The Morphological Characteristics of Mandibular Glands and Tergal Glands in Asian Honeybee (Apis cerana) Virgin Queens

The mandibular glands and the tergal glands have been suggested to play a crucial role in queen pheromone production. However, very few studies have linked changes in mandibular and tergal gland morphology to variations in their pheromone secretions. In this study, we aimed to reveal the age-related morphological development of these glands based on the morphological images and traits. We provided detailed information about how the mandibles, the mandibular glands, and the tergal glands changed in Apis cerana virgin queens aged 0 to 10 days. We detected only slight variations in mandible size (length and width of bilateral mandibles) across different age groups. However, the age of virgin queens had a significant effect on the morphological development of their mandibular and tergal glands, as reflected by the mandibular gland area and the morphology of tergal gland cell nuclei. The mandibular gland area of the 7-day-old virgin queens was significantly larger than that of the other age groups. Concurrently, the development of tergal glands reached a stable plateau in queens aged 5 to 7 days. In addition, significant differences were also detected in the surface area of tergal gland cells and the cell nucleus, and the cell nucleus diameter among tergites III, IV, and V. Compared to tergites IV and V, the cell nucleus surface area and the nucleus/cytoplasm index in tergite III exhibited greater variations across different age groups. These results are valuable for expanding our understanding of exocrine gland development in A. cerana queens.