Chambered Nautilus Nautilus pompilius

Nautilus are several species of cephalopod (related to octopus and cuttlefish) with an external, snail-like shell. They are all native to deep water of the Indo-Pacific Ocean. They have remained little-changed for hundreds of millions of years. The largest and most common is the Emperor Nautilus, also called the Chambered Nautilus, but all are chambered and the latter name is also applied to the others. The shell of all is cryptic red and white striped above and white below for counter-shaded camouflage. Shells are matt externally but a pearlescent white inside. The chambers inside are almost a constant mathematical growth ratio within the spiral (not quite a Golden nor Fibonacci spiral) and grow with the nautilus which adds new chambers as it grows, moving its organs into the new space and using the old chambers for water-regulated buoyancy. They swim in open water by jet propulsion. They have simple eyes and a simple brain, capable of learning and memory.

They take 5-10 years to reach maturity. The Emperor can grow typically to some 20cm (8 inches) diameter. They are mostly scavengers. Their main threat is overcollection for their shells.