Induction of Oviposition by the Administration of Oxytocin in Hawksbill Turtles

We set out to develop an oviposition induction technique for captive female hawksbill turtlesEretmochelys imbricata. The infertile eggs of nine females were induced to develop by the administration of follicle-stimulating hormone, after which we investigated the effects of administering oxytocinon oviposition. Seven of the turtles were held in a stationary horizontal position on a retention stand, and then oxytocinwas administrated (0.6–0.8 units/kg of body weight; 5 mL). The seven turtles were retained for a mandatory 2 h period after oxytocinadministration, and were then returned to the holding tanks. As the control, normal saline (5 mL) was administered to the other two turtles, followed by the administration of oxytocinafter 24 h. The eggs in oviductsof all nine turtles were observed by ultrasonography at 24 h after oxytocinadministration. The control experiment validated that stationary retention and normal saline administration had no effect on egg oviposition. Eight of the turtles began ovipositing eggs at 17–43 min after oxytocinadministration, while one began ovipositing in the holding tankimmediately after retention. All turtles finished ovipositing eggs within 24 h of oxytocinadministration. This report is the first to demonstrate successful induced oviposition in sea turtles. We suggest that the muscles in the oviductsof hawksbill turtlesmay respond to relatively lower doses of oxytocin(inducing contractions) compared to land and freshwater turtles (4–40 units/kg) based on existing studies.