The Sense Organs of Nautilus

Abstract

The soft parts of Nautilus differ from those of coleoid cephalopods in numerous ways; one of the most obvious is that there is an array of tens of tentacles in place of the eight or ten arms of octopuses or squids. The eyes, although large, have no lens; rather, each has a small “pinhole” opening to allow the entry of light. In front of and behind the eyes are two sensory tentacles, the pre- and postocular tentacles (Willey, 1898a). There are also pairs of digital tentacles which are used for prehension and have a sensory function, and buccal (labial) tentacles that surround the buccal region (Willey, 1898b). The pre- and postocular tentacles and the digital tentacles are accommodated in sheaths, but the buccal tentacles are not. Below the eye is a sensory sac, the rhinophore, and there is also a pair of simple statocysts.