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What is a Nautilus?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon

Over 400 million years ago, the genus Nautilus was widely distributed throughout the world's oceans. Numerous fossils survive to provide clues about the evolution of life on Earth, as do a limited number of individual living species. These animals are known as nautiluses, and are sometimes called “living fossils,” because their form has remained the same for hundreds of millions of years. The unique cephalopod mollusks can be found in the Indian and Pacific Oceans, living in rock crevices and coral reefs.

Several characteristics make the nautilus stand out from other mollusks and marine animals. Unlike other mollusks, the nautilus has a hard external shell, which takes the form of a spiral. As the animal grows, it seals off chambers in the shell which fill with gas, making the shell buoyant so that the nautilus can swim. The unique air chambers lead to an alternate name, the chambered nautilus, to distinguish it from the paper nautilus, a different animal in the genus Argonauta.


A nautilus can have up to 90 grasping tentacles which are used to seize prey. Like many other mollusks, a nautilus will emit ink if it is stressed or threatened, allowing it to escape. The nautilus also uses jet propulsion to move, by forcing air out of the shell chamber which the animal is currently living in, which happens to be the newest and largest. The shell is also designed to help camouflage the animal, having dark stripes on top which blend in with the ocean floor when viewed from above. The bottom of the shell is a creamy white.

Many animals are used as a food source by a nautilus, including small fish, crabs, and others. The animals are nocturnal, preferring to remain hidden during the day and coming out to feed at night, and their shells are pressure resistant to 2,624 feet (800 meters) deep. The animals are also able to fully retreat into their shells. A leathery hood covers the opening of the shell to further protect the nautilus.

Approximately 20 years is the lifespan for a nautilus. The animals are harvested by humans for their distinct and beautiful shells, and are also preyed on by larger marine animals. They reproduce by laying eggs annually, and the eggs take nine to 12 months to fully develop and hatch. Because the animals take so long to reproduce, concerns have been raised about the conservation status of the nautilus, since excessive hunting by humans for their shells may threaten their continued existence.

Frequently Asked Questions

What exactly is a nautilus?

A nautilus is a marine mollusk belonging to the cephalopod family, which also includes squid, octopuses, and cuttlefish. It is known for its distinctive spiral shell and numerous tentacles. Unlike its cephalopod cousins, the nautilus has a hard external shell that provides protection and buoyancy. It is a living fossil, with a lineage that dates back over 500 million years.

How does the nautilus differ from other cephalopods?

The nautilus is unique among cephalopods due to its external shell, which is not present in other members like squid and octopuses. It also has more tentacles—up to 90—which are simpler and lack suckers. Additionally, nautiluses have a primitive eye structure without a lens, and they use jet propulsion to navigate through the water.

Where can nautiluses be found in the wild?

Nautiluses inhabit the tropical waters of the Indo-Pacific region. They are typically found at depths of 100 to 500 meters, preferring the dimly lit environment of the ocean's twilight zone. They are known to migrate vertically, coming closer to the surface at night to feed and retreating to the depths during the day.

What do nautiluses eat?

Nautiluses are scavengers and predators, feeding on a diet that includes crustaceans, carrion, and small fish. They use their tentacles to capture prey or pick food particles from the ocean floor. Their slow metabolism and low energy needs are well-suited to their deep-sea habitat, where food can be scarce.

How do nautiluses reproduce?

Nautiluses have a long maturation period, with sexual maturity reached between 10 to 15 years. They lay eggs, which are larger than those of most other cephalopods. The female attaches the fertilized eggs to rocks or other substrates, where they incubate for about a year before hatching into fully formed miniature adults.

Are nautiluses endangered?

Some species of nautilus are considered threatened due to overfishing and habitat destruction. Their slow reproductive rate makes them particularly vulnerable to population decline. International trade of nautilus shells is regulated under the Convention on International Trade in Endangered Species (CITES) to help protect these ancient creatures from extinction.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...

Discussion Comments


@StarJo - It's too bad the people who sell nautilus shells don't collect them like you do. I'm perfectly okay with the use of animal parts in jewelry and such -- it's very natural, biodegradable, beautiful and unique -- so long as the animal was already dead when you got the material from it.

Things like killing animals for their shells, horns, fur or leather just make me mad. The animal deserves to have a life -- a nautilus can live for two decades, and takes longer than humans do to be born, for goodness' sake.

Anyway, kudos to you for being responsible and just picking up your nautilus shells from the beach. You're lucky you live in a place where they just wash up in groups like that. I would love to own a piece of nautilus shell jewelry, but I don't want to order it from most places since they probably killed a nautilus to get it.

I discourage anybody else reading this from buying nautilus shells from just anywhere -- see if you can confirm that they are humanely collected from beaches or from already-dead animals, please.


The article says a nautilus can have 90 tentacles -- 90, can you even imagine them all grabbing at a fish at once? To things that are smaller than a nautilus, they probably look like a terrifying sea monster!

