Tuesday, 9 April 2013

Giraffe placenta

Giraffes in winter quarters at Odense Zoo
Courtesy af Jonathan Thorvaldsen

Recent phylogenies (here and here) show a basal split among pecoran ruminants in the Late Oligicene, with Giraffidae (giraffe and okapi) and Antilocapridae (pronghorn) on one branch and Bovidae (cattle, sheep and goats, antelopes), Moschidae (musk ox) and Cervidae (deer) on the other. Hitherto, detailed knowlege about placentation has been limited to domesticated species from the latter group.

Delivered giraffe placenta with cotyledons from Benirschke (here)

The new study of of the maternal-fetal interface in two giraffe placentas by Sandra Wilsher and others (here) is therefore important. It confirms that the placenta is polycotyledonary and that binucleate trophoblast cells are present in fewer numbers than in sheep, cattle and deer. Binucleate cells in the placentomes stained intensely for prolactin whereas binucleate cells in the intercaruncular regions did not. This hormone might play a role in the production of accessory corpora lutea in the ovaries of the mother and the female fetus. It remains to be determined if the antibody was binding to a protein identical to pituitary prolactin or to a placental lactogen. The giraffe genome would appear to be uncharted territory.

At the edges of each placentome there were marginal folds of allantochorion situated above the openings of dilated uterine glands, suggesting a route for histiotrophic nutrition.

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