Chambered nautilus

앵무조개

A cephalopod in a spiral shell divided into chambers, which it fills with gas or liquid to rise or sink. Little changed over hundreds of millions of years, it is called a living fossil and rises from the deep toward reefs at night.

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At a glance

Class: Molluscs
Diet: Scavenger
Habitat: coral reefs, deep sea

Quick answers

Where does the Chambered nautilus live?

It lives in coral reefs, deep sea of the Pacific and Indian oceans.

What does the Chambered nautilus eat?

Its diet: scavenger.

The chambered nautilus is a shelled relative of octopuses and squid, living in the south Pacific. It has been found near reefs and on the seafloor off Australia, Japan and Micronesia, from near the surface to about 750 metres down.

Its spiral shell is divided into chambers and forms an almost perfect equiangular spiral. The animal lives in the newest chamber at the opening, and the older rooms behind are used for floating. Unlike an octopus, the nautilus keeps its hard shell all its life. The animal is a distant cousin of squid and cuttlefish and is a good example of an ancient group still alive.

A built-in float

Inside the shell, the empty chambers hold gas or liquid, and by changing the mix the nautilus can rise or sink. The shell is dark on top and light below. Seen from above it blends into the dark sea, and seen from below it blends into light from the surface. Cutting a shell open shows a shiny, pearly lining. It lives from near the surface to about 750 metres on hard continental shelves and slopes, especially near coral reefs.

Odd eyes and arms

Its eyes are simple and have no lens, working like a pinhole camera. It has about 90 arm-like cirri with no suckers, and chemical-sensing organs near the eyes that help it find food. Fossils of this species go back to the early Pleistocene, off Luzon in the Philippines. The shell's flame-like stripes cover most of the shell, and it can reach about 20 centimetres across.

Fun facts

It floats up and down by changing the gas and liquid inside the chambers of its shell.
The shell grows up to about 20 centimetres across.
Its lensless eye works like a pinhole camera.
Nautiluses are often called living fossils, but scientists say this species is very different from ancient ammonites.