Morphological variation in the testes and accessory sex organs of Australian rodents in the genera Pseudomys and Notomys.

The relative size and histology of the testes of sexually active adult Pseudomys and Notomys differed markedly between species. Average weight of testes (as % of body wt) ranged from about 3% in P. australis and P. nanus to about 0.15% in most Notomys. In the testes of most species, interstitial tissue was relatively sparse, but in P. apodemoides, P. delicatulus and P. hermannsburgensis it was abundant and consisted of a mass of lipid-rich epithelioid Leydig cells. Seminiferous tubule diameters were similar in all species, but epididymides ranged from about 500 mg in weight (about 1% body wt) in P. australis to about 20 mg (about 0.05% body wt) in most Notomys. Likewise numbers of spermatozoa in the paired cauda epididymidis ranged from about 500 x 10(6) in P. australis and P. nanus to about 2 x 10(6) in 3 of 4 Notomys species.