Metatheria: Marsupials

Abstract

Marsupials have a distinctive reproductive physiology and developmental pathway characterised by short gestation with a fully functional placenta, delivering altricial neonates that depend on a long and sophisticated lactation. Their reproductive anatomy differs from that of eutherian mammals with three vaginae, and two separate uteri in females, and a pre-penile scrotum in males. Aspects of somatic sexual differentiation are independent of gonadal hormones, but are controlled directly by sex-chromosomal genes. Genetic and genomic studies in marsupials are illuminating the evolution of fundamental processes such as genomic imprinting and X-inactivation that are so essential to mammalian repr..