SCHRIEFER, J.E. *; HALE, M.E.; Univ. of Chicago; Univ. of Chicago: Are strikes and startles similar? Kinematics and EMGs of S-start escape and feeding in northern pike.

S-start behaviors of fishes have been shown to function in both escape startles and feeding strikes. We examine S-start behaviors and muscle activity patterns to compare the motor control of prey capture and predator avoidance. High-speed video (250Hz) and electromyograms (EMGs) were collected from northern pike (Esox lucius). While stimulated to feed or escape, pike were filmed from ventral view and behaviors were analyzed through the end of the first propulsive tail stroke. In the feeding trials examined, prey capture occurred during the first propulsive tail stroke. We recorded muscle activity from seven electrodes, one in the left adductor mandibulae and in anterior, midbody and posterior epaxial white muscle on both sides of the fish. Kinematic and EMG data reveal that feeding S-starts differed significantly from escape S-starts in both behavior and motor pattern. Behaviorally, stage 1 (pre-propulsive movements) was significantly slower in feeding strikes and involved primarily caudal bending with significantly less head movement than escape behaviors. Similarly, strong posterior muscle activity was recorded prior to more anterior activity during feeding while in escape, posterior activity of epaxial muscle generally occurred with simultaneous contralateral activity of anterior epaxial muscle. During escape, activity of jaw adductor muscle was initiated simultaneously with the activity of axial muscle prior to body propulsion. Adduction was delayed relative to axial muscle activity during feeding. This pattern reflects the capture of prey during the propulsive stage of movement. These data suggest that, although strikes and startles are similar, the behaviors involve fundamentally different motor control mechanisms.