Hummel Jennifer, Kössl Manfred, Nowotny Manuela
Department of Neurobiology and Biosensors, Institute of Cell Biology and Neuroscience, Goethe University, Frankfurt am Main, Germany.
J Comp Neurol. 2017 Jul 1;525(10):2443-2455. doi: 10.1002/cne.24218. Epub 2017 Apr 18.
The tonotopically organized hearing organs of bushcrickets provide the opportunity for a detailed correlation of morphological and structural properties within hearing organs that are needed to establish tonotopic gradients. In the present study of a tonotopic insect hearing organ, we combine mechanical measurements of sound-induced hearing organ motion and detailed anatomical investigations to explore the anatomical basis of tonotopy. We compare mechanical data of frequency responses along the auditory organ to several anatomical parameters. Low frequency responses are related to larger organ and cap cell size in the proximal part of the hearing organ while in the distal part of the organ, small organ and cap cell size is related to high-frequency representation. However, the correlation between organ and cap cell size with continuous frequency representation along the organ is not very tight. Instead, the height of the organ and the corresponding length of the sensory dendrites are best correlated to tonotopic frequency representation. The sensory dendrite contains a ciliary root with a pronounced cross-banding of electron-dense material that should be important for the stiffness of the dendrite. The geometry of surrounding structures like the hemolymph channel and the acoustic trachea as well as the extension of the tectorial membrane are not correlated to the tonotopy. We provide evidence that tonotopy in the bushcricket hearing organ may depend on the size of ciliary structures. In particular, the ciliary root of the sensory cells is a likely cellular basis of tonotopy.
螽斯具有音频拓扑组织的听觉器官，这为详细关联听觉器官内建立音频拓扑梯度所需的形态和结构特性提供了机会。在目前对具有音频拓扑的昆虫听觉器官的研究中，我们结合了声音引起的听觉器官运动的力学测量和详细的解剖学研究，以探索音频拓扑的解剖学基础。我们将沿听觉器官的频率响应的力学数据与几个解剖学参数进行了比较。低频响应与听觉器官近端较大的器官和帽细胞大小有关，而在器官的远端，较小的器官和帽细胞大小与高频表征有关。然而，器官和帽细胞大小与沿器官的连续频率表征之间的相关性并不是很强。相反，器官的高度和感觉树突的相应长度与音频拓扑频率表征的相关性最好。感觉树突包含一个具有明显电子致密物质交叉带的睫状根，这对树突的刚度应该很重要。周围结构的几何形状，如血淋巴通道和声气管以及盖膜的延伸与音频拓扑无关。我们提供的证据表明，螽斯听觉器官中的音频拓扑可能取决于睫状结构的大小。特别是，感觉细胞的睫状根可能是音频拓扑的细胞基础。
