Term placenta of the South American sea lion, Otaria flavescens (Shaw, 1800).

ROCIO HERNANDEZ; MONICA DIESSLER; GIMENA GOMEZ CASTRO; CLEOPATRA M. LOZA ; JUAN P. LOUREIRO; MARIANA A. WOUDWYK; MARIANO SCIANDA; ENRIQUE F. COSTA; MAURO A. PERGAZERE; CLAUDIO G. BARBEITO

Bogota

Simposio; IX SLIMP-Latin American Society for Materno Fetal Interaction and Placenta virtual meeting.; 2022

Rocío Hernández 1-2, Mónica E. Diessler 1, Gimena Gomez Castro 1-2, Cleopatra M. Loza 1-3, Juan P. Loureiro 5-6, Mariana A. Woudwyk 1, Mariano Scianda 1, Enrique F. Costa 4, Mauro A. Pergazere 6, Claudio G. Barbeito 1-2.1- Laboratorio de Histología y Embriología Descriptiva, Experimental y Comparada (LHYEDEC), Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata (FCV, UNLP), La Plata. Argentina; 2- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). FCV, UNLP, La Plata. Argentina;3- Morphos, Laboratorio de Morfología Evolutiva y de Desarrollo (CONICET), Facultad de Ciencias Naturales y Museo, UNLP, La Plata, Argentina;4- Instituto de Patología Bernardo Epstein, FCV, UNLP, La Plata. Argentina; 5- Catedra de Anatomía Descriptiva, FCV, UNLP, La Plata. Argentina;6- Fundación Mundo Marino, San Clemente del Tuyú, Buenos Aires, Argentina.TitleTerm placenta of the South American sea lion, Otaria flavescens (Shaw, 1800)Objective To describe morphological features of the term placenta of South American sea lion. MethodologyPlacentas from three sea lions that gave birth to normal puppies were analyzed. Those mothers were born in Mundo Marino oceanarium, where they live in a controlled environment. The placentas were formalin-fixed and processed by histologic techniques.ResultsThe placentas were zonary and belt-shaped. The surface facing the uterus was irregular and rough, with bulging grayish-orange margins. A few 3-5 cm ovoid grey structures, scattered through the belt, protruded from the fetal surface. Maternal and fetal structures formed a labyrinth in which the trophoblast, mostly syncytial, directly faced maternal vessels. A profusion of small fetal capillaries surrounded maternal vessels, frequently indenting the syncytiotrophoblast. This arrangement resulted in a thin endotheliochorial barrier. Maternal vessels were larger towards the fetal aspect of the labyrinth, alike the so-called ?sinusoidal? vessels in other pinnipeds, and they had high endothelia in most areas. In junctional areas, tertiary chorionic villi were evident. They were partially laying free, close to endometrial detritus in the uterine lumen, but focally anchored to the connective uterine tissue through projections of syncytiotrophoblast. The margins of the placenta were composed of folded chorionic villi surrounding abundant brilliant orange crystals. Similar folds delimited quite large areas of stagnant blood and necrotic tissue close to the pigmented zones.Conclusion Regarding its zonary, belt-shaped, labyrinthine and endotheliochorial nature, the Otaria flavescens placenta resembles that of most carnivores. Particularly, the ?sinusoidal? maternal vessels, and the large quantities of crystals regarded as bilirubin, are hallmarks of pinniped placentas. Beyond the scarce, isolated and mostly macroscopic data on Callorhinus ursinus and Zalophus californianus, most of the knowledge about pinniped placentas comes from Phocidae. Though, we cannot compare the present findings to others in Otariidae. Up to our knowledge, this is the first description of Otaria flavescens placenta.