INDUCED SPAWNING OF CATFISH, HETEROPNEUSTES-FOSSILIS (BLOCH), USING D-LYS(6) SALMON GONADOTROPIN-RELEASING-HORMONE ANALOG

In this study, the effect of D-Lys6 salmon gonadotropin-releasing horm one analog (sGnRH-A) on spawning of Heteropneustes fossilis has been e valuated. A single intramuscular injection of D-Lys6 sGnRH-A (25-500 m ug/kg body weight) induced spawning in all the fish. Spawning also occ urred at a lower dose (10 mug/kg body weight), but required the applic ation of gentle pressure on the soft and distended belly to shed the e ggs. Fish administered an equal volume of saline (controls) did not sp awn. The latency period (interval between the time of injection and sp awning) ranged consistently between 14 and 18 h. Injections of D-Lys6 sGnRH-A at different time-points of the photodiurnal cycle did not inf luence the induced spawning of fish and the same latency period was ma intained. The eggs produced after induced spawning were viable and fer tilizable in vitro. The dopamine antagonist domperidone did not potent iate the effect of D-Lys6 sGnRH-A in H. fossilis. To our knowledge, th is is the first report of D-Lys6 sGnRH-A being used for the spawning o f fish.