Fig. 1. Effect of the unc-23 bent-head phenotype on movement. (A) Morphology of typical wild-type and unc-23 worms. The bend in the head of the unc-23 mutant is indicated by an arrow. (B) Comparison of dispersion and chemotaxis behavior for wild-type (Biii,Biv) and unc-23 mutant (Bi,Bii) animals. Shown are representative tracks made by individual unc-23 mutants and wild-type animals in the absence of a gradient (Bi,Biii) and in the presence of a radial gradient of chemical attractant (NH₄Cl; Bii,Biv). The unc-23 track comprises a series of curls visible in the expanded inset. Note that the handedness of the curls, indicative of turning bias (clockwise), is opposite to the handedness of the spiral track (counterclockwise). Pirouette initiation events are indicated by orange crosses superimposed on the magnified track within the inset. Animals were started near asterisks; the gradient peak is indicated by the plus sign. Color represents time, as shown in the key. Elapsed time was 20 min for tracks Bi, Biii and Biv, and 90 min for the track in Bii. (C,D) Distributions of turning bias and instantaneous speed for wild-type (black lines) and unc-23 mutant (solid gray bars) animals. Arrowheads indicate the average for each distribution.