Cerebral Cortex Volume 8B, 1990, pp 215-262

Comparative and Evolutionary Anatomy of the Visual Cortex of the Dolphin

* Final gross prices may vary according to local VAT.

Get Access

Abstract

The cetaceans (great whales, dolphins, and porpoises) are known to have descended back to the sea more than 50 million years ago and thus are considered as secondary aquatic mammals (Kesarev et al., 1977a,b; Gaskin, 1982; Gingerich et al., 1983). They completely adapted themselves to the new conditions, not only in terms of changes in body shape, but also in the structure and function of their neuromuscular apparatus and internal organs and, especially, in regard to development of the brain. They appear to have preserved characteristic features of the original structure of the brain of primitive mammals in far greater measure than have more advanced land animals. At the same time the cetaceans were in a position in this new environment to develop specific features of adaptation not characteristic of land mammals. Thus, studies of the cetacean brain structure may make it possible to move closer to unraveling some important problems of evolution of the mammalian brain. Genetically related to terrestrial mammals, whales are of particular evolutionary value and uniqueness since they have adapted themselves to activity in an aqueous medium according to laws characteristic of this Order alone and, in so doing, have made evident the potential possibilities of the structural adaptations of the brain and, in particular, the great adaptability of the cerebral cortex (Nikitenko, 1965; Tomilin, 1968; Ladygina and Supin, 1974; Zvorykin, 1963, 1977; Kesarev et al., 1977a; Mehedlidze, 1984; Morgane et al., 1986a,b).