Photo credit: John Edwards
According to fossil records, the ancient nautilus have survived unchanged for about 550 million years. As they grow, they add narrow chambers to the outer layers of their hard shell in a spiral form. The Nautilus can float or sink by directing gas (generally oxygen, argon or nitrogen) in varying amounts into the hollow chambers of its shell.
Ordinarily, a nautilus swims backwards by expelling water through its gills. While they have eyes, their eyesight is poor and instead they rely on their sense of smell and tentacles to help assess their surroundings. Nautilus hunt for their food at night. Once their prey is captured they chew with their powerful jaws, and can take up to 30 hours to digest a single meal. Like a tree in the forest, the age of a nautilus can be approximated by counting the number of rings of sealed chambers.