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With a nearly global distribution the vespertilionid bat Myotis represents one of the most exceptional examples of adaptive radiation among mammals. We investigated the reproductive activity of the vespertilionid bat yellowish myotis, Myotis levis, from a highland area in Southeastern Brazil. The data were obtained through histological analyses of the male and female genital systems from February 2010 to May 2011. The testes of the adult yellowish myotis showed seasonal morphological characteristics which were categorized in the following stages: rest, maturing, mature, and mating. Rest and maturing males were recorded throughout the rainy season (October-March). In the rest stage no spermatogenesis was observed and the epididymal duct was devoid of spermatozoa. Maturing individuals had started spermatogenesis and few spermatozoa were found in the epididymal duct. Mature males were found toward the end (February-March) of the rainy season, when full spermatogenic activity was recorded and spermatozoa were packed in the epididymal duct. Although not recorded, mating probably occurred in the middle of the dry season (April-September) when the cauda epididymis was enlarged and packed with sperm. The spermatozoa remained stored in the cauda epididymis for at least three months when the testes entered into regression. The ovaries showed all types of ovarian follicles throughout the study period except mature follicles which were registered only in July (mid-dry season). Lactating females were captured in the beginning of the rainy season. The seasonal reproductive characteristics of the yellowish myotis from this Neotropical highland area were similar those of epididymal sperm-storing temperate vespertilionids.

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