Figure 4: Histograms of increasing and decreasing speed effects relative to the control levels for Daphnia magna exposed to different concentrations of esfenvalerate in the “Multi-DaphTrack” system. The average speed change relative to controls is calculated by dividing the average speed difference between exposed-Daphnia and controls by the average speed value of the controls at 7- fixed times (i.e., 1, 2, 4, 8, 12, 24 and 48h). * Significantly different from the control level (Pvalue<0.01).