Morphophysiological variations of the female reproductive organs of the vespertilionid bat Myotis nigricans during its different reproductive phases

Abstract

Myotis nigricans is an important species of insectivorous bat from the Vespertilionidae family, which is endemic of the Neotropics. Despite its wide distribution, no detailed study of the reproduction is found for this species. Thus, the aim of the present study was to evaluate and characterize morphological and morphometric variations of the female reproductive organs of M. nigricans during its different reproductive phases. Twenty adult females were collected, divided into four (4) sample groups, according to the reproductive status (nonreproductive, initial and advanced pregnancy and lactating), and submitted to anatomical, histological and morphometric analyses. The results demonstrated that the female reproductive organs of M. nigricans were composed of the ovaries, the uterus, the uterine tubes and the vagina, in addition to the mammary glands. The ovaries present a great number of interstitial glands and a small but persistent corpus luteum. Ovulation is simple, unilateral and non-preferential, possibly alternated in successive ovulations and may be sequential with the occurrence of postpartum estrus. The uterus is bicornuate, implantation is fundic and the placenta is chorioallantoic, discoidal and hemochorial. The vaginal epithelium is weakly keratinized and shows great disorganization during the periods of pregnancy and lactation.