Crab
Crab, a land- or water-dwelling crustacean with a short, flat body that is nearly circular. The crab is related to the crayfish, lobster, and shrimp. The head and thorax are fused together to form a shell, or carapace. The carapace is composed of chitin, a horny substance that is waterproof. The two eyes, supported on stalks, flank two pairs of hairlike antennae (feelers). Crabs have 10 legs. In some species, the front two are modified to form large, pincerlike claws. In ocean-dwelling crabs that swim, the two hind legs function as paddles.
Scallops are bivalves; they have two hard shells and a soft body. They are benthic animals; they spend most of their time on the sea bottom. Scallops mostly stay in underwater grass beds on a soft, shallow sea floor. Scallops use jet propulsion to move; they quickly open and close their shells, squirting the water out of the shells, moving in spurts. These invertebrate animals have a life span of about 1 1/2 years.
Mussels are molluscs with two hinged shells (bivalves) which filter their food from the surrounding water. Mussels can be found attached to gravel, seawall, and rocks in intertidal and subtidal coastal areas. They can survive out of water for an extended period of time if kept in a cold, moist environment. The most commonly marketed species is the Blue Mussel.