Telencephalic Evolution in Ray-finned Fishes

世界上一半以上的现存脊椎动物是鳍鱼，大约有30,000种，其中一种或多种已经适应了几乎所有现有的水生栖息地。这些栖息地差异很大，毫不奇怪，鳍鱼的大脑组织也显示出显著的差异。与其他脊椎动物一样，这种变异大部分发生在前脑的某些部位，前脑是大脑最高感官知觉中心--视觉、听觉等。这些区域是如何在鳍鱼中组织的，以及它们是如何进化的，人们对此知之甚少，原因有二：1)很少有人对具有更一般大脑的原始鳍鱼进行研究；2)对具有更专门大脑的高级鳍鱼的研究没有足够深入地研究适当的细胞群。这里提出的研究将使用生物示踪剂来揭示两种原始的鳍鱼--比基鱼和鲟鱼--的这些细胞群的组织，并在金鱼中更详细地建立它们的联系，金鱼是现代和种群最多的鳍鳍鱼类的代表。因此，这些实验的结果将为关于鳍鱼的大脑组织和进化提供有价值的信息。然而，更重要的是，深入了解脊椎动物大脑中最可变的结构是如何在世界上一半以上的脊椎动物身上进化的，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地脊椎动物前脑组织复杂性增加的选择性压力。

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.