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Production of Diploid Eggs through Premeiotic Endomitosis in the Hybrid Medaka between Oryzias latipes and O. curvinotus

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Title: Production of Diploid Eggs through Premeiotic Endomitosis in the Hybrid Medaka between Oryzias latipes and O. curvinotus
Authors: Shimizu, Yohei Browse this author
Shibata, Naoki Browse this author
Sakaizumi, Mitsuru Browse this author
Yamashita, Masakane Browse this author
Issue Date: Sep-2000
Publisher: 日本動物学会
Journal Title: Zoological Science
Volume: 17
Issue: 7
Start Page: 951
End Page: 958
Abstract: A hybrid medaka between Oryzias latipes and O. curvinotus spawns diploid eggs. We examined the cytological mechanisms of diploid egg formation in this hybrid. Oocytes in the hybrid passed through the first and second meiotic divisions and excluded two polar bodies, associated with reduction of the DNA content in oocytes. Each germinal vesicle in vitellogenic oocytes of the hybrid had 48 chromosomes with bivalent chiasmata, precisely twice the number of chromosomes in normal oocytes. These results suggest that before meiosis the chromosomes are doubled by mitosis without cytokinesis, that is, endomitosis, and that the resulting tetraploid oogonia undergo normal meiosis to produce diploid eggs. Except for a few vitellogenic oocytes that are probably derived from endomitotic oogonia, most oocytes were arrested at the zygotene stage in the hybrid ovary, suggesting the existence of checkpoint control that ensures the pairing of homologous chromosomes at prophase I, a situation differing from that in the male in which the checkpoint is at metaphase I. A sac-like structure was characteristic of the hybrid ovary. Although this structure was observed only in the hybrid, it may be a native component of the medaka ovary but difficult to observe because of its deformed outer structure due to enlargement of the inside oocytes. The present study confirms that this hybrid medaka provides a useful experimental system for investigations into the mechanisms of oogenesis and basic architecture of the ovary, which are difficult to analyze by using normal medaka.
Rights: (c) 日本動物学会 / 本文献の公開は著者の意思に基づくものである
Type: article
Appears in Collections:生命科学院・先端生命科学研究院 (Graduate School of Life Science / Faculty of Advanced Life Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 山下 正兼

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