PRELIMINARY EXPERIMENTS ON INDUCED OVULATIONOF SOME ECONOMICAL CYPRINIDS

Preliminary experiments of inducing ovulation by injection of pituitary (in a few cases also pregnancy urine) were carried out on Mylopharyngodon, Ctenopharyngodon, Hypophthalmichthys, and Aristichthys in their spawning ground in upper Yangtze River. For Hypophthalmichthys and Ctenopharyn-godon the result obtained was inconclusive inasmuch as the experiments were performed at a time too close to their natural spawning season. For Aristichthys, in one case out of four ovulation was induced, apparently two weeks earlier than the commencement of its natural spawning, by homoplastic pituitary injection. For Mylopharyngodon, 5 cases were recorded of induced ovulation some one week ahead of its natural spawning period by injection of pituitaries of Hypophthalmichthys. Failure in normal development of eggs obtained by induced ovulation is considered to be the consequence of the inavailability of necessary amount of semen during artificial fertilization rather than of the process of inducing ovulation itself. Incideatly, the males used in this experiment had not been receiving any treatment beforehand. Drawbacks in these experiments are discussed and suggestions for im-provement in further experimentation are made.