MICROSCOPICAL FEATURES OF THE MIROUNGA LEONINA PLACENTA (CARNIVORA, PINNIPEDIA, PHOCIDAE)

DIESSLER ME; MIGLIORISI L; MÁRQUEZ MEI; NEGRETE J; MENNUCCI JA; ZANUZZI CN; MIGLINO MA ; BARBEITO CG

MAR DEL PLATA

Simposio; VI SLIMP | V LASRI Maternal-Fetal Interaction: From Fertilization to the Next Generation; 2015

LASRI

Objective: The aim of the study was to describe the placental microscopic features of the Southern elephant seal, Mirounga leonina. No descriptions of the placentae from the genus Mirounga have been found in the available literature. Methods: Placentas from three elephant seals were collected after natural delivery at the Stranger Point rockery, close to the Argentinian Carlini Base scientific research station (South Shetland Islands, Antarctica), during the breeding period, the austral spring terrestrial phase in 2013. Samples were formalin-fixed and processed by histological routine techniques. Vimentin and cytokeratin filaments were immunohistochemically detected using a mouse monoclonal and a rabbit polyclonal antibody, Respectively, and revealed with the EnVision® detection system+HRP. Results: As in other carnivores, the choriovitelin placenta of Mirounga leonina is zonary. The anular band showed multiple macroscopic orange areas, both in the margins and in the center of the labyrinth, which corresponded to hemosiderin aggregates located among trophoblast villi. Macroscopic hematomal areas were not observed. Based on chorionic villous arrangements, Mirounga placenta was labyrinthine, reminding the canine placenta. In the chorioallantoic membrane, numerous and remarkably thick fetal arterial vessels were observed. This pospartum placental labyrinth showed scarce and flattened trophoblast cells and was almost composed of maternal and fetal intermingled blood vessels. Fetal vessels were typically small, round and regular in shape whereas maternal vessels were larger and irregular, and exhibited attenuated endothelial cells (unlike those from domestic carnivores) and numerous leukocytes. Fetal vessels were between trophoblast cells resulting in a very thin placental barrier, otherwise endotheliochorial. We did not find vimentin positive cells (other than endothelial cells or circulating leukocytes) similar to decidual cells of the cat placenta. Conclusions: Based on this preliminary study we conclude that Mirounga leonina placenta shares some basic features with that of other carnivores but shows some peculiarities, especially related to the source of iron for the fetuses.