The fate of ultraviolet receptors in the retina of the Atlantic salmon (Salmo salar).

We have shown that fully differentiated cones in the salmon retina die as a result of apoptosis (normal cell death). These putative UV cones begin to disappear from the main retina when the fish is aged 120 days and are completely absent at day 220. However, they continue to be produced in the growth zones, ora serrata and ventral fissure, where they are shortlived and never incorporated into the main retina. The dying cones in the main retina and the growth zones are engulfed by macrophages and Müller cells.