The oestrous cycle in the opossum

Uterine histology and reproductive cycles in pregnant and non-pregnant opossums, Didelphis virginiana

“…Recurrent cycles occur monthly from January to July, regardless of the breeding status of the female, if lactational anoestrus is prevented by removal of the young (Hartman, 1923;. Fertilization occurs in the oviduct, and a mucopolysaccharide layer and a keratinous cortical layer are secreted around the eggs and embryos before arrival in the uterus by Day 3 (McCrady, 1938).…”

“…Direct embryonic contact with the maternal environment is restricted to the period following Day 7 after loss of the cortical layer. Elaboration of the vascularized chorionic ectoderm over the convoluted surface of the uterine mucosa characterizes this non-invasive type of implantation during the final 3 days of gestation (Hartman, 1923;McCrady, 1938;Hughes, 1974). young are born after a 12-5-day gestation, a period that coincides with the luteal phase of the oestrous cycle in non-pregnant animals.…”

Uterine Proteins in the Marsupial, Didelphis Marsupialis Virginiana, During Gestation

“…The gestation period of 13 days is the same length as the luteal phase of the cycle (Hartman, 1923(Hartman, , 1925 (Hartman, 1923;Renfree, 1974). After ovulation, the two uteri increase greatly in size and turgidity, due to an accumulation of fluid in the hypertrophied mucosa and the development of a rich supply of capillaries and venules (Harman, 1923 (Renfree, 1974) were included for comparison.…”

“…The gestation period of 13 days is the same length as the luteal phase of the cycle (Hartman, 1923(Hartman, , 1925; the next pro-oestrous phase and ovulation are suppressed by the presence of sucking young in the pouch. During the breeding season, removal or loss of the young results in resumption of follicular growth and oestrous behaviour is evident 3 to 7 days later (Hartman, 1923;Renfree, 1974). After ovulation, the two uteri increase greatly in size and turgidity, due to an accumulation of fluid in the hypertrophied mucosa and the development of a rich supply of capillaries and venules (Harman, 1923 (Padykula & Taylor, 1971).…”

Uterine Response to Ovariectomy During the Proliferative and Luteal Phases in the Marsupial, Trichosurus Vulpecula

“…Histological studies of several marsupials (Hill & O'Donoghue, 1913;Hartman, 1923;Sharman, 1955a, b; Hughes, 1962a;Pilton & Sharman, 1962;Tyndale-Biscoe, 1963, 1970Shorey & Hughes, 1973a, b) have demonstrated the close correlation between growth and development of the CL, and the initiation and maintenance of the uterine luteal phase. Similar observations have been made in Trichosurus vulpécula, the brush-tailed possum, in which the hormonal control of the oestrous cycle and pregnancy appears to be similar (Shorey & Hughes, 1973a, b).…”