suspended in nets or on ropes, and grow rapidly thanks to the good circulation of oxygen and nutrients 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 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 Bivalve shells are normally held open mechanically, by means of a spring-like ligament that connects and pulls them together at the hinge end, and thus pulls the opposite wide ends apart To close the shells, the animal must power a muscle, called an “adductor” (from the Latin adducere, “to bring together”), which extends between the broad ends of the shell and contracts to overcome the spring force of the ligament Tender Quick, Tough Catch The adductor muscle has to perform two very different kinds of work One is to close the shell quickly to expel sediment, accumulated wastes, or eggs, or to slam the door on predators The other is to keep the shell tightly closed for hours, sometimes even days, until the danger passes These two jobs are performed by adjoining parts of the muscle The fast-contracting “quick” portion is quite similar to the fast muscles of fish and crustaceans; it’s white, translucent, and relatively tender But the slow, tensionmaintaining “catch” portion is among the strongest muscles known, and can maintain its contraction with very little expenditure of energy, thanks to biochemical tricks that lock ...“adductor” (from the Latin adducere, “to bring together”), which extends between the broad ends of the shell and contracts to overcome the spring force of the ligament Tender Quick, Tough Catch The. .. translucent, and relatively tender But the slow, tensionmaintaining “catch” portion is among the strongest muscles known, and can maintain its contraction with very little expenditure of energy, thanks to biochemical tricks that lock... tightly closed for hours, sometimes even days, until the danger passes These two jobs are performed by adjoining parts of the muscle The fast-contracting “quick” portion is quite similar to the fast muscles of fish and crustaceans;