Notch is required for successive cell divisions in the developing Drosophila retina

Abstract

Following activation by UV-irradiated sperm, diploid eggs of the allotetraploid hybrids (red crucian carp ♀×common carp ♂) developed into normal live gynogens. Cold-shocking these activated diploid eggs failed to induce the expected tetraploidy in them. All these gynogenetic progenies, generated with or without the cold shock, were female diploids with 100 chromosomes, indicating the XXXX genotype of the tetraploid females. The gynogenetic females matured at the age of 2+ suggesting delayed maturity, in comparison to the diploid females of the red crucian carp. Thirty percent of these gynogens were fertile with normal ovary and mature eggs. These gynogens were not morphologically distinguishable from the F2 hybrids. Like the diploid F2 hybrids, these diploid gynogens produced diploid eggs, for these eggs developed into triploids with 150 chromosomes, when crossed with red crucian carp. Without the treatment for doubling the chromosome number, the diploid eggs, produced by the F1 gynogens, developed into the F2 gynogens following activation by UV-irradiated sperm. Production of these diploid eggs from the diploid gynogens may have resulted from the pre-meiotic endoreduplication of chromosomes. For aquaculture, these diploid eggs remain an important gamete source for the production of tetraploids and triploids, and establishment of diploid gynogenetic hybrid line.