Didacna profundicola
Didacna profundicola is a brackish-water bivalve mollusc of the family Cardiidae, the cockles. It has a trapezoidal, thin, white or pink-white shell, up to in length, with flattened ribs. The species is the deepest-dwelling bivalve of the Caspian Sea. It lives in the middle and southern parts of the sea at depths between 75 and 475 m.
Description
Didacna profundicola has a trapezoidal, thin, moderately convex shell, with a narrower anterior margin, 25–38 flattened radial ribs and a distinct rounded posterior ridge. The shell length is up to, the height is up to, and the convexity is up to. The coloration is white or pink-white, with thin yellow-grey periostracum. The hinge consists of one cardinal tooth in both valves. The cardinal tooth of the left valve is distinctly curved towards the anterior margin.Distribution and ecology
Didacna profundicola is the deepest-dwelling bivalve of the Caspian Sea. It lives in the middle and southern parts of the sea at depths between 75 and 475 m. The species may presumably reach a depth of around or even.The species is only known from the modern fauna.
Taxonomy
Didacna profundicola was described by Boris Mikhailovich Logvinenko and Yaroslav Igorevich Starobogatov in 1966. Together with Didacna protracta the species has been placed in the new section Protodidacna which is now considered to be a possible synonym of the genus Didacna. The type locality of D. profundicola is in the central part of the Caspian Sea off Turkmenistan at a depth of. The holotype is kept in the Zoological Institute of the Russian Academy of Sciences.The specimens described by Oscar Andreevich Grimm in 1877 under the name Cardium catillus are now attributed to D. protracta and D. profundicola.