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Didacna protracta
Didacna protracta is a brackish-water bivalve mollusc of the family Cardiidae, the cockles. It has a rounded-trapezoidal, thick, whitish shell, up to 42 mm (1.7 in) in length, with a small umbo and flattened ribs. The species is endemic to the Caspian Sea. It lives in the middle and southern parts of the sea at depths between 25 and 85 m (82–279 ft), rarely deeper.
From the article Didacna protracta on Wikipedia (CC BY-SA), quoted section by section
Description
Didacna protracta has a rounded-trapezoidal, thick, moderately convex shell, with a small umbo, 30–40 flattened radial ribs, dense growth lines on the ventral margin and a smooth posterior ridge, which is more distinct near the umbo. The shell length is up to 42 mm (1.7 in). The coloration is whitish, with thin pale yellowish gray periostracum. The hinge consists of one or two cardinal teeth in the right valve and one cardinal tooth in the left valve. The right valve sometimes has weakly developed lateral teeth.
Similar species. Didacna profundicola has a smaller shell, up to 15 mm (0.59 in) in length. The fossil species Didacna catillus has a less equilateral and usually more convex shell, with a wider posterior slope and without the characteristic dense growth lines on the ventral margin.
Range & habitat
Didacna protracta is endemic to the Caspian Sea. It lives in the middle and southern parts of the sea at depths between 25 and 85 m (82–279 ft), rarely deeper. The species does not occur in waters with salinity of less than 5‰.
Wikipedia: “Distribution and ecology”
Where it lives
Recorded sightings
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geo-referenced records in GBIF, from museums, herbaria and field observers.
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In the stacks
Searching the stacks…
Every page naming Didacna protracta in the Biodiversity Heritage Library →
This page is assembled live from iNaturalist, GBIF, Wikipedia, the Source Library and the Internet Archive. It is not yet part of the hand-edited codex. iNaturalist taxon 856461.