Biology of Nautilus
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| The Pearly Nautilus (Nautilus Pompilius) is the only living representative of a unique form of cephalopod, recorded in fossils for over 500 million years. It has an external shell and many small, retractile, suckerless tentacles. There is no ink sac. The shell, pearly and beautifully colored, is spirally formed and consists of a series of chambers separated by curved cross plates. The last formed chamber houses the animal and is the largest. Another is added as the previous is outgrown. The chambers communicate by small holes in the septa and a body extension, the siphuncle, passes through these around the spiral coil. It is possible that gas produced by this varies the bouyancy so that the animal can rise or fall in the water. The head, when extruded, possesses two large but simple, lensless eyes, laterally placed. Dorsally it is covered by a freshy hood, mottled and warty. This seals in the retracted body. the nautilus is a bottom feeder on Crustaceans, usually in deep water, but can come to the surface. | |||
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