Fine structure and radioautography of retinal cone outer segments in goldfish and carp.

Cone but not rod outer segments (OSs) in the retinas of goldfish and carp are diffusely labeled after intravitreal injection of 3H-fucose. Among the different cone types, the OSs are heavily labeled in the long double, short single, and some long single cones. The OSs of short double and the remaining long single cones are consistently more lightly labeled. A correlation thus exists between heavy labeling of OSs maximally sensitive to red and blue light and lighter labeling of OSs with maximum sensitivity to green light, and this may reflect different carbohydrate compositions of the cone visual pigments. New information is presented on OS fine structure of rods and cones, and on differential marking of cone OSs with the extracellular tracers horseradish peroxidase (only green-sensitive cone OSs "stained") and microperoxidase (red- and blue- but not green-sensitive cones OSs "stained").