Secretory Activity in the Longitudinal Canal of Male Podarcis siculus Lizards

In lizards, the longitudinal canal conveys the sperm from the rete testis to the ductuli efferentes, which connect to the cranial end of the epididymal duct. Due to its reduced extension, the longitudinal canal has been largely ignored compared with the ductuli efferentes and the ductus epididymis. The objective of this study was to provide information on the structure and function of the longitudinal canal in the lizard Podarcis siculus by using light and transmission electron microscopy. For this purpose, testes and epididymides from adult male P. siculus lizards captured during the reproductive period were used. Light microscopy showed that the longitudinal canal was lined by a simple squamous or low cuboidal epithelium containing apical periodic acid-Schiff (PAS)-positive granules. Transmission electron microscopy revealed two types of epithelial cells: ciliated and non-ciliated. The non-ciliated cells showed electron-dense granules in the supranuclear and apical regions, suggesting probable secretory activity. These findings demonstrate, for the first time, that the longitudinal canal of the lizard Podarcis siculus is not merely a passageway for the sperm but may play a role in the composition of the medium in which these gametes are found during their flow towards the epididymis.