Meeting Abstract
Proprioceptive feedback from the limbs is fundamental to an organism’s sense of body position and movement. The pectoral fins of fishes have been shown to function as proprioceptive as well as propulsive structures. Here we examine the functions of pectoral fin-based proprioceptive feedback in hovering behavior. Hovering fish are dynamically unstable and must finely tune force production with their fins to remain balanced, suggesting proprioceptive feedback is important to this behavior. We examined hovering in the bluegill sunfish (Lepomis macrochirus), a model species for studying the behavior, biomechanics, and physiology of pectoral fin-based swimming. The bluegill beats its pectoral fins rhythmically, in coordination with median fin movement, to maintain a stationary position while hovering. To determine how pectoral fin proprioceptive feedback is used in bluegill fin-based hovering, we performed a series of experiments where we transected the sensory nerves innervating the pectoral fins and examined the effect on hovering behavior. The transection procedure involved severing all sensory nerves innervating the fin rays either unilaterally or bilaterally. Results of the bilateral transection experiments indicate that both the pattern and timing of fin movements change post-transection and that median fins may compensate for changes in pectoral fin function. After unilateral transections, asymmetries in kinematics were identified between the intact fin and the fin with transected nerves. In both unilateral and bilateral transection conditions removal of sensory inputs from the fin rays and membrane resulted in significant changes in pectoral fin use during hovering. These results suggest that proprioceptive feedback is critical for generating and maintaining a normal hovering gait.
