Biocenter, Zoology II, Emmy Noether Animal Navigation Group, University of Würzburg, Germany.
Vision Group, Department of Biology, Lund University, Lund, Sweden.
J Comp Neurol. 2018 Nov 1;526(16):2612-2630. doi: 10.1002/cne.24520. Epub 2018 Oct 22.
Despite their tiny brains, insects show impressive abilities when navigating over short distances during path integration or during migration over thousands of kilometers across entire continents. Celestial compass cues often play an important role as references during navigation. In contrast to many other insects, South African dung beetles rely exclusively on celestial cues for visual reference during orientation. After finding a dung pile, these animals cut off a piece of dung from the pat, shape it into a ball and roll it away along a straight path until a suitable place for underground consumption is found. To maintain a constant bearing, a brain region in the beetle's brain, called the central complex, is crucially involved in the processing of skylight cues, similar to what has already been shown for path-integrating and migrating insects. In this study, we characterized the neuroanatomy of the sky-compass network and the central complex in the dung beetle brain in detail. Using tracer injections, combined with imaging and 3D modeling, we describe the anatomy of the possible sky-compass network in the central brain. We used a quantitative approach to study the central-complex network and found that several types of neuron exhibit a highly organized connectivity pattern. The architecture of the sky-compass network and central complex is similar to that described in insects that perform path integration or are migratory. This suggests that, despite their different orientation behaviors, this neural circuitry for compass orientation is highly conserved among the insects.
尽管昆虫的大脑很小，但它们在短距离路径整合或跨越数千公里的整个大陆迁徙时表现出令人印象深刻的能力。天体罗盘线索通常在导航过程中作为参考发挥着重要作用。与许多其他昆虫不同，南非蜣螂完全依赖天体线索来进行定向视觉参考。在找到一堆粪便后，这些动物会从帕特上切下一块粪便，将其塑造成一个球，并沿着一条直线将其滚走，直到找到一个适合地下食用的地方。为了保持恒定的方位，甲虫大脑中的一个称为中央复合体的脑区在处理天光线索方面起着至关重要的作用，这与已经证明的用于路径整合和迁徙的昆虫相似。在这项研究中，我们详细描述了蜣螂大脑中天体罗盘网络和中央复合体的神经解剖结构。我们使用示踪剂注射，结合成像和 3D 建模，描述了中央脑中可能的天体罗盘网络的解剖结构。我们使用定量方法研究了中央复合体网络，发现几种类型的神经元表现出高度组织化的连接模式。天体罗盘网络和中央复合体的结构与进行路径整合或迁徙的昆虫中描述的结构相似。这表明，尽管它们的定向行为不同，但这种用于罗盘定向的神经回路在昆虫中高度保守。
