Telencephalic Evolution in Ray-finned Fishes

鳐鱼的远脑进化世界上一半以上的脊椎动物是鳐鱼，大约有3万种，其中一种或多种几乎适应了所有现有的水生栖息地。这些栖息地差异很大，毫不奇怪，鳍鱼的大脑组织也表现出显著的差异。和其他脊椎动物一样，这种变异大多发生在前脑的某些部位，而前脑是大脑最高的感官知觉中心——视觉、听觉等等。这些区域在鳍状鱼类中是如何组织的，以及它们是如何进化的，人们知之甚少，原因有两个：1)对原始鳍状鱼类的研究很少，它们的大脑更广义；2)对具有更专门的大脑的高级鳍状鱼类的研究，没有在足够深的地方检查适当的细胞群。本文提出的研究将使用生物示踪剂来揭示这些细胞群在两种原始的鳍状鱼类，双头鱼和鲟鱼中的组织，并在现代和人口最多的鳍状鱼类群体的代表金鱼中更详细地建立它们的联系。这些实验的结果将为鳐鱼的大脑组织和进化提供有价值的信息。然而，更重要的是，深入了解世界上一半以上的脊椎动物大脑中最多变的结构是如何进化的，将极大地有助于我们对大脑进化的总体理解，并使我们能够评估导致许多水生和陆生脊椎动物前脑组织复杂性增加的选择压力。

R. Glenn Northcutt #0236018Telencephalic 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.