Fig. 2. Cellular distribution of various photoreceptor cells. Transverse sections (A,C,D,E) and sagittal sections (B,F) of Atlantic halibut retina (dorsal is up) at the end of the yolk sac stage (40 days post-hatching) are shown. The various photoreceptors were visualised by in situ hybridisation analysis with specific opsin probes: ultraviolet (A,B), blue (C), green (D), red (E) and rod (F). Arrows indicate the photoreceptor layer. Scale bars, 100µm.