Tracts of putative ultraviolet receptors in the retina of the two-year-old brown trout (Salmo trutta) and the Atlantic salmon (Salmo salar).

We previously showed that the brown trout possesses UV-sensitive cones in its retina that are lost in 2-year-old fish. However, present investigations reveal that in the narrow growth zone along the periphery and the ventral embryonic fissure, the formation of these cones continues in trout and salmon.