The typical heart in aquatic invertebrate animals such as clams, oysters, and mussels has many strong similarities to the human heart. The Arctica islandica, or ocean quahog, is the longest-living, non-colony-dwelling animal ever identified; so far, the oldest identified specimen survived to age 508 (age is identified by counting shell growth rings).

via North Atlantic Clam That Lives for Centuries Yields Insights on Cardiac Aging | NCCIH.