Observations on the chorioallantoic placenta of the Indian flying fox, Pteropus giganteus giganteus.

The present study was undertaken to resolve (1) whether the interhaemal membrane of Pteropus giganteus at term is endotheliochorial or haemochorial and (2) how the trophoblast is layered. Females carrying late limb bud stage (CRL 12.95 mm) and advanced fetus (CRL 26.95 mm) were collected at Nagpur, India. The placenta in late limb bud stage was examined by light microscopy and that of advanced pregnancy by both light and electron microscopy. Our observations reveal that the chorioallantoic placenta at late limb bud stage is horse-shoe shaped and endotheliodichorial while that of advanced pregnancy is mesometrial, labyrinthine, and discoidal and shows a tendency toward becoming haemochorial. The junctional zone contained multinucleate giant cells. Detached endothelial cells were observed in the maternal capillary lumen during the advanced stage. Under light microscope a thick homogeneous layer was noticed deeper to the endothelial cells and in the regions devoid of such cells. A PAS-positive, highly reticulate and discontinuous interstitial membrane was noticed embedded in the thickness of the homogeneous layer. The ultrastructure of the interhaemal membrane of the chorioallantoic placenta in advanced pregnancy shows a tendency from endotheliodichorial to haemodichorial condition. The Pteropus interhaemal membrane is compared with that of bats of other families. The earlier conclusion that the maternal endothelium is typically different for primitive and extant families is denied on the basis of comparative ultrastructure.