The morphology of male accessory glands in the Glenea cantor (Fabricius, 1787) (Coleoptera: Cerambycidae: Lamiinae).

Male accessory glands of insects serve as secretory organs, exhibiting the ability to produce secretions that regulate reproductive processes. Their histology and ultrastructure are generally regarded as being diverse within insect groups, however, as one of the largest groups of insects, the ultrastructure of male accessory glands in Cerambycidae has never received sufficient attention. The longhorn beetle Glenea cantor (Fabricius, 1787) (Coleoptera: Cerambycidae: Lamiinae) is a wood-boring pest infesting urban landscape trees in southern China, significantly compromising urban greening. In this study, light and transmission electron microscopes were used to reveal the histological and ultrastructural characteristics of the male accessory glands of G. cantor. Results show that the males of G. cantor possess two pairs of morphologically distinct mesodermal glands (mesadenia). One pair exhibits an overall elongated tubular shape, while the other displays a tightly coiled, clew-like structure proximally and free-ending tubular regions distally. Ultrastructurally, both pairs of mesadenia exhibit identical cell types, with abundant secretory granules observed within the cytoplasm and lumen. Each gland possesses a muscular layer, an epithelium, and a lumen. The epithelial cell layer contains cellular structures and organelles indicative of active protein synthesis, including rough endoplasmic reticulum (RER), mitochondria, Golgi appartus, and secretory vesicles. This epithelium is also characterized by the presence of microvilli. The lumen is filled with electron-dense secretion. Notably, distinct morphological and ultrastructural differences exist both between the two mesadenial pairs and within each pair between their proximal and distal regions. This study provides the first comparative morphological and ultrastructural analysis of regional differentiation in two pairs of male accessory glands of G. cantor, revealing adaptive changes acquired during their evolution.