Spermatheca of the scorpionfly Sinopanorpa tincta (Navás, 1931) (Mecoptera: Panorpidae)

The spermathecal structure of the scorpionfly Sinopanorpa tincta (Navás, 1931) was investigated using light microscopy, scanning, and transmission electron microscopy. The spermatheca consists of a bean-shaped spermathecal reservoir and an elongated spermathecal duct. The spermathecal reservoir can be subdivided into a distal portion with well-developed muscles and a proximal transitional portion connected to the spermathecal duct. The spermathecal duct is slender for its basal three-fourths and is greatly thicker for its distal one-fourth, which is mainly responsible for secretory function. A spermathecal pump formed from longitudinal muscle fibers was attached to the reservoir to control the transport of sperm. The lumen of the spermathecal reservoir is lined with a cuticle and filled with spermatozoa after copulation. The epithelium of the distal reservoir comprises a single type of epithelial cells, while the epithelium of the proximal reservoir and the spermathecal duct has three types of cells: secretory cells, duct-forming cells, and common epithelial cells. The secretory cells are rich in mitochondria, rough endoplasmic reticulum, and electron-dense secretory vesicles. The duct-forming cells form cuticular ducts, which connect the secretory cells to the lumen of the spermatheca. The spermathecal reservoir mainly serves as the storage of sperm, but the proximal reservoir as well as the spermathecal duct serves as secretory functions that maintain sperm viability.