唇精子早期入卵观察

Observation Early on Sperm Penetration into Ovum of Hemibarbus labeo

用扫描电镜对唇成熟卵子及早期精子入卵过程进行观察。结果显示,唇成熟卵子在动物极中央有一深凹陷的表面光滑的精孔器,其外径2.512μm,内径2.330μm,精子直径1.567μm。混匀的精卵刚遇水时,没有精子进入精孔器。受精后1s,精孔器内出现精子。受精后5s,组织切片显示,精子已经进入卵子内,并形成具有强烈抑制多精入卵作用的受精锥。受精后10s,精子在精孔器前庭集结,尚未形成受精塞。受精后20s,在精孔器内形成受精塞。受精塞没有阻塞精孔管,经分析它不是来源于皮层反应产物。受精塞形成后,可以吸附入卵的精子,这对多精入卵有积极的抑制作用;精子尾部在入卵过程中相互缠绕,这也是减少多精入卵的重要机制。受精后30s,受精塞和吸附的精子向精孔器外移动。受精后50s,受精塞和吸附的精子堵塞精孔器。受精后60s,受精塞吸附的精子开始解体,但是由于精孔管未封闭,还有精子通过精孔管进入到质膜。在人工受精过程中,卵子的单精受精屏障会因其周围精子密度大、精子与卵子距离短、精子运动速度快而被打破,从而导致这些卵子出现多精入卵的现象。受精后80s,精孔管仍然没有封闭,精孔器附近的精子明显出现活动能力的差异:精孔器外面的精子活动能力最强,精孔管旁边的精子活动能力较弱;精孔管外堆积的精子活性消失,受精塞吸附的精子已开始解体,经初步分析,这可能是进入其内的精子耗能有所差异的结果。受精后100s,受精塞吸附的精子解体。

The fertilized eggs of Hemibarbus labeo were observed by scanning electron microscopy （SEM） and optical microscopy （OM）. The results suggested that the micropylar apparatus was deeply sunken with a short tunnel. The external diameter of the micropylar tube was 2. 512 μm, the interior diameter was 2. 330 μm, and the diameter of the sperm was 1. 567 μm, which suggested only one sperm entered into the micropylar tube at a time. Before fertilization, there was no sperm in the micropylar apparatus; One second after fertilization, sperm appeared near the micropylar apparatus, but still no sperm entered into micropylar apparatus. Five seconds after fertilization, sperm entered into the ovum and the fertilization cone appeared. In the ovum of H. labeo, the fertilization cone could prevent polyspermy forcefully. Twenty seconds after fertilization, the fertilizing pluf came into being in the micropylar apparatus, sperm entered into the micropylar apparatus un- ceasingly, but most sperm were attracted to the surface of the fertilizing pluf. Before the fertilizing pluf came appeared, a few sperms had entered into the bottom of the micropylar apparatus, near the micropylar tube, which suggests that the func- tion of the fertilizing pluf was limited in holding in polyspermy. In the micropylar apparatus, most of the sperms＇ tails twisted around each other. It was obvious that the twist of the tails could prevent polyspermy, too. Later, the fertilization pluf and attracted sperms moved outwards. Fifty seconds after fertilization, the micropylar apparatus was plugged up by fertilization pluf and absorbed sperm, and it was not possible for the remainder of the sperm to enter the ovum. One minute after fertili- zation, the absorbed sperm degenerated. Eighty seconds after fertilization, the inner surface of the micropylar apparatus was slick, and the micropylar tube was not plugged up by the fertilization pluf, which suggests that the fertilization pluf didn＇t come from the cortical reaction in the ovum. Sperm mobility in the micopylar apparatus was very different： near the micropy- lar tube, there were few sperm but they were much more mobile, while the sperm absorbed by fertilizing pluf were less mobile but higher in number. Outside the micopylar apparatus, there were few sperm but they were the most mobile. We deduced that sperm in the micopylar apparatus expended a greal deal of energy in the course of penetrating the egg. The con- sumed energy was so nmch that the sperm absorbed by fertilizing pluf were feeble ; however outside the mieopylar apparatus, the sperm consumed little energy, so the mobility was the strongest, and near the micrupylar tube, there was an average amount of mobility. One hundred seconds after fertilization, sperm absorbed by fertilization phaf were completely decomposed.