Department of Bioengineering, Imperial College London, London SW7 2AZ, UK.
Philos Trans R Soc Lond B Biol Sci. 2023 Dec 4;378(1891):20220546. doi: 10.1098/rstb.2022.0546. Epub 2023 Oct 16.
Insects use their mandibles for a variety of tasks, including food processing, material transport, nest building, brood care, and fighting. Despite this functional diversity, mandible motion is typically thought to be constrained to rotation about a single fixed axis. Here, we conduct a direct quantitative test of this 'hinge joint hypothesis' in a species that uses its mandibles for a wide range of tasks: leaf-cutter ants. Mandible movements from live restrained ants were reconstructed in three dimensions using a multi-camera rig. Rigid body kinematic analyses revealed strong evidence that mandible movement occupies a kinematic space that requires more than one rotational degree of freedom: at large opening angles, mandible motion is dominated by yaw. But at small opening angles, mandibles both yaw and pitch. The combination of yaw and pitch allows mandibles to 'criss-cross': either mandible can be on top when mandibles are closed. We observed criss-crossing in freely cutting ants, suggesting that it is functionally important. Combined with recent reports on the diversity of joint articulations in other insects, our results show that insect mandible kinematics are more diverse than traditionally assumed, and thus worthy of further detailed investigation. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.
昆虫的下颚用于多种任务，包括食物加工、材料运输、巢穴建造、幼虫照顾和战斗。尽管功能多样化，但下颚的运动通常被认为仅限于围绕单个固定轴的旋转。在这里，我们在一个使用下颚进行广泛任务的物种中对这种“铰链关节假说”进行了直接的定量测试：切叶蚁。使用多相机装置从受约束的活体蚂蚁重建下颚的三维运动。刚体运动学分析有力地证明，下颚的运动占据了需要超过一个旋转自由度的运动空间：在较大的开口角度下，下颚的运动主要是偏航。但在小开口角度下，下颚既偏航又俯仰。偏航和俯仰的组合允许下颚“交错”：当下颚关闭时，任何一个下颚都可以在上部。我们在自由切割的蚂蚁中观察到了交错，这表明它在功能上很重要。结合最近关于其他昆虫关节连接多样性的报告，我们的结果表明，昆虫下颚的运动学比传统上假设的更加多样化，因此值得进一步详细研究。本文是主题为“动物的食物加工和营养吸收”的一部分。
