Oral Administration of GnRH Via a Cricket Vehicle Stimulates Spermiation in Tiger Salamanders (Ambystoma tigrinum)

ORCID

DChen: https://orcid.org/0000-0001-6418-3801; LChen: https://orcid.org/0000-0002-9653-9814; CKouba: https://orcid.org/0000-0001-8466-6077; AKouba: https://orcid.org/0000-0002-9653-9814

MSU Affiliation

College of Forest Resources; Department of Wildlife, Fisheries and Aquaculture; College of Agriculture and Life Sciences; Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology

Creation Date

2026-10-30

Abstract

More than 50% of caudates are threatened with extinction and are in need of ex-situ breeding programs to support conservation efforts and species recovery. Unfortunately, many salamander populations under human care can experience reproductive failure, primarily due to missing environmental cues necessary for breeding. Assisted reproductive technologies (ARTs) are a useful suite of techniques for overcoming or bypassing these missing environmental cues to promote breeding. Exogenous hormones are used to stimulate natural breeding behaviors or gamete expression for in-vitro fertilization or biobanking and are typically administered intramuscularly in caudates. While effective, intramuscular injection is risky to perform in smaller-bodied animals, resulting in health and welfare risks. This research investigated the spermiation response to hormone administration through a noninvasive oral bioencapsulation route using the tiger salamander (Ambystoma tigrinum) as a model species. Male salamanders were randomly rotated six weeks apart through four treatments (n = 11 males/treatment) in which animals received a resolving dose of gonadotropin-releasing hormone (GnRH) as follows: (1) Prime-Only (0.0 μg/g); (2) Low (0.25 μg/g); (3) Medium (1.0 μg/g); and (4) High (2.0 μg/g). All males were given a GnRH priming dose (0.25 μg/g) 24 hours prior to the resolving dose. Exogenous hormone was delivered inside of a cricket (Gryllodes sigillatus) that was presented as a food item by tweezers. Sperm samples were collected at 1, 3, 6, 9, 12, and 24 hours after the resolving dose and analyzed for quantity and quality. For all treatments, sperm concentration was produced in an episodic pattern over time. The Prime-Only treatment had a lower (p < 0.05) percent of sperm exhibiting normal morphology compared to treatments utilizing a resolving dose of GnRH. Overall, oral administration of GnRH is a feasible route of inducing spermiation in salamanders, yielding sperm of sufficient quantity and quality for in-vitro fertilization and biobanking efforts.

Keywords

sperm, salamanders, hormonal therapy, crickets, hormones, oral administration, urine, fertilization

Publication Date

7-25-2024

Publication Title

PLOS ONE

Publisher

Public Library of Science

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Rights

© 2024 Chen et al.

Link to Full Text

Share

COinS
 

Digital Object Identifier (DOI)

https://doi.org/10.1371/journal.pone.0289995