Cardium

Cardium is a genus of marine bivalve mollusks in the family Cardiidae, commonly known as cockles. The name derives from the heart-shaped outline of many shells. In modern taxonomy Cardium remains a recognized genus within Cardiidae, though numerous species formerly placed in Cardium have been reassigned to other genera such as Cerastoderma and Acanthocardia.

Members of Cardium typically have rounded, heart-like shells with a prominent umbo and strong, radiating ribs. The shells are usually thick and may vary in color from white to brown, often with patterned markings. They are benthic filter feeders living on sandy or muddy substrates in shallow coastal waters, from the intertidal zone to subtidal areas.

Distribution and habitat: Cardium species occur in temperate coastal waters of the Northern Hemisphere, including parts of Europe, North America, and the Mediterranean. They are common in sheltered bays, lagoons, and tidal flats where sediment is fine to moderately coarse.

Ecology and reproduction: Cardium members are filter feeders that consume phytoplankton, detritus, and other suspended particles. Reproduction is typically sexual with external fertilization; larvae are free-swimming planktonic before settling to the substrate.

Fossil record and human use: The genus has a long fossil record, with members appearing in the Mesozoic era and continuing to the present. Some species have been harvested as food in various regions, and shells have been used for ornaments, crafts, or as a source of calcium carbonate in certain contexts.