A shift in environmental conditions impacts the evolution of complex developmental and behavioral traits. The Mexican cavefish, Astyanax mexicanus, is a powerful model for examining the evolution of development, physiology, and behavior because multiple cavefish populations can be compared to an extant, ancestral-like surface population of the same species. Many behaviors have diverged in cave populations of A. mexicanus, and previous studies have shown that cavefish have a loss of sleep, reduced stress, an absence of social behaviors, and hyperphagia. Despite these findings, surprisingly little is known about the changes in neuroanatomy that underlie these behavioral phenotypes. Here, we use serial sectioning to generate brain atlases of surface fish and three independent cavefish populations. Volumetric reconstruction of serial-sectioned brains confirms convergent evolution on reduced optic tectum volume in all cavefish populations tested. In addition, we quantified volumes of specific neuroanatomical loci within several brain regions that have previously been implicated in behavioral regulation, including the hypothalamus, thalamus, and habenula. These analyses reveal an enlargement of the hypothalamus in all cavefish populations relative to surface fish, as well as subnuclei-specific differences within the thalamus and prethalamus. Taken together, these analyses support the notion that changes in environmental conditions are accompanied by neuroanatomical changes in brain structures associated with behavior. This atlas provides a resource for comparative neuroanatomy of additional brain regions and the opportunity to associate brain anatomy with evolved changes in behavior.

中文翻译：

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成年脑图谱揭示了独立​​进化的墨西哥穴居鱼种群的广泛神经解剖学变化。

环境条件的变化会影响复杂的发育和行为特征的演变。墨西哥洞穴鱼 Astyanax mexicanus 是研究发育、生理和行为进化的强大模型，因为多个洞穴鱼种群可以与同一物种现存的类似祖先的地表种群进行比较。墨西哥穴居鱼的许多行为都存在差异，之前的研究表明穴居鱼睡眠不足、压力减轻、缺乏社交行为和食欲亢进。尽管有这些发现，但令人惊讶的是，人们对这些行为表型背后的神经解剖学变化知之甚少。在这里，我们使用连续切片来生成表层鱼类和三个独立洞穴鱼种群的大脑图谱。连续切片大脑的体积重建证实了所有测试的洞穴鱼种群中视顶盖体积减小的趋同进化。此外，我们还量化了先前与行为调节有关的几个大脑区域内特定神经解剖位点的体积，包括下丘脑、丘脑和缰核。这些分析揭示了所有洞穴鱼种群的下丘脑相对于表层鱼类的扩大，以及丘脑和前丘脑内亚核特异性的差异。总而言之，这些分析支持这样的观点：环境条件的变化伴随着与行为相关的大脑结构的神经解剖学变化。该图集为其他大脑区域的比较神经解剖学提供了资源，并有机会将大脑解剖学与进化的行为变化联系起来。