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Pearly Nautilus Nautilus pompillus
Common across the entire Indo-Pacific region, these ancient cephalopods have not changed in millions of years. They spend most of their lives in deep water to beyond 300 metres. They are the only living examples of ancient cephalopods which still retain an external shell.
Pearly Nautilus migrate up the reef faces at night into shallow water (20 metres) to feed on sleeping fish and hermit crabs. It is at this time (and early mornings) that divers get an opportunity to see them.
Some enterprising live-aboard operators in Papua New Guinea put traps down into deep water to catch them so guests can get photographs when the animals are released.
Unlike their modern counterparts (squid, octopus and cuttlefish) the Pearly Nautilus have only simple eyes with a small pupil opening but no focussing lens. They have around 90 extendible tentacles (without suckers) which have both tactile and chemoreactive functions.
Found on early morning dive at the edge of a deep water reef, this Pearly Nautilus was the first I had ever seen in the wild. (Vila, Vanuatu).
(Photo Neville Coleman)
To obtain calcium for their shells Pearly Nautilus have been observed feeding on cast off Rock Lobster shells. They are also efficient scavengers and actively hunt sleeping fish.
(Photo Neville Coleman)
A section of the Pearly Nautilus shell showing the many gas filled chambers by which it can control its buoyancy.
(Photo Neville Coleman)
A number of live-aboard dive boats and research vessels trap these animals on a regular basis in Australia and Papua New Guinea to give their underwater photographers the opportunity to photograph them. Then they are returned to the depths. They are harvested this way commercially in the Philippines, where they utilised as food and the shells sold to tourists.
(Photo Neville Coleman)