The hypopharyngeal gland (HPG) of the honeybee worker produces royal jelly (RJ) and has a developmental cycle closely related to the division of labor. In this study, we investigated to compare the HPG acini diameter of differently aged worker bees with high royal jelly producing colony (HRC) or less producing colony (LRC). Additionally, we also evaluated whether the fresh weight of the head is a reliable indicator of the developmental status of HPG. The HRC showed a significantly higher RJ production about two-times as compared with those of the LRC. We measured the HG-diameters on days 1, 3, 6, 9, 12, 15. The microscopic analysis revealed that the acini size of the HRC was significantly larger than the LRC. In addition, the acini diameter of HRC was 15% longer than the LRC on the first day after emerging. It was shown that the fastest development during 3 days which is preparing for nurse the brood. The HPG acini diameters increased in both colonies in a similar fashion until day 12 and then decreased. We also compared the fresh head weight of the experimental colonies, differences were similar to the development of HPG. Therefore, high royal jelly production may have a positive correlation between HPG acini size and the fresh head weight.

Although it is believed that internal nutrient sensors play important roles in feeding behaviors, their molecular and neural mechanisms underlying of the modulation of physiological status and cell growth are poorly understood. Using a Ca2+ imaging experiments with heterologous expression systems, we show that one of the gustatory receptors in the western honey bee Apis mellifera is selectively tuned to amino acids. Remarkably, we report that this gustatory receptor of the honey bee is highly expressed in hypopharyngeal gland, which plays a role in caste differentiation as well as royal jelly production and secretion. Knocking down this gustatory receptor gene reduces cellular pathways responsible for nutritional sensing such as mTOR signals in hypopharageal gland. Furthermore, the interfering expression of this gustatory receptor gene not only alters morphological changes and developmental retardation of the hypopharyngeal gland, but it also blocks cellular growth signals to induce autophagy. This new report indicates that internal sensing and downstream signals detecting nutrients is essential for honey bee to maintain the cellular growth and development of internal organs essential for caste development and maintenance of social structure in the honey bee.