Measuring the Effects of a Single Dose of Human Chorionic Gonadotropin (hCG) on Plasma Testosterone Concentrations in Leopard Geckos (Eublepharis macularius)

Abstract

Current estimates suggest that one-fifth of all reptiles are currently threatened with extinction because of anthropogenic activity, and that if nothing is done to mitigate these impacts, massive extinctions will occur over the coming decades. Assisted reproductive technologies (ART) can be used to develop ex vivo conservation programs to ensure species survival until environmental deficiencies can be corrected. Geckos represent one of the most diverse groups of reptiles on earth and need protection; however, to date, no ART have been developed for these animals. Exogenous human chorionic gonadotropin (hCG) is routinely used to alter reproductive hormones of vertebrates and are integrated in ART. The purpose of this study was to determine if a single dose of hCG could increase plasma testosterone concentrations in the leopard gecko (Eublepharis macularius) within 24 h of administration. The study was performed in September, which is considered the nonbreeding season for this species in the northern hemisphere. Twelve captive-bred, adult, male leopard geckos were randomly divided into three treatment groups and administered an intramuscular injection of hCG (50 or 100 IU) or saline. Whole blood was collected prior to injection (baseline) and 12 and 24 h after injection. Plasma testosterone concentrations were measured using an enzyme immunoassay kit. There was no significant difference (P = 0.195) in testosterone concentrations between treatment groups. Because there was no difference, an observed testosterone range (61.0 ± 42.5, 5.5–149.0) for September was calculated. These results suggest that captive leopard geckos may be in a recrudescence phase in September in the northern hemisphere.