Glycoconjugates within the oviduct and their functional significance with special reference to marsupials

In placental (eutherian) mammals, a number of important events take place within the oviduct including the pre-fertilisation maturation of gametes (including sperm storage), sperm-egg interactions, egg activation and early embryonic development. Many of these events involve interactions of glycoconjugates; both on the surface of the gametes and with the secretions of the oviductal epithelium and these have best been studied in eutherian mammals. In marsupials, however, while the oviduct is known to produce the extracellular egg coat, the mucoid layer, that comes to surround the zona pellucida, its role in the maturation of gametes is only now being elucidated, particularly in the oocyte. This review emphasises what is known of the structure and function of the oviduct and its secretions in marsupials and briefly compares it with data from eutherians. In particular, knowledge of oviductal glycoconjugates in the structure of the post-ovulatory oocyte and its vestments around the time of fertilisation in Australian marsupials is outlined.