Ultrastructure of the enlarged labial gland in the ant Camponotus japonicus associated with labial gland disease

Abstract

The labial (salivary) glands of insects play a crucial role in the vectoring of pathogens. Electron microscope observations on enlarged labial gland dissected from minor workers of Camponotus japonicus show a concurrent infection of the labial gland with rod-shaped virus particles and bacteria. Virus particles were found within the cytoplasm, nuclei, and lumen, where they are especially numerous. An apparently multilayered epithelium and gland enlargement are prominent features of the observed condition. The cells of the diseased labial gland reservoir exhibit secretory characteristics and undergo age-related changes. The epithelial thickness reaches its peak approximately one week after emergence and declines thereafter. Similarly, the degree of basement membrane invaginations and the abundance of endoplasmic reticulum in glandular cells followed this same pattern. These observations suggested that biological associations between the labial gland and diverse microbes may be more common than previously recognized.