Ultrastructural organization of seminal vesicles in the African catfish (Clarias gariepinus) during the spawning season.

The seminal vesicle is an important accessory reproductive organ in male teleosts, but detailed ultrastructural information on its organization in Clarias gariepinus remains limited. This study examined the seminal vesicle of sexually mature male African catfish during the spawning season using transmission electron microscopy (TEM). Forty wild-caught males from the Lake Chad region of Maiduguri, Nigeria were examined. Seminal vesicle tissues were fixed in phosphate buffered glutaraldehyde, post-fixed in osmium tetroxide, embedded in Epon 812, sectioned, and examined using TEM. The seminal vesicle consisted of elongated tubular projections associated with the sperm duct. The epithelium contained numerous spermatogonia within the sperm cysts that were flanked by intercellular junctional specializations in the basal part of the tubule. The apical part of the tubule contained abundant secretory vesicles, seminal vesicle villi, and intervilli spaces. Numerous clusters of oval and elongated mitochondria were located in both the basal and apical parts of the tubule. At the junction between the seminal vesicle projections and the sperm duct, the tissue showed dense connective tissue, lamina propria, and muscular components. These findings provide baseline ultrastructural data on the seminal vesicle of C. gariepinus and may support future studies on teleost reproductive biology and aquaculture reproduction.