Quasi-Olfaction of Dolphins

Abstract

Since olfactory bulbs regress in toothed whales long before the moment of birth (Sinclair, 1966; Oelshlager, Buhl, 1985), they possess no olfaction. Taste buds are found in neonates and young animals, but they are reduced to such a degree that the adults appear to possess no gusta- tory perception (Yamasaki et al., 1978; Li Yemin, 1983). Morphological data have made it possible to conclude that the toothed whales do not possess the typical vertebrate senses of olfaction and taste. This unique situation is one major reason why the experimental investigation of chemical perception in dolphins is a very important issue for the solution of a number of general vertebrate chemoreception problems. It may also be important for the solution of such general neurology problems as structure-function relationships in the vertebrate brain. In particular, it is not clear why all of the olfactory brain structures (with the exception of the anterior olfactory nuclei) are present in dolphins when, at the same time, olfactory bulbs and tracts are absent (Filimonov, 1965; Jacobs et al., 1971). The question of chemoreceptivity in these animals brings together the interests of many different biological fields. The study of this question represents the main focus of the author's 20 year investigation of dolphin chemoreceptivity. DOLPHIN