RETINAL ELLIPSOSOMES - MORPHOLOGY, DEVELOPMENT, IDENTIFICATION, AND COMPARISON WITH OIL DROPLETS

We report some unique features of retinal cone ellipsosomes in mountai n-stream teleosts. They have also been compared with oil droplets occu rring pre dominantly in many reptilian and avian retinas. Ontogenetica lly, ellipsosome differentiation from ellipsoidal mitochondria occurs with advanced eye growth (diameter> 1 mm). In juvenile leaches, they a rise almost simultaneously in the dorsal and ventral retina, whereas i n cyprinids, they appear first dorsally in bottom-dwelling early juven iles (approximate age 3-4 months), and then in the ventral retina in m igratory late juveniles (eye diameter>4 mm, approximate age 2 years). The significance of the pattern of ontogeny of ellipsosomes in these s tream fishes is discussed in relation to their utilization of a comple x habitat during life. All adult cones possess conspicuous ellipsosome s. Histochemically, they react strongly with phosphotungstic-acid hema toxylin, a dye specific for proteins, whereas oil droplets refuse to d o so (studied in turtle and pigeon). This reflects a major chemical di fference between the two types of globules. Since ellipsosomes are pre sent in the double cone accessory unit (which in higher vertebrates la cks an oil droplet) and since they appear late ontogenetically during advanced eye growth, they cannot be related to oil droplets, which hav e an embryonic developmental program.