Vogel P
Department of Ecology and Evolution, University of Lausanne, Switzerland.
Placenta. 2005 Sep-Oct;26(8-9):591-6. doi: 10.1016/j.placenta.2004.11.005. Epub 2005 Jan 27.
Based on histology, the placentae of eutherians are currently grouped in epitheliochorial, endotheliochorial and haemochorial placentae. In a haeckelian sense, the epitheliochorial contact with marked histiotrophic feeding by uterine milk is generally considered as primitive, especially since similar contacts exist in Marsupials. In contrast, the more intimate endotheliochorial and haemochorial contact, facilitating haemotrophic nutrition, is interpreted as a derived state. A cladistic analysis based on the phylogenetic relationships established by molecular analyses reveals that the basic clades are all characterized by an endotheliochorial or haemochorial placenta, and that the epitheliochorial placenta evolved at least three times in a convergent manner. This evolution may be explained by the fact that the epitheliochorial placenta in eutherians is more efficient in nutritional transfer (flow rate by exchange surface). Moreover, this arrangement may confer an advantage to the mother who can probably reduce the degree of manipulation by a genetically imprinted embryo.
根据组织学，目前真兽类动物的胎盘可分为上皮绒毛膜胎盘、内皮绒毛膜胎盘和血绒毛膜胎盘。从海克尔的意义上来说，通过子宫乳进行显著组织营养性喂养的上皮绒毛膜接触通常被认为是原始的，特别是因为有袋类动物中也存在类似的接触。相比之下，促进血源性营养的更为紧密的内皮绒毛膜和血绒毛膜接触则被解释为衍生状态。基于分子分析所建立的系统发育关系进行的分支系统学分析表明，基本分支的特征均为内皮绒毛膜胎盘或血绒毛膜胎盘，并且上皮绒毛膜胎盘至少以趋同的方式进化了三次。这种进化可能是由于真兽类动物的上皮绒毛膜胎盘在营养物质转移方面（通过交换表面的流速）效率更高。此外，这种结构可能会给母体带来优势，因为母体可能能够降低基因印记胚胎的操纵程度。
