Electron microscopic structure of the cephalic gland of the bee Andrena variabilis Smith (Hymenoptera: Apoidea)

The structure of the glandular tissue located beneath the eye sulcus in Andrena variabilis Smith was studied by means of light and electron microscopy. The glandular tissue was found to be constituted of single-layered, high cylindrical epithelial cells. Electron microscopy revealed strong foldings of the cell membrane on the basal pole of the gland cells. Next to the basal lamina, nerve fibres were found with great frequency. The central, perinuclear zone of the gland cells was rich in cell organelles. The lamellae of the rough-surfaced endoplasmic reticulum (rer) were mostly observed near the nuclear membrane. The vesicles and tubules of the smooth-surface endoplasmic reticulum (ser) were found to be congregated in contiguous compact regions. A well-developed and complicated canalicular system was enclosed between the rer and ser compartments, presumably serving as a passage for the secretory products. Membrane-bound electron-dense granules (secretory granules) were also a characteristic finding in the ser. In a small proportion of the gland cells, strong vacuolization indicated the degradation processes. From the light and electron microscopic characteristics of the gland cells, the existence of pheromone-producing secretory activity of exocrine type in the cephalic gland is presumed.