Figure 1.

Drosophila Females Were Attracted by Sucrose and Avoid Caffeine

(A) (Left) Still frame taken during the video recording (t = 240 min) of an experiment with 12 arenas, each containing 10 females and two drops of feeding solution (in blue). The top 8 arenas contain one drop of H₂O (left) and one drop of 50 mM sucrose (right). The bottom 4 arenas contain one drop of 50 mM sucrose + 10 mM caffeine (left) and one drop of 50 mM sucrose (right). (Right) The drawing illustrates the 2 distances (d1 and d2) measured at every time frame of the video (see main text).

(B) Flies displayed a strong preference for sucrose and aversion to caffeine + sucrose. (Top) Per graphs: Kinetics of the attraction index (AI) for sucrose in a sucrose versus H₂O experiment (left), in a 50 mM sucrose versus 5 mM sucrose experiment (middle), or in a sucrose versus sucrose + caffeine experiment (right). The black lines and the gray zones correspond, respectively, to the mean and the standard deviation. (Bottom) Cumulative attraction index (CAI) area for each specified solution (arrows) and its distribution over time. For simplicity, only the mean value of the CAI obtained with multiple replicates is shown in black.

(C) Histograms built with the CAI values from (B) showing that flies have a strong and statistically significant preference for sucrose versus H₂O and for 50 mM sucrose versus 5 mM sucrose and a strong aversion for a mixture of caffeine + sucrose versus sucrose only. ∗p < 0.05 and ∗∗p < 0.01. Wilcoxon matched-pairs signed rank test, Two-tailed p value. Error bars correspond to standard deviation. The preference indexes for sucrose, for 50 mM sucrose, and for caffeine are calculated with the CAI values from C. n indicates the number of independent experimental replicates. a.u.: arbitrary unit. Data are represented as mean ± SD.