Sex Differentiation And Hormonal Sex Reversal Of Pelteobagrus Fulvidraco

Pelteobagrus fulvidraco is a kind of important economic fish,which has little bone among muscle,taste delicious and has high nutritional value.But it's small and grows slowly, which restricts the development of the aquaculture. Nevertheless,its growing takes on sexual othemess. The male fish always grows bigger and faster than the female.In order to increase the speed of growing in the aquaculture,members of the research teams have applied themselves to the monosexual breeding for a long time.In this research,histological methods were used to observe the sex differentiation of Pelteobagrus fulvidraco,providing the scientific foundation for the sex reversal.The hormonal sex reversal was carded out by dietary treatment,using estradiol-17B or 17a- methyltestosterone with concentration of 20ppm.The results were as follows:(1)Pelteobagrus fulvidraco belonged to the differentiated species of gonochoristic fish and ovary differentiated before spermary.The anatomical sign of ovarian differentiation was the formation of ovarian cavity,which appeared after hatching for 13 days.The anatomical sign of spermatic differentiation was the formation of spermaduct and seminiferous lobular,appeared after hatching for 55 days. The cytologic symbol of sex differentiation was the meiosis of oogonia and spermatogonia after hatching for 34 days and 64 days each.Besides,the mitosis of oogonia and spermatogonia happened in different times,oogonia in 28 days after hatching and spermatogonia in 50 days.In the early developing period,the number of primary germ cells in male and female larval gonads was different, female more than male.(2)In the research of sex reversal,17a-methyltestosterone treatment induced 90.9ï¼…male of Pelteobagrus fulvidraco and estradiol-17B induced 83.6ï¼…female.Statistical analysis indicated that the sex rote of hormone treated groups was remarkably different from that of control group.The result of histological observation of gonad development of Pelteobagrus fulvidraco showed that the treatment of estradiol-17B accelerated the ovarian development in the early period but restrained it in the late.On the other hand,it delayed the spermatic development.The treatment of 17a-methyltestosterone hardly affected the ovarian development in the early period but restrained it in the late.Nevertheless,it accelerated the ovarian obviously.There was no intersexuality or sterility appeared during sex reversal and the developed gonads had no comeback after hormonal treatment.However,the treatment of both hormones depressed the growth and increase the mortality rate of Pelteobagrus fulvidraco .