STUDIES ON THE OOPLASMIC SEGREGATION IN THE EGG OF THE FISH, ORYZIAS LATIPES. III. ANALYSIS OF THE MOVEMENT OF OIL DROPLETS DURING THE PROCESS OF OOPLASMIC SEGREGATION

¹ Department of Biology, Tokyo Metropolitan University, Tokyo, Japan

The movement of oil droplets in Oryzias eggs, natural and artificially injected, was analyzed during ooplasmic segregation. (a) During 2-4 minutes after fertilization, natural oil droplets are shifted transiently toward the animal pole, followed by a stationary phase of about 20 minutes. After this phase, all of the oil droplets coming either from the animal or from the vegetal side assemble at about -60° below the equator as a ring and later reach the vegetal pole. The migration is faster in droplets coming greater distances than in those coming shorter distances. (b) The pattern of the migration of injected oil droplets is the same as that of the natural ones, irrespective of their nature. The migration is possible in weakly centrifuged eggs in which the protoplasm remains undisturbed in the cortex. However, injected oil droplets no longer move after shifting of the protoplasm by strong centrifugation or after the completion of ooplasmic segregation.