Crustaceans are a type of Arthropod. The name might not sound familiar, but you probably know them. You might even have eaten one. Crustaceans live mostly in the ocean or in other waters. The most commonly known crustaceans are crabs, lobsters, and barnacles.
Crustaceans have a hard, external shell that protects the body. The head has antennae that are part of the sensory system. The abdomen contains the heart, the digestive system, and the reproductive system. Extending from the abdomen are appendages, including legs, that the crustacean can use for crawling, swimming, and eating. Some crustaceans have claws that they can use not only for eating, but also to help with crawling.