Variation in egg quality after hormonally-induced ovulation in goldfish is more related to female variability than to short term post-ovulation ageing
The development of biotechnologies such as nuclear transfer in goldfish (Carassius auratus) requires that the spawns be available all year round. For this reason, an off-season maturation procedure was set up in our laboratory. The aim of this study was to describe how these artificially maturated females responded to induced ovulation, and how egg quality varied in the female tract at 20°C. Thirty two females maintained at 14°C after wintering were conditioned at 20°C for 6 days before they were treated with Ovaprim® to induce ovulation. Most females (63%) ovulated between 13 and 14h after the Ovaprim® induction although 6 females ovulated before induction and 6 remained irresponsive to Ovaprim®. Egg quality after stripping was estimated by the embryo development at 24 h (20°C) and by the hatching rate. Egg quality was better one hour after ovulation than at the onset of ovulation, and some variability in the hatching rate was observed between females. It is only 5 hours after ovulation that some spawns exhibited some overripening although most of the spawns still sustained the highest development rates. We conclude that artificially maturated goldfish were responsive to hormonal induction of ovulation, and that variation in egg quality between spawns at a given time was more related to the female factor than to an overripening process in the first hours after ovulation.