Twin Formation in Xenopus laevis Eggs Centrifuged before First Cleavage : Developmental Biology

概要

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Twin formation was studied in the fertilized Xenopus eggs by means of low speed centrifugation (15-30×g) for a short period (20sec to 5min) before first cleavage. Dejellied eggs were embedded in gelatin with a vertical orientation (animal pole up), but randomly oriented with reference to the sperm entrance site. They were then spun with the centrifugal force vector at right angles to the animal-vegetal axis. When the eggs were centrifuged at T = 0.3-0.6 (30-60% of the time interval to first cleavage), a large number of twin embryos developed, whereas when centrifuged after T = 0.7 twin embryos were almost never obtained. Morphological features of the twin embryos were briefly described. They showed a rather continuous spectrum from almost normal to completely double-axes embryos. The twin embryos were tentatively grouped into 6 categories based on the degree of twinning. Twin embryos with clear double-axes were divided into 3 groups in regard to the spatial relationships between the two axes. All double-axes embryos developed from the gastrulae which had shown two blastoporal lips. Possible mechanisms of twinning are discussed in terms of a postcentrifugal modification of the localization of the "dorsal determinants" which specify the future dorsal side of the embryos.
社団法人日本動物学会の論文
1987-06-15