Blue-ringed octopus hunt barnacles.
Blue-ringed octopus . They hunt small crabs , hermit crabs , shrimp , and other small crustaceans . Crustaceans ( Crustacea [ krʌˈsteɪʃə ] ) form a large , diverse arthropod taxon which includes such familiar animals as crabs , lobsters , crayfish , shrimp , krill , woodlice and barnacles . The scientific study of crustaceans is known as carcinology ( alternatively , malacostracology , crustaceology or crustalogy ) , and a scientist who works in carcinology is a carcinologist .