The marsupial placenta: A phylogenetic analysis
The marsupial placenta: A phylogenetic analysis
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DOI：
10.1002/jez.a.10291
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发表时间：
2003-09-01
影响因子：
2.8
通讯作者：
Renfree, MB
中科院分区：
文献类型：
--
作者：
Freyer, C;Zeller, U;Renfree, MB
本文对不同有袋动物类群卵黄囊胎盘的结构、生理学和内分泌学进行了比较和系统发育分析，为有袋动物茎类胎盘的特征提供信息。我们认为有袋类茎类动物具有功能性卵黄囊胎盘。妊娠后期子宫分泌的组织营养减少，蛋壳破裂时卵黄囊至少有一半血管化。由于卵黄囊的融合，大部分无血管的双层卵黄囊在妊娠后期不能作为胎盘。双层卵黄囊在单卵澳大利亚类动物中获得了相对更重要的营养。在大足类中，卵黄囊在外壳破裂时保持双层结构的比例高于茎类。大足体的另一个衍生特征是持续的血浆黄体酮合成，这反过来又导致子宫分泌期延长和妊娠期延长。有袋类干类动物的胎盘可能能够代谢组织因子和造血因子。在发育的早期阶段对怀孕的认识是大足类动物的衍生特征，我们认为这在有袋类动物中没有发生。然而，在有袋类的茎类物种中，前列腺素明显地诱导了生育和生育行为。虽然卵黄囊形成了最终的胎盘，但在有袋动物的茎类物种中，尿囊可能提供了一种补充胎盘的功能，但在有袋动物胎盘的进化过程中，尿囊的作用逐渐变得不那么重要。(C) 2003 Wiley-Liss, Inc。
The structure, physiology, and endocrinology of the yolk sac placenta of different marsupial groups is compared and phylogenetically analyzed to provide information on placental characters in the marsupial stem species. We conclude that the marsupial stem species possessed a functional yolk sac placenta. Histotrophic nutrition by uterine secretion decreased during late pregnancy and at least half of the yolk sac was vascularized at the time of shell coat rupture. Due to yolk sac fusion, the larger part of the avascular, bilaminar yolk sac could not serve as a placenta at late gestation in the polyovular marsupial stem species. The bilaminar yolk sac gained a relatively greater importance for nutrition in monovular australidelphians. In macropodids a greater proportion of the yolk sac remained bilaminar at the time of shell coat rupture than in the stem species. Another derived feature of macropodids is the sustained plasma progesterone synthesis that is in turn responsible for an extended secretory phase of the uterus and a lengthened gestation. The placenta of the marsupial stem species was probably capable of metabolising histo- and hemotrophes. Recognition of pregnancy during early stages of development is a derived character of macropodids that we suggest did not occur in the marsupial stem species. However, birth and birth behaviour were apparently induced by prostaglandins in the marsupial stem species. Although the yolk sac formed the definitive placenta, it is likely that the allantois provided a supplementary placental function in the marsupial stem species, but that the role of the allantois became progressively less important during the evolution of marsupial placentation. (C) 2003 Wiley-Liss, Inc.