The horizontal cells in the retina of the owl, Tyto alba, and owlet, Carinae noctua

Abstract One type of short-axon horizontal cell (HC) and one type of axonless HC are described in the retina of Carinae noctua , a crepuscular bird and Tyto alba , a pure nocturnal bird. The axonless HCs in both birds are similar to type II axonless HC found in diurnal birds. The short-axon HC of Carinae noctua is similar to the same cell type found in diurnal birds; the only differences being the axon length. The short-axon HC of the Tyto alba retina is morphologically different from the same cell type found in the retina of diurnal birds and Carinae noctua and very similar to the short-axon HC described in the mammalian retina and the primate retina in particular. The striking similarity between the short-axon HCs found in the retinas of owl and primates may be related to the same rod-cone ratio found in these retinas.