Meeting Abstract

P3.66  Jan. 6  Mechanical power output of the pectoral fin abductor and adductor muscles of the bluegill sunfish (Lepomis macrochirus). LUCEY, K.S.*; JONES, E.A.; ELLERBY, D.J.; Wellesley College; Wellesley College; Wellesley College dellerby@wellesley.edu

Bluegill sunfish swim in the labriform mode at low swimming speeds, generating lift and thrust by beating their pectoral fins. The range of pectoral fin beat frequencies used in labriform swimming was measured in a recirculating flume at 22 ºC. The maximum speed sustained by labriform swimming was 1.22 � 0.08 body lengths/s (N = 6). At speeds greater than this, myotomal muscle is recruited to supply additional power by beating the caudal fin. The range of pectoral fin beat frequencies across the labriform speed range was 1.1 � 0.2 to 2.8 � 0.2 Hz (N = 6). The maximum mechanical power available from the adductor profundus and abductor superficialis muscles was measured across the finbeat frequency range adopted during labriform swimming using the work loop technique. The drag force acting on the body across the labriform range of speeds was determined by towing dead bluegill in the flume behind a force transducer. The ratio of power required to overcome body drag to available mechanical power increases across the labriform range. This may indicate an increase in propeller efficiency with speed. Alternatively, the maximum power available at a given fin beat frequency may exceed that actually produced in vivo. Power output of the pectoral fin musculature may be modulated by changes in strain and activation patterns in addition to the observed changes in fin beat frequency. Further data regarding in vivo muscle strain and recruitment intensity are required to resolve this uncertainty. All data are shown as mean � SEM.