The thin heart cockle, likely referring to the genus Corculum, is an Indo-Pacific marine bivalve known for its thin, heart-shaped and often translucent shell with radially arranged windows that act like fiber optic cables to transmit sunlight for symbiotic algae. These clams sit on their sides on sandy bottoms or reefs and have flat-bottomed shells adapted for photosynthesis. They can vary in colour, with bright flecks of red and yellow, and are sometimes even bright blue on the underside.