Functional morphology of the crop of Drosophila auraria.

The crop epithelium of Drosophila auraria consists of a single layer of thin epithelial cells whose apex is covered with cuticle. The epithelial cells contain small amounts of rough endoplasmic reticulum, Golgi complexes and secretory granules. The digestive activities of the crop cavity are probably due to enzymes provided by the salivary glands and midgut cells. The epithelium displays continuous folds, which are more frequent in the upper region. The crop of Drosophila is capable of expanding and shrinking, as indicated by starvation and refeeding experiments. Starvation resulted in extensive epithelial folds and a concomitant decrease in the crop volume, while the refed insects displayed an unfolded crop epithelium and a voluminous crop.