Determination of Efficacy of Single and Double 4.7 mg Deslorelin Acetate Implant on the Reproductive Activity of Female Pond Sliders (Trachemys scripta)

SIMPLE SUMMARY: North American pond sliders (Trachemys scripta) are invasive alien species that, following the release of pet specimens in the wild over the decades, have established breeding populations outside their native habitat, with detrimental effects on local biodiversity. Their commerce and breeding have been recently banned in the European Union, and national programs are being introduced by Union Members to eradicate and control their presence. Among other means of population control, the use of long-acting drugs for chemically induced infertility could be a promising tool to prevent the reproduction of these animals. Efficacy of single and double intramuscular deslorelin acetate implants was investigated during a one-season follow-up: plasmatic sexual hormones concentration and morphometric evaluation of ovarian activity by computed tomography were performed about every 30 days to detect the differences between the control group (no implant), single-implant group, and double-implant group. Results show no inhibition of reproductive activity for the ongoing reproductive season, but suggest possible infertility starting from the following season. ABSTRACT: The use of long-acting gonadotropin-releasing hormone (GnRH) agonists to suppress fertility has been poorly investigated in reptiles, and the few available studies show inconsistent results. The efficacy of single and double intramuscular 4.7 mg deslorelin acetate implants in captive pond sliders (Trachemys scripta) was investigated, with 20 animals divided into three groups: a single-implant group (6 animals), a double-implant group (6 animals), and a control group (no implant). During one reproductive season (March to October), plasmatic concentration of sexual hormones (estradiol, progesterone, and testosterone) and ovarian morphometric activity via computed tomography were monitored about every 30 days. A significative decrease in the number of phase II ovarian follicles was detected in the double-implant group compared with the control group, but no significant difference was noted in the number of phase III and phase IV follicles, egg production, and plasmatic concentration of sexual hormones. Results show that neither a single nor a double deslorelin acetate implant can successfully inhibit reproduction in female pond sliders during the ongoing season, but the lower number of phase II follicles in the double-implant group can possibly be associated with reduced fertility in the following seasons.