MUSCLE LENGTH CHANGES DURING SWIMMING IN SCUP - SONOMICROMETRY VERIFIES THE ANATOMICAL HIGH-SPEED CINE TECHNIQUE

Recent attempts to determine how fish muscles are used to power swimmi ng have employed the work loop technique (driving isolated muscles usi ng their in vivo strain and stimulation pattern). These muscle strains have in turn been determined from the anatomical high-speed cine tech nique. In this study, we used an independent technique, sonomicrometry , to attempt to verify these strain measurements and the conclusions b ased on them. We found that the strain records measured from sonomicro metry and the anatomical-cine techniques were very similar. The ratio of the strain measured from sonomicrometry to that from the anatomical -cine technique was remarkably close to unity (1.046+/-0.013, mean +/- S.E.M., N=15, for transducers placed on the muscle surface and correc ted for muscle depth, and 0,921-c0,028, N=8, in cases where the transd ucers were inserted to the average depth of the red muscle). These mea surements also showed that red muscle shortening occurs simultaneously with local backbone curvature, unlike previous results which suggeste d that white muscle shortening during the escape response occurs prior to the change in local backbone curvature.