LIGHT AND ELECTRON-MICROSCOPIC STUDY OF 2 TYPES OF ENDOCRINES CELL INTHE MIDGUT OF THE ADULT WORKER HONEYBEE (APIS-MELLIFERA)

The occurrence, development and ultrastructure of two types of gut end ocrine cell have been studied in the midgut of adult honeybees. These cells, one of a basal granular type and one of a vesicular type, are e venly distributed throughout the posterior three-quarters of the midgu t. Each crypt complex contains one of each cell type, both of which ma y be derived from the same stem cells as the enterocytes. They already contain their respective secretory product while still in the nidus. Both reach the midgut lumen by a narrow apex and are therefore of the open type. The granular cells release their secretory granules at the cell base in a typical endocrine way. In young vesicular cells the sec retory vesicles are released at the cell base and in the intercellular spaces. Old cells are still filled with vesicles when they are shed i n the midgut lumen. This seems to indicate that these cells have both an endocrine (or paracrine) and an exocrine function, the latter appar ently by holocrine release.