| This study focus mainly on the early gonadal development and the distribution of MAPK in oocytes of Pingxiang red transparent crucian carp by means of histological and immunohistochemical methods, which provides a theoretical basis for fish gonadal development and its farming production. The results were shown as follows:The histologic studies showed that the Primordial germ cells (PGCs) migrated along the dorsal mesentery during the early period of gonadal development, underwent the continuous proliferation and cell development, and finally gathered to the genital ridge (near the intestine and kidney tubes), forming the primordial gonads. It is the first time to observe PGC in the pre-film near the dorsal mesentery and yolk sac, and the cell is large, bright and light staining, yolk sac provided nutrients for PGCs. At5days, PGCs were observed to migrate to the genital ridge and formed primitive gonad. And the yolk sac was completely absorbed. At the50days, histological differentiation occurred in juvenile fish, and the primordial gonads developed into ovaries.The result of the morphology analysis indicated:oocytes of Pingxiang red transparent crucian carp were divided into six phases including1～6according to the size, nucleus/cytoplasmic ratio, number of nucleolus, eosinophilic alkaline, the appearance and quantity change of yolk granules and oil drop, the appearance and change of vacuole and zona radiata, the composition of follicular membrane. For the Phase1:oogonium arranged in clusters, being round or ovoid, and the nucleus overflowed most of the cells, meantime, phase1appeared only once at the lifetime in oocytes of Pingxiang red transparent crucian carp, the size of the cell was15.77μm～32.77μm.2phase oocytes showed round, ovoid and polygonal, in addition, the volume of cells became greater, the number of nucleolus increased, the ovarian wall formed spawning plate, the cells were basophilic, and the size of cell was69.40μm～119.92μm.3phase oocytes showed round or ovoid, appearing vacuole and zona radiata, vacuole growed from small and larger and increased in quantity which distributed in the cytoplasm. Furthermore, these oocytes opossess double vacuole membrane, were weakly eosinophilic, and generated yolk granules later. The size of cell was68.63μm～372.73μm.4phase oocytes:yolk granules gradually filled all of the oocytes, yolk granules increased in late period and were fused into a large piece, the nucleus became smaller and smaller and moved to the animal pole, oil drops became from small to large, radial costa is obvious. The size of cell was317.2μm～1003.06μm.5phase oocytes:the nucleus disappeared leaving only a nuclei region similar to the nucleus, nuclear membrane and nucleolus both disappeared. Oocytes of this period get already mature for being fertilized. The size of oocyte is maximum shown as1043.28μm～1144.23μm. Degradation of oocytes happened in6phase. Histological observation of ovary in this phase indicated that a lot of digestion and absorption of oocytes happened, and some2,3,4phase of oocytes were observed.The result of Immunohistochemistry showed that MAPK had no expression at the2phase oocytes and began to be produced at the3phase oocytes. Its expression first existed in the cytoplasm near the plasm membrane, and at the4phase oocytes, the expression of MAPK increase rapidly, almost full of the cytoplasm;5phase oocytes, MAPK not only distributed in the cytoplasm, but also migrated to nuclear area, The phenomenon suggested that MAPK migrated from the cytoplasm near the egg membrane to the nucleus in space, And it began to express from the3phase, and disappeared (afterfertilization) until5phase in time. Above all, MAPK in Pingxiang red transparent crucian carp oocyte meiosis regulated the first meiotic arrest starting. |
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