Reprodução induzida da rã-touro Lithobates catesbeianus (Shaw, 1802), utilizando diferentes tipos e dosagens do hormônio liberador da gonadotropina - GnRH

Abstract

The technique of use of gonadotrophin releasing hormone (GnRH) in the reproduction of amphibians can be used to control spawning throughout the year, avoiding production delays resulting from the seasonality of the reproductive cycle. The objective was to study the induced breeding of bullfrog Lithobates catesbeianus using different types and dosages of GnRH to the optimization of the hormone and the consequent reduction in operating costs in commercial production. Breeders (average weight 650 g) were previously prepared, and conditioned to an average temperature of 26°C, submitted to a photoperiod of 15 hours of light. We tested three different hormone treatments; treatment 1 (T1) with 5 μg Etilamid hydrated acetate, treatment (T2) 2.5 μg Etilamid hydrated acetate and treatment 3 (T3) with 0.8 μg of Buserelin acetate, divided in three experimental groups. For each treatment, three applications were made at intervals of 12 hours hormones application in females and a single one for males. After the hormone treatment was done the extrusion of eggs in females and spermiation in males fertilized eggs hydrated with water at neutral pH. All males responded to the hormones applied resulting in a "pool of sperm" used to fertilize the females. Females of treatments T1 and T2 ovulated in its entirety and there was a failure only in T3. From the first and second trials, it could be detected that the dosages of 2.5 μg Etilamid hydrated acetate and 0.8 μg Buserelin acetate are more technically and economic viable for induced breeding of bullfrog. The average weight of spawning was 92.8 and 93.7 g respectively. The fertilization rate was estimated from the percentage of eclosion, with rates of fertilization rates average with 84.2 % (T2) and 60.3 % (T3). Based on the results, we conclude that the reduction in usual dosages for Etilamid hydrated acetate and the use of Buserelin acetate were efficient on ovulation and spermiation in bullfrogs, but it is necessary to adjust the dosage of Buserelin acetate as well to get a better improvement through environmental control and breeder maturation conditions in further experiments.