Figure 4

Figure 4

Assessment of rheotaxis reflects the function of the lateral line system. (A) A U-shaped tank was designed to test the rheotaxis behavior of larvae. A peristaltic pump was used to form the flow at the bottom of the tank. Larvae were placed in the right platform one by one, and they sensed the water flow from right to left. Rheotaxis was recorded by an infrared CCD. A larva with excellent rheotaxis (B) and a larva with poor rheotaxis (C) were analyzed by behavioral analysis software. Movement traces are plotted in the left panels, and the motion vectors are displayed in the right panels. The lengths of the blue segments represent the distance of each sprint, and the direction of the blue segment represents the direction of that sprint. The length of the red line segment is the ratio of the motion vectors’ sum to the motion arithmetic sum, and the direction is the direction of the sum of the vectors. (D) The rheotaxis score shows that at 0 hpi, both the CuSO₄ and BRS+CuSO₄ groups had poor rheotaxis. At 24 hpi, the rheotaxis of the BRS+CuSO₄ group was significantly lower than that of the control group and CuSO₄ group. Until 48 hpi, the rheotaxis score of the BRS+CuSO₄ group was still significantly lower than that of the control group. On the contrary, the rheotaxis of the CuSO₄ group was not significantly different from that of the control group within 24 hpi. n = 49, control group; n = 49, BRS group; n = 46, CuSO₄ group; n = 47, BRS+CuSO₄ group. The speed (E) and distance (F) of sprints were consistent across different times and between different groups. For (D–F), comparisons were performed using two-way ANOVA, with Tukey’s multiple comparisons test. All error bars show the mean ± S.E.M., *** p < 0.001, ** p < 0.01, * p < 0.05.