The black mastiff bat (Molossus ater): a novel, mammalian model for studies of ovarian, uterine, and placental biology.

The reproductive biology of the black mastiff bat has been examined using animals maintained in a laboratory colony. Ovulation was found to be spontaneous and occurred only from the right ovary. The corpora lutea appeared to be functional, and decidual reactions developed in the uterus during the luteal phase of the cycle even in the absence of an implanting blastocyst. At the end of nonpregnant, ovulatory cycles much of the endometrium became necrotic and was desquamated with associated bleeding. In the event of pregnancy only a single blastocyst implanted in the right uterine horn, and the discoidal chorioallantoic placenta then developed at the cranial end of that horn. This was preceded by the development of an unusual vascular tuft in the endometrium in that region. The endothelial cells of the tuft vessels became hypertrophied during early pregnancy and developed more prominent basal laminae. Trophoblast then grew preferentially around these vessels. These observations suggest that factors secreted by endometrial endothelial cells and incorporated at least in part into their basal laminae may play a central role in controlling early trophoblastic growth during the morphogenesis of the discoidal chorioallantoic placenta in this bat.