Fig. 8. Micrographs of sections from the large alevin/parr retina following double label in situ hybridization with the rainbow trout UV and blue riboprobes. (A,B). Tangential (A) and radial (B) sections from the centro-temporal retina showing single cones expressing UV opsin mRNA (red colour), blue opsin mRNA (blue colour), and both UV and blue opsin mRNAs (purple colour, green arrow). (C) Tangential section from the centro-ventral retina showing corner cones expressing UV opsin mRNA and centre cones expressing blue opsin mRNA. (D) Radial section from the nasal periphery showing single cones expressing UV or blue opsin mRNA. (E–G) Tangential (E) and radial (F) sections from the mid-dorsal retina show that all single cones express UV opsin mRNA exclusively, as do single cones from the distal dorsal retina (G). (H) Radial section from the distal temporal retina showing that the majority of cones express UV opsin mRNA, though some show early signs of co-expression (green arrow). Other symbols and nomenclature as in Fig. 5. Magnification bar (in A) is 25 µm and relates to all panels.