Chorioallantoic and yolk sac placentation in the plains viscacha (Lagostomus maximus) e A caviomorph rodent with natural polyovulation

FLAMINI MA; PORTIANSKY EL; FAVARON PO; MARTINS DS; AMBROSIO CE; MESS A; MIGLINO MA; BARBEITO CG

PLACENTA

W B SAUNDERS CO LTD

Año: 2011 vol. 32 p. 963 - 968

0143-4004

Objectives: Reproduction in the plains viscacha is characterized by the polyovulation of hundreds ofoocytes, the loss of implantation and the development of 1e3 offspring. Our goal was to determinewhether placental development was affected by these specializations.Study design: Thirteen placentas from early pregnancy to near-term pregnancy were analyzed using histological, immunohistochemical and transmission electron microscopy.Results: An inverted, villous yolk sac was present. Placentas were formed by the trophospongium,labyrinth and subplacenta. A lobulated structure with a hemomonochorial barrier was established early in pregnancy. Proliferating trophoblast that was clustered at the outer border and inside the labyrinthwas responsible for placental growth. Trophoblast invasion resulted from the cellular trophoblast and syncytial streamers derived from the subplacenta. Different from other caviomorphs, numerous giant cells were observed.Conclusions: The principle processes of placentation in caviomorphs follow an extraordinarily stable pattern that is independent of specializations, such as polyovulation.