A review of the evolution of viviparity in lizards: Structure, function and physiology of the placenta

Michael B. Thompson*, Brian K. Speake

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

107 Citations (Scopus)


The aim of this review is to collate data relevant to understanding the evolution of viviparity in general, and complex placentae in particular. The wide range of reproductive modes exhibited by lizards provides a solid model system for investigating the evolution of viviparity. Within the lizards are oviparous species, viviparous species that have a very simple placenta and little nutrient uptake from the mother during pregnancy (lecithotrophic viviparity), through a range of species that have intermediate placental complexities and placental nutrient provision, to species that lay microlecithal eggs and most nutrients are provided across the placenta during development (obligate placentotrophy). In its commonest form, lecithotrophic viviparity, some uptake of water, inorganic ions and oxygen occurs from the mother to the embryo during pregnancy. In contrast, the evolution of complex placentae is rare, but has evolved at least five times. Where there is still predominantly a reliance on egg yolk, the omphaloplacenta seems to be paramount in the provision of nutrition to the embryo via histotrophy, whereas the chorioallantoic placenta is more likely involved in gas exchange. Reliance on provision of substantial organic nutrient is correlated with the regional specialisation of the chorioallantoic placenta to form a placentome for nutrient uptake, particularly lipids, and the further development of the gas exchange capabilities of the other parts of the chorioallantois.

Original languageEnglish
Pages (from-to)179-189
Number of pages11
JournalJournal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology
Issue number3
Publication statusPrint publication - 1 Mar 2006


  • Embryo
  • Lecithotrophy
  • Nutrition
  • Placentotrophy


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