A HISTOLOGICAL STUDY OF THE GONAD DEVELOPMENT OF GYMNOCYPRIS PRZEWALSKII PRZEWALSKII

The gonadal development of naked carp,Gymnocypris przewalskii przewalskii,in the Qinghai Lake was studied by lightmicroscope ,and the characters of the ovary and testis at different stages were described.The fish spawns from early April to late July.The gonadal developments of the fish were divided into 6 stages,and the development of oocytes from Phase Ⅲto Phase Ⅳ was synchronous. In the ovaries at late stage Ⅳ,the sizes of oocytes were uniform and the average diameter was 213mm.The oocytes at Phase Ⅳaccounted for above 85 % of the number of all phases,and above 96 % of the section area.Few oocytes at Phase Ⅱand Ⅲremained in these ovaries. After spawning,the ovaries transferred gradually from Stage Ⅵto Stage Ⅱand Ⅲ,and to Stage Ⅳ.The mature individuals wintered,with 68.12%females and 83.9% males having gonads at Stage Ⅳ,21.01% females and 10.7% males at Stage Ⅲ,and 10.87%females and 5.4% males at Stage Ⅱ.According to the observations on the seasonal changes of the gonads,it is believed that the mature individuals do not spawn every year and there is an interval between spwanings.This implies acclimatization to the cold and changeful climate of the tableland. Besides ,the role of yolk nucleus and nucleoli in the vitellogenesis,the spawning type and the spawning interval were discussed.