Nautilus pompilius, an externally shelled cephalopod, a type of mollusk. Cephalopods are found in all of the world's oceans, from the warm water of the tropics to the near-freezing water at the poles.
Cephalopods are an ancient group that appeared some time in the Late Cambrian, several million years before the first primitive fish began swimming in the ocean. Scientists believe that the ancestors of modern cephalopods such as octopus, squid and cuttlefish, diverged from the primitive externally shelled Nautiloidea (Nautilus) very early on, possibly in the Ordovician some 438 million years ago. Nautilus has been around for 500 million years and are considered living fossils. (Year of image: 2003)
Interior of Nautilus pompilius
An interior view showing the rigid open chambers within Nautilus pompilius.
Although the animal lives in the outmost chamber, a narrow strand of it's soft body penetrates the chamber walls each by a small hole. Nautilus uses the chambers for a type of locomotion. The chambers are filled with both water and gas. When the nautilus absorbs gas from the chamber, the chamber pressure decreases and water enters from outside. The shell becoming heavier and makes the nautilus sink. When the nautilus presses gas into the chamber, water is pressed out, which makes the shell lighter and the nautilus rises, like a submarine blowing the tanks. Unfortunately, because of the beauty of their shell, many Nautilus are killed each year for collection and export. (Year of image: 2003)
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