Fig. 7. Retinal maps of cone distributions in the retina of rainbow trout from the alevin to the adult (N=4 per map). (A,B) Mean cone density and percentage of single cones that express UV opsin mRNA (in brackets) in the retina of the alevin (A) and parr (B). All locations had square mosaics complete with corner cones such that d/s was 1. The overwhelming majority of single cones in the alevin retina expressed UV opsin. Shown for the parr retina (B) are the approximate regions with cones expressing only blue opsin mRNA (blue), a combination of UV and blue opsin mRNA (mostly as corner cones expressing UV opsin mRNA and centre cones expressing blue opsin mRNA, but with some cones co-expressing the two transcripts; UV-blue), and cones expressing only UV opsin mRNA (UV). (C,D) Mean cone density and associated d/s ratio (in parentheses) in the retina of the smolt (C) and the adult (D). All single cones in the main (non-peripheral) retina expressed blue opsin mRNA. For each retina, the area within the red perimeter had high corner cone densities (d/s ratio <1.4). Cone densities are expressed in thousands per square millimetre. A larger circle indicates that the mean cone density for that location was at least 1 s.d. above the mean from all locations pooled together. A smaller circle indicates the opposite. In salmonid fishes, the embryonic fissure (ef) runs from the ventral to the central retina (approximate location of the optic nerve head), pointing toward the temporal retina. D, dorsal, N, nasal. Magnification bar is 0.11 cm in A, 0.12 cm in B, 0.33 cm in C and 0.39 cm in D.