Growth of ovarian Follicles in the Natal clinging bat

Abstract

Growth and atresia of the ovarian follicles of Miniopterus schreibersi natalensis (A. Smith, 1834) were studied from females collected on the southern Transvaal Highveld. In this hibernating subspecies no storage of sperm or delayed ovulation occur and females enter hibernation in a pregant condition. Only one Graafian follicle develops, which is characterized by a large antrum with the ovum-bearing mass of cells occupying only a relatively small portion of the antrum. Many follicles develop to a medium size before undergoing regression. Basically two types of regression occur; usually destruction of the stratum granulosum takes place before the oocyte is affected. The reverse condition was also observed but was very uncommon. Corpora lutea atretica resulting from the luteinization of medium-sized Graafian follicles were commonly found.