Ultrastructure of female accessory glands in the scorpionfly Panorpa sexspinosa Cheng (Mecoptera: Panorpidae)

The histology and ultrastructure of the female accessory glands in the scorpionfly Panorpa sexspinosa Cheng was studied using light and transmission electron microscopy. The glands consist of a pair of distal elongate gland tubes and a basal common duct, which opens in the genital cavity at the dorsal side of the genital plate. The whole gland tubes and common duct are similar histologically and ultrastructurally. The epithelium of female accessory glands consists of two cell types: the outer secretory cells and the inner duct-forming cells. These two cells that join with a cuticular duct connecting to the inner intima constitute a functional glandular unit belonging to Class 3 glandular cells of epidermal glands. The secretory cells are rich in organelles, such as mitochondria, rough endoplasmic reticulum, and Golgi complex, indicating that they are active in secretion. The duct-forming cells are flattened with sparse-distributed organelles. These two kinds of cells are connected by septate junctions. The cuticular duct consists of a receiving and a conducting canal and is responsible for transferring the secretions of the secretory cell to the lumen. The receiving canal is formed of interrupted multilayered inner epicuticle and located in the irregular extracellular cavity of the secretory cell, bounded by microvilli. The conducting canal connects the inner intima and opens into the central lumen. The tentative functions of the secretions are briefly discussed.