Fig. 3. Mechanosensory neurons affect the frequency but not the shape of the forward-swimming gait. (A) The shape of the forward swimming gait of mec-4(d) (light gray) and mec-6(u450) (dark gray) mutant worms does not vary with mechanical load. The solid line shows the line fit to wild-type data from Fig. 2A. (B) The temporal frequency of the swimming gait of mec-4(d) and mec-6(u450) mutants decreases with increasing mechanical load but is offset to higher temporal frequencies than in wild-type worms. The solid line shows the line fit to wild-type data from Fig. 2B. Each measurement in A and B corresponds to data from 10-15 worms and 30-60 s of video (means ± 1 s.e.m.). (C) The shape of the forward-swimming gait of young adult worms in 1% methylcellulose is unaffected by the mec-4(d) or mec-6(u450) mutations or by ablation of the ALM or PLM touch receptor neurons. The number of worms analyzed in each measurement is shown in parentheses. Standard deviation errors bars, typically ±5% of the mean value of each measurement, are smaller than the data points. Neither mec-4(d) or mec-6(u450) mutants are distinguishable from wild-type (P>0.01). None of the laser-ablated worms are distinguishable from the mock surgical controls, in which worms were prepared for laser surgery but not irradiated (P>0.01). (D) The temporal frequency of the swimming gait of young adult worms is significantly increased by mutation or laser ablation. Error bars indicate one standard deviation. Differences between mutant and wild-type and between laser-ablated worms and mock surgical controls are indicated at P<0.01 and at P<0.001.