Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, 07745 Jena, Germany.
Chem Senses. 2011 Jan;36(1):43-61. doi: 10.1093/chemse/bjq096. Epub 2010 Oct 20.
Myriapods represent an arthropod lineage, that originating from a marine arthropod ancestor most likely conquered land independently from hexapods and crustaceans. Establishing aerial olfaction during a transition from the ocean to land requires molecules to be detected in gas phase instead of in water solution. Considering that the olfactory sense of myriapods has evolved independently from that in hexapods and crustaceans, the question arises if and how myriapods have solved the tasks of odor detection and odor information processing in air. Comparative studies between arthropod taxa that independently have established a terrestrial life style provide a powerful means of investigating the evolution of chemosensory adaptations in this environment and to understand how the arthropod nervous system evolved in response to new environmental and ecological challenges. In general, the neuroethology of myriapods and the architecture of their central nervous systems are insufficiently understood. In a set of experiments with the centipede Scutigera coleoptrata, we analyzed the central olfactory pathway with serial semi-thin sectioning combined with 3-dimensional reconstruction, antennal backfilling with neuronal tracers, and immunofluorescence combined with confocal laser-scanning microscopy. Furthermore, we conducted behavioral experiments to find out if these animals react to airborne stimuli. Our results show that the primary olfactory and mechanosensory centers are well developed in these organisms but that the shape of the olfactory neuropils in S. coleoptrata is strikingly different when compared with those of hexapods and malacostracan crustaceans. Nevertheless, the presence of distinct neuropils for chemosensory and mechanosensory qualities in S. coleoptrata, malacostracan Crustacea, and Hexapoda could indicate a common architectural principle within the Mandibulata. Furthermore, behavioral experiments indicate that S. coleoptrata is able to perceive airborne stimuli, both from live prey and from a chemical extract of the prey. These results are in line with the morphological findings concerning the well-developed olfactory centers in the deutocerebrum of this species.
多足动物代表了一个节肢动物谱系，它们起源于一种海洋节肢动物祖先，很可能独立于六足动物和甲壳动物从海洋中登上陆地。在从海洋到陆地的过渡过程中建立空气嗅觉需要分子在气相中而不是在水溶液中被检测到。考虑到多足动物的嗅觉已经独立于六足动物和甲壳动物进化，那么问题就出现了：多足动物是否以及如何解决在空气中进行气味检测和气味信息处理的任务。对独立建立陆地生活方式的节肢动物类群进行比较研究，提供了一种强大的手段来研究这种环境中化学感觉适应的进化，并了解节肢动物神经系统如何应对新的环境和生态挑战而进化。一般来说，多足动物的神经行为学及其中枢神经系统的结构还不够了解。在一系列与蜈蚣 Scutigera coleoptrata 的实验中，我们通过连续半薄切片结合 3 维重建、用神经元示踪剂进行触角回灌以及免疫荧光结合共聚焦激光扫描显微镜分析了中央嗅觉通路。此外，我们还进行了行为实验，以确定这些动物是否对空气传播的刺激物作出反应。我们的结果表明，这些动物的初级嗅觉和机械感觉中心发育良好，但与六足动物和软甲纲甲壳动物相比，S. coleoptrata 的嗅觉神经丛形状明显不同。然而，S. coleoptrata、软甲纲甲壳动物和六足动物中存在用于化学感觉和机械感觉特性的明显神经丛，这表明在 Mandibulata 中存在共同的结构原则。此外，行为实验表明，S. coleoptrata 能够感知空气传播的刺激物，无论是来自活体猎物还是来自猎物的化学提取物。这些结果与该物种后脑中发达的嗅觉中心的形态学发现一致。
