A Sensory Basis for Orientation in Cephalopods

Abstract

This brief review describes the sense organs involved in orientation by cephalopods with a view to providing a basis for understanding the mechanisms involved. As in many other animals, vision is probably the most important sense involved in orientation. Cephalopods have paired eyes, sometimes providing binocular vision, and generally similar to those of many vertebrates in terms of their gross structure and performance. The main feature apparently lacking in most cephalopods is colour vision, although many have polarized vision. The second most important sense in cephalopods is the sense of balance provided by the statocysts. These paired organs, are functionally similar to the vertebrate vestibular system, and detect both linear and angular accelerations, giving the animal information on its spatial orientation and rotational movements. The statocysts may also be involved in hearing, for there is no doubt that they can detect some vibrations carried in the water and ground. The recently discovered cephalopod lateral line system also detects water-borne vibrations, but this is more probably used for locating other animals in low light conditions. Behavioural experiments have shown that olfaction is also important in cephalopod orientation, but, although there is good morphological data on the structures involved in olfaction, there are little supporting physiological data. Of the remaining senses used in orientation, touch is important for bottom living species, but less so for the free swimming animals. There is no evidence, so far, for electroreception or magnetic sensitivity in cephalopods.