Efficacy of hormone stimulation on sperm production in an alpine amphibian (Anaxyrus boreas boreas) and the impact of short-term storage on sperm quality

Authors: LANGHORNE, CECILIA - Mississippi State University; CALATAYUD, NATALIE - Mississippi State University; KOUBA(VANCE), CARRIE - Mississippi State University; WILLARD, SCOTT - Mississippi State University; SMITH, THEODORE - Colorado Parks And Wildlife; RYAN, PETER - Mississippi State University; KOUBA, ANDREW - Mississippi State University

Submitted to: Zoology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2021
Publication Date: 3/1/2021
Citation: Langhorne, C.J., Calatayud, N.E., Kouba(Vance), C.K., Willard, S.T., Smith, T., Ryan, P.L., Kouba, A.J. 2021. Efficacy of hormone stimulation on sperm production in an alpine amphibian (Anaxyrus boreas boreas) and the impact of short-term storage on sperm quality. Zoology. 146, 125912, pp. 1-8. https://doi.org/10.1016/j.zool.2021.125912.
DOI: https://doi.org/10.1016/j.zool.2021.125912

Interpretive Summary: We are using amphibians as model species for studies in reproduction of fishes in aquaculture and birds in poultry sciences, and the effects of external stressors to reproductive output. Assisted Reproductive Technologies (ART) spans a wide range of approaches (e.g., hormone therapy, egg expression, in vitro fertilization), which are used to either facilitate or circumvent specific steps in the natural cycle when reproductive failure becomes apparent. Amphibians share many of the main reproductive neuropepetides, pituitary hormones, and gonadal steroids with other vertebrates but arm or closely related to fish than mammals. Thus ART can be implemented in amphibians as model species to study the neuroendocrinology of reproductive cycles of lower vertebrates such as fish. An important aspect in implementing ART in amphibians is identifying which stages of the reproductive cycle might be compromised if there is reproductive failure. This is not a trivial step because the environmental cues and breeding behaviors are often species specific, because reproduction is a complex sequence of events that couples environmental, social, and physical cues leading to hormonal cascades associated with the breedinig events. Here we demonstrate the dose dependence of hormone regimens needed for collection of sperm from an alpine amphibian species and the mechanism of storage needed for transportation to aquatic species germ plasm repositories for genetic management.

Technical Abstract: The Southern Rocky Mountain boreal toad (Anaxyrus boreas boreas) has disappeared from much of its range in the alpine regions of Central and Western North America, and restoration efforts are compromised by limited knowledge of this species’ reproductive biology. This study aimed to establish whether assisted reproductive techniques could be used to improve breeding output in captive boreal toads by determining the most effective concentration of human chorionic gonadotropin (hCG) for induction of spermiation and viability of sperm during cold storage. Male toads (n = 21) were treated with a Low (3 IU g-1), Medium (10 IU g-1), or High (15 IU g-1) concentration of hCG and spermic urine samples were collected over 24 hrs. Treatment effectiveness was evaluated by measuring the response rate, Total Motility (TM), Forward Progressive Motility (FPM), Quality of FPM (QFPM), and concentration. For short-term cold storage, spermic urine samples (n = 13) were stored at 4 'C for 14 days and sperm TM and FPM monitored daily. All treatments induced spermiation; however, a greater number of toads produced sperm in the Medium and High treatments compared to the Low. Overall, TM, FPM, QFPM and sperm concentration were similar across all three treatments, but variation existed in the timing and duration of peak sperm production. Sperm motility was maintained for up to 14 days in cold storage, although the quality slowly decreased over time. An effective reproduction strategy for the boreal toad will provide a means to improve captive breeding efforts and increase our understanding of the reproductive physiology of alpine Bufonids.