Figure 4.

Age-related changes in the phototaxis of wild-type, glass and hazy mutant flies. Box plots show the light preference indices (PIs) of wild-type (yellow), glass (cyan) and hazy mutants (pink) of different ages. Bold lines represent medians. The upper and lower quartiles are represented by the top and the bottom of each box. Whisker lines indicate the maximum and minimum data point that are closer than 1.5 interquartile range of its nearest quartile. Circles indicate outliers. We used Welch's t-test for comparing the PIs between groups (n = 7 per age and genotype) and to zero. Significance levels represent p > 0.05 (not significant, n.s.), p ≤ 0.05 (*), p ≤ 0.01 (**), and p ≤ 0.001 (***). In a 2-choice assay, groups of wild-type flies of every age showed positive phototaxis, which decreases with age (indicated by positive PI values, which were significantly different from zero). glass mutants were photoneutral at all ages (their PIs were not significantly different from zero). Newly eclosed hazy mutants showed positive phototaxis, not different from that of wild-type flies (p = 0.67, median wild-type PI = 0.83). Five day old hazy mutants and wild-type flies show a decreased positive phototaxis, but their PIs are not different from each other (p = 0.30, median wild-type PI = 0.42). Ten day old hazy mutants were photoneutral, with their PIs comparable to zero (p = 0.08) or to glass mutants (p = 0.56), and significantly different from wild-type (median wild-type PI = 0.22).