Fine structure of the Malpighian tubes in the blood-sucking insect,Triatoma infestans Klug

Summary The ultrastructure of the distal cells in the Malpighian tubes ofTriatoma infestans Klug differs from that of the proximal cells in terms of types of striated border, and distribution of mitochondria and laminated concretions. This is in accordance with published data for another blood-sucking insect,Rhodnius prolixus Stahl. Other observations, however, elucidate cytoplasmic structures not yet reported inReduviidae insects. Layered membranous formations ending in spiral configurations are found in both cell types giving rise to layered membranous globules. Bundles of fibers made up of tubuli occur in the apical regions of the proximal cells in fasted animals. Glycogen deposits surround vacuole-like areas which are probably representing a stage in the formation of laminated concretions. Several globule types [lysosome-like structures, and layered membranous globules sometimes containing cell organelles (cytolysomes?)], are present in the distal and proximal cells, whereas laminated concretions are displayed only by the distal cells. The different globules are ascribed to various stages in the excretion of substances and the elimination of organelles. No special ultrastructural findings could be related to the diversified nuclear phenotypes previously described in the Malpighian tubes ofT. infestans.