Induced spawning of the Indian catfish, Heteropneustes fossilis, by GnRH analogue alone or in combination with dopamine-affecting drugs.

摘要

Mature female Indian catfish, Heteropneustes fossilis were induced to spawn in spawning season (July-August 1997) by various ovulation-inducing agents, and the frequency of ovulation was checked after 12-14 h. Egg mass and fertilization rate were taken as end-points of spawning performance. [D-Ala6-Pro9] ethylamide, a GnRH analogue, in dosages of 0.075, 0.15, 0.2, and 0.5 鎔/g of body weight resulted in 28.5%, 71%, 86% and 86% ovulation respectively but the lower doses of 0.01 and 0.05 鎔/g body weight failed to induce ovulation in early spawning phase (July). The dopamine-2 (DA2) receptor antagonists pimozide, domperidone and metoclopramide potentiated the anovulatory dose of 0.05 鎔 GnRH analogue to induce ovulation in 86%, 86% and 50% of the females respectively in the early spawning phase (July). The DA precursor, L-dihydroxyphenylalanine (L-DOPA; 10 鎔/g body weight) and the DA agonist bromocriptine (10 鎔/g body weight) decreased markedly the ovulatory response of 0.2 鎔 GnRH analogue to 29%. The catecholamine-synthesis inhibitor alpha-methylparatyrosine (alpha-MPT) produced a mild depressing effect on the ovulatory response of 0.2 鎔 GnRH analogue. Egg mass was high in groups that yielded a high ovulatory response (71% and above) except the alpha-MPT groups. The fertilization rate was not affected irrespective of the ovulatory response. The results show that the Indian catfish can be induced to spawn by superactive GnRH analogue alone in a dosage range of 0.15-0.2 鎔/g body weight or incombination with DA2 antagonists, such as pimozide or domperidone at a very low dosage of 0.05 鎔/g.