Ras mutants exhibit abnormal locomotion behavior under poor circumstances. (A, B) Tracks representative of wild type and the let-60(n2021lf) mutant in blank plates. The wild-type crawls around the field randomly, whereas the let-60(lf) mutant continues to move in a loopy pattern, termed circular locomotion (CL). (C, D) Average curving rate of wild type and let-60(lf) mutants for a fixed time (20 minutes) (C) or a fixed distance (30 mm) (D) of exploratory behavior (n ≥12,000 data points). Positive or negative values indicate curves toward ventral or dorsal sides, respectively. Asterisks indicate significant differences compared with wild-type animals (***P <10−10, Student’s t-test). (E) Histograms of curving rate in wild type and let-60(lf) mutants in the fixed distance (30 mm). (F) Quantitative analysis of directional locomotion. The median of log10(Lδ/L0) at the distance of size δ in wild-type and let-60(lf) mutants is shown in log-log scale (n ≥30 animals) when analyzed in the fixed distance (30 mm). Error bars represent the first and the third quartile.