Abstract
We evaluated the effect of gonadotropin in controlled-release implant together with temperature manipulation in the reproduction of Astyanax altiparanae (lambari) during the non-breeding season. Three groups of adult females were maintained at 20 degrees C and three at 28 degrees C. For each temperature, one group was treated with 4 mu g GnRHa g(-1), other with 8 mu g GnRHa g(-1) and other was sham implanted as a control during 4 weeks. Afterwards, 4 females/experimental group were induced to spawn with human chorionic gonadotropin, while 4 females/group were injected with saline. GnRHa implants increased fsh beta and lh beta gene expression in females maintained at 28 degrees C. The vtgA gene expression increased in the high GnRHa dose at 20 degrees C, while this higher GnRHa dose associated with the higher temperature increased Gonadosomatic Index. The hCG injection increased the plasma Mature Induction Steroid levels and trigger ovulation, except in control at 28 degrees C. The control females at 20 degrees C spawned but with low reproductive performance, confirming that this is not a limiting temperature for reproduction. The administration of GnRHa as implant increased gonadotropin gene expression at 28 degrees C, temperature at which GSI also increased. Qualitatively, the implants improved reproduction at 20 degrees C, providing offspring out of the reproductive season, improving lambari production throughout the year.