The shell is thin but firm. It appears whitish with some brown-tinged spots. The ornamentation consists of 20 to 22 radial ribs angled in profile. The spaces between the ribs are narrower than the ribs. On the juvenile cases the ribs are studded with knots at wide intervals; on the adult housings they are only present at the edge of the housing and at the front end. In the middle and back of the case, they are usually completely worn off. The periostracum is permanent and often present as a border on the ribs.
Geographical distribution and habitat
The distribution area extends from Norway , along the coasts of the eastern Atlantic to the Iberian Peninsula , to North Africa and across the Mediterranean to the Black Sea . The triangular cockle is also found in the North Sea and the western Baltic Sea . It lives shallowly buried on muddy, sandy or gravelly soils from the deeper tidal range to about 55 meters water depth. She prefers calmer water without strong currents. It is a brackish water species that also penetrates into estuary areas, where it tolerates salinity levels of only 6 ‰. On the other hand, she cannot stand normal sea water; the salinity limit is around 30 ‰. The locations where it occurs are mostly overgrown with plants.
Taxonomy
The taxon was introduced into literature in 1791 by Johann Friedrich Gmelin as Cardium exiguum . The species is generally accepted as part of the genus Parvicardium Monterosato, placed in 1884.
supporting documents
literature
- 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 p., Verlag Christa Hemmen, Wiesbaden 1993 (2000 unaltered reprint), ISBN 3925919104 (p. 97)
- 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
On-line
Individual evidence
- ^ Rainer Willmann: Mussels and snails of the North and Baltic Seas. 310 p., Neumann-Neudamm, Melsungen 1989, ISBN 3-7888-0555-2 (p. 132)
- ^ Johann Friedrich Gmelin: Caroli a Linné, systema naturae. Tom. I. Pars VI. Pp. 3021–3910, Lipsia / Leipzig, Beer, 1791 Online at www.biodiversitylibrary.org (p. 3255)
- ↑ MolluscaBase: Parvicardium exiguum (Gmelin, 1791)
