The chambered nautilus is a mollusk, related to the octopus, squid, clam and snail.
A nautilus, along with the cuttlefish, squid, and octopus, are all cephalopods, meaning "head-foot," so named because the feet (tentacles) are attached to the head.
The nautilus is the only cephalopod that has a fully developed shell for protection. Unlike a squid, cuttlefish or an octopus, the nautilus has poor vision and its primitive eyes have no lenses. The nautilus has more than 90 suckerless tentacles. Grooves and ridges on the tentacles are used to grip prey and deliver food to a crushing, parrot-like beak.
Unlike snails, the spiraled shell of the nautilus is divided into chambers with the animal occupying the outermost chamber. A newly hatched nautilus begins life with about four chambers and develops an average of 30 chambers by adulthood. The inner chambers are filled with gas and help the nautilus to maintain neutral buoyancy. The nautilus adds liquid to the chambers in order to dive.
The nautilus is considered to be a "living fossil," as it has undergone little change in more than 400 million years. The nautilus dominated the ancient seas before the rise of fishes, and appeared about 265 million years before the first dinosaurs. In prehistoric times, there were about 10,000 different species of the nautilus, but only a few species survived to the present.
A newly hatched nautilus (about the size of a quarter) feeds on small shrimp and other small prey. Adults feed on crabs, shrimp, and fish, and scavenge on dead animals. Food is most likely located by smell.
Up to 8 inches
The chambered nautilus can be found along the slopes of coral reefs of the tropical Indo-Pacific.
The nautilus moves to deeper waters (600–2,000 feet deep) during the day to avoid predators. At night it ascends up to the coral reefs (300 feet deep) to hunt for prey.
Some nautilus populations are in decline due to over-collection for their beautiful shells. While the export of chambered nautilus shells is banned in some countries, other countries continue to allow commercial trade. To help curtail the demand for their shells, do not purchase a nautilus shell.
The octopus, shark, triggerfish, and sea turtle all prey on the nautilus.
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