Evaluation of different temporal periods between hormone-induced ovulation attempts in the female Fowler’s toad Anaxyrus fowleri

Abstract

Lay summaries: Several temperate toads undergo oogenesis soon after breeding which could be exploited by captive breeding programs to increase tadpole production. In this study, non-hibernated Fowler’s toads produced fertilizable oocytes after a four month refractory period without significantly impacting the number of ovulating females, total egg production, or egg quality.

Influence of oviposition-inducing hormone on spawning and mortality in the endangered Panamanian golden frog (Atelopus zeteki)

“…Priming refers to administration of low doses of hormone 24–96 h prior to a resolving ovulatory dose, which is meant to stimulate the final stages of oocyte growth (stages 4–6) and maturation (stage 7) generating a grade 5 female ready to ovulate. A variety of hormones, including GnRHa, human chorionic gonadotropin (hCG) and progesterone, have been evaluated for their effectiveness in promoting oocyte growth and maturation, and usually the concentration of the priming doses are ~ 20% of the resolving ovulatory dose [ 25 ]. Female PGFs in this study were already at the oogenesis stage required for ovulation and did not clearly require priming hormones.…”

“…A direct comparison of GnRHa alone to GnRHa + MET was conducted in the dusky gopher frog, with results suggesting that the addition of MET to GnRHa was beneficial as it induced eight females to spawn compared to only five for GnRHa alone [ 24 ]. However, addition of MET to GnRHa in this species was no more beneficial than adding human chorionic gonadotropin (hCG) to GnRHa; cocktails of hCG and GnRHa have been demonstrated to induce ovulation in various anuran species [ 19 , 20 , 23 – 25 , 47 ]. In the present study on PGFs, GnRHa yielded similar spawning rates and latency to egg laying as GnRHa + MET, suggesting GnRHa alone is sufficient to induce egg release by female PGFs.…”

“…However, there are amphibian species in which priming or pulses of hormones are required to facilitate the spawning process. The beneficial impacts of primed or pulsed hormones on increased spawning rates have been described for Wyoming toad ( Anaxyrus baxteri) [ 19 ], Fowler’s toad ( Anaxyrus fowleri ) [ 25 ], Günther’s toadlet ( Pseudophryne guentheri ) [ 22 ], corroboree frog ( Pseudophryne corroboree ) [ 20 ], dusky gopher frog [ 24 , 40 ], Puerto Rican crested toad ( Peltophryne lemur ) [ 37 ] and Chiricahua leopard frog (Lithobates chiricahuensis) (Kouba per. communication).…”

“…communication). Previous studies by our lab on hormone priming effects on spawning rates [ 19 , 24 , 25 , 40 ] were primarily designed to bypass unknown environmental cues necessary for ovulation, which are often required to complete oogenesis and vitellogenesis, once oocytes are arrested at the diplotene stage of meiotic prophase. Thus, hormone priming is meant to complete oocyte maturation, while pulsed hormones increase spawning rates by capitalizing on a two-phased process similar to that seen in nature.…”

Near-Infrared Spectroscopy (NIRS) as a Method for Biological Sex Discrimination in the Endangered Houston Toad (Anaxyrus houstonensis)

“…Sex identification is critical for informing management decisions surrounding captive breeding programs, such as breeding pair selection, maintenance of an appropriate sex ratio, avoidance of inbreeding among tank mates, management and transfer of juveniles for the purpose of optimizing genetic diversity, and informing practitioners on what reproductive technologies should be applied for propagating the species of interest. For example, the reproductive hormone regimens (e.g., hCG, human chorionic gonadotropin and GnRH, gonadotropin-releasing hormone) used to induce spermiation in males and ovulation in females are often sex-specific and should therefore be tailored to the individual’s sex [ 8 , 9 , 10 ]. However, sex classification remains a challenge, particularly for monomorphic species, many dimorphic species outside of the breeding season, and most juvenile amphibians [ 11 , 12 ].…”