Data - raw_data_atta_vollenweider from Three-dimensional kinematics of leaf-cutter ant mandibles: not all dicondylic joints are simple hinges

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: <i>Atta vollenweideri</i> 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 nutrition assimilation in animals’.

昆虫凭借大颚（mandibles）执行多项生理与行为任务，包括食物加工、物料转运、筑巢、育幼以及御敌等。尽管功能多样，学界此前普遍认为大颚的运动仅局限于绕单一固定轴的旋转。本研究以一类将大颚用于多样化任务的物种——沃氏切叶蚁（Atta vollenweideri）为研究对象，对这一“铰链关节假说”开展了直接的定量检验。研究借助多相机采集装置，对被束缚固定的活体蚂蚁的大颚运动进行了三维重构。刚体运动学分析结果清晰表明，大颚运动所占据的运动学空间需要不止一个旋转自由度：当开口角度较大时，大颚运动以偏航（yaw）为主；而当开口角度较小时，大颚同时发生偏航与俯仰（pitch）运动。偏航与俯仰的组合可使大颚实现交叉运动：闭合时两侧大颚可交替处于上方。本研究在自由切割的蚂蚁个体中观察到了该交叉运动，提示其具备重要的功能意义。结合近期其他昆虫关节咬合结构多样性的相关报道，本研究结果表明，昆虫大颚的运动学特征比此前的传统认知更为多样，因此值得开展进一步的细致研究。本文属于“动物的食物加工与营养同化”专题议题的组成部分。