Uterine factors and delayed implantation in macropodid marsupials

Local factors controlling uterine functions in macropodids are reviewed and the components of uterine fluids are examined. Activation of the diapausing blastocyst and subsequent development of the expanding vesicle are associated with a changing uterine environment. Concentrations of proteins, calcium and zinc in uterine exudates alter during gestation; the changes appear to be related both to the stage of development of the conceptus and to the hormonal milieu. In addition the endometrium itself may have an active endocrine role in the control of development. Cation concentrations in uterine exudates of the quokka (Setonix brachyurus) are not clearly related to events leading to blastocyst activation.