Evolution of the olfactory system in Myriapoda

多足动物代表了一种节肢动物谱系，起源于海洋节肢动物祖先，最有可能独立于六足动物征服陆地。成功地从海洋生物过渡到陆地生物需要许多生理适应，这对于离开水的生存是很重要的。陆生物种的感觉器官必须能够在空气中而不是在水中发挥作用。在化学接收中，建立气相嗅觉意味着分子需要在气相而不是在水溶液中被检测到。总的来说，对多足类动物的神经行为学和它们中枢神经系统的结构了解得很少。在一组初步实验中，我们用扫描电镜、连续半薄切片结合三维重建、神经元示踪剂回填和免疫荧光结合共聚焦激光扫描显微镜分析了蜈蚣触角和中央嗅觉通路的形态。此外，这种动物对空气刺激的反应能力通过行为分析和天线图记录进行了测试。这些实验共同表明，该物种具有良好的空中嗅觉。此外，其嗅觉神经的结构明显不同于六足动物，也不同于陆生甲壳类动物，这表明其嗅觉是在征服土地的过程中独立进化的。在此，我们建议在广泛的其他多足类动物中研究中央嗅觉通路的形态，包括七足目、前肢目、联门目，并将这些研究与行为论文结合起来。我们也会把蝎子作为外组。在神经系统发育方法中，我们的数据还将与六足动物和甲壳类动物的嗅觉系统形态进行比较，以提取数据重建节肢动物系统发育和了解节肢动物嗅觉系统的进化。

Myriapods represent an arthropod lineage that, originating from a marine arthropod ancestor, most likely conquered land independently from hexapods. The successful transition from marine to terrestrial life requires a number of physiological adaptations that are important for survival out of water. The sensory organs of terrestrial species must be able to function in air rather than in water. In chemoreception, establishing aerial olfaction means that molecules need to be detected in gas phase instead of in water solution. In general, the neuroethology of myriapods and the architecture of their central nervous systems are poorly understood. In a set of preliminary experiments with the centipede Scutigera coleoptrata we analyzed the morphology of the antennae and the central olfactory pathway with scanning electron microscopy, serial semithin sectioning combined with 3D reconstruction, antennal backfilling with neuronal tracers, and immunofluorescence combined with confocal laser-scan microscopy. Furthermore, the ability of this animal to respond to airborne stimuli was tested in behavioral assays and electroantennogram recordings. These experiments collectively indicate a good sense of aerial olfaction in this species. Furthermore, the architecture of its olfactory neuropils is clearly distinct from hexapods and also from terrestrial crustaceans indicating an independent evolution of its olfactory sense in response to the conquest of land. We propose here to study the morphology of the central olfactory pathway in a broad range of other myriapods covering Chilopoda, Progoneata, Symphyla and combine these studies with behavioral essays. We will also include Scorpions as an outgroup. In a neurophylogenetic approach, our data will also be compared to the morphology of the olfactory systems in hexapods and crustaceans in order to extract data for reconstructing arthropod phylogeny and for understanding the evolution of arthropod olfactory systems.