Oral Presentation The Annual Scientific Meeting of the Endocrine Society of Australia and the Society for Reproductive Biology 2013

How complex are lizard placentae? (#5)

Mike B. Thompson 1
  1. University of Sydney, School of Biological Sciences, NSW, Australia

Lizards provide a particularly good model to study the evolution of placentation in amniote vertebrates because viviparity has evolved in lizards many times and structurally complex placentae that support varying degrees of placentotrophy have evolved four or five times in the family Scincidae.  I have used skinks as a comparative model to identify commonalities and differences in structure and molecular mechanisms between these different independent origins of viviparity and identify constraints in the ways that viviparity and placentotrophy have evolved.  The questions are divided into understanding two phenomena – the evolution of viviparity from oviparity, and the evolution of complex placentation and placentotrophy from lecithotrophic viviparity.  Using electron microscopy and immunohistochemistry, and more recently, transcriptomics, we have discovered that the story is much more complex than we had anticipated. Structurally and using a candidate gene approach, we have shown that common structural changes and molecular processes occur during pregnancy across a wide range of amniote vertebrates.  Nevertheless, our transcriptomic work has not identified a “smoking gun” gene for the evolution of viviparity, but has revealed that many genes that have changed during the evolution of viviparity are common to different lineages of lizards and mammals.