In some ways, the nautilus is like its cousins, the squid and octopus. It uses tentacles to pull in its prey and a sharp beak to rip it apart, and it’s jet propelled. But in another way, it’s more like a submarine. It has a hard shell that protects it and allows it to move up and down in the water.
A nautilus can move itself up and down in the water. Credit: WikipediaThe nautilus lives in the tropical waters of the western Pacific Ocean. It can grow up to several inches long, and live 15 years or longer.
Its most remarkable feature is its shell -- a beautiful spiral that’s lined with mother of pearl.
When a nautilus hatches, the shell consists of four tiny chambers. As the animal grows, though, it creates new chambers, each one a little bigger than the last -- up to 30 or more in a mature adult. It seals off each chamber behind it, and lives in the newest one. If it’s attacked, it pulls in its body and seals the entrance with a tough membrane.
The abandoned chambers are connected by a thin tube, which the nautilus uses to change the ratio of liquid to gas in each chamber. During the day, it fills the chambers with liquid. That makes it heavier, so it sinks to lower depths -- up to 1500 feet or so -- where it can avoid predators. And at night, it fills the chambers with more gas -- like a submarine blowing water out of its ballast tanks. That makes it lighter, so it rises to depths of only a few hundred feet, where it feeds.
That system has helped the nautilus survive for about 500 million years -- making it one of the oldest species on Earth.
