Histological observations on the ovarian development of Acipenser schrenckii

The process of ovarian development in artificially-bred Amur sturgeon(1-8 years old) was investigated histologically.It shows that in fish one year old,ovarian was made p of a lot of oogonium clusters and two or three years old,germ cells of phase I ovarium was primary gonocyte stage(10-60#mu#m) or chromatin stage and had a large nucleus occupying the greater part of oocyte.The germ cells of phase II ovarium in four or five years were esarly growth period oocyte I(60-200#mu#m) or perinucleolus stage and had 7-26 nucleolus in them and phase III ovarium in six or seven years were middle growth period oocyte I (200-1600#mu#m).In this stage,oil droplets,yolk and pigment granules appeared at the periphery of the nucleus in a cytoplasm.The cell membrane had complete three layers.The germ cells of phase IV ovarium in eight years were late period oocytes I(1600-3300#mu#m).The nuclear membrane disappeared and the nucleus dissolved.Oocytes at the most advanced stage had the nucleus moving to the micropylar region of the animal pole.The germ cells of phase V ovarium were ripe oocytes(3400-3750#mu#m) and were released from follicle to body cavity.After spawning,the phase VI ovarium had a few phase 2 ovum,so results show that the cycle of ripe ovarium again is about three or four years.