Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, USA.
Proc Biol Sci. 2020 May 27;287(1927):20200428. doi: 10.1098/rspb.2020.0428. Epub 2020 May 20.
Tendon springs often influence locomotion by amplifying the speed and power of limb joint rotation. However, less is known about elastic recoil action in feeding systems, particularly for small aquatic animals. Here, we ask if elastic recoil amplifies the speed of gape closing during aquatic food processing in the Axolotl (). We measure activation of the adductor mandibulae externus via electromyography and strain of the jaw adductor muscle-tendon unit (MTU), and gape kinematics via fluoromicrometry. The muscle is pre-activated coincident with gape opening, which causes MTU stretch. Activation lasts significantly shorter for fish than cricket processing, and muscle shortening during MTU lengthening yields significantly greater elastic strain for cricket processing. The speed of MTU shortening, which dictates the speed of gape closing is 2.5-4.4 times greater than the speed of the initial shortening of the muscle fascicles for fish and cricket gape cycles, respectively. These data demonstrate a clear role for elastic recoil, which may be unexpected for a MTU in a feeding system of a small, aquatic animal. Amplification of jaw-closing speed resulting from elastic recoil likely confers ecological advantages in reducing prey escape risks during food processing in a dense and viscous fluid environment.
肌腱弹簧通常通过放大肢体关节旋转的速度和力量来影响运动。然而，对于摄食系统中的弹性回弹作用，人们知之甚少，特别是对于小型水生动物。在这里，我们想知道弹性回弹是否会在水生物处理过程中增加颌骨闭合的速度。我们通过肌电图测量下颌外收肌的激活情况，通过荧光微测量法测量颌骨内收肌肌腱单元 (MTU) 的应变和张口运动学。肌肉与张口同时预激活，导致 MTU 拉伸。对于鱼类来说，肌肉的激活时间明显短于蟋蟀处理，而在 MTU 延长过程中肌肉缩短会导致蟋蟀处理产生更大的弹性应变。MTU 缩短的速度决定了张口的关闭速度，对于鱼类和蟋蟀的张口周期，MTU 缩短的速度分别比肌肉束的初始缩短速度快 2.5-4.4 倍。这些数据表明弹性回弹在一个小型水生动物的摄食系统中起着明显的作用，这可能是出乎意料的。由于弹性回弹而导致的闭口速度的放大可能会在密集和粘性流体环境中的食物处理过程中降低猎物逃脱的风险，从而带来生态优势。
