Temporal and Cell-numerical Organization of Embryos in the Starfish, Asterina pectinifera

概要

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In order to learn more about starfish early development the temporal and cell-numerical organization of the embryo of Asterina pectinifera was examined. The oocyte was fertilizable at any maturation stage after the breakdown of the germinal vesicle, but the optimum period for insemination resulting in normal development was between germinal vesicle breakdown and the appearance of the first polar body. In oocytes that were inseminated during this period, the timing of initiation of the first cleavage did not depend on the time of insemination, but a definite time length existed between the commencement of 1-methyladenine treatment and the first cleavage. Blastomeres divided quite synchronously until at least the 8th cleavage, and about 256 constituent cells of the blastula after the 8th cleavage were counted. Up to the 7th cleavage the intervals between cleavages were constant, and thereafter the intervals grew gradually longer. The number of constituent cells increased almost linearly up to the late gastrula stage ; the newly hatched blastula consisted of about 3,500 cells and the late gastrula, about 7,700 cells.
社団法人日本動物学会の論文
1980-09-25