Localization of a putative epiboly-determining factor in oocytes of the goldfish (Carassius auratus)

It is unknown whether cytoplasmic determinants in goldfish eggs are asymetrically localized before maturation. In this study fully grown goldfish oocytes with intact germinal vesiles (GVs) were ligated with baby hair loops along desired planes into two parts, matured in vitro, and inseminated. Embryos developed from the animal halves with GV of oocytes ligated along the equator were unable to undergo epiboly, while those developed from the GV-containing parts of oocytes ligated along the animal-vegetal axis were able to. Also, embryos developed from the animal halves obtained from fertilized eggs could undergo epiboly. From these results, it was postulated that the goldfish's premature oocyte possessed a putative factor in the vegetal hemisphere which was responsible for epiboly of the embryonic cells. This work was supported by the NSFC and the “Climb Plan B” (PD-B6-1-1) of the Chinese Commission of Science and Technology. Contribution No. 2915 from the Institute of Oceanology, Chinese Academy of Sciences.