FIGURE 4.

Age-dependent startle responses evoked by illumination changes and thigmotaxis in 4–6 dpf Dc larvae. (A) Startle responses with standard error of the mean (SEM; shaded area) of 4 dpf (green, n = 32), 5 dpf (blue, n = 28), and 6 dpf (red, n = 40) Dc larvae depicted from 2 s before (2,398 s) to 18 s after (2,418 s) the first light (swimming phase; blue) to dark (dark phase 1; gray) switch (see also Supplementary Figure 2A); a dotted black rectangle indicates the 1 s time interval that was used to compare the velocity of the larvae in (B). (B) Violin plots depicting the velocity of 4–6 dpf Dc larvae during 1 s (2,400–2,401 s) following the first light to dark switch (see also Supplementary Figure 2B). (C) Startle responses of 4–6 dpf Dc larvae depicted 2 s before (2,998 s) and 18 s after (3,018 s) the first dark (gray) to light (yellow) switch; see also Supplementary Figure 2C; a dotted black rectangle indicates the 1 s time interval that was used to compare the velocity of the larvae in (D). (D) Violin plots depicting the velocity of 4–6 dpf Dc larvae during 1 s (3,002–3,003 s) following the first dark to light switch (see also Supplementary Figure 2D). Note that 5 and 6 dpf Dc larvae increase their velocity significantly more than 4 dpf. Kruskal–Wallis test followed by Dunn’s multiple comparisons test was used to analyze differences in velocity between 4 and 6 dpf Dc; p > 0.05 is abbreviated as not significant (n.s.). (E,F) Violin plots depicting the time spent in the outer zone of the wells show an age-dependent increase in thigmotaxis in 5 and in 6 dpf compared to 4 dpf Dc larvae during the habituation and swimming (E) and also during the light and dark phases (F). Two-way ANOVA followed by Šídák’s or Tukey’s multiple comparisons test was used to analyze differences in thigmotaxis between phases of the light-dark test in and between 4 and 6 dpf Dc; p > 0.05 is abbreviated as not significant (n.s.).