Polanska Marta A, Kirchhoff Tina, Dircksen Heinrich, Hansson Bill S, Harzsch Steffen
Department of Animal Physiology, Institute of Zoology, Faculty of Biology, University of Warsaw, 1 Miecznikowa Street, 02-096, Warsaw, Poland.
Zoological Institute and Museum, Department of Cytology and Evolutionary Biology, University of Greifswald, Soldmannstrasse 23, 17498, Greifswald, Germany.
Cell Tissue Res. 2020 Jun;380(3):449-467. doi: 10.1007/s00441-020-03199-5. Epub 2020 Apr 2.
Terrestrial hermit crabs of the genus Coenobita display strong behavioral responses to volatile odors and are attracted by chemical cues of various potential food sources. Several aspects of their sense of aerial olfaction have been explored in recent years including behavioral aspects and structure of their peripheral and central olfactory pathway. Here, we use classical histological methods and immunohistochemistry against the neuropeptides orcokinin and allatostatin as well as synaptic proteins and serotonin to provide insights into the functional organization of their primary olfactory centers in the brain, the paired olfactory lobes. Our results show that orcokinin is present in the axons of olfactory sensory neurons, which target the olfactory lobe. Orcokinin is also present in a population of local olfactory interneurons, which may relay lateral inhibition across the array of olfactory glomeruli within the lobes. Extensive lateral connections of the glomeruli were also visualized using the histological silver impregnation method according to Holmes-Blest. This technique also revealed the structural organization of the output pathway of the olfactory system, the olfactory projection neurons, the axons of which target the lateral protocerebrum. Within the lobes, the course of their axons seems to be reorganized in an axon-sorting zone before they exit the system. Together with previous results, we combine our findings into a model on the functional organization of the olfactory system in these animals.
椰子蟹属的陆生寄居蟹对挥发性气味表现出强烈的行为反应，并被各种潜在食物来源的化学线索所吸引。近年来，人们对它们的空气嗅觉的几个方面进行了探索，包括其行为方面以及外周和中枢嗅觉通路的结构。在这里，我们使用经典的组织学方法以及针对神经肽促心肽和咽侧体抑制素、突触蛋白和血清素的免疫组织化学方法，来深入了解它们大脑中主要嗅觉中枢——成对的嗅叶的功能组织。我们的结果表明，促心肽存在于靶向嗅叶的嗅觉感觉神经元的轴突中。促心肽也存在于一群局部嗅觉中间神经元中，这些中间神经元可能在叶内的一系列嗅觉小球之间传递侧向抑制。根据霍姆斯 - 布莱斯特的方法，使用组织学银浸染法也观察到了小球广泛的侧向连接。这项技术还揭示了嗅觉系统输出通路——嗅觉投射神经元的结构组织，其轴突靶向侧前脑。在叶内，它们的轴突在离开系统之前似乎在一个轴突分选区进行了重新组织。结合之前的结果，我们将我们的发现整合到这些动物嗅觉系统功能组织的模型中。
