# Chambered Nautilus (*Nautilus pompilius*)

> The chambered nautilus (Nautilus pompilius) is a cephalopod often called a living fossil, whose relatives have looked much the same for hundreds of millions of years. It lives on deep reef slopes of the tropical Indo-Pacific inside a coiled shell about 20 to 25 cm across, drifting and swimming slowly by gentle jet propulsion. It scavenges and hunts shrimp, crabs, and carrion, can live 15 to 20 years, and is listed as Least Concern.

- **Category:** Invertebrate
- **Conservation status (IUCN):** Least Concern
- **Range:** Deep reef slopes of the tropical Indo-Pacific, from the Andaman Sea to the waters around Australia and Fiji.
- **Canonical page:** https://globalanimalguide.org/animals/nautilus/
- **Last reviewed:** 2026-07-16

## Scientific classification

- **Kingdom:** Animalia
- **Phylum:** Mollusca
- **Class:** Cephalopoda
- **Order:** Nautilida
- **Family:** Nautilidae
- **Genus:** Nautilus

## Facts at a glance

| Attribute | Value |
| --- | --- |
| Scientific name | Nautilus pompilius |
| Diet | Carnivore and scavenger (shrimp, crabs, carrion) |
| Habitat | Deep reef slopes of the tropical Indo-Pacific |
| Lifespan | 15–20 years |
| Size | Shell about 20–25 cm (8–10 in) across |
| Top speed | Slow; drifts by gentle jet propulsion |
| Conservation status | Least Concern (IUCN) |

## The chambered shell

The nautilus is named for its beautiful spiral shell, which is divided inside into a series of sealed chambers. As the animal grows it builds new, larger chambers and moves forward into the outermost one, leaving the empty rooms behind. A thin living tube called the siphuncle threads through the chambers, adjusting the balance of gas and fluid inside them to control buoyancy. This clever system lets the nautilus hover almost weightlessly in the water without constant effort, and the shell itself grows to about 20 to 25 cm across.

## A living fossil

Nautiluses are often called living fossils because their basic body plan has changed remarkably little over hundreds of millions of years, long before the age of the dinosaurs. They are the only cephalopods that still carry an external coiled shell, unlike their relatives the octopus, squid, and cuttlefish, which lost theirs. Fossils of ancient shelled cephalopods show forms strikingly similar to today's nautilus. Studying them offers a window into a very old branch of ocean life that has otherwise almost entirely vanished.

## How it moves

Like other cephalopods, the nautilus swims by jet propulsion, drawing water into its shell cavity and pushing it out through a flexible funnel to glide slowly, usually backwards. It is a gentle, unhurried swimmer rather than a fast one, drifting along reef slopes at just a few kilometres per hour at most. By fine-tuning the gas in its shell chambers it can also rise and sink through the water column with little effort. At night it moves up the slope to feed, then drifts back down to deeper water by day.

## Feeding and its many tentacles

A nautilus has dozens of small tentacles, far more than a squid or octopus, though they lack suckers and instead grip with sticky ridges. It is both a hunter and a scavenger, feeding on shrimp, crabs, and the moulted shells and carrion it finds along the reef. With poor eyesight from its simple pinhole eyes, it relies heavily on a keen sense of smell to track down food in the dark. Once located, prey is passed to a hard beak that crushes shells and tough material.

## Habitat and life cycle

The chambered nautilus lives on the deep outer slopes of coral reefs across the tropical Indo-Pacific, generally at depths of a few hundred metres where the water is cool and dim. It is long-lived for an invertebrate, reaching 15 to 20 years, and grows and matures slowly. Females lay only a small number of large eggs, each taking many months to develop before a fully formed young nautilus hatches. This slow, low-output breeding makes the species vulnerable to overharvesting.

## Conservation and the shell trade

Although the chambered nautilus is currently assessed as Least Concern, its striking shell is widely collected and sold, and heavy fishing for the ornamental trade has raised concern about local populations. Because nautiluses breed slowly and mature late, they cannot quickly replace numbers lost to over-collection. International trade in nautilus shells is now regulated to help guard against decline. Protecting the deep reef slopes where they live is key to keeping this ancient lineage thriving.

## Frequently asked questions

### Why is the nautilus called a living fossil?

The nautilus is called a living fossil because its body plan has changed very little over hundreds of millions of years, and fossils of its ancient shelled relatives look much like it does today. It is also the only cephalopod that still has an external coiled shell.

### How does a nautilus move?

A nautilus swims slowly by jet propulsion, drawing water into its shell cavity and pushing it out through a funnel to glide, usually backwards. It also rises and sinks by adjusting the gas and fluid in its shell chambers to control buoyancy.

### What does a nautilus eat?

The nautilus is a carnivore and scavenger that feeds on shrimp, crabs, and carrion, including moulted shells it finds along the reef. It uses its many sticky tentacles to grip food and a hard beak to crush it.

### How long does a nautilus live?

The chambered nautilus is long-lived for an invertebrate, reaching about 15 to 20 years. It grows and matures slowly and produces only a few large eggs, so populations recover slowly if reduced.

### How is a nautilus different from a squid or octopus?

Unlike squid and octopuses, the nautilus keeps an external coiled shell and has dozens of simple, suckerless tentacles rather than a few sucker-lined arms. It also has primitive pinhole eyes and moves far more slowly than its fast, sharp-sighted relatives.

### Is the nautilus endangered?

The chambered nautilus is currently listed as Least Concern, but its slow breeding and heavy collection for the shell trade have caused concern about local declines. International trade in its shells is now regulated to help protect it.

## Sources

- [IUCN Red List — Nautilus pompilius.](https://www.iucnredlist.org/search?query=Nautilus%20pompilius&searchType=species)
- [Animal Diversity Web — Nautilus pompilius. University of Michigan Museum of Zoology.](https://animaldiversity.org/accounts/Nautilus_pompilius/)
- [Wikipedia — Chambered Nautilus.](https://en.wikipedia.org/wiki/Chambered_nautilus)

---
Source: Global Animal Guide (https://globalanimalguide.org/animals/nautilus/). Licensed CC BY-NC 4.0 — free for non-commercial reuse with attribution.