Studies On Gonad And Sex Control In Amur Sturgeon

Amur sturgeon is endemic economic fish in Heilongjiang River and become important culture fish at present. The studies on gonad and sex control in Amur sturgeon are necessary for artificial propagation and breeding and hologynic production in the process of sturgeon cultivation. Using histological, biochemical and radioimmunologic methods, this article observed the gonads in different decelopment periods and determined the blood and tissue sex steroid hormone and feminination ratio after sex control, and investigated the proportion of cultured female and male.Under the condition of artificial cultivation, the serum level of testosterone (T) in Amur sturgeon increased following the age from 1-year to 4-year and began to decrease at 5-year. In contrast, the serum level of estradiol-17 β (E2) was constantly low during 1-year and much lower at 2-year, then increased slowly until 4-year, at 5-year it increased rapidly and reached 904pmol·L^-1 in female but kept low level in male.Sexual maturation is late and the period of gonad development is long in Amur sturgeon. The female need 9¹1 years and the male need 6⁷ years while the cultured female 1-2 years earlier. The primordial gonad, genital fold which composed of epithelial cells formed below the nephridium area 12 days after hatching. When fish was 6 months old, primordial germ cells had mitosis and became gonium. The gonad still not sex differentiate at that time. At the age of 7 months some structural features in different sex gonad could be observed by microscope so the testis and ovary could be distinguished. At the second stage the fat was accumulating a lot, and a large number of auxocyte had emerged. This period lasted a long time to several years. At the third stage the gonad grew fast so the weight of it increased obviously. The rate of fat consumption was high. The testis was fusiform shape, light red or yellow, from the front of swim-bladder to cloacal chamber. The ovary was digitation juxtaposed shape, and was wrapped up by fat. The pigment and fat was in the middle and lateral part of the ovary, and the blood vessels distributed on it. The sex of gonad was identified easily at the fourth stage. The gonad was getting close to physiological maturity. A little fat remained in the testis, and the testis was pink because of the bulk of blood vessels. There were some spermatozoa on the face of testis. Testicular duct expanded containing a small quantity of spermatozoa. The volume of ovary with no fat was large. There were a plenty of egg cells which were coated by diaphanous membrane, and the diameter of the ovum macroaxis was between 2.5-4mm. In the fifth stage the abdomen of fish was inflated and soft, and the gonad was matured. Pressing the abdomen lightly, the ivory sperm or pitchy egg would flow from the cloacal opening. After mature, the...