title: Free blastocyst and implantation stages in the European brown hare: correlation between ultrasound and histological data.
abstract: The European brown hare (Lepus europaeus) is the only species with superconception, whereby the maternal reproductive tract hosts two sets of conceptuses at different developmental stages. The embryonic development of the hare has not yet been described. To understand the mechanism of superconception, we studied oviduct transport and implantation stages by embryo flushing and live high-resolution ultrasound. Ultrasound data of implantation stages is correlated with histology. In the oviduct, a mucin coat is deposited on the zona pellucida. The blastocysts enter the uterine horns on Day 5, 1 day later than in the rabbit, and directly expand approximately threefold. Spacing is accompanied by peristaltic movement of the endometrium. The mucin coat disappears and the conceptuses attach. The yolk-sac expands in the blastocoel and syncytial knobs invade the antimesometrial endometrium. Maternal blood lacunae appear in the mesometrial endometrial folds, which are subsequently invaded by the syncytiotrophoblast. The haemochorial chorioallantoic placenta forms. The yolk-sac cavity is gradually replaced by the allantois and finally by the exocoel. The different reproductive strategies of the precocial hare and the altricial rabbit are discussed. We assume that the lagomorph-specific mucin coat and the hare-specific delay of the oviduct-uterine transition are prerequisites for superconception.
authors.affiliation: Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Strasse 17, 10315 Berlin, Germany. drews@izw-berlin.de
authors.forename: Barbara
authors.initials: B
authors.lastname: Drews
authors.forename: Jennifer
authors.initials: J
authors.lastname: Ringleb
authors.forename: Romy
authors.initials: R
authors.lastname: Waurich
authors.forename: Thomas Bernd
authors.initials: TB
authors.lastname: Hildebrandt
authors.forename: Katharina
authors.initials: K
authors.lastname: Schröder
authors.forename: Kathleen
authors.initials: K
authors.lastname: Roellig
mesh_terms: D000482:Allantois / Q000000981:diagnostic imaging / Q000502:physiology; D000818:Animals; D000835:Animals, Wild; D000836:Animals, Zoo; D001755:Blastocyst / Q000166:cytology / Q000000981:diagnostic imaging / Q000502:physiology*; D010064:Embryo Implantation; D004622:Embryo, Mammalian / Q000166:cytology / Q000000981:diagnostic imaging / Q000502:physiology*; D047108:Embryonic Development; D004717:Endometrium / Q000166:cytology / Q000000981:diagnostic imaging / Q000502:physiology; D005187:Fallopian Tubes / Q000000981:diagnostic imaging / Q000502:physiology; D005260:Female; D005858:Germany; D034621:Hares / Q000196:embryology*; D009077:Mucins / Q000378:metabolism; D010920:Placenta / Q000000981:diagnostic imaging / Q000502:physiology; D011247:Pregnancy; D013045:Species Specificity; D014327:Trophoblasts / Q000166:cytology / Q000000981:diagnostic imaging / Q000502:physiology; D014463:Ultrasonography; D015017:Yolk Sac / Q000166:cytology / Q000000981:diagnostic imaging / Q000502:physiology; D015044:Zona Pellucida / Q000000981:diagnostic imaging / Q000378:metabolism
chemical_list: D009077:Mucins