The nautilus seems like a funky mixture of several other familiar sea creatures to me. I mean, it squirts ink like an octopus, hunts with tentacles like a squid, and live sin a shell an awful lot like a snail's. I wonder if all of those originally descended from the nautilus? If so, nautilus might taste a lot like escargot. Just saying.


Wow, I learned something new about these neat creatures today! I had no idea that the famous nautilus "clothing" -- that distinctive spiral shaped shell -- was sealed off into little gas areas as the creature grows to make the shell float. I always figured nautiluses -- and snails, for that matter -- made more shell as their bodies got longer and filled up more space inside.

Instead, it seems they got bigger around, so they need to move forward into a piece of the shell that is larger around, and they fill up the space behind them with gas and then seal it into sections.

This explains why snail shells tend to have little cross pieces inside the spiral -- I can't believe this never occurred to me before.


When I think of nautilus shells, it tends o make me think of science fiction and fantasy stories that are dear to my heart and involve humans and dinosaurs. The first is the Dinotopia book series. The author is an amazing painter, and he often used nautilus shell motifs in the frames of the pictures, or in the carved stone monuments and such that his characters would visit during the stories.

The second science fiction story (this one more science fiction than Dinotopia for sure) is the British television series called Primeval. Primeval is mostly about larger prehistoric creatures coming to the earth in the present age through time rifts called anomalies that keep spontaneously opening up.

In one poignant scene, though, someone who has been living in the dinosaur era for several years shows another character she is back by leaving a live nautilus on his desk. It moves its tentacles and it's still wet; every time I watch that episode, I'm simultaneously creeped out and feeling bad for the nautilus since I know they're deep sea creatures.

After reading here on WiseGEEK that they also require salt water, I feel even worse, because I know the character who found it couldn't have just popped it into some fresh water...


The beauty of the nautilus shell has inspired many beach-oriented establishments or brands to name themselves after it. One example is the Nautical Hotel in Santa Teresa, Costa Rica.

Though the design of the hotel itself bears no resemblance to the nautilus shell, the name conveys a sense of paradise. When I think of that word, I envision myself collecting shells on a peaceful beach somewhere. It also makes me think of ships. I guess this is because of its resemblance to the word “nautical.”

Come to think of it, since Costa Rica is in the tropics, I guess you really could gather these shells on its beaches. Maybe the Nautilus Hotel really got its name from nearby shells!


I live nowhere near the beach, but I love nautilus shells. I saw a website online that sells the shells. They offer fully intact ones and ones that have been sliced in half to show the compartments.

These compartments start at the tiny end of the shell and become progressively larger toward the outer end. In a living nautilus, a tube pierces the chamber walls and connects to the creature. Through this tube, the nautilus moves its liquids and gas to alter its buoyancy.

The website has some shells that have the brown and white striped exterior removed. This reveals the pearl sheen underneath. The mother-of-pearl rainbow appearance is strikingly beautiful.


@Animalz – Actually, nautilus shells are often used in jewelry. They’re also used in sand ceremonies and wedding rituals around the world. You can buy sliced and pearlized (whitened and buffed to a pearl-like finish) nautilus shells in bulk online. I found slices online for $7 each.

Many people love jewelry made with real shells, and there are few shells that can match the beauty of a nautilus shell. That’s unfortunate for the nautiluses.


I collect paper nautilus shells. I gather them myself on the beach.

I live in the tropics, and paper nautilus dwell here in the ocean water near the surface instead of at the bottom. Probably because of this, they wash up on shore often, sometimes in big groups.

The shells have a beautiful pearly, off-white, ribbed surface. The keel has several small knobs on it. They look like something straight out of a mermaid fairy-tale. I have also seen shells that are sort of bronze or sepia colored. The cream colored ones are more common around here, though, and they are so beautiful in the sunlight.


People kill nautiluses for their shells? What do they use the shells for? I’ve never seen one on jewelry or anything.


@kangaBurg – The nautilus is my favorite animal, and I’ve studied them for a while. I don’t recommend owning one. They live in the deep sea, where it’s really cold, so you’d need to keep your fish tank super cold for one to be comfortable. They need salty water, which can be hard to keep at the proper salinity.

And most of them live where there isn’t much light, so you’d have to cover the tank up so the poor thing doesn’t get blinded. Then you’d need to give it enough room to swim around in, which means you’d need a really tall tank (they like to float up and down). And they’re close to being endangered, too. I don’t think it’s a good idea.


Nautiluses are so beautiful! I really want one for a pet. I love fish and have a few fish tanks. I haven’t seen a nautilus in any pet stores, though. Is it illegal to have one, or are they just really hard to take care of?


I watched an undersea life program on TV that showcased the paper nautilus. It is actually octopus-like and has eight tentacles.

The female paper nautilus is the only one who builds a shell. She uses the shell only to protect her eggs, which she places inside the shell in long threads. She lives in the entry of the shell and guards them until they hatch.

The paper nautilus has wide flaps that resemble sails on the ends of her first pair of tentacles. She will hold these over the shell and use them to catch food as it swims into them.

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