A native of the tropical Pacific, this cousin of the octopus is a living link with the past—little changed for more than 150 million years. Its simple eyes can only sense dark and light, but the nautilus uses more than 90 tentacles—the most of any cephalopod—to touch and taste the world. A nautilus's tentacles, unlike those of other cephalopods, have grooves and ridges that grip food and pass it to the nautilus's mouth. A parrotlike beak rips the food apart, and a radula (found in most molluscs) further shreds the food.
To avoid predators by day, some nautilus linger along deep reef slopes as deep as 2,000 feet (610 m). At night, they migrate to shallower waters and cruise the reefs, trailing their tentacles in search of food. While most cephalopods are fairly short lived, nautiluses may live for more than 20 years, reaching maturity in five to 10 years. The female lays only a dozen or so eggs in a year, which take 14 months to hatch.
A nautilus swims using jet propulsion—it expels water from its mantle cavity through a siphon located near its head. By adjusting the direction of the siphon, a nautilus can swim forward, backward or sideways.
Collectors seek nautilus shells, which are beautiful with their mother-of-pearl lining and red-striped, cream-colored exterior. In the past, beachcombers gathered only shells, but now demand for perfect shells is encouraging deep-water trapping of nautilus. Since these animals mature late and produce few offspring, shell collecting results in a significant decline in nautilus (and other mollusc) populations. For this reason, the Aquarium doesn't sell sea shells in its gift shops.
A newly hatched nautilus wears a shell divided into four small chambers. As a nautilus grows, it gains more living space by building new chambers connected to the old ones; adult shells have 30 chambers.
The nautilus is the only cephalopod with an external shell.
The tentacles of a nautilus have no suckers or hooks, but hold prey with a sticky glue.
Nautiluses may live more than 20 years—a very long time compared to other cephalopods.
To control its buoyancy, a nautilus pumps fluids in and out its shell chambers, which are connected by tubes called "siphuncles."
For unknown reasons, nautilus populations tend to be 75 percent male and 25 percent female.