title: Ultrasonography of wallaby prenatal development shows that the climb to the pouch begins in utero.
abstract: Marsupials have a functional placenta for a shorter period of time compared to that of eutherian species, and their altricial young reach the teats without any help from the mother. We have monitored the short intrauterine development of one marsupial, the tammar wallaby, with high-resolution ultrasound from reactivation of the 100-cell diapausing blastocyst to birth. The expanding blastocyst could be visualized when it had reached a diameter of 1.5 mm. From at least halfway through pregnancy, there are strong undulating movements of the endometrium that massage the expanding vesicle against the highly secretory endometrial surface. These unique movements possibly enhance exchange of uterine secretions and gases between the mother and embryo. There was a constant rate of development measured ultrasonographically from mid-gestation, regardless of when the blastocyst reactivated. Interestingly climbing movements by the fetus began in utero about 3 days before birth, mimicking those required to climb to the pouch.
authors.affiliation: Department of Reproduction Management, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Drews
authors.forename: Kathleen
authors.initials: K
authors.lastname: Roellig
authors.forename: Brandon R
authors.initials: BR
authors.lastname: Menzies
authors.forename: Geoff
authors.initials: G
authors.lastname: Shaw
authors.forename: Ina
authors.initials: I
authors.lastname: Buentjen
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Herbert
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Hildebrandt
authors.forename: Marilyn B
authors.initials: MB
authors.lastname: Renfree
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000502:physiology*; D004622:Embryo, Mammalian / Q000000981:diagnostic imaging / Q000196:embryology / Q000502:physiology; D004717:Endometrium / Q000000981:diagnostic imaging / Q000196:embryology / Q000502:physiology*; D005260:Female; D005333:Fetus / Q000196:embryology / Q000502:physiology; D007614:Macropodidae / Q000196:embryology / Q000502:physiology*; D010920:Placenta / Q000000981:diagnostic imaging / Q000196:embryology / Q000502:physiology*; D011247:Pregnancy; D013997:Time Factors; D016216:Ultrasonography, Prenatal