Evolution of the Mauthner Axon Cap
Evolution of the Mauthner Axon Cap
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DOI：
10.1159/000222562
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发表时间：
2009-01-01
影响因子：
1.7
通讯作者：
Hale, Melina E.
中科院分区：
文献类型：
--
作者：
Bierman, Hilary S.;Zottoli, Steven J.;Hale, Melina E.
对脊椎动物大脑进化的研究主要集中在基因表达模式或大脑主要区域大小和组织的变化上。毛特纳细胞是一种重要的网状脊髓神经元，在许多物种的惊吓反应中起作用，它提供了在细胞水平上进行进化比较的机会。尽管毛氏细胞形态具有广泛的种间相似性，但它引发的运动模式和惊吓行为却有显著差异。响应多样性的假设部分是由毛特纳细胞相关轴突帽的结构和功能差异造成的。我们使用光学显微镜技术比较了广泛物种的轴突帽形态，包括所有四个现存的基本放线鱼目，各种硬骨鱼谱系和肺鱼的代表，并将我们的数据与已发表的轴突帽结构描述相结合。在硬骨鱼中观察到的“复合”轴突帽是有组织的胶质细胞和抑制性和兴奋性中间神经元纤维的聚集。肺鱼、两栖蝌蚪和几种基础放线爬行类鱼类具有“简单”的轴突帽，似乎缺乏胶质细胞，包括很少的纤维。其他几种底栖放光翼鱼有“简单致密”帽，比简单帽含有更多的纤维，但缺乏复合帽的额外元素和组织。系统发育图谱显示，在进化过程中，轴突帽的形态发生了离散的转变，这些转变发生在颌口基部、基部放光翅目和硬骨鱼辐射的基部。将轴突帽的进化与惊吓行为和运动模式的进化进行比较，可以深入了解毛特纳细胞相关结构与其行为功能之间的关系。版权所有(C) 2009 S. Karger AG，巴塞尔
Studies of vertebrate brain evolution have focused primarily on patterns of gene expression or changes in size and organization of major brain regions. The Mauthner cell, an important reticulospinal neuron that functions in the startle response of many species, provides an opportunity for evolutionary comparisons at the cellular level. Despite broad interspecific similarities in Mauthner cell morphology, the motor patterns and startle behaviors it initiates vary markedly. Response diversity has been hypothesized to result, in part, from differences in the structure and function of the Mauthner cell-associated axon cap. We used light microscopy techniques to compare axon cap morphology across a wide range of species, including all four extant basal actinopterygian orders, representatives of a variety of teleost lineages and lungfishes, and we combined our data with published descriptions of axon cap structure. The 'composite' axon cap, observed in teleosts, is an organized conglomeration of glia and fibers of inhibitory and excitatory interneurons. Lungfish, amphibian tadpoles and several basal actinopterygian fishes have 'simple' axon caps that appear to lack glia and include few fibers. Several other basal actinopterygian fishes have 'simple-dense' caps that include greater numbers of fibers than simple caps, but lack the additional elements and organization of composite caps. Phylogenetic mapping shows that through evolution there are discrete transitions in axon cap morphology occurring at the base of gnathostomes, within basal actinopterygians, and at the base of the teleost radiation. Comparing axon cap evolution to the evolution of startle behavior and motor pattern provides insight into the relationship between Mauthner cell-associated structures and their functions in behavior. Copyright (C) 2009 S. Karger AG, Basel