title: Superconception in mammalian pregnancy can be detected and increases reproductive output per breeding season.
abstract: The concept of superfetation, a second conception during pregnancy, has been controversial for a long time. In this paper we use an experimental approach to demonstrate that female European brown hares (Lepus europaeus) frequently develop a second pregnancy while already pregnant and thereby increase their reproductive success. After a new, successful copulation, we confirmed additional ovulations before parturition in living, late-pregnant females by detecting a second set of fresh corpora lutea using high-resolution ultrasonography. The presence of early embryonic stages in the oviduct, demonstrated by oviduct flushing, next to fully developed fetuses in the uterus is best explained by passage of semen through the late-pregnant uterus; this was confirmed by paternity analysis using microsatellite profiling. Subsequent implantation occurred after parturition. This superfetation, categorized as superconception, significantly increased litter size and permitted females to produce up to 35.4% more offspring per breeding season. It is therefore most likely an evolutionary adaptation.
authors.affiliation: Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, Berlin 10315, Germany. kathleen_roellig@gmx.de
authors.forename: Kathleen
authors.initials: K
authors.lastname: Roellig
authors.forename: Frank
authors.initials: F
authors.lastname: Goeritz
authors.forename: Joerns
authors.initials: J
authors.lastname: Fickel
authors.forename: Robert
authors.initials: R
authors.lastname: Hermes
authors.forename: Heribert
authors.initials: H
authors.lastname: Hofer
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Hildebrandt
mesh_terms: D000818:Animals; D001947:Breeding; D003338:Corpus Luteum / Q000000981:diagnostic imaging; D005260:Female; D005306:Fertilization / Q000502:physiology*; D034621:Hares; D008297:Male; D010057:Oviducts / Q000000981:diagnostic imaging; D011247:Pregnancy; D012098:Reproduction / Q000502:physiology*; D014463:Ultrasonography; D014659:Vasectomy