Morphofunctional Evaluation of the Epididymis and Sperm Survival in a Neotropical Sperm-Storing Vespertilionid Bat: A Possible Conserved Phylogenetic Characteristic.

Yellowish myotis presented four reproductive stages and long-term sperm storage in cauda epididymis. Aiming to investigate the morphofunctional aspects of the epididymis and spermatozoa of yellowish myotis, 48 adult male bats were captured in Santuário do Caraça, Minas Gerais, Brazil, for histomorphometric evaluations of the epididymis and sperm analysis. Yellowish myotis spermatozoa were observed in the caput and corpus epididymis only during the Mature and Regressed stages, coinciding with increased epithelial height in these stages, indicating their possible role in sperm maturation. In contrast, spermatozoa were found in the cauda epididymis during all reproductive stages, with the epithelium maintaining a consistent height, which suggests that this region is adapted for long-term sperm storage. The spermatozoa remained alive and motile for up to 25 days during the Regressed and Early Rest stages. Mating period in yellowish myotis occurs during the Rest stage, when spermatozoa in the cauda epididymis exhibit reduced DNA fragmentation and minimal chromatin abnormalities. During this period, sperm with wider heads and longer midpieces dominate, reflecting selection for traits that would enhance fertilization success. These results reinforced the importance of cauda epididymis physiology for sperm survival and future events of capacitation and fertilization.