The Journal of Experimental Biology 202, 529–541 (1999) 529 Printed in Great Britain © The Company of Biologists Limited 1999 JEB1633 MUSCLE STRAIN HISTORIES IN SWIMMING MILKFISH IN STEADY AND SPRINTING GAITS STEPHEN L. KATZ*, ROBERT E. SHADWICK AND H. SCOTT RAPOPORT Center for Marine Biotechnology and Biomedicine and Marine Biology Research Division, Scripps Institution of Oceanography, La Jolla, CA 92093-0204, USA *Present address and address for correspondence: Zoology Department, Duke University, PO Box 90325, Durham, NC 27708-0325, USA (e-mail:
[email protected]) Accepted 10 December 1998; published on WWW 3 February 1999 Summary Adult milkfish (Chanos chanos) swam in a water-tunnel over that speed range, while tail-beat frequency increased flume over a wide range of speeds. Fish were instrumented by 140 %. While using a sprinting gait, muscle strains with sonomicrometers to measure shortening of red and became bimodal, with strains within bursts being white myotomal muscle. Muscle strain was also calculated approximately double those between bursts. Muscle strain from simultaneous overhead views of the swimming fish. calculated from local body bending for a range of locations This allowed us to test the hypothesis that the muscle on the body indicated that muscle strain increases rostrally shortens in phase with local body bending. The fish swam to caudally, but only by less than 4 %. These results suggest at slow speeds [U<2.6 fork lengths s−1 (=FL s−1)] where only that swimming muscle, which forms a large fraction of the peripheral red muscle was powering body movements, and body volume in a fish, undergoes a history of strain that is also at higher speeds (2.6>U>4.6 FL s−1) where they similar to that expected for a homogeneous, continuous adopted a sprinting gait in which the white muscle is beam.