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 hormone analog (sGnRH-A) on spawning of Heteropneustes fossilis has been evaluated. A single intramuscular injection of D-Lys6 sGnRH-A (25-500 mug/kg body weight) induced spawning in all the fish. Spawning also occurred at a lower dose (10 mug/kg body weight), but required the application of gentle pressure on the soft and distended belly to shed the eggs. Fish administered an equal volume of saline (controls) did not spawn. The latency period (interval between the time of injection and spawning) ranged consistently between 14 and 18 h. Injections of D-Lys6 sGnRH-A at different time-points of the photodiurnal cycle did not influence the induced spawning of fish and the same latency period was maintained. The eggs produced after induced spawning were viable and fertilizable in vitro. The dopamine antagonist domperidone did not potentiate the effect of D-Lys6 sGnRH-A in H. fossilis. To our knowledge, this is the first report of D-Lys6 sGnRH-A being used for the spawning of fish.