Ricerche istochimiche e al micro scopio elettronico sui tubi malpighiani di Dacus oleae Gmel.

Summary The Dacus oleae larva possesses four Malpighian tubules, two anterior and two posterior ones, which in pairs enter into a ureter. Before opening into the gut, at the level of the transition zone between the mid- and hindgut, each ureter is dilated into an ampulla.The anterior tubules are divided into four regions: distal, transition, middle and proximal ones: while in the posterior tubules only middle and proximal segments are detectable. The distribution of the enzyme systems is indicated in Fig. 3, while the ultrastructural organization which is typical of the cells composing the different regions is schematically represented in Fig. 1. According to the ultrastructural and enzymatic findings, and the discussion on this subject in the literature, the authors are led to assume that in the distal segment occurs the segregation of uric acid, urates and calcium salts. In the transition segment, and still more in the intermediate one, an indiscriminate transport of water and solutes occurs from the haemocoel into the lumen of the tubule by pinocytosis. A fraction of the catabolites is precipitated as chromolipoidal pigments. The transition stages between cytosomes and pigment are described. Along with secretory phenomena the resorption of useful substances occurs in the proximal region. A similar function is performed by the ureter. In the ampulla, which is characterized by a conspicuous system of deep tubular infoldings both at the apical and basal surfaces of its cells, a massive water resorption is presumed to occur.