Biological Properities and Reproductive Ability of Chimeric Fish Produced by Blastderm Reconstruction.

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(1) In order to contribute developmental technology, the pre-gastrula stage were studied by cytological, histological or biochemical viewpoints in goldfish. Synchronous cleavages occur 9 times every about 30min from 50min to 6h post-fertilization at 20C,and, thereafter, transpose asynchronous phase, suggesting mid-blastula transition (MBT). This timing is staged as the mid-blastula. Genomic expression of mesodermal markers, goosecoid and no tail, are detected with in situ hybridization assay from 8h post-fertilization. This timing is staged as the late-blastula.(2) Histological observation was performed for diffentiation of primordial germ cells (PGCs) in goldfish and zebrafish. PGCs were histologically detected at the 7 to 9 somite stage in goldfish and at the 6 somite stage in zebrafish, but did not before the stages.(3) In order to elucidate the origin or primordial germ cells (PGCs) of goldfish, it was investigated whether partial deletion or duplication of blastoderm at the mid-blastula stage effects on the numbers of PGCs in 10-day-larva after fertilization or not. The number of PGCs were decreased in larvac developed from the embryos extirpated lower half of blastoderm, but not in larvae from the embryos extirpated upper half of blastderm. Those were increased in larvae developed from the embryos duplicated lower half of blastoderm.(4) The chimeric fish which lower part of crucian-carp blastoderm was transplanted to the middle part of goldfish blastoderm at the midblastula stage, reproduced the eggs from two strains. The chimeric fish in zebrafish, in which entire blastoderm of golden strain was transplanted to animal part of blastoderm of wild strain at the mid-blastula stage, also reproduced the eggs of two strains.