Complex carbohydrate presence in the gut and Malpighian tubules of Drosophila auraria larvae (Insecta, Diptera): a cytochemical study.

Cytochemical techniques were used for the qualitative characterization of carbohydrates in the foregut, midgut, hindgut and Malpighian tubules of Drosophila auraria larvae. Periodate-reactive (neutral) polysaccharides were present in the foregut cuticle, peritrophic membrane, cells of the proventriculus which produce the peritrophic membrane, as well as the glycocalyx of the midgut and Malpighian tubule cells. Sulphated and carboxylated complex carbohydrates were detected in the cuticle of both foregut and hindgut, as well as the 'vacuoles with granules' in the Malpighian tubules. Periodate-reactive sulphated and carboxylated polysaccharides were detected in dense bodies appearing in all cells 10-20 h before pupation of larvae. The significance of the presence or absence of complex carbohydrates in D. auraria larval digestive system is discussed and compared with results found in the digestive system of other insects. In addition, the efficiency of the HID-TCH-SP and LID-TCH-SP techniques in staining lysosomes is discussed.