School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Proc Natl Acad Sci U S A. 2013 Jun 11;110(24):9746-51. doi: 10.1073/pnas.1302428110. Epub 2013 May 20.
Locomotion emerges from effective interactions of an individual with its environment. Principles of biological terrestrial locomotion have been discovered on unconfined vertical and horizontal substrates. However, a diversity of organisms construct, inhabit, and move within confined spaces. Such animals are faced with locomotor challenges including limited limb range of motion, crowding, and visual sensory deprivation. Little is known about how these organisms accomplish their locomotor tasks, and such environments challenge human-made devices. To gain insight into how animals move within confined spaces, we study the locomotion of the fire ant Solenopsis invicta, which constructs subterranean tunnel networks (nests). Laboratory experiments reveal that ants construct tunnels with diameter, D, comparable to body length, L = 3.5 ± 0.5 mm. Ants can move rapidly (> 9 bodylengths per s) within these environments; their tunnels allow for effective limb, body, and antennae interaction with walls, which facilitate rapid slip-recovery during ascending and descending climbs. To examine the limits of slip-recovery in artificial tunnels, we perform perturbations consisting of rapid downward accelerations of the tunnels, which induce falls. Below a critical tunnel diameter, Ds = 1.31 ± 0.02 L, falls are always arrested through rapid interaction of appendages and antennae with tunnel walls to jam the falls. Ds is comparable to the size of incipient nest tunnels (D = 1.06 ± 0.23 L), supporting our hypothesis that fire ants construct environments that simplify their control task when moving through the nest, likely without need for rapid nervous system intervention.
运动是个体与其环境有效相互作用的结果。在无约束的垂直和水平基底上已经发现了生物陆地运动的原理。然而，许多生物在有限的空间内构建、居住和移动。这些动物面临着运动挑战，包括有限的肢体运动范围、拥挤和视觉感官剥夺。人们对这些生物如何完成它们的运动任务知之甚少，而且这些环境对人造设备构成挑战。为了深入了解动物在受限空间内的运动方式，我们研究了火蚁 Solenopsis invicta 的运动方式，火蚁构建了地下隧道网络（巢穴）。实验室实验表明，蚂蚁建造的隧道直径 D 与身体长度 L 相当，L=3.5±0.5mm。蚂蚁可以在这些环境中快速移动（>9 个体长度/秒）；它们的隧道允许肢体、身体和触角与墙壁有效互动，这有助于在上升和下降攀爬时快速恢复滑动。为了检查在人工隧道中恢复滑动的极限，我们进行了由隧道快速向下加速引起的扰动，这会导致蚂蚁掉落。在临界隧道直径 Ds=1.31±0.02L 以下，通过触角和附肢与隧道壁的快速相互作用，总是会阻止掉落，从而使掉落停止。Ds 与初始巢穴隧道的大小（D=1.06±0.23L）相当，这支持了我们的假设，即火蚁构建的环境在它们通过巢穴移动时简化了它们的控制任务，可能不需要快速的神经系统干预。
