University of Cologne, Biocenter, Zoological Institute, Department for Animal Physiology, Zülpicher Straße 47b, 50694 Cologne, Germany.
J Exp Biol. 2013 Nov 15;216(Pt 22):4172-83. doi: 10.1242/jeb.092106. Epub 2013 Aug 15.
In its natural habitat, Carausius morosus climbs on the branches of bushes and trees. Previous work suggested that stick insects perform targeting movements with their hindlegs to find support more easily. It has been assumed that the animals use position information from the anterior legs to control the touchdown position of the ipsilateral posterior legs. Here we addressed the question of whether not only the hindleg but also the middle leg performs targeting, and whether targeting is still present in a walking animal when influences of mechanical coupling through the ground are removed. If this were the case, it would emphasize the role of underlying neuronal mechanisms. We studied whether targeting occurred in both legs, when the rostral neighboring leg, i.e. either the middle or the front leg, was placed at defined positions relative to the body, and analyzed targeting precision for dependency on the targeted position. Under these conditions, the touchdown positions of the hindlegs show correlation to the position of the middle leg parallel and perpendicular to the body axis, while only weak correlation exists between the middle and front legs, and only in parallel to the body axis. In continuously walking tethered animals, targeting accuracy of the hindlegs and middle legs parallel to the body axis barely differed. However, targeting became significantly more accurate perpendicular to the body axis. Our results suggest that a neural mechanism exists for controlling the touchdown position of the posterior leg but that the strength of this mechanism is segment specific and dependent on the behavioral context in which it is used.
在其自然栖息地，Carausius morosus 会爬上灌木和树木的树枝。之前的研究表明，竹节虫会用后腿进行瞄准运动，以便更容易找到支撑物。人们假设动物会利用前腿的位置信息来控制同侧后腿的触地点位置。在这里，我们提出了一个问题，即不仅后腿，而且中腿是否也进行瞄准，以及当通过地面去除机械耦合的影响时，行走中的动物是否仍然存在瞄准。如果是这样，它将强调潜在神经元机制的作用。我们研究了当靠近头部的腿（即中间腿或前腿）相对于身体被放置在确定的位置时，两条腿是否都发生了瞄准，并且分析了瞄准精度对目标位置的依赖性。在这些条件下，后腿的触地点位置与中腿平行和垂直于身体轴的位置相关，而中腿和前腿之间仅存在弱相关性，并且仅在平行于身体轴的方向上存在相关性。在连续行走的系绳动物中，后腿和中腿平行于身体轴的瞄准精度几乎没有差异。然而，垂直于身体轴的瞄准精度变得明显更高。我们的结果表明，存在一种控制后腿触地点位置的神经机制，但这种机制的强度是特定于节段的，并取决于其使用的行为背景。
