Structure and Function of the Malpighian Tubules, and Related Behaviors in Juvenile Cicadas: Evidence of Homology with Spittlebugs (Hemiptera: Cicadoidea & Cercopoidea)

Abstract Anatomical and histological study of the Malpighian tubules in the cicada genera Tibicen and Magicicada (Cicadoidea) demonstrated that, at the nymphal stage, these organs display a glandular modification, similar to one involved in the production of the “froth” in spittlebug nymphs (Cercopoidea). Proximal parts of the tubules contain a short smooth inflated segment, which produces granules of an acid mucopolysaccharide. A more distal long nodulose segment comprises cells which display extensive rough endoplasmic reticulum and numerous secretory vacuoles, indicating the manufacture of a proteinaceous product. These cells are strongly PAS-positive, suggesting the secretory product also contains carbohydrates. The production of secretory products in the tubules ceases at the adult stage. Available observations of the behaviors of cicada nymphs suggest that the tubule secretory products mix with copious watery excretion of the gut to form the anal liquid, which is used by the nymphs to cement the walls of the burrows and clean the body. The Malpighian tubule products apparently account for the adhesive properties of the anal liquid. The regional differentiation of the tubules, details of the cell ultrastructure in each of the segments, and the major secretory products are similar to those of spittlebug nymphs, which live immersed in their excretion which is conditioned with the Malpighian tubule secretory products. The results suggest that the distinctive adaptations of juvenile Cicadoidea and Cercopoidea have a common origin.