Figure 5

Optomotor response (OMR) of the lws^a:b mutant under monochromatic red light. The lws^a:b mutants (n = 6) were individually tested for OMR at every 10 nm in λ = 720–750 nm and 800–850 nm (light-grey bars). Dark-grey bars indicate the wild type (n = 5)³¹. Mean and standard error of the mean are shown. An asterisk indicates a significant difference between the wild type and mutant (P < 0.05; Student’s t test without correction). Different letters in the bars (a–d in the wild type and w–z in the mutant) indicate a significant difference according to a one-way ANOVA and the Tukey post hoc HSD test (P < 0.05). The OMR was evaluated by three parameters: (a) the average time (s) when fish started OMR (delay), (b) the average period (%) fish continued the OMR (duration), and (c) the total distance of swimming (round) towards the direction of the rotating stripes (distance). The fish occasionally showed no interest in the rotating stripes, which leads to values supporting low OMR (e.g., at λ = 730 nm of the lws^a:b mutants). However, such low OMR could be recovered at longer wavelength (e.g., λ = 810 nm), indicating that the low OMR was because of not decreased photosensitivity but decreased interests in the rotating stripes.