Reproductive and Genetic-Studies With a Laboratory Colony of the Dasyurid Marsupial Sminthopsis-Crassicaudata

Abstract

The fat-tailed dunnart, Sminthopsis crassicaudata, is a small insectivorous dasyurid (adult weight about 16 g) widely distributed in Australia. A laboratory colony of this marsupial, which has been built up over many years, is providing material for studies of dasyurid reproductive biology and genetics. In the area of reproductive biology, we have found a marked disparity in the age of maturation between the two sexes, and we are currently studying certain aspects of spermatogenesis, sperm transport, fertilisation and early embryonic development. Genetical studies have revealed large differences between the sexes in autosomal linkage values and meiotic chromosome behaviour. In females, we have observed very limited intrachromosomal recombination and this is reflected in the distal localisation of chiasmata on the autosomes. Extreme localisation of chiasmata has not hitherto been found in a mammal, and it will be interesting to see how widely it occurs in other marsupial species. The genetical and cytological findings lead to a number of predictions that are being tested in further experimental work with the colony. Although we have been able to raise litter production to a high level, the very variable and unpredictable nature of male reproductive performance currently limits the wider use of the S. crassicaudata colony. It is clear, however, that this dasyurid has the potential to become a very useful laboratory marsupial and that it will be especially valuable for comparative biomedical studies.