Fig. 1.

Regulation of reversals and omega turns during feeding, local search, and dispersal. (A) Four different examples of reversals of different lengths and degrees of reorientation. Tracks are visible as indentations in the agar. r1, reversal with a single head swing followed by an ≈40° change in direction; r2, reversal with two head swings and an ≈70° change in direction; R3, reversal with three head swings and an ≈90° change in direction; R4, reversal with four head swings followed by an omega turn, resulting in an ≈170° change in direction. Blue dots indicate position of the animal's head at the start of the reversal. Anterior is up. In R4, D indicates the dorsal side and V indicates the ventral side of the animal during the omega turn. (B) Some omega turns occur in the absence of a reversal, but most occur after a reversal. Most omega turns occur after a reversal of length R3+ (three head swings or greater). n = 285 omega turns. Animals were scored at 1–12 min off food. (C) The longer a reversal, the more likely it is to terminate in an omega turn. n = 249 omega turns. Animals were scored at 1–12 min off food. (D) Tracks of individual animals feeding on food, in the local search period during the first 12 min off food, and during dispersal after 40 min off food. The time intervals shown represent ≈10 min, 5 min, and 30 s, respectively. (E) Frequency of short reversals (r1 and r2), long reversals, and omega turns during 5-min intervals on food and at different intervals off food.