Fig. 2. Distribution and movement of wild-type, fed worms on a temperature gradient. Wild-type N2 adults either (A) maintained in our laboratory or (B) freshly obtained from the Caenorhabditis Genetics Center (CGC) fed at 15°C (open circles), 20°C (filled circles) or 25°C (open triangles) were placed around the center of an agar plate (which corresponds to a temperature of approximately 19°C) and incubated on a temperature gradient, as described in Materials and methods. After 1 h of incubation, distribution of worms along the gradient was determined. Approximately 30 worms were tested in one experiment and the results of several experiments were combined. Total numbers of worms (N) and experiments (in parentheses) were as follows: A: 25°C, N=130 (5); 20°C, N=175 (6); 15°C, N=163 (6); B: 25°C, N=79 (3); 20°C, N=109 (4); 15°C, N=117 (4). (C) N2 worms (CGC line) fed at 20°C were put on a temperature gradient and movement was observed for approximately 10 min. Instantaneous velocities (upper panel) and their elements in directions of the gradient (lower panels) are shown (dots) with their means in each area of the gradient (line). Positive values of velocity elements indicate movement up the gradient, and negative values indicate movement down the gradient. Results of 3743 points are shown. (D) Examples of traces observed in C are shown with starting positions (closed circles). Broken vertical lines show positions on the temperature gradient. (E) Movement of N2 (CGC) worms fed at 15°C was observed for approximately 10 min on a temperature gradient. Means of instantaneous velocities (filled circles) and their elements in directions of the gradient (open circles; positive values indicate upward movement; negative values indicate downwards movement) were obtained from 1141 intervals in total. (F) Examples of traces observed in E are shown with starting points (filled circles) and positions on the temperature gradient (broken lines).

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