title: Placentation in dolphins from the Amazon River Basin: the Boto, Inia geoffrensis, and the Tucuxi, Sotalia fluviatilis.
abstract: A recent reassessment of the phylogenetic affinities of cetaceans makes it timely to compare their placentation with that of the artiodactyls. We studied the placentae of two sympatric species of dolphin from the Amazon River Basin, representing two distinct families. The umbilical cord branched to supply a bilobed allantoic sac. Small blood vessels and smooth muscle bundles were found within the stroma of the cord. Foci of squamous metaplasia occurred in the allanto-amnion and allantochorion. The interhemal membrane of the placenta was of the epitheliochorial type. Two different types of trophoblastic epithelium were seen. Most was of the simple columnar type and indented by fetal capillaries. However, there were also areolar regions with tall columnar trophoblast and these were more sparsely supplied with capillaries. The endometrium was well vascularised and richly supplied with actively secreting glands. These findings are consistent with the current view that Cetacea are nested within Artiodactyla as sister group to the hippopotamids.
authors.affiliation: National Institute of Amazonian Research, Manaus, AM, Brazil. tucuxi@inpa.gov.br
authors.forename: Vera M F
authors.initials: VM
authors.lastname: da Silva
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Carter
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Ambrosio
authors.forename: Ana F
authors.initials: AF
authors.lastname: Carvalho
authors.forename: Marina
authors.initials: M
authors.lastname: Bonatelli
authors.forename: Marcelo C
authors.initials: MC
authors.lastname: Lima
authors.forename: Maria Angelica
authors.initials: MA
authors.lastname: Miglino
mesh_terms: D000482:Allantois / Q000033:anatomy & histology / Q000098:blood supply / Q000502:physiology; D000650:Amnion / Q000033:anatomy & histology / Q000098:blood supply / Q000502:physiology; D000818:Animals; D001938:Brazil; D002196:Capillaries / Q000033:anatomy & histology / Q000502:physiology; D004289:Dolphins / Q000033:anatomy & histology* / Q000502:physiology; D004717:Endometrium / Q000033:anatomy & histology* / Q000098:blood supply / Q000502:physiology; D004848:Epithelium / Q000033:anatomy & histology / Q000502:physiology; D005260:Female; D010802:Phylogeny; D010920:Placenta / Q000033:anatomy & histology* / Q000098:blood supply / Q000502:physiology; D021041:Placental Circulation / Q000502:physiology; D011247:Pregnancy; D014470:Umbilical Cord / Q000033:anatomy & histology* / Q000502:physiology