Pregnancy in a marsupial, the Tasmanian pademelon (Thylogale billardierii)

The Tasmanian pademelon, Thylogale billardierii, is a medium-sized wallaby that adapts well to captivity and, unlike the well-studied tammar wallaby, is capable of breeding all year round. It may, therefore, be a useful model species for research into the reproductive biology of macropod marsupials. This paper presents necessary background data on histological changes in the reproductive organs and the rate of embryonic growth during gestation in T1 billardierii. After Day 4 RPY (removal of young from the pouch) the gravid and non-gravid uteri differ significantly in some histological parameters. The corpus luteum becomes active by Day 6 RPY and is fully developed by Day 14 RPY; it begins to degenerate from Day 19 RPY. Plasma progesterone concentrations through gestation follow a pattern similar to that in the tammar wallaby. There is an early, smaller, peak at Day 5 RPY, with plasma concentrations of progesterone then falling until the larger pre-partum peak occurs several days before birth.