[Ultrastructure of the midgut in Ornithodoros papillipes (Acarina, Argasidae) nymphs in the blood assimilation period].

Three types of cells (reserve, digestive and secretory) differing in their ultrastructural characters were found to exist in the epithelium of the midgut of nymphs of O. papillipes during the blood assimilation. Reserve and secretory cells are dominant at the first stage of digestion while digestive cells are most abundant at the second one. Ultrafine structure of secretory and digestive cells points to the labile relationship between these types of cells. The same digestive cells assimilate blood both by means of phagocytosis of formed elements and by pinocytosis of its liquid components. The identity of ultrastructural peculiarities of endocytosis and intracellular blood digestion in ixodid and argasid ticks is shown.