Studies on The Development and Annual Change in The Ovary and The Breeding Habits of A Freshwater Catfish (Leiocassis longirostris)

The present paper deals with the characteritics of ovarian stages and the breeding habits of a freshwater catfish Leiocassis longirostris Gunther in the Jialing River.According to the external shape and histological featrues,development of the ovary is divided into six stages:1.oogonia;2.oocyte with follicular epithelium consisting of a single layer of follicle cells;3.oocyte with yolk vesicles;4.oocyte filled with yolk;5.complete maturation;6.degeneration of oocyte.Stage Ⅰ of ovaries can be seen one year old fishes only.The stage Ⅱ lasts about 2 years and then develops into the stage Ⅲ,Ⅳ,Ⅴ before maturation.Age at first maturity is 3 years old.Ovarian annual changes of adult fish only undergo the stages Ⅱ-Ⅵ.The spawning period is from April to June.After spawning,the ovaries quickly degenerate to the stage Ⅱ and then develop to the stage Ⅲ again.Each year the catfish has a single spawning season,in which the female is confirmed to spawn once.Many nucleoli are observed in oocytes.They can be divided into 2 types I.e.large and small.The sticky membrane of eggs is derived from the follicle cells.Degeneration of the atretic follicle and the resorption of yolk in Leiocassis longirostris is subdivided into five consecutive stages.