Evidence from plasma progesterone concentrations for male-induced ovulation in the brush-tailed bettong, Bettongia penicillata

Abstract

Female brush-tailed bettongs, Bettongia penicillata, were housed with either an intact or vasectomized male or isolated from males in the peripartum period. Development of the quiescent corpus luteum formed at the post partum oestrus was initiated by removing the pouch young. Blood samples for analysis of plasma progesterone were collected from the females 2 days before removal of pouch young, daily for 5 or 6 days and then 2-3 times each week until 19 days after removal of pouch young. Plasma progesterone profiles were similar in pregnant and nonpregnant cycles. There was an early progesterone peak (1206 +/- 121 pg ml-1, mean +/- SEM; n = 16) between days 2 and 5 after removal of pouch young, and a second period of high concentrations (greater than 800 pg ml-1) before birth on day 17.4 +/- 0.2 (n = 16). The interval between the early peak and birth was 14 or 15 days. On five of 34 occasions, no increases in plasma progesterone concentrations occurred after removal of pouch young. On 12 of 15 occasions for 13 females that had been isolated from males post partum, plasma progesterone concentrations also remained low (less than 100 pg ml-1) and did not change after removal of pouch young. Females that showed no increases in plasma progesterone concentration after removal of pouch young had significantly lower (P less than 0.001) plasma progesterone concentrations while lactating than those females that did undergo a cycle after removal of pouch young (60 +/- 4 pg ml-1, n = 17 and 225 +/- 23 pg ml-1, n = 30, respectively). Females isolated from males post partum, and monitored until day 12 after removal of the pouch young, and that showed no increases in progesterone in this period, had ovaries that contained no corpus luteum, only corpora albicantia and numerous atretic or developing follicles. We conclude that brush-tailed bettongs are induced ovulators, a characteristic described for only one other marsupial, Monodelphis domestica, from South America.

The association between basal body temperature, plasma progesterone and the oestrous cycle in a marsupial, the Tasmanian bettong (Bettongia gaimardi)

“…This second peak is coincident with a short-lived peak in plasma progesterone (0.8 ng ml~) on day 3, similar to that found by Jones and Rose (1992) at day 4 after removal of pouch young in the same species. Such a progesterone peak is also found in several other macropodid species (Cake et al, 1980;Hinds and Tyndale-Biscoe, 1982;Walker and Gemmell, 1983;Curlewis et al, 1987;Hinds and Smith, 1992). In the latter half of the oestrous cycle, the basal body temperature remains high before falling 2 days before oestrus.…”

Female reproductive behaviour, ovarian hormones and vaginal cytology of the induced ovulator, Ctenomys talarum

“…Nonetheless, male presence or interaction with females did not cause enhanced follicular development. Corpora lutea, a clear evidence of ovulation (Hinds andSmith 1992 in Malherbe et al 2004), were only found in mated females, consistent with Weir (1974), but not in females that only experienced body contact or even courtship to the males. Nearly all solitary subterranean rodents are induced ovulators, as most solitary mammals.…”

Establishment of a captive colony of Bettongia tropica (Marsupialia: Potoroidae) by cross‐fostering; and observations on reproduction

“…B. tropica lies between B. penicillata and B. gaimardi in this respect. Reproduction in B. penicillata is unusual in that females do not come into oestrus unless a mature male is present (Hinds & Smith, 1992;Smith, 1992), a phenomenon that has not been reported for either B. lesueur (Tyndale-Biscoe, 1968) or B. gaimardi (Rose, 1987). The present study did not address the question of male-induced oestrus in B. tropica and, considering the apparent variation within the genus, the situation in B. tropica requires clari®cation.…”