Meeting Abstract

39.3  Monday, Jan. 5  Caudal fin shape modulation and control during acceleration, braking, and backing maneuvers in bluegill sunfish, Lepomis macrochirus FLAMMANG, B.E.*; LAUDER, G.V.; Museum of Comparative Zoology, Harvard University; Museum of Comparative Zoology, Harvard University bflammang@oeb.harvard.edu

Evolutionary patterns of intrinsic caudal musculature show that control of the dorsal lobe of the tail evolved first, followed by the ability to control the ventral lobe. This progression of increasing differentiation of musculature suggests specialization of caudal muscle roles. Fine control of fin elements is likely responsible for the range of fin conformations observed during different maneuvering behaviors. The kinematics of the caudal fin and the motor activity of the intrinsic caudal musculature during kick and glide, braking, and backing maneuvers, are examined and compared to our previous work on the caudal fin during steady swimming. Kick and glide maneuvers consisted of large amplitude, rapid lateral excursion of the tail fin, followed by forward movement of the fish with the caudal fin rays adducted and in line with the body to reduce surface area. Just prior to the kick, the flexors dorsalis and ventralis, hypochordal longitudinalis, infracarinalis, and supracarinalis showed strong activity. When braking, the dorsal and ventral lobes of the tail moved in opposite directions, forming an S-shape, accompanied by strong activity in the interradialis muscles. During backing up, the ventral lobe initiated a dorsally-directed wave along the distal edge of the caudal fin. Relative timing of the intrinsic caudal muscles varied among maneuvers and their activation was independent of the activity of the red muscle of the axial myomeres in the caudal region. There was no coupling of muscle activity duration and electromyographic burst intensity in the intrinsic caudal muscles during maneuvers as was observed in previous work on steady swimming.