A Study of Serum Steroid Hormone Levels in Captive Female Bottlenose Dolphins, Their Correlation with Reproductive Status, and Their Application to Ovulation Induction in Captivity

摘要

Little is known about reproductive endocrinology in captive Atlantic bottlenose dolphins (Tursiops truncatus). Conception is rare in captive animals. In order to artificially facilitate this provess, reproductive parameters were studied and manipulated in fully grown captive females greater than 9 years of age, 160 kg in weight, and 211 cms in length. Baseline serum levels of the steroid hormones progesterone and estrogen were determined for intact and ovariectomized captive females as well as newly captured wild adult females. Wild females were found to have twice the circulating estrogen levels of females held in captivity greater than five years. Stimulation of ovarian follicular growth and sexual receptiveness were attempted by intramuscular injection of pregnant mare serum gonadotropin. Relatively high doses of pregnant mare serum gonadotropin were found to increase serum estrogen levels and sexual receptiveness. Following these pregnant mare serum gonadotropin injections, human chorionic gonadotropin was injected and ovulation induced, as indicated by subsequent high levels of serum progesterone. From these observations, it appears that (1) the relative infertility of captive female dolphins to their wild counterparts may be due to a lack of ovarian activity; and (2) female captive dolphins, although relatively resistant to pregnant mare serum gonadotropin, can be induced to ovulate in captivity using a combination of relatively high intramuscular injected doses of pregnant mare serum gonadotropin followed by human chorionic gonadotropin.