Figure 5. Distinct roles of serotonin receptors in food-driven pumping.

(a) Average pumping rates of wild-type (N2) worms, tph-1 mutants and a range of serotonin receptor mutants at different food concentration. (b) The average fraction of time spent by these worms in fast pumping at OD₆₀₀=3. Error bars as in Fig. 2, sample sizes in Supplementary Table 2. Here the threshold rate for fast pumping was taken to be 200 pumps per min for ser-4(ok512) worms and 250 pumps per min otherwise (based on c and on Supplementary Fig. 5A). The statistical significance of the difference from wild type is indicated (*P<0.05; **P<0.01; ****P<0.0001; NS, P>0.05). (c) F(r), the fraction of time spent in intervals longer than 1/r, for wild-type worms and ser-1(ok345), ser-4(ok512) and ser-4(opy024) mutants at OD₆₀₀=3, with the best fit lines (dashed) between 100 pumps per min and 250 pumps per min. The dotted vertical lines indicate the last point of the linear segment of F(r), taken as the threshold rate for fast pumping, demonstrating its slowdown in ser-4(ok512) mutants.