Fig. 8. Tail stiffness k predicts the kinematic phenotypes (A) swimming speed U and (B) robot wobble W. Data for competition experiments (open circles) are means of 12 navigation trials for each of 30 tails. Data for biomechanical analysis (closed circles) are means of three straight-swimming trials for each of 30 tails. Lines indicate significant (<0.01) regressions on log-transformed data; data without a line failed the significance test at <0.05. Note that W for the competition experiments includes wobble caused by swimming and maneuvering (see Fig. 5).