qrfp expression is not regulated by the circadian clock. A, WT larvae were entrained in 14 h/10 h light/dark conditions and transferred to constant dark at 6:00 P.M. at 6 dpf. Starting 24 h later, mRNA samples were collected every 6 h for 24 h. qRT-PCR shows that the level of per1b mRNA (gray) oscillates in a circadian manner while the level of qrfp mRNA (black) does not. Data points represent the mean ± SEM. B, WT larvae were entrained in 14 h/10 h light/dark conditions and transferred to constant dark at 12:00 P.M. at 6 dpf. Starting 24 h later, larvae were fixed every 12 h. ISH using a qrfp-specific probe shows no difference in qrfp expression during subjective day or subjective night. Each image is a 20 μm sum-of-slices projection. Three representative larval brains are shown for each time point. Scale bar, 50 μm.