Studies On Ferlization Biology Of Myxocyprinus Asiaticus

From March 2005 to March 2007, we got the Chinese sucker (Myxocyprinus asiaticus) embryos which were developed by artificial oxytocin, dry fertilization and pond water activation from the Wanzhou Fisheries Institute. Disscussed the histological structure and ultrastructure of the fertilized eggs, the process of sperm going into eggs, the male and female nuclear migration and integration, the change of zygotes, and the variety of the Ca²⁺ and Ca²⁺ during the process of fertilization by the means of histology, histochemistry, scanning electron microscopy, transmission electron microscopy, cell chemistry and so on. The results indicates that: There is rich in villiform structures in addition to the area which is of a diameter about 100μm arounds the micropylar apparatus in the egg surface. The micropylar apparatus is constituted by the atria and the micropylar tube. The atria is funnelform, and the largest diameter is 64.94 urn and in the depth of 78.64μm. The micropylar tube with 2.55μm long and a diameter of 2.40μm is on the bottom of the micropylar apparatus. From the scanning electron microscope the micropylar apparatus is of a type which is up to the chin, and its atria erea is formed in spiral structure. 3s after fertilizition, sperm starts going through the micropylar tube, and it forms sperm stars in 10s after fertilizition. 35s after fertilization, there forms fertilization cone in the bottom of the micropylar apparatus. 40s after fertilization, there gatheres alarge number of sperms in the micropylar apparatus, then the hole is pluged, and the sperms inside the micropylar apparatus begins to get together and lose their integrated morphology. 80s after fertilization, the micropylar tube were blocked up and were in the form of fertilization cone. The sperms inside the micropylar apparatus get more collective to form a agglomerate. 180s after fertilization, the sperms inside the micropylar apparatus start to break up, and the boundery between two sperms gets illegible which only can see Mission membranes together. The chromosomes of mature egg's have stagnated in the second meiotic metaphase, with the entry of sperm, the Animal pole begins forming the blastoderm. 15min after fertilization, the egg is in the second anaphase, which starts to form the second polar body. 20 minutes after fertilization, the egg is at the end of the second meiosis and the second polar body is formed completely. 90 minutes after fertilization, the male and female nuclears integrates. 140min After fertilization, the egg is in the M phase of the first mitosis. 180 minutes after fertilization, the first mitosis ends, and two cells formed.The egg cortex vesicles is the metabolic waste which is accumulated during the process of growth and deveploment. According to the characteristics of the morphologic, contents, biochemical characteristics and ultrastructural of Chinese sucker, the cortex is devided intoâ… -â…£types; cortical area cortex vesicles are derived from the physiological changes of oocytes during their growth process; classâ…£cortex vesiclesis transformed by a kind of particular degradated yolk particles which are basophilic. They appears in the late phase of cortex reaction and the cleavage period respectively. The release order of the cortex vesicles in the cortical reaction shows some regularity, which isâ… -â…£cortex vesicles are released in order. There is process of extrapolation and integration in the relaesement, in the process, the electronic density of the containing objects is a weakening process too. According to the release intensity of the cortex vesicles, cortical reaction can be divided into the latent period, development period, climactic period, declining period. 10s after fertilization, there starts weak cortical reaction in the region which is 352.85μm away from the micropylar apparatus, and it's the starting point of the cortical reaction; 80s-120s after fertilization is the climax of cortex reaction; 10 minutes after fertilization, the cortical reaction ends. 50min-60min after fertilization, there appears cortical vesicle in the animal pole cortex, and which occurred exocytosis, the second cortical reaction begin. Cortical vesicles are speculated not only join in the cortical reaction, but also provide adequate membrane systems for the latter part of the plasma membrane repairation and the egg cleavage.During the process of fertilization, the content of calcium fluctuate. This change is closely relates to the cortical reaction of the egg. The release of the cortical vesicles is based on the increase of the calcium in the egg. There are two phases which Ca²⁺-ATPase is in higher activity in the sperm-egg binding process. 80s after fertilization, it's the climax of the cortical reaction, the calcium ion concentration maximizes at this time, and the Ca²⁺-ATPase activity is the highest too. So, during the fertilization, the calcium and Ca²⁺-ATPase play a relevant role in the process of a series of dynamic changes, and relates to the cortical reaction. To make more reasonable explanation of the egg activation mechanism, we integrated predecessors' study, and according to the change of the calcium in the egg during the fertilization process, we propose a calcium channel hypothesis: Exogenous signals (various ions and even water) activate receptor which reside in the egg membrane, and induce intracellular calcium release through various signal transduction pathways, then trigger cortex reaction. During the cortical reaction, the release of the inclusion from vesicles and sop up the water causes swelling and the sub-structure of the egg membrane change, so that the calcium ion channels in the egg membrane openes. The opening of the ion channels causes the calcium ions enter into the egg, and shows the increases of the content. The calcium influx causes the change of the membrane potential. In order to maintain the balance of the membrane potential, Ca²⁺-ATPase pumps the calcium out of eggs, which shows active fluctuations, and then the calcium content reduces. Therefore the Ca²⁺-ATPase active fluctuation is relate to the calcium content related; Ca²⁺ and Ca²⁺-ATPase's role eventually leads to the egg activation.