Theunissen Leslie M, Vikram Subhashree, Dürr Volker
Department of Biological Cybernetics, Faculty of Biology, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany Cognitive Interaction Technology - Center of Excellence, Bielefeld University, Inspiration 1, 33615 Bielefeld, Germany.
Department of Biological Cybernetics, Faculty of Biology, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany Cognitive Interaction Technology - Center of Excellence, Bielefeld University, Inspiration 1, 33615 Bielefeld, Germany
J Exp Biol. 2014 Sep 15;217(Pt 18):3242-53. doi: 10.1242/jeb.108167. Epub 2014 Jul 10.
Animals that live in a spatially complex environment such as the canopy of a tree, constantly need to find reliable foothold in three-dimensional (3D) space. In multi-legged animals, spatial co-ordination among legs is thought to improve efficiency of finding foothold by avoiding searching-movements in trailing legs. In stick insects, a 'targeting mechanism' has been described that guides foot-placement of hind- and middle legs according to the position of their leading ipsilateral leg. So far, this mechanism has been shown for standing and tethered walking animals on horizontal surfaces. Here, we investigate the efficiency of this mechanism in spatial limb co-ordination of unrestrained climbing animals. For this, we recorded whole-body kinematics of freely climbing stick insects and analysed foot placement in 3D space. We found that touch-down positions of adjacent legs were highly correlated in all three spatial dimensions, revealing 3D co-ordinate transfer among legs. Furthermore, targeting precision depended on the position of the leading leg. A second objective was to test the importance of sensory information transfer between legs. For this, we ablated a proprioceptive hair field signaling the levation of the leg. After ablation, the operated leg swung higher and performed unexpected searching movements. Furthermore, targeting of the ipsilateral trailing leg was less precise in anteroposterior and dorsoventral directions. Our results reveal that the targeting mechanism is used by unrestrained climbing stick insects in 3D space and that information from the trochanteral hair field is used in ipsilateral spatial co-ordination among legs.
生活在空间复杂环境（如树冠层）中的动物，需要不断在三维（3D）空间中找到可靠的立足点。在多足动物中，腿部之间的空间协调被认为可以通过避免后腿的搜索运动来提高找到立足点的效率。在竹节虫中，已经描述了一种“靶向机制”，该机制根据同侧前腿的位置来引导后腿和中腿的足部放置。到目前为止，这种机制已在水平表面上站立和系留行走的动物身上得到证实。在这里，我们研究了这种机制在无约束攀爬动物的空间肢体协调中的效率。为此，我们记录了自由攀爬竹节虫的全身运动学，并分析了3D空间中的足部放置。我们发现，相邻腿部的着陆位置在所有三个空间维度上都高度相关，揭示了腿部之间的3D坐标传递。此外，靶向精度取决于前腿的位置。第二个目标是测试腿部之间感觉信息传递的重要性。为此，我们切除了一个发出腿部抬起信号的本体感受毛场。切除后，手术腿摆动得更高，并进行了意外的搜索运动。此外，同侧后腿在前后和背腹方向上的靶向精度较低。我们的结果表明，无约束攀爬的竹节虫在3D空间中使用靶向机制，并且来自转节毛场的信息用于腿部之间的同侧空间协调。
