(B) Distance travelled during 5 minutes of spontaneous swimming at 6 dpf quantified by motion tracking software (Noldus Ethovision). At 6 dpf, both smyhc1-/- (n = 24) and smyhc1R673H/+ (n = 11) larvae travelled significantly less than smyhc1+/+ larvae (n = 13). The central bands of the boxplots represent the median, the boxes of the boxplots represent the interquartile range (between the first and third quartile), and the whiskers represent the minimum and maximum values, up to 1.5 times the interquartile range. Outliers displayed are outside of this range. 