REPRODUCTIVE BIOLOGY OF SILURUS MERIDIONALIS CHEN:THE DEVELOPMENT AND ANNUAL CHANGE IN THE GONADS

This paper describes the morphology, histology and annual cyclical changes of gonads in Silurus meridionalis Chen collected from the lower reaches of the Jialing River. According to the morphological and histological features, the development of gonads can be divided into six stages and the change of germ cells of male and female can be divided into six phases. The duration of spermatogenous cells in the male larvae is longer than the ovogonia in the female. The spermatocytes develop at different rates during the early and middle stages, but in the later the development of all the cells becomes synchronized. The oocyte of early phase 3 has a yolk nucleus too. Many nucleon which can be divided into 2 types i.e. large and small, are observed in oocytes. The number of the nucleon changes with the oocyte development. The micropylar cell and the stick membrance of the egg are derived from the follicular cells. The maturation age of male and female are 3 years old. The spawning period lasts from March to May. The results of this paper indicate that this fish spawns only once a year, and not all of mature eggs in the ovary can be laid out during spawning.