The scallop family includes about 400 species that range from a few millimeters to a yard across. Most food scallops are still harvested from the ocean floor. Large “sea scallops” (species of Pecten and Placopecten) are dredged from deep, cold waters year-round on trips that may last weeks, while smaller “bay” and “calico” scallops (Argopecten) are either dredged or hand-gathered by divers closer to shore during a defined season.
Unlike all the other molluscs, the scallop is mostly delectably tender, sweet muscle! This is because it’s the only bivalve that swims. It defends itself from predators by clapping its shells together and forcing water out the hinge end, using a central striated muscle that can be an inch/2 cm or more across and long. This adductor muscle makes up such a large portion of the scallop’s body that it also serves as protein and energy storage. Its sweet taste comes from large amounts of the amino acid glycine and of glycogen, a portion of which is gradually converted by enzymes into glucose and a related molecule (glucose 6 phosphate) when the animal is killed.