Ryan Photographic - Nautilidae - Nautilus
The family Nautilidae contains six species in two genera. They are restricted to the tropical Indo-Pacific region. There is an excellent Wikipedia entry on the nautiloids and this is recommended for further information.
I have yet to encounter a nautilus in the wild. However when I was working at the University of the South Pacific they were regularly trapped by the Institute of Marine Resources. A colleague of mine designed an experiment to test their visual acuity. To do this he intended to put the nautilus in a large circular tank and then rotate a band of vertical bars around the circumference. Many organisms, when in a current, will use visual cues to orient themselves. The idea was that the nautilus would slowly rotate to maintain its position relative to the bars. This colleague spent hours making vertical-barred targets, as each was around 3 m long it took a while, especially with the finally gradated bars. Eventually the great day came, he put in a medium bar target and rotated it. The nautilus just sat there. The nautilus did finally move on a subsequent run with the coarsest target. He still doesn't know whether the nautilus had really crappy vision or simply couldn't be bothered. Susbequent runs with different specimens produced the same results. Biology can be frustrating sometimes.
Nautilus pompilius, Chambered or pearly nautilus
Nautilus pompilius, Chambered or pearly nautilus, captive.
Nautilus pompilius Pearly nautilus, aquarium shot, Fiji
Nautilus pompilius, Pearly nautilus eye, captive, Fiji