Department of Behavioural Physiology and Sociobiology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
J Exp Biol. 2023 Jun 15;226(12). doi: 10.1242/jeb.244246. Epub 2023 Jun 22.
Polymorphic leaf-cutting ants harvest leaf fragments that correlate in size with the workers' body size. When cutting, workers anchor their hind legs on the leaf edge and rotate, removing approximately semicircular fragments. Workers show behavioural plasticity and modify their leg extension while holding onto the leaf edge depending on, for instance, leaf toughness, cutting smaller fragments out of tough leaves. What sensory information workers use to control the cutting trajectory remains unknown. We investigated whether sensory information from both the leg contact with the leaf edge and from head movements underlies fragment size determination. In the laboratory, we recorded Atta sexdens workers cutting standardised ®Parafilm pseudoleaves of different thickness, and quantified cutting behaviour and body reach, i.e. the distance between the mandible and the anchored hind leg tarsus. Experimentally preventing contact with the leaf edge resulted in smaller fragments, evincing that workers control the cutting trajectory using information from the contact of the hind legs with the leaf edge. However, ants were able to cut fragments even when contact of all six legs with the edge was prevented, indicating the use of additional sensory information. Ablation of mechanosensory hairs at the neck joint alone did not influence fragment size determination, yet simultaneously preventing sensory feedback from both mechanosensory hairs and edge contact led to a loss of control over the cutting trajectory. Leaf-cutting ants, therefore, control their cutting trajectory using sensory information from both the leg contact with the leaf edge and the lateral bending of the head.
多态切叶蚁会收割与工蚁体型大小相关的叶片碎片。在切割时，工蚁用后腿固定在叶片边缘并旋转，从而切除大约半圆形的碎片。工蚁表现出行为可塑性，并根据叶片的韧性等因素，改变其在叶片边缘的腿部伸展程度，以切割出较小的碎片。工蚁用来控制切割轨迹的感觉信息尚不清楚。我们研究了工蚁是否利用后腿与叶片边缘接触的感觉信息和头部运动的感觉信息来确定碎片的大小。在实验室中，我们记录了 Atta sexdens 工蚁切割不同厚度标准的 Parafilm 假叶的行为，并量化了切割行为和身体伸展程度，即下颌和固定的后腿跗节之间的距离。实验中阻止后腿与叶片边缘接触会导致切割出较小的碎片，这表明工蚁利用后腿与叶片边缘接触的信息来控制切割轨迹。然而，即使阻止所有六条腿与边缘接触，蚂蚁也能够切割出碎片，这表明它们还利用了其他感觉信息。仅切除颈部关节处的机械感觉毛并不会影响碎片大小的确定，但同时阻止机械感觉毛和边缘接触的感觉反馈会导致失去对切割轨迹的控制。因此，切叶蚁利用来自后腿与叶片边缘接触和头部侧向弯曲的感觉信息来控制切割轨迹。
