Marine Animal Encyclopedia
Nautilus Nautilus pompilius
The six remaining species of Nautilus belong to a once numerous group of shelled cephalopods that existed from 400 to 65 million years ago. They are often referred to as “living fossils” because they are so little changed from their ammonoid ancestors. Their shell protects them from predation, while gas trapped in its inner chambers provides buoyancy. The head protrudes from the shell and has up to 90 suckerless tentacles, which are used to capture prey such as shrimp and other crustaceans; the head also features a pair of rudimentary eyes that lack a lens and work on a principle similar to a pinhole camera. The nautilus swims using jet propulsion, drawing water into its mantle cavity and expelling it forcefully through a tubular siphon, which can be directed to propel the nautilus forward, backward, or sideways. Unlike most other cephalopods, nautiluses mature late, at about ten years of age, and produce only about twelve eggs per year.