Anna Mirocha
Nov 29, 2016 · 3 min read

Who isn’t a little weird? Here at the Center for Biological Diversity, we celebrate peculiarity in every one of its human and animal forms. After all, who’d want to live in a world without weirdness?

The Chambered Nautilus: One Odd Cephalopod

In this installment of Save the Weirdos: cilia, siphuncles, radulas — oh my! Or: The octopus’s weird(er) cousin.

Nautilus photo by Greg J. Barord.

The chambered nautilus is one of the oddest oddballs in nature. In our humble opinion, this tropical-water-dwelling cephalopod (i.e., member of the octopus family) is even stranger than its eight-tentacled cousins — the figurative black sheep of one of the most eccentric families in the ocean. Its most obvious distinction is its exceptional spiraling, chambered shell, which grows from containing four chambers at hatching time to an average of 30 chambers in adulthood, with the animal itself always living in the most recent, biggest chamber, scores of tentacles spilling out the shell’s opening.

Sound cool? It’s only the beginning of the nautilus’s beautiful, almost-infinite weirdness.

1. The chambered nautilus (Nautilus pompilius) lives near coral reefs, in the tropical waters of the Indian and Pacific oceans, between 500 and 2,000 feet beneath the ocean’s surface — pretty deep. But because of its unique shell, going too deep (scientists say 2,575 feet) can be a fatal mistake: Water pressure will make a chambered nautilus implode.

2. Nautilus shell chambers are connected by a tube called the “siphuncle,” which adjusts the amounts of gas and water in their chambers to let the animal float or sink. A siphon near the shell opening shoots out water so it can zip around by jet propulsion.

3. Unlike its intelligent octopus relatives — who’ve been caught on camera using tools — the nautilus isn’t believed to be the sharpest tool in the box.

4. A nautilus mates once a year, when the male’s tentacles act as sex organs to deliver sperm packages into the bodies of a female, who later releases huge, leathery eggs (the largest eggs of any cephalopod, at about an inch long).

5. Unlike all other cephalopods, the nautilus has no lenses on its eyes, which might be compared to pinhole cameras, making for pretty poor eyesight (that is, all it can really see is light and darkness). Luckily, it has an amazing sense of smell.

6. Nautiluses have lived on Earth, with their current appearance, for 500 million freakin’ years. (The oldest known octopus fossil belongs to an animal that lived about 296 million years ago.)

7. Eight tentacles? Please! Nautiluses have up to 90 tentacles.

8. Octopuses and squids use suckers and hooks to grab things. Nautilus arms are instead coated with a sticky substance helps ensnare prey. Tiny hairs called “cilia” also help form sticky pads near tentacle tips.

9. After grabbing its fave prey (like shrimp, crabs and fish), the nautilus slices and dices it with a sharp beak and then grinds it up in a “radula” — a rather gruesome-looking, tooth-filled organ. (Nautiluses also eat carrion.)

10. Nautiluses have leathery hoods they can close to hide in their shells if a predator comes along (like a shark, turtle or cousin octopus). Unfortunately the hoods don’t protect them from large predators — the worst of which are humans, who collect them in massive numbers for their beautiful shells.

The Center is working to protect the chambered nautilus under the U.S. Endangered Species Act. Want to help us save this and other imperiled weirdos around the world? Join our email list, donate if you can, and make sure to LIKE this article (just click the ❤ symbol to the lower left).

Center for Biological Diversity

The Center for Biological Diversity is a national, nonprofit conservation organization with more than 1.6 million members and online activists dedicated to the protection of endangered species and wild places. More info at

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