Placentation in dolphins from the Amazon River Basin: the Boto, Inia geoffrensis, and the Tucuxi, Sotalia fluviatilis
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Placentation in dolphins from the Amazon River Basin: the Boto, Inia geoffrensis, and the Tucuxi, Sotalia fluviatilis Vera MF da Silva1, Anthony M Carter*2, Carlos E Ambrosio3, Ana F Carvalho4, Marina Bonatelli3, Marcelo C Lima3 and Maria Angelica Miglino3 Address: 1National Institute of Amazonian Research, Manaus, AM, Brazil, 2University of Southern Denmark, Odense, Denmark, 3University of Sao Paulo, Sao Paulo, SP, Brazil and 4School of Veterinary Medicine, Sao Joao da Boa Vista, SP, Brazil Email: Vera MF da Silva - [email protected]; Anthony M Carter* - [email protected]; Carlos E Ambrosio - [email protected]; Ana F Carvalho - [email protected]; Marina Bonatelli - [email protected]; Marcelo C Lima - [email protected]; Maria Angelica Miglino - [email protected] * Corresponding author
Published: 28 June 2007 Reproductive Biology and Endocrinology 2007, 5:26
doi:10.1186/1477-7827-5-26
Received: 14 May 2007 Accepted: 28 June 2007
This article is available from: http://www.rbej.com/content/5/1/26 © 2007 da Silva et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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.
Background Little is known of placentation in whales [1]. Turner [2] showed that they have epitheliochorial placentation. For the baleen whales (suborder Mysticeti) our knowledge has advanced little further [3], since available specimens often have been in too poor condition for histology [4]. There is an excellent study of the early development of the fetal membranes in the humpback whale [5], but it does not extend to the establishment of the placenta. Rather more is known about the toothed whales (suborder Odontoceti), although based on descriptions of single specimens of bottlenose dolphin [6], harbour porpoise
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