Fig. 4

Fig. 4 BL-induced migration of melanophores allows temporal disruption of pattern formation. mitfa:ChR2(C128S/D156A) stable transgenic fish were reared under different light conditions. Fish were maintained under normal light until 5 wpf. (A, B) Transgenic fish continuously maintained in the dark starting from 5 wpf showed a near-normal stripe pattern at 10 wpf (A, 17.5 mm SL, number of samples: n = 7) and 15 wpf (B, 21.4 mm SL, n = 3). (C, D) Transgenic fish continuously exposed to BL starting from 5 wpf showed a disrupted stripe pattern at 10 wpf (C, 17.5 mm SL, n = 3) and 15 wpf (D, 22.5 mm SL, n = 12). (E, F) Transgenic fish exposed to BL from 5 to 10 wpf and then transferred to the dark showed a disrupted stripe pattern at 10 wpf (E, 19.4 mm SL, n = 6); a pattern was regenerated at 15 wpf, but the stripes in the trunk mostly lacked horizontal directionality, especially anteriorly, whereas those in the tail regained a pattern highly reminiscent of that of the WT (F, 23.2 mm SL, n = 3). (G–J) Magnified images showing the time course of pattern regeneration in the dark; ambiguous stripe boundaries became distinct after 5 weeks. Numbers above each panel indicate weeks elapsed after transfer to the dark condition. White dashed lines indicate boundaries between melanophore and xanthophore regions at 5 weeks after transfer to the dark (J). The boundaries were overlaid on images of 1 week and 3 weeks after transfer (H, I). The pattern disruption/regeneration experiments were perfumed more than three times. Black scale bar, 10 mm; white scale bar, 500 µm.