Meeting Abstract
Mechanosensory feedback is critical to the motor performance and fine control of appendages in animals. In fishes, the pectoral fin is outfitted with mechanosensors that sense ray bending and it functions as a propulsor. During propulsion fishes modulate thrust and efficiency by finely control the shape of their fins. Here we examine the control of fin shape and movements by integrating previous work on afferent physiology with new data on fin kinematics and motor patterns. We hypothesize that sensory input from fin ray afferents modulates motor output and the fine movements of the fins. To test these ideas, we examine how the loss of pectoral fin ray sensation impacts muscle activity patterns and kinematics during labriform swimming in a parrotfish, Scarus quoyi. In the intact fish, the basic motor pattern is alternating activity of the antagonist abductor and adductor groups. Bilateral transections of all sensory nerves that innervate the pectoral fin rays resulted in increased fin beat frequency and a transition to the body-caudal fin gait at slower speeds. 3D kinematics reveals that the trajectory of the fin resembles a figure eight in control fish, and the anteroposterior translation and twisting of the fin is reduced after transection. The duration of muscle activity was significantly greater after transection, which we suggest enhances control and stability after sensory loss through the co-contraction of antagonistic muscles. To more deeply explore the feedback loop of fin shape impacting activity of fin ray afferents, which modulates fin movements, we additionally examine neural encoding of fin bending in relation to typical and post-nerve transection motor control patterns and movements.
