The nautilus (Nautilus pompilius) is a remarkable creature that is regarded as a “living fossil” because it closely resembles animals that lived in the oceans between 400 and 65 million years ago. Six species of nautilus have survived to the present day, with that in the photo living in the western Pacific Ocean and in open waters around Indonesia and southeast Asia. It is found at depths up to 500 metres (1,650 feet).
The shell protects the nautilus from predators and buoyancy is provided by gas trapped in the inner chambers. It swims by using jet propulsion – water is taken into the shell cavity and expelled through a tube which can be directed to propel the nautilus in the required direction.
The head sticks out of the shell and has up to 90 tentacles that are used to trap prey that includes shrimps. The eyes of the nautilus are very primitive, being without lenses and working like pinhole cameras.
The nautilus only becomes sexually mature after about ten years, and then produces as few as twelve eggs per year. Having survived for so long, the species has clearly found an environmental niche that presents few dangers and allows for a slow rate of reproduction.