Telencephalic Evolution in Ray-finned Fishes

University Of California-San Diego, La Jolla CA

Investigators

Abstract

R. Glenn Northcutt #0236018 Telencephalic Evolution in Ray-Finned Fishes Over half of the world's living vertebrates are ray-finned fishes, a group of some 30,000 species, one or more of whom have adapted to virtually every existing aquatic habitat. These habitats vary widely, and, not surprisingly, the brain organization of ray-finned fishes also shows remarkable variation. As in other vertebrates, much of this variation occurs in parts of the forebrain, which houses the brain's highest centers for sensory perception - seeing, hearing, and so forth. How these areas are organized in ray-finned fishes, and how they evolved, are poorly understood for two reasons: 1) Few studies have ever been carried out on primitive ray-finned fishes, with more generalized brains; and 2) Studies of advanced ray-finned fishes, with more specialized brains, have not examined the appropriate cell groups in sufficient depth. The research proposed herein will use biological tracers to reveal the organization of these cell groups in two primitive ray-finned fishes, bichirs and sturgeons, and to establish their connections in greater detail in goldfish, a representative of the modern and most populous group of ray-finned fishes. The results of these experiments will thus provide valuable information about brain organization and evolution in ray-finned fishes. Of broader importance, however, insights into how the most variable structure in vertebrate brains has evolved in over half the world's vertebrates will contribute greatly to our understanding of brain evolution in general and should allow us to assess the selective pressures responsible for the increased complexity in forebrain organization seen in many aquatic and terrestrial vertebrates.