Figure 1.

Figure 1.

Orienting behavior of zebrafish toward conspecifics. A, Apparatus for orienting behavior. Two large tanks (L 9 × W 18 × H 6 cm, filled to 5.7 cm with water) were placed across a divider made of a light-dimming electrochromic film. The 25% area of the tank divider side was set as the ROI. B, Orienting angle. Behavior of looking at fish in the opposite tank at the head angle ±22.5–67.5° (orienting angle) from the direction perpendicular to the divider was considered orienting behavior. C, Time course of orienting behavior assay. Zebrafish were first placed in the tanks and allowed to swim ad libitum for 20 min to acclimate to the tanks (acclimatization). The swimming behavior was then recorded for 5 min when the divider was opaque (no-stimulus), followed by 5 min of swimming behavior when the divider was transparent (social stimulus). D, The percentage of the time in which zebrafish stayed in the ROI under no-stimulus or social stimulus conditions. E, The percentage of the time in which zebrafish exhibited the orienting angle in the ROI under no-stimulus or social stimulus conditions. Wild-type zebrafish stayed in the ROI and showed the orienting angles for a significantly longer period under the stimulus condition compared with the no-stimulus condition (n = 20 each in D; n = 20 each in E). F, G, The percentage of the time spent in the ROI and the percentage of the time that fish show the orienting angle when using a combination of standard (L 9 × W 18 × H 6 cm) and short (L 9 × W 9 × H 6 cm) tanks. Zebrafish behavior in the large tanks was analyzed. They stayed in the ROI and showed the orienting angle for a longer period under the stimulus condition than the no-stimulus condition (n = 10 each in F; n = 10 each in G). H, I, The percentage of the time spent in ROI and the percentage of the time showing orienting angles for isolated zebrafish reared with no other fish in sight until adulthood. Two large tanks were used. Isolated zebrafish stayed in the ROI and showed the orienting angles comparable with those of control zebrafish (n = 10 each in H; n = 10 each in I). J, K, Zebrafish orienting behaviors toward medaka. After analyzing the orienting behavior of zebrafish toward zebrafish, the orienting behavior of zebrafish toward medaka was analyzed. When medaka was used as a stimulus, zebrafish stayed in the ROI and showed the orienting angle for less time than when zebrafish was used as stimulus (n = 10 in J; n = 10 in K). See Extended Data Figure 1-1 for more details.