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The Placenta and Gravid Uterus of Carcharhinus falciformis
Perry W. Gilbert and Donald A. Schlernitzauer
Vol. 1966, No. 3 (Sep. 7, 1966), pp. 451-457
Stable URL: http://www.jstor.org/stable/1441064
Page Count: 7
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Elasmobranchs demonstrate diverse means of nurturing their embryos, there being within this vertebrate group oviparous, ovoviviparous, and truly viviparous, or placental, species. Carcharhinus falciformis is of the latter type. Observations, gross and microscopic, made on a single uterus of this species and its contained embryos and placentae are presented. All elasmobranch placentae are of the yolk-sac type, but within this single classification rather wide structural variations occur. The placenta of C. falciformis possesses a discoidal shape and is completely nondeciduate. The following layers intervene between the foetal and maternal blood systems: (1) maternal endothelium, (2) maternal epithelium (essentially not reduced), (3) possibly the egg-case membrane, depending on factors stated in the paper, (4) foetal epithelium (greatly reduced), and (5) foetal endothelium.