Morphology, histochemistry and ultrastructure of the yellow glands of Xylocopa pubescens spinola (Hymenoptera : Anthophoridae)

Abstract

The females of the carpenter bee Xylocopa pubescens have 3 pairs of abdominal glands, one each on the ventrolateral aspect of segments 5, 6 and 7. The glands are active during the nesting period, when their color is bright yellow. Before that, in young bees, they are compact and white. The glands are composed of numerous unicellular secretory elements, each of which is connected to a ductule that empties into the intersegmental membrane. The fine structure of the secretory cell includes an end-apparatus and other well-known features such as secretory vesicles, microvilli and RER. The end-apparatus, which is extracellular, is surrounded by a rather dense intracellular network of compact filaments that are arranged in ring-like structures and may serve as supporting and/or contractile elements. The extensive rough endoplasmic reticulum is indicative of the production of proteinaceous substances to be secreted. In addition, a mucopolysaccharide, containing carboxyl groups of the hyaluronic acid type, is secreted. These materials can be seen accumulating in a cavity outside the gland, and probably serve to coat the inside of the cells in which the bees' progeny develops. Each gland cell passes through a cycle from inactivity through a secretory phase to degeneration. However, the activity cycles of the different cells in each gland are asynchronous, thus prolonging the glands' period of activity, to fit with the length of the bee's nesting period.