most crustaceans are aquatic, mostly marine. some have moved onto land permanently. crustaceans that live on land include some crabs, and woodlice. crustacea range in size from a parasite 0.1mm long, to the japanese spider crab with a leg span of up to 14 ft (4.3 m) and a mass of 44 lb (20 kg). the north atlantic lobster can weigh more than 40 pounds.