The Chambered Nautilus (Nautilus pompilius).

The Chambered Nautilus, Nautilus pompilius, is a cephalopod, related to squid, octopi, and cuttlefish, ranging through the tropical Pacific and Indian Oceans. Individuals live in deep water by day (down to 610m/2000 feet depth). At night, they swim up to shallow water to feed. They have poor eyesight and rely on touch and smell to detect prey. To capture prey items, they use their tentacles which, in contrast to other cephalopods, are free of suction cups. Some Nautilus species have up to 90 tentacles. Nautilus can adjust the direction they travel by changing the orientation of a structure called the siphon. They use jet propulsion to move, pumping water out of their siphon. Adult Nautilus pompilius can grow to about 8 inches (20 cm) in length. The shell of Nautilus pompilius is filled with gasses and liquids; the animal’s body is accommodated only within the outer most chamber. The nautilus can move liquids into and out of the chambers to regulate buoyancy. The liquids move between chambers through tube-like connections called siphuncles. Nautilus pompilius are little changed over the last 150 million years and have extinct relatives that date back as far as 450 million years. Nautilus pompilius is threatened owing to over harvest for the shell trade.