Figure 1.

Ethanol attraction of Drosophila melanogaster larvae. (a) Scheme of the experimental procedure. Larvae were allowed to choose within 5 min between control agarose and a substrate containing different concentrations of ethanol ranging from 1 to 50%. (b) Wild-type Canton-S (red) and mutant w¹¹¹⁸ (white) larvae are attracted to ethanol following a Gaussian-shape like dose response curve. The highest behavioral response (preference index (Pref)) was seen at 8% ethanol for both strains (Pref^Canton-S = 0.62, ci = 0.53–0.68, Pref^w1118 = 0.60, ci = 0.51–0.74). All groups are significant different from zero, except for 1% w¹¹¹⁸ (one-sample t test, p < 0.17). Multiple comparison indicates a significant difference between the two genotypes for 10% and 20% ethanol (Wilcoxon-Rank, p^10% < 0.001, p^20% < 0.001). Letters above each box-plot indicate differences between only Canton-S (red) and mutant w¹¹¹⁸ (white) larvae, respectively. (c) Larval 8% and 20% ethanol substrate choice over a test period of 120 min. Canton-S larvae did not vary in their attraction within 120 min to 8% ethanol (Kruskal Wallis, p < 0.032). (Pref^5min = 0.55, ci = 0.47–0.6, Pref^10min = 0.65, ci = 0.53–0.69, Pref^15min = 0.63, ci = 0.6–0.73, Pref^30min = 0.53, ci = 0.5–0.67, Pref^60min = 0.5, ci = 0.45–0.61, Pref^120min = 0.57, ci = 0.39–0.59). However, the initial attraction for 20% ethanol turns into an avoidance after about 15 min of ethanol presentation (Pref^5min = 0.15, ci = 0.03–0.25, Pref^10min = 0.1, ci = − 0.04 to 0.25, Pref^15min = − 0.16, ci = − 0.38 to 0.1, Pref^30min = − 0.33, ci = − 0.52 to − 0.05, Pref^60min = − 0.46, ci = − 0.64 to − 0.27, Pref^120min = − 0.62, ci = − 0.5 to − 0.69). Indicated values show medians; error bars represent standard errors. (d) Canton-S larvae raised on standard food that contains 1% ethanol (ethanol +) shows a substrate choice behavior that was not different from larvae that were raised for one (ethanol—[1]) or two generations (ethanol—[2]) on ethanol free food (TukeyHSD, p^standard-w/o < 0.202, p^{standarad-w/o2} < 0.639). Note a slight increase in ethanol substrate choice with increasing generations of ethanol food free raised flies (TukeyHSD, p < 0.03). Differences against zero are indicated in red and black at the bottom of each panel. Sample size for each box plot is n = 16. Significant differences between the two groups are given with letters. Preference scores and statistical tests underlying the different indices are documented in the Supplementary material.