Unilateral Oviductal and Uterine Reactions in the Little Bulldog Bat, Noctilio albiventris

The reproductive tracts of 112 female Noctillio albiventris were collected around the time of a synchronized peak in conceptions in a wild population and examined histologically. The bats were generally found to be monovular. Ovulation could occur from either ovary with embryonic development taking place in the ipsilateral oviduct and uterine horn. Prior to the development of a mature follicle, the ampullary and isthmic secretory cells of 1 oviduct frequently contained more glycogen and exhibited greater cytoplasmic vacuolation than did those in comparable regions of the other oviduct. When a mature follicle, a newly ruptured follicle or a new corpus luteum (CL) was present, the more developed oviduct was consistently ipsilateral. Local dilation of just this oviduct with fluid was noted in a preovulatory and several recently postovulatory bats. With the exception of some mitotic activity in the uterine epithelium, little endometrial development was observed prior to ovulation and both uterine horns appeared similar in most preovulatory bats. However, higher glycogen levels were detected in the epithelium of the horn ipsilateral to the mature preovulatory follicle or newly ruptured follicle in 4 bats. During tubal passage of the embryo epithelial cell size and glycogen levels were often greater in the horn ipsilateral to the CL than in the contralateral horn. In some of these animalsstromal development also differed between the 2 horns. These observations suggest that an efficient, local pathway exists for ovarian stimulation of the ipsilateral oviduct and uterine horn in N. albiventris . The cranial end of each uterine horn, where the unilateral endometrial reactions were most pronounced, was found to be vascularized by a branch of the ipsilateral ovarian artery. This is consistent with the hypothesis that the unilateral effects may be attributable to a local countercurrent exchange of hormones between the ovarian venous and/or lymphatic drainage and the arterial supply of the ipsilateral oviduct and uterine horn. A direct effect of hormones diffusing out of the ovarian venous and/or lymphatic vessels upon arteries supplying these accessory organs also seems conceivable.