An electron microscope study on the pharyngeal glands of the honeybee

Abstract

The pharyngeal gland cells of the worker honeybee function as unicellular glands; each is possessed of a relatively long, sacculated and unbranched ductule. The ductule takes a sinuous course around the nucleus in a position more or less midway between it and the cell membrane. Electron micrographs reveal the wall of the ductule to be composed of an inner relatively dense and incomplete layer arranged as circular bands or spirals, so that in sections it appears as plates of relatively dense material; in addition, there is a middle granular layer as well as an outer less well-defined membrane layer. The secretion collects in relatively large masses about the ductule and probably diffuses into its lumen through that portion of the granular layer free of the inner bands or plates. Because the density of the inner layer of the ductule and that of the epicuticle appear similar, it is suggested that they are probably homologous structures. If this be true, diffusion of the secretion through the wall of the ductule must take place in the interval between the plates of the inner layer. The pharyngeal gland cells are highly basophilic and possess a relatively large amount of endoplasmic reticulum. Tubules of the endoplasmic reticulum are sometimes entrapped within the secretion masses, and, in which case, they are probably discharged from the cell along with the secretion. Mitochondria and Golgi bodies were also observed in the pharyngeal gland cells in addition to intracellular tracheoles.