MILT PRODUCTION IN COMMON CARP (CYPRINUS-CARPIO) - STIMULATION BY A GOLDFISH STEROID PHEROMONE

This study examined the effect of a putative steroidal pheromone, 17 a lpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) on milt volume a nd serum gonadotropin-II in precocious male common carp (40-285 g). 17 ,20 beta-P significantly increased both milt volume (14-18 h post-expo sure) and GtH level (90 min post-exposure) at both doses tested (5 x 1 0(-11) and 5 X 10(-10) M in aquarium water), whereas a conjugated form of 17,20 beta-P (17,20 beta-P-sulphate) was ineffective at the only d ose tested (5 X 10(-11) M). Increases in milt, packed sperm volume, an d GtH following exposure 5 X 10(-10) M 17,20 beta-P also were compared to those induced by injection of Ovaprim (Syndel; mixture of salmon G nRH analogue and dopamine receptor antagonist) at two doses (0.1 and 0 .5 ml/kg body weight). Increases in milt and GtH induced by the high O vaprim dose were significantly greater than those induced by 5 X 10(-1 0) M 17,20 beta-P. Increases in milt, and packed sperm volume, and GtH induced by the lower Ovaprim dose were not significantly larger than those induced by 17,20 beta-P. The results suggest: (1) in common carp , 17,20 beta-P has a pheromonal role in milt production similar to tha t demonstrated in goldfish; (2) waterborne 17,20 beta-P might be a pra ctical non-invasive technique for enhancing milt production in culture d common carp.