title: Induction of oviposition by the administration of oxytocin in hawksbill turtles.
abstract: We set out to develop an oviposition induction technique for captive female hawksbill turtles Eretmochelys 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 oxytocin on oviposition. Seven of the turtles were held in a stationary horizontal position on a retention stand, and then oxytocin was administrated (0.6-0.8 units/kg of body weight; 5 mL). The seven turtles were retained for a mandatory 2 h period after oxytocin administration, 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 oxytocin after 24 h. The eggs in oviducts of all nine turtles were observed by ultrasonography at 24 h after oxytocin administration. 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 oxytocin administration, while one began ovipositing in the holding tank immediately after retention. All turtles finished ovipositing eggs within 24 h of oxytocin administration. This report is the first to demonstrate successful induced oviposition in sea turtles. We suggest that the muscles in the oviducts of hawksbill turtles may respond to relatively lower doses of oxytocin (inducing contractions) compared to land and freshwater turtles (4-40 units/kg) based on existing studies.
authors.affiliation: 1 Okinawa Churashima Foundation, 888 Ishikawa, Motobu, Okinawa 905-0206, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Kawazu
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Kino
authors.forename: Konomi
authors.initials: K
authors.lastname: Maeda
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Sawamukai
mesh_terms: D000818:Animals; D005260:Female; D010058:Oviposition / Q000187:drug effects*; D010120:Oxytocics / Q000008:administration & dosage / Q000494:pharmacology*; D010121:Oxytocin / Q000008:administration & dosage / Q000494:pharmacology*; D014426:Turtles / Q000502:physiology*
chemical_list: D010120:Oxytocics; D010121:Oxytocin
keywords: clutch size; egg diameter; induced oviposition; oviposited eggs; oxytocin dosage