Figure 4

Somatostatin 1.1 null mutant larvae explore more by deploying longer and faster forward swims. (a) Left, Superimposed images illustrating the sequence of positions observed during a forward swim (scale bar, 1 mm); right, typical forward swim showing the tail angle trace over time with a maximal bend amplitude below 25 degrees. Subsequent peaks (grey circles) correspond to each bend amplitude. (b) Left, superposed images illustrating the sequence of movements during routine turn (scale bar, 1 mm); right, tail angle trace over time of typical routine turn showing the maximal bend amplitude above 25 degrees. (c1–c6) Forward swims in sst1.1^icm40/icm40 mutant (red, ‘−/−’) had larger distance traveled (c1, mean ± SEM 0.56 ± 0.02 mm versus 0.48 ± 0.03 mm in WTs; Wald χ²(1) = 7.340, p = 0.027), bout duration (c2, mean ± SEM 0.27 ± 0.004 s versus 0.26 ± 0.004 s in WTs; Wald χ²(1) = 7.171, p = 0.030), speed (c3, mean ± SEM 1.96 ± 0.06 mm/s versus 1.78 ± 0.07 mm/s in WTs; Wald χ²(1) = 6.955, p = 0.033) and median bend amplitude (c4, mean ± SEM 2.88 ± 0.10 degrees versus 2.57 ± 0.07 degrees in WTs; Wald χ²(1) = 6.529, p = 0.042) but no difference in number of oscillations (c5, mean ± SEM 3.47 ± 0.07 versus 3.29 ± 0.08 in WTs; Wald χ²(1) = 2.789, p = 0.380), tail beat frequency (c6, mean ± SEM 11.66 ± 0.09 Hz versus 11.84 ± 0.10 Hz in WTs; Wald χ²(1) = 1.785, p = 0.726). Black lines, median; Orange lines, mean. M_eff = 4.003. (d1–d6) Routine turns were undistinguishable in sst1.1^icm40/icm40 mutant larvae compared to WTs siblings: Bout distance (d1, mean ± SEM 1.57 ± 0.04 mm versus 1.49 ± 0.05 mm in WTs; Wald χ²(1) = 1.910, p = 0.755); bout duration (d2, mean ± SEM 0.38 ± 0.01 s versus 0.37 ± 0.01 s in WTs; Wald χ²(1) = 4.025, p = 0.203); speed (d3, mean ± SEM 3.86 ± 0.05 mm/s versus 3.86 ± 0.07 mm/s in WTs; Wald χ²(1) = 0.021, p = 1); median bend amplitude (d4, 4.87 ± 0.14 degrees versus 4.60 ± 0.17 degrees in WTs; Wald χ²(1) = 1.853, p = 0.784); number of oscillations (d5, 5.42 ± 0.16 versus 5.12 ± 0.13 in WTs; Wald χ²(1) = 2.464, p = 0.526); tail beat frequency (d6, 11.68 ± 0.08 Hz versus 11.84 ± 0.07 Hz in WTs; Wald χ²(1) = 2.054, p = 0.686). Black lines, median; Green lines, mean. Each point represents the median for one fish over the 5 min-long recording. M_eff = 4.518. Comparison between 62 WT larvae from 4 clutches (17 834 bouts) and 58 sst1.1^icm40/icm40 mutant larvae from 4 clutches (16 043 bouts) were tested with Wald χ².