Nasal hormone administration can support ambystomid salamander ex situ conservation breeding programs

Over half of all species within the order Caudata are threatened and in need of conservation breeding efforts to prevent further population declines. Unfortunately, amphibians under human care can often face breeding difficulties due to challenges associated with mimicking natural environmental cues that initiate hormonal cascades for successful reproduction. Exogenous hormone administration can be an effective approach to overcome such seasonal and behavioral barriers in captivity. This research aimed to evaluate two different gonadotropin releasing hormone (GnRH) administration pathways on sperm quantity and quality in eastern tiger salamanders ( Ambystoma tigrinum ). Each male tiger salamander (n = 14 males/treatment) was randomly rotated through six treatments, which included a Low (0.02 μg/g), Medium (0.1 μg/g), and High (0.5 μg/g) resolving GnRH concentration 24 h after a prime of 0.025 μg/g of GnRH, administered either intramuscularly or nasally. There was no significant difference (p > 0.05) in the number of spermic responders among treatments. The Medium nasal treatment resulted in the highest sperm concentration (5.2 ± 2.4 × 10 6 sperm/mL) and was not different (p > 0.05) from the Medium (1.7 ± 0.5 × 10 6 sperm/mL) or High (3.5 ± 1.3 × 10 6 sperm/mL) intramuscular treatments. Sperm morphology and velocity were not different (p > 0.05) among the doses and administration routes. We show that nasal administration of GnRH in tiger salamanders can result in sperm samples with high concentration and motility. Less invasive hormone administration routes may provide an alternative strategy for hormone treatment in at-risk caudates, especially when injections are unfeasible.