Developmental staging in goldfish during the pre-gastrula stage

In order to contribute developmental technology, the early embryonic stages during the pre-gastrula were studied by cytological, histological or bioch emical viewpoints in goldfish Carassius auratus. Synchronous cleavages occur 9 times every about 30 min from 50 min to 6 h p ost-fertilization at 20 degrees C, and, thereafter, transpose asynchronous phase, suggesting mid-blastula transition (MBT). This timing is staged as t he mid-blastula. Genomic expression of mesodermal markers, goosecoid and no fail, are detected with in situ hybridization assay from 8 h post-fertiliz ation. This timing is staged as the late-blastula. Cytoplasmic protrusions as cell movement are ovserved after MET, and autonomous mixing of blastomer es from the late-blastula stage. Deep cells were produced from the surface part of blastomeres and central part of yolk cell during the late-blastula stage. Marginal yolk syncytial layer forms during the mid-blastula stage, b ut central yolk syncytial layer forms after the late-blastula stage. This r esult suggests that each yolk syncytial layer has a different origin of nuc lei.