Ultrastructure of the seminal vesicle and sperm storage in Panorpidae (Insecta: Mecoptera)

The histology and ultrastructure of the seminal vesicle, male accessory gland and the epididymis in Panorpa and Sinopanorpa were observed using light microscopy and scanning and transmission electron microscopy. The seminal vesicle consists of a mono-layered elongated columnar epithelium, which contains abundant electron-dense granules and secretory vesicles, and a small central lumen. In the apical region of the epithelium of the seminal vesicle, the intense secretory activity seems to be effected by means of merocrine mechanisms. The epithelium of the accessory gland is rich in rough endoplasmic reticulum and Golgi complex, and secretes seminal fluid into the lumen via both apocrine and merocrine mechanisms. The seminal vesicle is similar to the accessory gland in the epithelium structure and their secretory activity, mainly serving a secretory function rather than storing sperms. Instead, the sperms are stored in the epididymis, whose epithelium secretes nutrients into the large lumen by merocrine mechanisms. The secretory activity and function of the seminal vesicle are briefly discussed.