Meeting Abstract
Proprioception, the ability to sense movement and position of the limbs, provides critical sensory feedback for locomotion in many terrestrial vertebrates and insects. Although fish also use paired limbs, the pectoral fins, as primary propulsors, little is known about proprioceptive feedback from the fins or its function. Here we used bluegill sunfish (Lepomis macrochirus) to examine proprioception during swimming. The bluegill uses its pectoral fins extensively in locomotion, and electrophysiological recordings have shown that fin ray afferents respond to bending at frequencies typical for steady swimming. In this study, we transected afferent nerves and recorded behavior to examine the role of fin proprioceptive feedback in forward swimming. To assess baseline kinematics, pectoral fin swimming was recorded in a flow tank at range of speeds. Bilateral nerve transections were then performed to remove sensory input from the rays. As transected nerves did not contain motor efferents, transections only removed sensory function. Behavioral trials were repeated after a short recovery period. In contrast to the fin movements of control behaviors, we found marked variability among fin beats within a trial post-transection. In addition, there was a lack of coordination in the timing of fin beats between the left and right sides. Overall, we found a decrease in stroke amplitude and an increase in fin beat frequency. Engagement of the body axis and caudal fin during swimming occurred at lower speeds post-transection than in controls, perhaps compensating for decreased force generation by the pectoral fins. Together these data indicate that proprioception provides important feedback for controlling pectoral fin movements during swimming.
