Seasonal changes in spermatogenesis of the Japanese lesser horseshoe bat, Rhinolophus cornutus from a morphological viewpoint.

Seasonal changes in spermatogenesis of Japanese lesser horseshoe bats, Rhinolophus cornutus, captured in Aomori Prefecture (Japan) were examined by light microscopy. In March, the seminiferous tubules revealed almost no lumen. The seminiferous epithelium consisted of Sertoli cells and spermatogonia. The interstitium occupied a relatively large area. In June, the seminiferous tubules gradually increased in diameter. Lumen was clearly seen at the center of seminiferous tubules. Mitotic figures of spermatogonia and spermatocytes were occasionally recognized. Interstitium occupation was still abundant. In August, the diameter of seminiferous tubules maximized. The interstitium occupied only a small area. Active spermatogenesis was obvious at this time. Released spermatozoa were frequently observed within the expanded lumen. In October, although spermatogenesis was still active, the diameter of seminiferous tubules tended to decrease in size. In December, active spermatogenesis completely disappeared. The diameter of tubules greatly decreased. In most cases, the seminiferous epithelium contained only Sertoli cells and spermatogonia. Thus, spermatogenesis in Japanese lesser horseshoe bats occurs from the middle or late summer to the middle autumn in Aomori Prefecture. In epididymal tracts, aggregated spermatozoa were recognized throughout the year. The cytoplasm of all Leydig cells in the interstitium was positive for 3beta-hydroxysteroid dehydrogenase throughout the year.