Effect of testosterone and cortisol administration on the reproductive tract of male Antechinus stuartii (Marsupialia).

The life history of Antechinus stuartii, a marsupial, is highly synchronized and culminates in a brief mating period that is followed by complete male mortality. The accessory reproductive tracts of male A. stuartii enlarge in association with testosterone and cortisol hormone concentrations, but this appears to be unrelated to the spermatogenic cycle. The present study examined the effects of testosterone and cortisol on the male reproductive tract. Four groups of adult males from May (when plasma testosterone and cortisol concentrations are low) were given depot injections of testosterone esters or synthetic cortisol in doses that mimic concentrations found in males in the breeding period (August). Males were given either saline, testosterone only, cortisol only, or testosterone plus cortisol. Experimental groups did not differ in the seminiferous tubule morphology. However, the cells from the caudal end of the epididymides of both testosterone groups were considerably hypertrophied compared with males treated with saline or cortisol only. Testosterone treatment significantly increased prostate and bulbourethral gland mass, although addition of cortisol to the testosterone administration diminished this effect. The morphology of the accessory reproductive tract of males treated with either saline or cortisol only was similar to that of untreated males at the same time of year, and the morphology of the accessory reproductive tract of males treated with testosterone plus cortisol was similar to that of untreated males in the breeding season. Like some other marsupials, the spermatogenic cycle in A. stuartii is apparently not correlated with androgen activity, while the accessory reproductive tract is affected by androgens.