The Ovary Development And Oogenesis Of Lenok (Brachymystax Lenok)

From 2001 to 2003, the mature Brachymystax lenok(Pallas) were collected in the Hai-lang stream, the breach of Mu-dan river. After hatching, the first generation artificial propagation young fishes were got. The specimens, including the ovary of young fish, juvenile fish and ripe fish, were collected in the wild population and the first generation artificial propagation population in 2005. The ovary development and oogenesis of B. lenok were studied using light and transmission electron microscope. The results were as the following:The fertilized ovum of B. lenok ruptured of membrane at 213.00℃·d; the yolk sac was post absorption and became floating young fish at 377.00℃·d; the urostyle of floating fish bent up, the developing of fin almost finished, and proto- gonad was at undifferentiating condition at 385.30℃·d; at 523.50~596.35℃·d(40~45d), the gonad of the part of the young fish begin to differentiate, and the female fish first began to differentiate and formed unilateral ovary, in which emerged limpid oogonium; after 15 days, the gonad of male emerged spermatogonium. At 703.50℃·d, the young fish formed two bilateral symmetry ovarian cavities, which lie between swim bladder and digestive canal and their termination join at oviduct.At 125 d, every lay eggs appeared a oocyte. After H.E. stained, the oogonium cytoplasm is amethyst; oocyte's is shiny red by light microscope. The diameter of oogonium is 15~35μm, oocyte's is 40~80μm. There are more mitochondria in the oocyte than the oogonium, and appeared endocytoplasmic reticulum and Golgi body.B. lenok belong to dioecism fish, so the mature fish has only spermary or ovary. B. lenok ovaries can be classified different stages according to ovum cell morphology, physiological characteristic and histology composition. In this paper, the ovary was divided into 6 stages(I~VI)according to the characteristic of stages. In the stage I, the ovaries are petty common burreed tuber; changed to little transparent. In the stage II, the ovaries, in which distributed compact strip lay eggs board and the blood vessel concentrate in the gastro of ovaries, are flat common burreed tuber. The juvenile fish (at the age of 4~17 months) and postnatal convalescent period mature fish (about postnatal 3 months) always are in this stage. In the stage III, as the ovaries of young fish (at the age of 18~30 months) or about postnatal 5 months mature fish growth, the ovaries entered in yolk forming stage. The ovaries are buff; volume increasing and the round adumbration can be recognizing by naked eyes. In the stage IV, the yolks of oocyte accumulate, but the volume and weight of ovaries don't change. The diameter of the oocyte are about 3.12~5.10 mm. In the stage V, the ovum are full maturity, the ovaries become liberation and entered ovulation period. In the stage...