Ovariectomy During Gestation in the American Opossum, Didelphis Marsupialis Virginiana

Ovariectomy during gestation in mammals usually results in abortion or death of the embryos. In some mammals, however, the embryos survive and can develop for a short time. In ferrets, implantation occurs when ovariectomy is performed on Day 10 post coitum (p.c.) but resorption follows immediately (Buchanan, 1969). In the guinea-pig, implantation occurs if ovariectomy is performed more than 48 hr p.c. (Deanesly, 1960, 1966) but development continues normally only up to the 14th day. Ovariectomy of the nine-banded armadillo during delay results in precocious implantation (Buchanan, Enders & Talmage, 1956) which occurs 18 to 20 days after operation (Enders, 1966); embryonic and fetal development proceed normally (Enders & Buchanan, 1959). Marsupials, like armadillos, can dispense with their ovaries for the greater part of gestation. In the quokka, Setonix brachyurus, and the tammar, Macropus eugenii, the blastocysts