STUDY ON THE GONADAL DEVELOPMENT IN XENOCYPRIS DAVIDI BLEEKER

The age at first maturity is 2 years for both male and female Xenocypris davidi in the reservoirs in Hunan. This species can reproduce naturally in the reservoirs with favourable conditions for spawning. However, in the reservoirs without favourable conditions, the fish fails to spawn. The oocytes can only develop to the primary stage (phase Ⅳ), though the spermatids can fully develop from spermatogonia to sperm. In winter, the ovaries of the mature female are at phase Ⅲ, and the testes of the male are at phase Ⅳ. The gonads start to ripen in April. The peak of spawning occures from mid May to early June. The development of primary oocytes from phase Ⅲ to phase Ⅳ is synchronous. The coefficient of maturition in the female shows only one peak in a year. Evidence from histology and from breeding practice led to the conclusion that this fish spawns only once in a year.