Sea scallops are one of the most valuable fisheries in the United States. They are invertebrates (meaning they don’t have backbones) in the phylum Mollusca, a category that also includes snails, sea slugs, octopuses, mussels and oysters. Within the phylum, sea scallops are part of class Bivalvia, which includes animals with hinged two-part shells made of calcium carbonate. You might have seen bivalve shells washing up on the shore on your last beach trip.

Sea scallops can swim by quickly opening and closing their shells, allowing them to escape from predators. They also open their shells to filter plankton out of the seawater for food—the tiny organisms get caught in the scallop’s mucus, then tiny hairs called cilia move the food towards the mouth.