Study On The Development Of Gonad At Early Stages In Amur Sturgeon

Amur sturgeon (Acipenser schrenckii Brandt) is a kind of endemic economic species in Heilung-kiang and now become a capital culture fish. At present, the goal of cultivation has changed from the production of commodity fish to expensive caviar. So more female fish are needed, and the gonad should mature as earlier as possible. That will do cut down the cost of produce, elevate the efficiency of produce and create higher profit. It is thus evident that the most important thing is breeding hologynic group. This article overviewed the process of genesis, differentiation, development and the changes of structure on Pisces gonad and germ cell during different periods. The gonadal development of the Amur sturgeon was studied by histological method. From the study we can definite the period of sexual differentiation on the Amur sturgeon. So it will offer the theory evidence for artificial sex reversal and hologynic group.Conclusions from the studies are as follows:1. For the first time, the gonadal development of the Amur sturgeon was studied using domesticated stock. By histological method, the original and differentiated regularity of the gonads were revealed. Stage 0 includes the formation of genital fold, the migration and accumulation of primordial germ cell and the formation of gonad. At stage â… , some structural characteristics of different sexual gonad were observed by microscope. In stage â…¡, fatty tissue accumulated a lot, the quantity of adipose cells increased, and gonad was jostled to one side. Because of the great quantity of fat, gonad was light red or light yellow. During this period, plenty of primary gonocyte emerged. And the persistence time of this stage was very long, especially in ovary. When process came into stage â…¢, gonad grew fast, and the weight of it raised obviously. The fatty tissue was used a lot. In stage â…£, gonad was getting close tophysiological maturity. It was easy to identify the sex of gonad. Abdominal part was inflated and hard. Then it became soft in stage V. In this stage, gonad completed sexual mature. Milky sperm or pitchy ovum flew from cloacal orifice when pressed the abdomen. This period was short and correlated with external factor closely. After ovulation, spermiation or natural degeneration, the volume of gonad was smaller in stage VI. The structure of gonad was similar to it in stage.2. A study on the ultramicrostructure of the gonocyte on the Amur sturgeon juvenile was performed using eletron microscope for the first time. There were two ways of germ plasm formation of the oogonium and primary oocyte.