Female reproductive anatomy and development of ovarian follicles in Miniopterus fraterculus

Abstract

The uterus of Miniopterus fraterculus (Thomas & Swan 1906) is bicornuate and asymmetrical, the right uterine horn being larger than the left in parous and nulliparous females. Ovarian and uterine function is asymmetrical; 94% of observed ovulations originated in the left ovary and all implantations occurred in the right uterine horn. Growth and development of ovarian follicles follow the typical eutherian mammalian pattern. The preovulatory Graafian follicle differs from that of most hibernating verspertilionids in that the cumulus oophorus is relatively small. Two types of follicular atresia occur. The first type, in which the stratum granulosum degenerates before degeneration of the oocyte, occurs in multilaminar follicles. The second type occurs in primary and early secondary follicles and is characterized by the oocyte showing the first signs of regression.