Why are the testes of the hopping mouse so tiny?
Comparative studies of testis size across species of native Australian rodents have shown that the Spinifex hopping mouse has remarkably small testes that are an order of magnitude smaller than those of most rodent species of similar body mass (see Bauer and Breed 2008 Journal of Zoology 274: 349-356) as well as having highly variable spermatozoa (Bauer and Breed 2006 Reproduction Fertility and Development 18: 797-605). These reproductive traits suggest that hopping mice either lack of genetic heterozygosity, and/or exhibit a monogamous mating system with resultant low levels of intermale sperm competition. Using tissue samples that we have recently obtained from a wild population of hopping mice near Roxby Downs in northern South Australia we wish to use microsatellite markers to genotype the individuals so that the population structure and incidence of multiple paternity can be determined. This project may also enable the student to collect further material from the area of Roxby Dow
