GAMETE BIOLOGY OF THE NEW-WORLD MARSUPIAL, THE GREY SHORT-TAILED OPOSSUM, MONODELPHIS-DOMESTICA

Mammalian gametes undergo a series of functional and developmental cha nges that culminate in fertilization. In order to appreciate the neces sity for such complex processes as sperm maturation, capacitation and the intimate sperm-egg interactions leading to gamete fusion, it is im portant to understand how gametes may have evolved. In this respect, m arsupials are particularly relevant since they exhibit features remini scent of both non-mammalian vertebrates and eutherian mammals. The gre y short-tailed opossum, Monodelphis domestica, is a New World marsupia l from Brazil. It breeds well under laboratory conditions and is an ex cellent animal model to investigate marsupial gamete biology. As in ot her American marsupials, the spermatozoa of the opossum form pairs in the epididymis. Here, a number of studies carried out in this laborato ry, related to sperm maturation, capacitation and fertilization in M. domestica, are reviewed and the gamete biology in this species is comp ared with what is known in other marsupials and eutherian mammals.