[Ultrastructure of the excretory system of the tick Ornithodoros papillipes (Argasidae)].

The ultafine structure of the Malpighian tubes in O. papillipes (Argasidae) was studied. It has been shown that the cells of different parts of the Malpighian tubes have their own peculiarities. The distal cells are characterized by the inclusions which can be interpreted as mucopolysaccharide ones. The main part of the tube was found to contain cells of two types. Most of the cells belonging to the first type have well developed microvilli and poorly developed basal invaginations. The cells of the second type, the number of which increases towards the proximal end of the tube, have small microvilli and narrow folds of the basal labyrinth entering deeply the cytoplasm. The cells of the second type are rich in mitochondria. The ultrastructure of the rectal sac has been studied. The cells of this organ have a polar structure: the apical surface is covered with microvilli, the plasmotic membrane forms deep folds at the base.