MULLERIAN DUCT REGRESSION IN A MARSUPIAL, THE TAMMAR WALLABY

Mullerian duct regression is first apparent in male pouch young of the tammar wallaby (Macropus eugenii) 6-7 days after birth and, as in eut herian mammals, is characterised by a condensation of the periductal m esenchyme into a whorl around the ductal epithelial cells. A decrease in the density of the extracellular matrix was observed in the region of the whorl. In contrast to eutherian mammals no changes were observe d in the mean outer diameter of the Mullerian duct during the early st ages of regression. The time at which these mesenchymal changes occur corresponds to the period of Mullerian inhibiting substance secretion in the postnatal tammar testis.