Nautiluses

Nautiluses are relatives of squids and octopuses that are found in warm waters. Unlike them, but like other mollusks such as snails, nautiluses grow a protective shell on the outside of their bodies.

Present-day nautiluses live in waters between 250 and 1,000 feet deep, and swim mainly near the sea bottom. Nautiluses are nocturnal, retreating to deeper water during the day, presumably to avoid predators. The beautiful coiled shell of a nautilus is divided internally into separate airtight compartments. Most are empty, and the animal’s body occupies only the biggest and most recently formed compartment. The empty chambers, mainly filled with air at low pressure, make the nautilus lighter in the water. The animal is not light enough to float, however, and squirts water from

its body to swim upward through the water.

Male and female nautiluses mate head to head, holding each other by their tentacles. The female lays only a few very large eggs per year.These hatch into fully formed small nautiluses, complete with shells.

An Ancient Group

Scientists have found fossil nautiluses that date back more than 400 million years. Modern-day nautiluses show many differences from their cephalopod (squid and octopus) cousins, apart from their shells. For example, nautiluses’ eyes are more primitive than those of other cephalopods. They also do not have the special skin cells that allow squids and octopuses to change color. Finally, the nautiluses’ ability to breed year after year is unique among cephalopods; squids and octopuses die after just one breeding season.