| 摘要: |
| 采用连续切片和光镜技术,对三疣梭子蟹卵子发生、激活和早期卵裂进行了细胞学观察。结果表明,在发育及再发育的卵巢中,三疣梭子蟹卵子发生主要经历了卵原细胞的增殖和初级卵母细胞的分化、生长、成熟这两个阶段。依据卵子发生过程中雌性生殖细胞形态的变化,这两个阶段又可细分为卵原细胞期、卵黄发生前卵母细胞期、小生长期、大生长期、近成熟卵母细胞期和成熟卵母细胞期等6期。成熟卵母细胞处于第一次减数分裂中期,这可作为卵子成熟的形态学标志。第一次减数分裂中期纺缍体长轴的旋转可以发生于卵巢中,与精子及海水的刺激无关。初级卵母细胞达到形态和生理上都成熟的时间窗口很窄。精子入卵引起卵子的激活和减数分裂的完成。23℃下离体培养时,第一和第二极体分别在卵产出后约40min和2h释放。雄原核的形成早于雌原核。雌、雄原核在卵产出后约5h通过联合形成合子核。卵产出后约6h,受精卵处于第一次核分裂后期,但卵裂沟直到卵产出后13h才能观察到,此时核已完成了2次分裂,形成合胞体胚胎。 |
| 关键词: 三疣梭子蟹 卵子发生 卵子激活 早期卵裂 |
| DOI： |
| 分类号: |
| 基金项目:浙江省自然科学基金资助项目,301213号;浙江省重大科技攻关农业项目,2004C12029号;宁波市青年基金项目,2004A620014号;’宁波市科技计划项目,01N40107-2号 |
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| OOGENESIS, OOCYTE ACTIVATION AND EARLY CLEAVAGE OF PORTUNUS TRITUBERCULATUS (MIERS) |
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ZHU Dong-Fa, WANG Chun-Lin, YU Hong-Wei
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Faculty of Life Science and Biotechnology, Ningbo University, Ningbo, 315211
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| Abstract: |
| Cytological observations were made on oogenesis, oocyte activation and early cleavage of Portunus trituberculatus (Miers) by tissue section technique and light microscopy. Oogenesis of developing or re-developing ovaries can be divided into two stages, the stage of oogonia proliferation, and the stage of differentiation, growth and maturation of primary oocytes. According to the size and shape of cells, and vitelline accumulation, six oogenetic substages, i. e. , oogonium, previtellogenic, small growth, large growth, nearly-mature and mature, were recognized. The ovary index (OI) was calculated (OI=G×100/B, where G for the gonad weight; B, the body weight). Estimated OI values were greater than 15.0 in individuals with mature oocytes. The mature oocytes were in the metaphase of the first meiosis that could be regarded as themorphological marker of oocytes maturation. The rotation of the metaphase spindle in the first meiosis could be observed in the mature oocytes of ripe ovary. The rotation was irrelevant to sperm stimulation or sea-water. The physiological maturity of primary oocyte was reached during a very narrow time-span, less than 3h, before ovulation. Newly ovulated eggs were nearly spherical in shape and about 300μm in diameter. The newly ovulated eggs were still in the metaphase of the first meiosis, and activated to accomplish the meiosis by sperm penetration. When incubated at 23°C, a condensed sperm nucleus came to rest beneath the plasmic membrane of egg, and the egg was in the anaphase of the first meiosis about ten minutes after ovulation. The first polar body was releasing about forty minutes after ovulation. Another 40 min later, the first polar body rested beneath egg envelope, and the egg was in the metaphase of the second meiosis. The long axis of the metaphase spindle in the second meiosis was nearly perpendicular to the plasmic membrane of egg. The second polar body was releasing about two hours after ovulation. It was not until one and a half hours later that the second polar body was entirely released. No further division occurred in the first polar body. The male pronucleus, with an aster, formed earlier than the female pronucleus did. And the female pronucleus formed from the daughter chromosome mass within egg plasm after the extrusion of the second polar body. The male and female pronucleus moved closer toward each other and matched into an association nucleus about five hours after ovulation. About 30 min later, the fertilized egg was in the metaphase of the first karyokinesis. And the anaphase of the first karyokinesis occurred about six hours after ovulation. Though the first karyokinesis had finished, no cytoplasmic division occurred synchronistically in zygote nor did any cleavage furrow appear. And a shallow cleavage furrow could be observed on the surface of the syncytial embryo with four daughter nuclei. This information would contribute to the chromosome set manipulations in P. trituberculatus. |
| Key words: Portunus trituberculatus, Oogenesis, Oocyte activation, Early cleavage |
