Fig. 5
From: Search strategy is regulated by somatostatin signaling and deep brain photoreceptors in zebrafish
Local and outward movement strategies differentially facilitate locating local and remote light. a Schematic of covert phototaxis assay. The light spot (14 mm diameter) was projected 7 mm directly behind a freely swimming larva. We then measured the time for the larva to enter the light spot. b Time to light spot perimeter when activated either 2 s (T0) or 3–5 min (T4) (mean 248 ± 19.6 s, depending on when larvae entered the motion trigger region of interest (ROI)) after loss of full field illumination. Controls: no target light. N = 33 (T0 control), 40 (T0 with spot), 18 (T4 control), 20 (T4 with spot). c Turn maneuver trajectories for larvae oriented with the light spot to their right, when tested 2 s (T0) or 3–5 min (T4) after loss of full-field illumination. d R-turn direction bias during phototaxis relative to a static light spot. Light spot (9 mm diameter, intensity of 20 μW/cm2) was illuminated either 2 s (grey; N = 22 groups of 15 larvae) or 3 min (black; N = 20 groups) after loss of full field illumination. Orientation of larvae relative to the target spot is indicated. * P < 0.05 between T0 and T4 orientation-matched groups. Bias is the proportion of R-turns directed toward the target spot, normalized between –100 (consistently away from target) to +100 (always toward target). e Phototaxis in a large area (200 × 200 mm) using a 55-μW light spot. Representative swim trajectories for larvae tested when the light spot was activated 1 s (T0, grey traces) or 3–5 min (T4, black traces) after loss of illumination. Arrowheads indicate start positions. Box plot shows closest approach to the light spot for larvae tested 1 s (T0, grey) or 3–5 min (mean 247.7 ± 21 s; T4, black) after loss of illumination, and for trials where the light spot was not activated (No spot). N = 11 larvae (dark, T0), 13 (dark, T4). f Representative swim trajectories for larvae tested when the light spot was activated 1 s (T0, grey traces) or 3–5 minute (T4, black traces) after loss of illumination. Arrowheads indicate start positions. g Quantification of concealed target test. Closest approach to the light spot for larvae tested 1 s (T0, grey) or 3–5 min (mean 236 ± 13 s; T4, black) after loss of illumination with either no target light (No spot), or targets of the indicated intensities. Horizontal black line represents position of barrier. N = 12 larvae (no spot, T0), 12 (no spot, T4), 10 (15 μW, T0), 11 (15 μW, T4), 12 (55 μW, T0), and 9 (55 μW, T4). # P < 0.05, * P < 0.001 between T0 and T4 groups. Experiment was performed as for (e) except with an interior barrier