Morphology of Nasonov and Tergal Glands in Apis mellifera Rebels

Abstract

Social insect societies are characterized by a high level of organization. This is made possible through a remarkably complex array of pheromonal signals produced by all members of the colony. The queen’s pheromones signal the presence of a fertile female and induce daughter workers to remain sterile. However, the lack of the queen mandibular pheromone leads to the emergence of rebels, i.e., workers with increased reproductive potential. We suggested that the rebels would have developed tergal glands and reduced Nasonov glands, much like the queen but contrary to normal workers. Our guess turned out to be correct and may suggest that the rebels are more queen-like than previously thought. The tergal gland cells found in the rebels were numerous but they did not adhere as closely to one another as they did in queens. In the rebels, the number of Nasonov gland cells was very limited (from 38 to 53) and there were fat body trophocytes between the glandular cells. The diameters of the Nasonov gland cell nuclei were smaller in the rebels than in the normal workers. These results are important for understanding the formation of the different castes of Apis mellifera females, as well as the division of labor in social insect societies.

The Morphological Image of Fat Body and Tergal Gland Cells in Uninseminated Apis mellifera Queen Bees

“…According to the authors of this study, these are, in all likelihood, melanotic lumps developed as a result of the accumulation of large amounts of eumelanines, i.e., products of melanization, which protect the chitinous covering from pathogen penetration. This suggests better protection of the organism against the impact of external environmental factors [11,14,25,29,33,34]. The authors did not encounter a description of these lumps in the tergal gland tissue of queen bees in the literature, which suggests that we were the first to notice them.…”

“…We analyzed the literature and did not find any studies devoted to the analysis of the tergal glands in queen bees on such a detailed level. The results of Strachecka et al [14] described the morphology of tergal glands in rebel workers, which are primed to reproduce rather than participate in the rearing of the next generation of sister-queen offspring. We showed what the tergal gland cells look like in 8-day-old queens.…”

“…In worker bees, such dark-colored lumps are present in the trophocytes of the fat body and in the Nasonov gland. While the lumps in the trophocytes contain iron, calcium, magnesium, and phosphate ions [14,35], the lumps in the Nasonov gland are a cluster of melanin, proteins, or ions of metals that are accumulated in cells as a result of the aging processes in the organism, defense reactions and environmental factors [11,33,34,[36][37][38]. The tendencies in the changes in surface area of the tergal gland cells of the queen bees corresponded with the changes in surface area of the fat body located at the tergites.…”

“…From each cell departs the outlet ducts, from which pheromones are emitted with pulsating movements. No differences are observed in the morphological images between the glands from various tergites (III, IV, and V), but these glandular cells differ in their nucleus diameters-the largest nuclei are found in the third tergite and the smallest ones in the fifth [14]. In order for the queen to be valuable and perform her functions, the tergal gland cells should be compact and in adequate numbers.…”

“…Nowadays, it is known that the fat body and tergal glands are tissues which play a crucial role in bee immunity [13][14][15]. The role of the fat body is not limited to storing energy reserves in the form of fat, protein, and glycogen.…”