Fig 1

(A) Schematic of the experimental procedure. Embryos were kept under constant darkness (solid black bar) or a 14/10 h day/night cycle (striped bar) until the behavioral experiments. Each behavioral section had two components; free-swimming for 10 min under light (open circle; white) or dark (solid circle; black) conditions after a 50 min acclimation period under same illumination condition, and a set of startle responses (280 ms) where a sequence of three taps was executed with 6-minute interval; arrows designate timing of taps. (B, C) Both larvae housed under continuous darkness or a day/night cycle showed significantly more activity during free-swimming when tested under light conditions, compared to dark test conditions. (D, E) For larvae housed under continuous darkness we observed no differences in startle behavior, but larvae housed under a day/night cycle showed significantly lower activity during startle behavior when tested under light conditions, compared to dark test conditions. Free-swimming: n = 23–24 per group, startle response: n = 18–21 per group. Data is presented in scatterplots showing individual values and group mean or median. Significance: *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001.