CONICET | Buscador de Institutos y Recursos Humanos

The main evolutionary milestone in the oviparityviviparity transition is placentation.The placenta is an organ with great morphological diversity among eutherians. Theexpression of different glycosidic residues (Gr) in the near‐term placenta constitutesits glycotype. In this study, the expression of different Gr was determined by lectinhistochemistry in early, midterm, and near‐term placentas of the plains viscacha(Lagostomus maximus), a caviomorph rodent with the highest poliovulatory rate andembryonic resorption rate among eutherians. Besides, a matrix with the expressionof each Gr in the exchange trophoblast of viscacha and other eutherians wasconstructed to map and infer phylogenetic and evolutionary relationships. Betweenearly, midterm, and near‐term placentas, variations in the pattern expression of Grwere observed. The glycotype of the near‐term placenta is composed of a highdiversity of Gr. Reconstruction of the ancestral state for each Gr present in the neartermplacenta showed a diverse scenario: some sugars were common to the speciesof Placentalia included in this study. In the analyzed species with synepitheliochorialand epitheliochorial placentas, no differential glycosylation patterns between themwere observed. In species with invasive placentas, such as the endotheliochorialplacentas of Carnivora, some common Gr were detected among them, while otherswere species‐specific. In species with hemochorial placenta, the same Gr are shared.Particularly, in the viscacha greater differences with species of the Hominidae andeven Muridae families were observed. Nevertheless, greater similarities with othercaviomorph rodents were detected. Placental glycotype of each species constitutesan excellent tool to achieve phylogenetic and evolutionary inferences amongeutherians.

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