Fig. 3. Movement preceding isothermal tracks. (A) Scatter plot indicating the duration and direction of the run preceding each isothermal track of wild-type worms navigating a linear thermal gradient with 0.7°C cm^-1 steepness. Black arrow indicates direction of the thermal gradient. For presentation purposes, the start points of all isothermal tracks are centered at the origin, and the isothermal tracks corresponding to each data point are aligned to the direction of the gray arrow. Black circles indicate the start point of the run preceding each isothermal track relative to the start-point of that isothermal track. Radial distance from the origin represents the duration of the preceding run (see scale bar), and the orientation is indicated by the angle with respect to the directions of the linear thermal gradient. Data corresponding to 700 isothermal tracks are shown. Preceding runs <10 s in duration are excluded. (B) Histogram of the orientation of the run preceding each isothermal track, using data from Fig. 2A. The dip at 0° indicates that isothermal tracks are not typically preceded by runs with strong isothermal alignment in the opposite direction. Also, the dip at 180°C indicates occurs because preceding runs closely aligned with the isothermal track tend to be categorized as part of the same isothermal track. (C) Representative trajectories of C. elegans that left one isothermal track and rapidly began tracking a new isotherm at a different temperature. Open circles indicate worm centroid position at 5 s intervals.