 Molluscs used as a food source by humans include many species of clams, mussels, oysters, winkles, and scallops.Some crustaceans that are commonly eaten are shrimp, lobsters, crayfish, and crabs.Echinoderms are not as frequently harvested for food as molluscs and crustaceans; however, sea urchin roe is quite popular in many parts of the world, where the live delicacy is harder to transport.