Harder J D, Stonerook M J, Pondy J
Department of Zoology, Ohio State University, Columbus 43210.
J Exp Zool. 1993 Aug 1;266(5):463-79. doi: 10.1002/jez.1402660511.
Estrus, gestation, and placentation were studied in the Virginia opossum (Didelphis virginiana) and the gray short-tailed oppossum (Monodelphis domestica), representatives of the prototypic, New World marsupial family Didelphidae. Didelphis is a large (3,000 g), pouched opossum that exhibits a 28-day estrous cycle, spontaneous estrus and ovulation, and a high ovulation rate (60 ova per cycle). Monodelphis is a small (100 g), pouchless opossum with male-induced estrus and ovulation and a moderate ovulation rate (12 ova per cycle). Implantation occurs on day 10 of the 13-day gestation period in Didelphis and on day 12 of the 15-day gestation in Monodelphis. Gestation and placentation, including the ultrastructural features of trophoblastic apposition to the uterine mucosa, are very similar in Didelphis and Monodelphis. Differences, such as a larger increase in uterine volume and a more highly folded endometrium following implantation in Monodelphis are minor. They appear to be related to the smaller maternal body size and the relatively larger uterine load of embryos in Monodelphis. Because body size is one of the major variables among New World marsupials, the descriptions of gestation and placentation presented here for Didelphis and Monodelphis, provide a basis for comparison in future studies of didelphid marsupials.
对弗吉尼亚负鼠（Didelphis virginiana）和灰短尾负鼠（Monodelphis domestica）进行了发情期、妊娠期和胎盘形成的研究，它们是新袋类有袋动物原型家族袋鼬科的代表。弗吉尼亚负鼠是一种大型（3000克）有袋负鼠，具有28天的发情周期、自发发情和排卵，排卵率高（每个周期60个卵子）。灰短尾负鼠是一种小型（100克）无袋负鼠，由雄性诱导发情和排卵，排卵率适中（每个周期12个卵子）。在弗吉尼亚负鼠13天的妊娠期的第10天着床，在灰短尾负鼠15天的妊娠期的第12天着床。弗吉尼亚负鼠和灰短尾负鼠的妊娠和胎盘形成，包括滋养层与子宫黏膜附着的超微结构特征，非常相似。灰短尾负鼠在着床后子宫体积增加更大、子宫内膜折叠更高度等差异较小。它们似乎与灰短尾负鼠母体体型较小以及胚胎相对较大的子宫负荷有关。由于体型是新袋类有袋动物的主要变量之一，这里对弗吉尼亚负鼠和灰短尾负鼠妊娠和胎盘形成的描述，为未来袋鼬科有袋动物的研究提供了比较基础。
