Chambered Nautilus
Nautilus pompilius
Quick answer
The chambered nautilus is a deep-water cephalopod that lives inside a coiled, chambered shell, often called a living fossil because its kind has changed little in hundreds of millions of years. Unlike its relatives the octopus and squid, it has dozens of simple tentacles, primitive pinhole eyes, and an external shell divided into gas-filled chambers that control buoyancy. Found on deep reef slopes of the Indo-Pacific, it grows slowly and can live more than 15 years.
Chambered Nautilus facts at a glance
| 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) |
| Kingdom | Animalia |
|---|---|
| Phylum | Mollusca |
| Class | Cephalopoda |
| Order | Nautilida |
| Family | Nautilidae |
| Genus | Nautilus |
Where it lives
Deep reef slopes of the tropical Indo-Pacific, from the Andaman Sea to the waters around Australia and Fiji.
A living fossil
Nautiluses belong to an ancient group of shelled cephalopods that flourished hundreds of millions of years ago, and modern species look much like their distant ancestors. This has earned them the nickname living fossils. Unlike octopuses and squid, they keep a hard external shell, making them the only living cephalopods to do so.
The chambered shell
The nautilus shell is divided into a series of sealed chambers, with the animal living only in the largest, outermost one. As it grows it builds new chambers and adjusts the mix of gas and liquid inside the older ones to control buoyancy, much like a submarine's ballast tanks. A tube called the siphuncle threads through the chambers to regulate this balance.
Tentacles and senses
A nautilus can have up to about 90 simple, sucker-less tentacles that it uses to grip food and surfaces. Its eyes are remarkably basic, working like a pinhole camera with no lens, so it relies heavily on smell to find food in the dark. It moves slowly by jet propulsion, drawing water into its body and expelling it through a flexible funnel.
Diet and conservation
Nautiluses are carnivores and scavengers that feed on shrimp, crabs, and the molted shells and remains of other animals, rising from deep water at night to forage. They grow slowly, mature late, and produce few eggs, which makes them vulnerable to overharvesting for their attractive shells. International trade is now regulated to protect wild populations.
Frequently asked questions about the Chambered Nautilus
Why is the nautilus called a living fossil?
Nautiluses belong to an ancient lineage of shelled cephalopods that has survived for hundreds of millions of years with little change. Modern nautiluses closely resemble their prehistoric ancestors, earning them the nickname living fossil.
How does a nautilus float?
A nautilus controls its buoyancy by adjusting the balance of gas and liquid inside the sealed chambers of its shell. A thin tube called the siphuncle moves fluid in and out, letting the animal rise or sink.
What do nautiluses eat?
Nautiluses are carnivores and scavengers that eat shrimp, crabs, and the remains and molts of other animals. They forage at night using a strong sense of smell to locate food in the dark.
How is a nautilus different from an octopus or squid?
Unlike octopuses and squid, the nautilus keeps a hard external shell, has many more tentacles without suckers, and has simple pinhole eyes. It is the only living cephalopod group to retain an outer shell.
How long do nautiluses live?
Chambered nautiluses are long-lived for cephalopods, often surviving 15 to 20 years. They grow slowly and do not reach maturity until they are over a decade old.
Are nautiluses endangered?
The chambered nautilus is listed as Least Concern overall, but slow growth and harvesting for its shell make it vulnerable to overfishing. International trade is now regulated to help protect wild populations.
