Locomotion is altered in mbl-1 mutants . (A, B) Cartoon of typical backwards locomotion stimulated by tapping the head for wild type (A) and mbl-1(tm1563) (B). The thick gray line and gray arrow indicate tracks and direction of forward movement. The solid black line represents backwards movement. In the diagram, anterior is to the left and dorsal is up. A red triangle on the circular diagram indicates the final angle that would be recorded in this example of the backwards locomotion assay. (C, D) Frames from movies of backwards locomotion where the stimulus is delivered at t = 0 s (C', D'). Both (C, D) are at -2 s. (C", D'') Images of the final worm position before re-starting forwards locomotion (C'', t = 2 s; D'', t = 6.3 s). (E) Quantification of the angle of backwards locomotion for wild type, mbl-1(tm1563) and transgenic strains where mbl-1 is expressed under the control of neuronal- or muscle-specific promoters. A positive angle represents a ventral preference during backing. Error bars represent standard error of the mean. ***P < 0.0001, t-test.