The breeding season of the opossum (Didelphis virginiana) and the rate of intrauterine and postnatal development

Abstract

AUTHOR'S ABSTRACTThe breeding season of the opossum a t Austin. Texas. begins in J a n u a r y , following a three months' anoestroun period. The modal point for ovulation days is reached in the third week.The rate of intra-uterine development was investigated chiefly by surgical removal of one uterus, noting the stage attained hy the ova therein and allowing the surviving uterus to incubate its ova a precalculated period of time. Unique charts epitomize the results. The primitive-streak stage is completed, the medullary groovc a n d chorda hegin a t seven a n d one-half days post coitum, seven days post ovulationem, leaving only five a n d one-half days' actual development of the emhryc to birth. The rate of development is compared with Entherian mammals.The curve of postnatal Srowth hns the shape of embryonic growth curve of higher mammals. The ryes a n d lips open, a t ahout fifty days (young the size of mice). At this time the young leave the teat for the first time, h u t are not weaned for ahout thirty days more. Soon a f t e r weaning, t,he mother may become pregnant again. At ninety to one hundred days (young size of large r a t s ) , the young may begin to shift for themselves. P 148 P P W Text fig. C Chart 1, to show rate of development from one stage t o another, both stagrs taken from the same female, The numbers are the protocol c2 the intervening intervals of time controlled t o the minute. (For details see text, p a r t 11.) numbers of the animals furnishing the eggs and embryos.

Development of Caluromys philander (Didelphimorphia, Didelphidae) Foetuses with Estimated Ages of 20 and 25 days

“…In addition, the lips do not fully open until after 50 days of age [14]. These findings are in agreement with the results of the present study, where a central opening between the lips was noted in both groups, and the pups were strongly attached to the nipples, confirming their prematurity and need for the maternal presence.…”

“…According to Monteiro-Filho and Cáceres [13] and Hartman [14] in the genus Didelphis, the eye opening and teeth eruption do not occur until approximately 60 days after birth, and these features were not observed in the current analysis. The eyes in both stages were closed, but eyelid opening had progressed further in Group II than in Group I.…”

“…Regarding these aspects, Monodelphis domestica and Didelphis virginiana are the best-studied species among the Didelphidae. The craniofacial and neurologic ontogenetic features of M. domestica and some features of the intra-and extra-uterine developmental stages of D. virginiana are the main characteristics that have been reported [14][15][16][17][18][19].…”

Progesterone concentration in the marsupial Sminthopsis macroura: relationship with the conceptus, uterine glandular regeneration and body weight

“…The composition of secreted proteins differs between the two uteri in M. eugenii (Renfree 1973), and in T. vulpecula the mitotic rate of the ipsilateral glandular epithelium is significantly higher on day 2 post-oestrus (Von der Borch 1963), equivalent to day 1 post-ovulation (Shorey & Hughes 1973b). In the polyovular dasyurids A. agilis (Cruz & Selwood 1993) and Sminthopsis macroura (Cruz & Selwood 1997), the endometrial stroma, luminal and glandular epithelium are significantly thicker in pregnant cycles compared with non-pregnant cycles at specific stages of the luteal phase, but in the polyovular didelphid Didelphis virginiana, the non-pregnant uterine endometrium is significantly thicker on day 11 (Fleming & Harder 1981), the day of implantation (Hartman 1928).…”

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

“…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. Although several descriptive studies have concluded that the maternal reproductive system was unaltered by the presence of the conceptus based on approximate temporal coincidence of cycles and similarities in uterine morphology (Hartman, 1923(Hartman, , 1928Morgan, 1946;Reynolds, 1952), no-one has sampled pregnant and non-pregnant opossums systematically to determine the degree of similarity between these two reproductive states. In comparison, an Australian marsupial, the tammar wallaby (Macropus eugenii), has shorter cycles (Merchant, 1979) and altered uterine composition (Renfree, 1972) when pregnant.…”