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Lueders I.,Leibniz Institute for Zoo and Wildlife Research | Niemuller C.,Kingfisher International Inc. KFI | Rich P.,African Lion Safari and Game Farm Ltd. ALS | Gray C.,African Lion Safari and Game Farm Ltd. ALS | And 3 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2012

The corpus luteum, a temporally established endocrine gland, formed on the ovary from remaining cells of the ovulated follicle, plays a key role in maintaining the early mammalian pregnancy by secreting progesterone. Despite being a monovular species, 2-12 corpora lutea (CLs) were found on the elephant ovaries during their long pregnancy lasting on average 640 days. However, the function and the formation of the additional CLs and their meaning remain unexplained. Here, we show from the example of the elephant, the close relationship between the maternally determined luteal phase length, the formation of multiple luteal structures and their progestagen secretion, the timespan of early embryonic development until implantation and maternal recognition. Through three-dimensional and Colour Flow ultrasonography of the ovaries and the uterus, we conclude that pregnant elephants maintain active CL throughout gestation that appear as main source of progestagens. Two LH peaks during the follicular phase ensure the development of a set of 5.4±2.7 CLs. Accessory CLs (acCLs) form prior to ovulation after the first luteinizing hormone (LH) peak, while the ovulatory CL (ovCL) forms after the second LH peak. After five to six weeks (the normal luteal phase lifespan), all existing CLs begin to regress. However, they resume growing as soon as an embryo becomes ultrasonographically apparent on day 49±2. After this time, all pregnancy CLs grow significantly larger than in a non-conceptive luteal phase and are maintained until after parturition. The long luteal phase is congruent with a slow early embryonic development and luteal rescue only starts 'last minute', with presumed implantation of the embryo. Our findings demonstrate a highly successful reproductive solution, different from currently described mammalian models. © 2012 The Royal Society. Source


Lueders I.,Leibniz Institute for Zoo and Wildlife Research | Niemuller C.,Kingfisher International Inc. KFI | Gray C.,African Lion Safari and Game Farm Ltd. ALS | Rich P.,African Lion Safari and Game Farm Ltd. ALS | Hildebrandt T.B.,Leibniz Institute for Zoo and Wildlife Research
Reproduction | Year: 2010

The occurrence of multiple corpora lutea (CLs) in the ovaries of the cycling and pregnant elephant, a monovulatory mammal, has driven scientific discussions during the past five decades. However, fundamental knowledge on luteogenesis is lacking. In this long-term study, CL formation and regression throughout the estrous cycle were monitored using transrectal 2D- and 3D ultrasonography in 33 captive Asian elephants. Serum or urinary progestagens (Pm) were measured to determine the reproductive cycle stage. In seven females, serum Pm and LH concentrations were directly related to ovarian events.We have found two different modalities of luteal development: one for the accessory CL (acCL) and one for the ovulatory CL (ovCL). acCLs were derived from luteinization of larger, subordinate follicles after the first anovulatory LH peak. The dominant follicle produced the largest CL after the second (ovulatory) LH peak. The first luteal tissue formation became visible ∼10 days after the respective LH peak. After ovulation, it took 29.8±5.0 days for the acCLs to reach their maximum diameter, whereas the ovCL reached a significantly larger size (33.2±2.3 mm, P<0.0001) about 10-15 days later. All CLs were visible throughout the new follicular phase, with some of the larger ones still present in the subsequent luteal period. In this study, we have demonstrated that Asian elephants have evolved a novel method for luteal development and function, and by repeatedly forming two types of distinctly different CLs for every reproductive cycle, they have ensured that there will be sufficient luteal capacity for maintaining a 22-month pregnancy should conception occur. © 2010 Society for Reproduction and Fertility. Source

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