Chambered nautilus. Nautilus pompilius (Linnaeus, 1758).
Diameter: 16.5 cm
The chambered nautilus, Nautilus pompilius, one of the four closely related species in the genus Nautilus, is a shelled cephalopod that inhabits the seas around the Indochina peninsula at depths of up to 700 metres. Nautilus is considered a living fossil – its ancestors appeared on Earth approximately 500–550 million years ago. Already in 1808 the collections of our museum included several nautilus species, including Nautilus pompilius. However, it is impossible to determine now whether this specimen was one them.
The beautifully patterned shell of the nautilus internally divides into numerous chambers (up to 30). The animal itself inhabits the last and largest chamber. The empty chambers are filled with gas whose volume the animal is able to regulate by means of a system of blood vessels that pass through the chambers. The shell functions as a flotation device which keeps the mollusc at a suitable depth. At night, nautiluses often rise closer to sea surface to feed between coral reefs. Very little is known about the life habits of the chambered nautilus. Chambered nautiluses do not adapt to aquarium conditions. Their exquisite shells, however, are prized by souvenir hunters and overfishing has seriously endangered their population. Today, nautiluses are included among protected species and any trade in the animal's shells is subject to international regulation.