Induction of oocyte maturation and ovulation in the freshwater Asian catfish, Clarias macrocephalus by LHRHa and pimozide
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Three experiments were conducted to determine the effects of a simultaneous injection of varying doses of luteinizing hormone-releasing hormone analogue (LHRHa; 0.005–0.10 μg)/body weight (BW) in combination with a fixed dose of pimozide (PIM; 1 μg)/g BW on oocyte maturation and ovulation in the catfish Clarias macrocephalus (body weight: 39 to 167 g). This was done by monitoring the development and size of the oocytes after hormone injection at various sampling intervals for 48 hours. In Experiment I (March 1989), only the fish injected with 0.10 μg LHRHa + 1μg PIM/g BW underwent final maturation and ovulation. However, oocyte maturation and ovulation were observed in all treated fish in Experiment II (April 1989). Oocyte maturation and ovulation were also induced except in fish injected with the lower dose combination (0.005 μg LHRHa + 1 μg PIM/g BW) or PIM alone (1 μg/g BW) in Experiment III (September 1989). No maturation was observed in all vehicle-injected control fish in the three experiments. Mean egg diameter of fish that were induced to mature increased during ovulation but remained similar in size in fish which did not undergo final maturation. This study showed that captive C. macrocephalus can be induced to undergo oocyte maturation and ovulation at 15 to 16 h after a simultaneous injection of 0.01 to 0.10 μg LHRHa + 1 μg PIM/g BW.