Fig. 5

The optomotor response (OMR) under monochromatic lights after light or dark adaptation. (a) and (b) Validation criteria during the O-O test: a, OMR-positive; b, OMR-negative. Yellow dotted arrows indicate directions of the cylinder rotation. Blue arrows indicate all fish in the aquarium (n = 5) are following the stripes, whereas red arrows indicate the fish are swimming independent of the cylinder rotation. We switched the direction of cylinder rotation every 30 s and observed if all the fish started following within 10 s. These pictures are frames of movies recorded at λ = 760 nm using the control (a) and lws ⁻ (b) fish. (c) Summary of the results using light-adapted fish. We started the OMR test at λ = 720 nm, where both the control (blue) and lws ⁻ (red) fish had followed the stripes in the preceding experiments (data not shown). After each test, we repeated it under monochromatic light with a wavelength 10 nm longer until λ = 840 nm (yellow arrow), where all the fish had stopped following the stripes. Each circle is an average of two independent experiments. Error bars are attached when applicable. Note that the lws ⁻ mutants stopped following stripes by λ = 750 nm, whereas the control fish continued following until λ = 830 nm. (d) Summary of the results using dark-adapted fish. We started the OMR test at λ = 840 nm, where none of the control (blue) or lws ⁻ mutant (red) fish had followed the stripes in the preceding experiments (data not shown). After the test, we repeated it under monochromatic light with a wavelength 10 nm shorter until λ = 800 nm (blue arrow), where all the fish started following the stripes. Note that both the control and lws ⁻ mutant fish started to respond to lights at λ = 820 ~ 830 nm. That is, the lws ⁻ mutants could behaviorally respond to monochromatic lights at λ = 750 ~ 830 nm only when they had been dark-adapted