Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA
Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA.
J Exp Biol. 2020 Jan 23;223(Pt 2):jeb211466. doi: 10.1242/jeb.211466.
For many fish species, rhythmic movement of the pectoral fins, or forelimbs, drives locomotion. In terrestrial vertebrates, normal limb-based rhythmic gaits require ongoing modulation with limb mechanosensors. Given the complexity of the fluid environment and dexterity of fish swimming through it, we hypothesize that mechanosensory modulation is also critical to normal fin-based swimming. Here, we examined the role of sensory feedback from the pectoral fin rays and membrane on the neuromuscular control and kinematics of pectoral fin-based locomotion. Pectoral fin kinematics and electromyograms of the six major fin muscles of the parrotfish, , a high-performance pectoral fin swimmer, were recorded during steady swimming before and after bilateral transection of the sensory nerves extending into the rays and surrounding membrane. Alternating activity of antagonistic muscles was observed and drove the fin in a figure-of-eight fin stroke trajectory before and after nerve transection. After bilateral transections, pectoral fin rhythmicity remained the same or increased. Differences in fin kinematics with the loss of sensory feedback also included fin kinematics with a significantly more inclined stroke plane angle, an increased angular velocity and fin beat frequency, and a transition to the body-caudal fin gait at lower speeds. After transection, muscles were active over a larger proportion of the fin stroke, with overlapping activation of antagonistic muscles rarely observed in the trials of intact fish. The increased overlap of antagonistic muscle activity might stiffen the fin system in order to enhance control and stability in the absence of sensory feedback from the fin rays. These results indicate that fin ray sensation is not necessary to generate the underlying rhythm of fin movement, but contributes to the specification of pectoral fin motor pattern and movement during rhythmic swimming.
对于许多鱼类物种来说，胸鳍（前鳍）的有节奏运动驱动着它们的运动。在陆生脊椎动物中，正常的基于肢体的节律步态需要肢体机械感受器的持续调节。考虑到流体环境的复杂性和鱼类在其中游动的灵活性，我们假设机械感觉调节对于正常的鳍基游动也是至关重要的。在这里，我们研究了来自胸鳍鳍条和膜的感觉反馈对基于胸鳍的运动的神经肌肉控制和运动学的作用。在稳定游泳期间，我们记录了鹦鹉鱼的胸鳍运动学和六个主要胸鳍肌肉的肌电图，鹦鹉鱼是一种高性能的胸鳍游泳者，在双侧切断延伸到鳍条和周围膜的感觉神经之前和之后。在神经切断之前和之后，拮抗肌肉的交替活动观察到并驱动鳍以八字形的鳍划轨迹。在双侧切断后，胸鳍的节律性保持不变或增加。失去感觉反馈的鳍运动学差异还包括鳍运动学中划水平面角度明显更倾斜、角速度和鳍拍频率增加，以及在较低速度下过渡到身体-尾鳍步态。在切断后，肌肉在更大比例的鳍划中活跃，拮抗肌肉的重叠激活很少在完整鱼的试验中观察到。拮抗肌肉活动的重叠增加可能会使鳍系统变硬，以便在没有来自鳍条的感觉反馈的情况下增强控制和稳定性。这些结果表明，鳍条感觉对于产生鳍运动的基本节律不是必需的，但有助于在有节奏的游泳中指定胸鳍运动模式和运动。
