Evidence for the Activation of Female Reproduction by Males in a Marsupial, The Gray Short-Tailed Opossum (Monodeiphis Domestica)1

Abstract

Although social factors are known to influence reproduction in a number of eutherian mammals, the effect of these factors on marsupial reproduction has not heretofore been studied. In this study, the temporal pattern of births and of the appearance of vaginal estrus following pairing with a male were examined in the gray short-tailed opossum, a small Brazilian didelphid. Although the estrous cycle is approximately 32 days long in this species, 75% of conceptions occurred within 9 days and 91.6% within 13 days following pairing. When sensory contact was permitted although mating was prevented, females tended to show vaginal estrus 3 to 7 days following pairing with a male. These findings are discussed with respect to possible mechanism, adaptive significance, and evolutionary perspective.

Characterization of oestrus and timed collection of oocytes in the grey short-tailed opossum, Monodelphis domestica

“…Even in this amenable species generation ofovulation on demand has so far been unobtainable. Reports have shown that the presence of a male activates oestrus as evidenced by behaviour and pregnancy (L. M. Baggott, unpublished observations), and by inference as seen from exfoliative vaginal cytology and pregnancy (Fadem, 1985). However, in isolation, females have been claimed to exhibit oestrous cycles as indicated by exfoliative vaginal cytology ranging from 10 to 32 days in length (Fadem & Rayve, 1985).…”

Evidence from the oestrous cycle for male-induced ovulation in Bettongia penicillata (Marsupialia)

“…Male-induced oestrus has been reported previously for one marsupial, Monodelphis domestica, in the Didelphidae (Fadem, 1985). The oestrous cycle is approximately 32 days long in this species, yet 91-6% of conceptions occur within 13 days of pairing, and isolated females do not show a regular oestrous cycle (Fadem, 1985(Fadem, , 1987.…”

“…The oestrous cycle is approximately 32 days long in this species, yet 91-6% of conceptions occur within 13 days of pairing, and isolated females do not show a regular oestrous cycle (Fadem, 1985(Fadem, , 1987.…”

The morphogenesis of the posterior neural tube and tail in Monodelphis domesticus.

“…andFADEM (1985) used successfully in our laboratory (JONES and MUNGER, 1985). Ten days following the initial contact between the male and female, the male was removed from the cage.…”