STRUCTURE AND FUNCTION OF THE PROTHORACIC GLAND IN HONEY-BEE (APIS-MELLIFERA L) DEVELOPMENT

The prothoracic gland of honey bee larvae was identified, and its deve lopmental characteristics were assessed by a combination of histologic al and physiological methods. The reticulate gland is attached to the intestinal tract at the junction of the esophagus and midgut. Ultrastr ucturally prothoracic gland cells show the typical characteristics of ecdysteroid-producing cells, i.e., a deep plasma membrane reticular sy stem and extensive smooth as well as rough endoplasmic reticulum. Smal l lipid vacuoles bounded by flattened SER sacs were found in considera ble numbers shortly before commencement of ecdysteroid synthesis. An e lement apparently unique to prothoracic gland cells of honey bees are tracheoles, which penetrate deeply into the gland. Ecdysteroid product ion of isolated glands was monitored in vitro by RIA analysis of relea sed products. Developmental profiles for hormone production in prothor acic glands of queen and worker larvae showed a high correlation to ca ste-specific differences in hemolymph ecdysteroid titer. Control tissu e did not liberate significant amounts of RIA-active material during d ecisive developmental phases.