Seasonal Dynamics of Reproductive Organs in Male Salamanders of the Species Hynobius nigrescens

Abstract

Seasonal changes in the testes and sex accessory structures are reported in hynobiid salamanders for the first time. No spermatogenic wave was discernible in the testes throughout the year, and spermatogenic progress was synchronized in all the testicular lobules. Spermiation did not occur in fall and winter months, and no spermatozoa were found in the vasa deferentia prior to spring breeding. In males with a nearly terrestrial phase morphology shortly after entering the pond water for spring breeding, spermiation was just beginning, and bundles of spermatozoa were seen in the vasa deferentia. In males with the distinctive aquatic phase morphology and showing active breeding behavior, spermatozoa were very rare in the testicular lobules, and spermatozoa in the vasa deferentia were entirely separated from each other. By this time, the epithelial cells of the vasa deferentia had discharged their secretion into the lumina. Sex accessory structures began to develop just after the completion of spermiogenesis, and remained during hibernation.