Bivalve Adductor Muscles

The two-shelled or “bivalve” molluscs must spread their shells apart to allow water and food particles in, and pull their shells together to protect their soft innards against predators or—in the case of intertidal mussels and oysters—the drying air. To do this work they have evolved a special muscle system, one that poses some challenges to the cook but is mostly a boon, since these prepackaged animals can survive for many days in the refrigerator covered only with a moist towel.