Morphology and ultrastructure of the mandibular gland in Camponotus japonicus

The mandibular gland is an important exocrine gland connected to the mandibles. In ants, it plays a crucial role in alarm communication and reproduction. While the overall morphology of the mandibular gland does not vary much between ant species, significant differences exist in the ultrastructural characteristics and gland size in some reported cases. However, there have been few systematic comparative studies on this subject. In this paper, we conducted microscopic observations to analyze the morphological and ultrastructural similarities and differences of the mandibular gland in different castes of Camponotus japonicus. Our findings revealed that the mandibular glands of males were significantly larger than those of females. In terms of relative size, within the female castes the mandibular glands of minor workers were the largest. Additionally, our observations of the ultrastructure showed that secretory substances were most abundant in queens. All female castes and males showed the presence of crystalline structures in the secretory cells. The content of these biocrystals decreased from minor workers to major workers, queens, and males. In males, however, crystalline structures were rare and the most abundant substances are droplet-like secretions. The differences in morphology and ultrastructure between different castes suggest that the function of the mandibular gland varies among castes. In conclusion, our study provides insights into the morphological and ultrastructural characteristics of the mandibular gland in different castes of C. japonicus. Further research is needed to fully understand the specific functions and mechanisms of this gland in ants.