Until very recently the agile Antechinus (Antechinus species), a small carnivorous marsupial, was known as the southern form of the brown Antechinus (Antechinus stuar-tii); but it has now been recognized as a separate species, although yet to be formally described. Reproduction in the agile Antechinus, as in the brown Antechinus, is unusual and has been the focus of much research. Field studies, for instance, indicate that females are monoestrous and that both sexes are promiscuous, with mating restricted to a 3-wk period in late winter. Despite this, however, total spermatogenic failure occurs in all males approximately 1 mo prior to mating, and the epididymis has limited capacity for sperm storage (< 3.5 X 106 sperm per epididymis). In addition, captive studies indicate that sperm are continually lost in the urine via spermatorrhoea (0.146 X 106 sperm per epididymis/ day) and that few sperm (0.08 X 106-0.48 X 106 sperm per ejaculate) are delivered at ejaculation. proventil inhaler
Consequently, few if any sperm remain in the reproductive tract of male Antechinus at the conclusion of the mating period, whether copulation has taken place or not. Furthermore, copulation has been reported to last for up to 8-12 h in the laboratory in this species; and a few weeks after the commencement of mating, often before the females have ovulated, the entire male population dies as a result of a stress-induced suppression of the immune system. Successful mating, sperm transport, storage, and fertilization in this species can therefore best be described as an exercise in reproductive brinkmanship.