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Review: Marsupials: placental mammals with a difference
1Department of Zoology, The University of Melbourne, Victoria 3010, Australia. m.renfree@unimelb.edu.au
Placenta
|January 19, 2010
Summary
Marsupial placentas, though different from eutherian mammals, are vital for pregnancy. These placental mammals utilize sophisticated lactation, exchanging umbilical cords for teats.
Area of Science:
- Comparative placental biology
- Mammalian reproductive physiology
Background:
- The placenta exhibits significant variation across Mammalia.
- Marsupial and eutherian mammal embryos share similarities but possess key differences, notably the marsupial blastocyst's lack of an inner cell mass.
Purpose of the Study:
- To explore the functional aspects and hormonal roles of marsupial placentas.
- To compare placental development and function between marsupials and eutherian mammals.
Main Methods:
- Comparative analysis of placental structures and functions.
- Hormonal and gene expression studies in marsupial placentas (e.g., tammar wallaby).
Main Results:
- Marsupial blastocysts develop a chorio-vitelline placenta from a single trophoblast layer.
- Despite lacking invasion, tammar wallaby placentas demonstrate maternal recognition of pregnancy and elaborate hormones like prostaglandin F2alpha, cortisol, growth hormone, IGF2, and relaxin.
- Genomic imprinting plays a crucial role in marsupial placental function.
Conclusions:
- Marsupials are indeed placental mammals, with their placentas being essential for successful pregnancy.
- Marsupials possess a unique reproductive strategy combining placentation with highly developed lactation.
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