Fig. 2. Starvation inactivates the mechanism for cryophilic movement. (A) When wild-type (WT) worms that were grown overnight at 15°C then starved for 24 h at 15°C are placed near the middle of the linear thermal gradient, they exhibit nearly random dispersal. (B) From snapshots of the temperature positions of individual worms on the spatial thermal gradients, we calculated the mean temperature of the population, and we plotted the mean temperature over time for worms that had been starved for different durations. Worms were initially placed near 20°C, and a subsequent decrease in the mean temperature indicates cryophilic movement. The speed of instantaneous forward-crawling movements exhibited by individual worms in each experiment is indicated in italics (mean ± s.d.), showing that the atactic behavior caused by starvation is not simply due to lack of mobility.