Nautilus, << NAW tuh luhs, >> is a group of ocean animals that have a soft body partly covered with a coiled shell. A nautilus is a mollusk, a large group of animals that have no bones. Nautiluses live at depths of 20 to 1,000 feet (6 to 300 meters) along the coral reefs of the South Pacific and Indian oceans. They eat mainly marine worms and small crustaceans, a type of animal with a shell and jointed legs. They also feed on crustacean shells and animal remains. There are several species (kinds) of nautiluses. The most familiar is called the chambered nautilus, though this name is also used for other nautiluses. Scientists have found at least 2,000 fossil forms of nautiluses.
The body of an adult nautilus is about the size of a person’s fist. Its cone-shaped head is surrounded by about 90 short tentacles (feelers) that can be pulled into the shell. These tentacles sense taste and touch. A nautilus shell is made up of many chambers. These chambers are lined with a rainbow-colored substance called mother-of-pearl or nacre. As a nautilus grows, it adds new chambers to its shell. Each new chamber is closed at the rear, so the animal always lives in the outermost chamber. The shell of an adult has about 30 chambers. The siphuncle, a coiled, blood-filled tube, extends through all the chambers of the shell.
