A re-examination is made of the old interpretation that the male reproductive system of the
short-beaked echidna (Tachyglossus aculateus), and monotremes in general, is ?primitive?.
There is an emerging concept of the significance of the male reproductive system in relation to
the role of males in conception. Even though some aspects of the male reproductive system of
T. aculateus may be considered primitive and impose limitations on their life style, they
nevertheless display significant specializations present in the male tract of other mammals: an
epididymis with the unique initial segment and a role in post-testicular sperm maturation and
storage, and homologues of the prostate gland and penis. The absence of a descended testis and
scrotum has not restricted the survival of T. aculateus in virtually all habitats in Australia.
However, it may restrict their capacity to breed throughout the year. It is suggested that T.
aculateus is also specialised for sperm competition. An estimate of the rate of spermatogenesis
indicates that it is comparable with other mammals. Consequently, the size of their testes and
number of extragonadal sperm compared with other mammals are indicative that they are
involved in sperm competition. The cooperation involved in the formation of sperm bundles is
also indicative of sperm competition. Further, the formation of ?echidna trains?, in which a
number of males will follow in line behind an oestrous female indicates that there is
competition between males to mate with a female.
Reversal of benign prostate hyperplasia by selective occlusion of impaired venous drainage in the male reproductive system: novel mechanism, new treatment