External power amplification drives prey capture in a spider web
External power amplification drives prey capture in a spider web
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DOI：
10.1073/pnas.1821419116
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发表时间：
2019-06-11
影响因子：
11.1
通讯作者：
Blackledge, T. A.
中科院分区：
文献类型：
--
作者：
Han, S. I.;Astley, H. C.;Blackledge, T. A.
力量放大使动物能够做出超越肌肉力量和速度生理极限的动作，比如螳螂虾的超快掠食性打击和跳蚤的跳跃。然而，所有已知的非人类的、肌肉驱动的力量放大的例子都涉及到从单个肌肉收缩周期中储存能量的解剖结构。在这里，我们描述了一个使用人造装置进行外部功率放大的非人类例子：三角编织蜘蛛（Hyptiotes cavatus）的网，它利用储存在丝线中的能量主动从远处缠结猎物。hypiotes通过在多个肢体运动周期中收紧一根单独的锚线来拉伸它的网，然后在昆虫撞击网时释放它对锚线的控制。蜘蛛和网都向前弹跳2到3厘米，峰值加速度高达772.85米/秒(2)，这样多达四条额外的粘性捕获线接触到猎物，而蜘蛛突然停止引起的抽搐随后从各个方向将丝缠绕在猎物周围。利用蛛网作为外部“工具”来储存能量，与内部组织为基础的能量放大相比，提供了巨大的机械优势，因为Hyptiotes能够在肌肉收缩的多个周期中加载蛛网，从而在捕获猎物时释放出比肌肉驱动的解剖弹性能量系统更多的储存能量。弹性功率放大是蛛丝在织网中的功能中一个未被充分认识的组成部分，它与人类设计出弹射器和弹道器等功率放大装置的基本机械优势表现出了显著的趋同。
Power amplification allows animals to produce movements that exceed the physiological limits of muscle power and speed, such as the mantis shrimp's ultrafast predatory strike and the flea's jump. However, all known examples of nonhuman, muscle-driven power amplification involve anatomical structures that store energy from a single cycle of muscular contraction. Here, we describe a nonhuman example of external power amplification using a constructed device: the web of the triangle-weaver spider, Hyptiotes cavatus, which uses energy stored in the silk threads to actively tangle prey from afar. Hyptiotes stretches its web by tightening a separate anchor line over multiple cycles of limb motion, and then releases its hold on the anchor line when insects strike the web. Both spider and web spring forward 2 to 3 cm with a peak acceleration of up to 772.85 m/s(2) so that up to four additional adhesive capture threads contact the prey while jerking caused by the spider's sudden stop subsequently wraps silk around the prey from all directions. Using webs as external "tools" to store energy offers substantial mechanical advantages over internal tissue-based power amplification due to the ability of Hyptiotes to load the web over multiple cycles of muscular contraction and thus release more stored energy during prey capture than would be possible with muscle-driven anatomical elastic-energy systems. Elastic power amplification is an underappreciated component of silk's function in webs and shows remarkable convergence to the fundamental mechanical advantages that led humans to engineer power-amplifying devices such as catapults and ballistae.