The flying insect thoracic cuticle is heterogenous in structure and in thickness-dependent modulus gradation
The flying insect thoracic cuticle is heterogenous in structure and in thickness-dependent modulus gradation
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DOI：
10.1016/j.actbio.2021.10.035
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发表时间：
2022-01-02
影响因子：
9.7
通讯作者：
Heveran, Chelsea M.
中科院分区：
文献类型：
--
作者：
Casey, Cailin;Yager, Claire;Heveran, Chelsea M.
胸部是昆虫飞行的核心特化结构。在胸部，飞行肌肉被一层薄薄的角质层包围。这种几丁质结构的结构、组成和材料特性可能会影响胸部在飞行中的效率。然而，这些属性，以及它们在整个胸部和昆虫类群之间的变化，是未知的。我们提供了一个多方面的评估胸部角质层的传单异步（蜜蜂，蜜蜂）和同步（天蛾，天蛾）肌肉。这些肌肉类型是由它们的激活频率和昆虫的翅拍频率之间的关系定义的。我们研究了角质层结构，组织学，节枝弹性蛋白分布，通过共聚焦激光扫描显微镜，和模量梯度与纳米压痕。我们的研究结果表明，胸部角质层的性质是高度依赖于解剖区域和物种。模量梯度，但不是平均模量，不同的两种类型的传单。在某些地区，A.从角质层内部到外部的线性模量梯度为正，约为2GPa。In M.通过角质层厚度的模量值不能很好地用线性拟合表示。我们利用有限元建模来评估测量的模量梯度如何影响角质层中的最大应力。从高模量侧压缩具有线性梯度的角质层时，应力减小。这些结果支持了A.意大利芹胸小皮我们多方面的评估推进了我们对胸部角质层结构和材料异质性的理解，以及材料分级对飞行昆虫的潜在益处。昆虫的胸部对于有效的飞行是必不可少的，但关于外骨骼角质层的贡献仍然存在疑问。我们研究了胸部角质层的微尺度特性，这是确定其在飞行中作用的关键一步。技术，包括组织学，纳米压痕，共聚焦激光扫描显微镜显示，角质层的性质不同，通过角质层厚度，胸部区域，物种之间的异步（蜜蜂;蜜蜂）和同步（天蛾;天蛾）肌肉。这种变化突出了高分辨率的角质层评估的重要性，为飞行昆虫谱系和点的因素，可能（模量梯度）和可能不会（平均模量）有助于不同的飞行形式。了解胸部的材料变化可能会为设计受昆虫启发的技术提供信息，例如移动的微型机器人。(c)2021 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The thorax is a specialized structure central to insect flight. In the thorax, flight muscles are surrounded by a thin layer of cuticle. The structure, composition, and material properties of this chitinous structure may influence the efficiency of the thorax in flight. However, these properties, as well as their variation throughout the thorax and between insect taxa, are not known. We provide a multi-faceted assessment of thorax cuticle for fliers with asynchronous (honey bee; Apis mellifera) and synchronous (hawkmoth; Manduca sexta) muscles. These muscle types are defined by the relationship between their activation frequency and the insect's wingbeat frequency. We investigated cuticle structure using histology, resilin distribution through confocal laser scanning microscopy, and modulus gradation with nanoindentation. Our results suggest that thorax cuticle properties are highly dependent on anatomical region and species. Modulus gradation, but not mean modulus, differed between the two types of fliers. In some regions, A. mellifera had a positive linear modulus gradient from cuticle interior to exterior of about 2 GPa. In M. sexta, modulus values through cuticle thickness were not well represented by linear fits. We utilized finite element modeling to assess how measured modulus gradients influenced maximum stress in cuticle. Stress was reduced when cuticle with a linear gradient was compressed from the high modulus side. These results support the protective role of the A. mellifera thorax cuticle. Our multi-faceted assessment advances our understanding of thorax cuticle structural and material heterogeneity and the potential benefits of material gradation to flying insects. Statement of significance The insect thorax is essential for efficient flight but questions remain about the contribution of the exoskeletal cuticle. We investigated the microscale properties of the thorax cuticle, a crucial step to determine its role in flight. Techniques including histology, nanoindentation, and confocal laser scanning microscopy revealed that cuticle properties vary through cuticle thickness, by thorax region, and between species with asynchronous (honey bee; Apis mellifera) and synchronous (hawkmoth; Manduca sexta) muscles. This variation highlights the importance of high resolution cuticle assessment for flying insect lineages and points to factors that may (modulus gradation) and may not (mean modulus) contribute to different flight forms. Understanding material variation in the thorax may inform design of technologies inspired by insects, such as mobile micro robots. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.