Nasal administration of gonadotropin releasing hormone (GnRH) elicits sperm production in Fowler’s toads (Anaxyrus fowleri)

Abstract

Abstract Background Declining amphibian populations around the world necessitate the establishment of captive assurance colonies as a hedge against extinction. For species that are difficult to breed in captivity, assisted reproductive techniques, such as treatment with exogenous hormones, are necessary for successful reproduction. The purpose of this study was to determine whether intranasal administration of a gonadotropin releasing hormone analog (GnRHa) elicits sperm production in anurans. Methods Male Anaxyrus fowleri (n = 15/trt) were nasally administered GnRHa (1, 5, 10, and 20 μg) in phosphate buffered saline (PBS) using a pipette. Spermic urine was collected from animals over an 8 h period. Samples were assessed for sperm presence, motility, and concentration. Results Treatment of male toads with a PBS control and 1 μg of GnRHa did not elicit sperm production. Nasal administration of GnRHa resulted in sperm production from 60, 93, and 80% of males in the 5, 10, and 20 μg treatment groups, respectively. Sperm motilities averaged 70, 63, and 52% within the 5, 10, and 20 μg treatment groups, respectively, with the highest (p < 0.05) sperm motility observed using 5 μg of GnRHa. Significantly higher sperm concentrations were observed in males treated with 10 μg of GnRHa compared with 5 or 20 μg of GnRHa. Conclusion Nasal administration of GnRHa was successful in eliciting spermiation from male Anaxyrus fowleri, which typically began less than 3 h after treatment. Nasal administration of GnRHa may provide a novel non-invasive method of hormone delivery for at-risk amphibian species that have low reproductive output.

Keywords

• Amphibian
• Toad
• Captive-breeding
• Hormones
• Sperm
• Reproduction