Efficacy of salmon GnRHa, Ovaprim® and hCG for hormonal stimulation of spermiation in the Fowler’s toad (Anaxyrus fowleri)

Authors: SAYLOR, ERIN - Mississippi State University; KOUBA, ANDREW - Mississippi State University; BOUDREAU, MELANIE - Mississippi State University; SONGSASEN, NUCHARIN - Smithsonian Institute; VANCE, CARRIE - Mississippi State University

Submitted to: Conservation Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2024
Publication Date: 8/21/2024
Citation: Saylor, E., Kouba, A., Boudreau, M., Songsasen, N., Vance, C. 2024. Efficacy of salmon GnRHa, Ovaprim® and hCG for hormonal stimulation of spermiation in the Fowler’s toad (Anaxyrus fowleri). Conservation Physiology. 12(1). https://doi.org/10.1093/conphys/coae056.
DOI: https://doi.org/10.1093/conphys/coae056

Interpretive Summary: Hormone induced egg laying is an important process when managing breeding events for aquatic species. yet not all reproductive hormones promote egg production and release in all species. Here we examine if a commercial fish hormone called Ovaprim, which contains salmon specific hormones could be used to promote egg laying in a novel species. Being able to use available and purified hormones in numerous species is a key mode to increase efficiency of breeding events and reproductive output for aquatic food species.

Technical Abstract: Ex situ amphibian populations can experience reproductive dysfunction due to the absence of environmental cues that trigger reproductive events. Assisted reproductive technologies (ART) for amphibians, specifically exogenous hormone regimens, can circumvent these external signals to induce gametogenesis and gamete release. Currently, the use of the mammalian reproductive hormones gonadotropin-releasing hormone (GnRH) and human chorionic gonadotropin (hCG) are used in a species-specific manner to stimulate amphibian breeding. Hormones or hormone mixtures that are effective in all breeding scenarios would provide the best option for conservation practitioners and some commercial products are already in use for breeding other ectotherms. Ovaprim®, which contains salmon GnRH analogue (sGnRHa) and the dopamine antagonist domperidone (DOM), is effective in fish aquaculture and may be effective for amphibians. To test this hypothesis, we treated Fowler’s toads (Anaxyrus fowleri) with either sGnRHa alone, a high or low dose of Ovaprim® or hCG. We then compared spermiation response, sperm quantity and quality parameters, and changes in animal mass over time within each treatment. We found administration of Ovaprim® resulted in more males producing sperm with better motility compared to administration of sGnRHa alone. In addition, the Ovaprim® and sGnRHa treatments resulted in lower response rates, lower sperm motilities, more abnormal sperm, and higher aggregations of sperm compared to the hCG treatment. Furthermore, Ovaprim®-treated males gained significant mass, suggesting an anti-diuretic effect of DOM. Together, these results show that neither Ovaprim® nor sGnRHa, at the concentrations tested, are likely suitable replacements for hCG in ex situ bufonid breeding programmes and that hormone mixtures developed for fish may have limited transferability to new world toad species.