University of Lincoln, School of Life & Environmental Sciences, Joseph Banks Laboratories, Lincoln, LN6 7DL, United Kingdom.
University of Lincoln, School of Life & Environmental Sciences, Joseph Banks Laboratories, Lincoln, LN6 7DL, United Kingdom.
Acta Biomater. 2022 Nov;153:399-410. doi: 10.1016/j.actbio.2022.08.056. Epub 2022 Aug 30.
Derived from the respiratory tracheae, bush-crickets' acoustic tracheae (or ear canals) are hollow tubes evolved to transmit sounds from the external environment to the interior ear. Due to the location of the ears in the forelegs, the acoustic trachea serves as a structural element that can withstand large stresses during locomotion. In this study, we report a new Atomic Force Microscopy Force Spectroscopy (AFM-FS) approach to quantify the mechanics of taenidia in the bush-cricket Mecopoda elongata. Mechanical properties were examined over the longitudinal axis of hydrated taenidia, by indenting single fibres using precision hyperbolic tips. Analysis of the force-displacement (F-d) extension curves at low strains using the Hertzian contact model showed an Elastic modulus distribution between 13.9 MPa to 26.5 GPa, with a mean of 5.2 ± 7 GPa and median 1.03 GPa. Although chitin is the primary component of stiffness, variation of elasticity in the nanoscale suggests that resilin significantly affects the mechanical properties of single taenidia fibres (38% of total data). For indentations up to 400 nm, an intricate chitin-resilin response was observed, suggesting structural optimization between compliance and rigidity. Finite-element analysis on composite materials demonstrated that the Elastic modulus is sensitive to the percentage of resilin and chitin content, their location and structural configuration. Based on our results, we propose that the distinct moduli of taenidia fibres indicate sophisticated evolution with elasticity playing a key role in optimization. STATEMENT OF SIGNIFICANCE: In crickets and bush-crickets, the foreleg tracheae have evolved into acoustic canals, which transport sound to the ears located on the tibia of each leg. Tracheae are held open by spiral cuticular micro-fibres called taenidia, which are the primary elements of mechanical reinforcement. We developed an AFM-based method to indent individual taenidia at the nanometre level, to quantify local mechanical properties of the interior acoustic canal of the bush-cricket Mecopoda elongata, a model species in hearing research. Taenidia fibres were immobilized on a hard substrate and the indenter directly approached the epicuticle surface. This is the first characterization of the nano-structure of unfixed tracheal taenidia, and should pave the way for further in vivo mechanical investigations of auditory structures.
从呼吸气管衍生而来，蝗科昆虫的声学气管（或耳道）是中空的管状结构，进化后可将外部环境的声音传递到内耳。由于耳朵位于前腿上，因此声学气管作为一种结构元素，可以在运动过程中承受较大的应力。在这项研究中，我们报告了一种新的原子力显微镜力谱（AFM-FS）方法，用于量化蝗科昆虫 Mecopoda elongata 中 taenidia 的力学特性。通过使用精密双曲形尖端在单个纤维上进行压痕，在水合 taenidia 的纵轴上检查了机械性能。使用 Hertzian 接触模型分析低应变下的力-位移（F-d）延伸曲线表明，弹性模量分布在 13.9 MPa 到 26.5 GPa 之间，平均值为 5.2 ± 7 GPa，中位数为 1.03 GPa。尽管几丁质是刚度的主要成分，但纳米尺度上弹性的变化表明，弹性蛋白显着影响了单个 taenidia 纤维的机械性能（占总数据的 38%）。对于高达 400nm 的压痕，观察到复杂的几丁质-弹性蛋白响应，表明在顺应性和刚性之间进行了结构优化。复合材料的有限元分析表明，弹性模量对弹性蛋白和几丁质含量的百分比、它们的位置和结构配置敏感。基于我们的结果，我们提出 taenidia 纤维的独特模量表明了复杂的进化，弹性在优化中起着关键作用。意义声明：在蟋蟀和蝗科昆虫中，前腿气管已进化成声学通道，将声音传输到位于每条腿胫骨上的耳朵。气管由称为 taenidia 的螺旋状表皮微纤维保持张开，taenidia 是机械增强的主要元素。我们开发了一种基于 AFM 的方法，可在纳米尺度上压痕单个 taenidia，以量化模型物种听觉研究中的蝗科昆虫 Mecopoda elongata 内部声学通道的局部力学特性。将 taenidia 纤维固定在坚硬的基底上，压头直接接近表皮表面。这是对未固定气管 taenidia 的纳米结构的首次表征，应该为进一步对听觉结构进行体内机械研究铺平道路。
