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.

Oxytocin mediated behavior in invertebrates: An evolutionary perspective

“…Some of the strongest insights into conservation and plasticity in behavioral genetics have emerged from studies of the oxytocin/arginine‐vasopressin neuromodulatory system. Peptides related to oxytocin and vasopressin (henceforth, “oxytocin‐related peptides”) are encoded in the genomes of animal species separated by 600 million years of evolution (Gwee et al, ), including invertebrate nematodes (Beets et al, , Garrison et al, ), insects (Proux et al, , Stafflinger et al, , Gruber and Muttenthaler, , Egekwu et al, ), annelids (Oumi et al, , Fujino et al, , Wagenaar et al, ), and molluscs (Van Kesteren et al, , Takuwa‐Kuroda et al, , Bardou et al, ); as well as vertebrate fish (Godwin and Thompson, ), amphibians (Searcy et al, ), reptiles (Kabelik and Magruder, , Kawazu et al, ), birds (Kelly and Goodson, ), and mammals (Donaldson and Young, , Stoop, ) (Fig. ).…”