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Figure 1


Fig. 1. Isothermal tracks. (A) Representative isothermal tracks of wild-type worms (N2 strain) cultivated at 20°C navigating a radial thermal gradient on the surface of a 9-cm diameter agar plate. The temperature from center to edge is 18.5 to 21.5°C, corresponding to 0.7°C cm-1 steepness. The trajectory of each isothermal track on the spatial gradient is shown by open circles connected by black lines, with each circle indicating position of the worm centroid at 10 s intervals throughout each track. For purposes of presentation, the undirected movements before and after each isothermal track are not shown. (B) Histogram of the absolute temperatures of ~400 isothermal tracks made by wild-type worms cultivated at 20°C navigating linear thermal gradients from 15-25°C. (C) Percentage of time spent in isothermal movement of wild-type worms navigating defined spatial thermal gradients, quantified for each data point by totaling the duration of each isothermal movement exhibited by 60 worms in 30 min of observation on linear thermal gradients, and then dividing by 1800 min. Error bars represent ± 1 s.e.m. (D) Histogram of the durations of ~400 isothermal tracks made by wild-type worms navigating a radial thermal gradient with 0.7°C cm-1 steepness. The solid line shows a fit to an exponential function ({tau}=80 s; P>0.5). (E) Mean durations of isothermal tracks of wild-type worms navigating radial spatial thermal gradients with 0.2, 0.7, and 1.2°C cm-1 steepness (black circles). Each point represents data from ~400 tracks. For comparison, the mean duration of ~1000 runs exhibited by wild-type worms navigating an isotropic environment at 20°C is also shown (open circle at 0°C cm-1). Error bars represent ± 1 s.e.m. (F) Percentage of time spent in isothermal movement of wild-type (WT) and mutant worms navigating spatial thermal gradients with 0.5°C steepness, quantified for each data point by totaling the duration of each isothermal movement exhibited by 60 worms in 30 min of observation on linear thermal gradients, and then dividing by 1800 min. Error bars represent ± 1 s.e.m.