Cytological Studies Of The Unreduced Diploid Eggs Generated From The Diploid Gynogenetic Progeny Of Allotetraploid Hybrids

Following activation by UV-irradiated sperms from scatter scale common carp and without the treatment for doubling the chromosome number, the eggs generated by the diploid gynogenetic progeny (G₁) with 100 chromosomes, developed into diploid gynogenetic progeny (G₂) with 100 chromosomes. Both the males and females of the tetraploids with 200 chromosomes were obtained from the offspring (G₁×AT) produced by mating the eggs of G₁ with the diploid sperms from the allotetraploid hybrids. The results provided the evidence that diploid G₁ was able to produce diploid eggs. Two years later, the G₂ has grown up with mature eggs. Following same methods as the production of G₂, the eggs generated by the diploid gynogenetic progeny (G₂) with 100 chromosomes, developed into diploid gynogenetic progeny (G₃) with 100 chromosomes. Some cytological characters such as chromosome number, appearance and fertilization cytology in G₂, G₁×AT, G₃ were studied in this paper, the results were as follow:1) In the oogonia of diploid six-month old G₂, only the chromosomes in the metaphase of mitosis were observed in all slides, no bivalent chromosome being found, suggesting that the oogonia in six-month old G₂ were not mature enough to meiosis I , The presence of the chromosome spreads with 100, 200 and even more than 380 chromosomes were observed in the metaphase indicated that the diploid G₂ has the potential ability to generated diploid eggs with the probable mechanism of pre-meiotic endoreduplication. In contrast, the spermatocytes of G₁×AT allotetraploids has the normal chromosomal behavior with only 100 bivalents forming in meiosis I . The one-year old G₂ possessed the slowly developmental ovary which stayed at the oogonium stage for a long time, in which no primary and mature occyte was found, whereas both the females and males of one-year old G₁×AT allotetraploids had the normal...