Interactions of sperm and the reproductive ducts of the male tammar wallaby, Macropus eugenii (Macropodidae: Marsupialia).

This review compares sperm production in the tammar wallaby and eutherian mammals, particularly the rat. The capacity of sperm to fertilize an ovum when they leave the testis and the changes they undergo in the epididymidis are considered. The structural differentiation and regulation of the extratesticular duct system is assessed and related to the reabsorption and secretion of water, inorganic ions and proteins, and the interaction of sperm and proteins synthesized and secreted by the epididymidis. Adaptations of the cauda epididymidis for storing spermatozoa are also considered. It is suggested that the tammar may be a good animal model to study the suppression of sperm motility and metabolism in the cauda epididymidis as it is possible to collect from them luminal samples of sperm which are initially immotile and then spontaneously activate during incubation in vitro.