Chambered Nautilus

The chambered nautilus is a marine mollusk found in the deep waters of the Indo-Pacific Ocean, best known for its coiled, pearly shell divided internally into a series of gas-filled chambers that the animal uses to control its buoyancy, moving between them through a thin tube called a siphuncle. It is one of the few living cephalopods to retain an external shell, a feature that links it to ancient relatives that were far more numerous and diverse hundreds of millions of years ago, earning it a reputation as a living fossil. During the day, chambered nautiluses typically stay in deep, cool water, rising toward shallower reefs at night to feed on small crustaceans, fish and carrion using dozens of tentacles arranged around the mouth. Slow growing and slow to reproduce, the species has become vulnerable to overharvesting for its ornamental shell, and populations in some areas have declined sharply.