Universität Bonn, Bonner Institut für Organismische Biologie (BIOB), Abteilung 2: Biodiversität der Tiere, An der Immenburg 1, 53121 Bonn, Germany.
J Exp Biol. 2024 Jan 15;227(2). doi: 10.1242/jeb.246341. Epub 2024 Jan 26.
Performance traits such as bite forces are crucial to fitness and relate to the niche and adaptation of species. However, for many insects it is not possible to directly measure bite forces because they are too small. Biomechanical models of bite forces are therefore relevant to test hypotheses of adaptation in insects and other small organisms. Although such models are based on classical mechanics, combining forces, material properties and laws of levers, it is currently unknown how various models relate to bite forces measured in vivo. One critical component of these models is the physiological cross-sectional area (PCSA) of muscles, which relates to the maximum amount of force they can produce. Here, using the grasshopper Schistocerca gregaria, we compare various ways to obtain PCSA values and use in vivo measurements of bite forces to validate the biomechanical models. We show that most approaches used to derive PCSA (dissection, 3D muscle convex hull volume, muscle attachment area) are consistent with the expected relationships between PCSA and bite force, as well as with the muscle stress values known for insects. The only exception to this are PCSA values estimated by direct 3D muscle volume computation, which could be explained by noisy variation produced by shrinkage. This method therefore produces PCSA values which are uncorrelated to in vivo bite forces. Furthermore, despite the fact that all other methods do not significantly differ from expectations, their derived PCSA values vary widely, suggesting a lack of comparability between studies relying on different methods.
性能特征，如咬合力，对适应性和物种的生态位有重要意义。然而，对于许多昆虫来说，由于它们太小，无法直接测量咬合力。因此，咬合力的生物力学模型对于测试昆虫和其他小生物体的适应假说很重要。虽然这些模型基于经典力学，结合了力量、材料特性和杠杆定律，但目前尚不清楚各种模型与体内测量的咬合力有何关系。这些模型的一个关键组成部分是肌肉的生理横截面积（PCSA），它与肌肉能够产生的最大力量有关。在这里，我们使用蝗虫 Schistocerca gregaria 来比较获得 PCSA 值的各种方法，并使用体内测量的咬合力来验证生物力学模型。我们表明，大多数用于推导 PCSA 的方法（解剖、3D 肌肉凸包体积、肌肉附着面积）与 PCSA 和咬合力之间的预期关系以及昆虫已知的肌肉应力值一致。唯一的例外是通过直接 3D 肌肉体积计算估计的 PCSA 值，这可能是由于收缩产生的噪声变化。因此，这种方法产生的 PCSA 值与体内咬合力无关。此外，尽管所有其他方法与预期值没有显著差异，但它们推导的 PCSA 值差异很大，这表明依赖不同方法的研究之间缺乏可比性。
