The fine structure of the midgut epithelium in Xerobiotus pseudohufelandi (Iharos, 1966) (Tardigrada, Eutardigrada, Macrobiotidae)

The aims of our studies were to describe the ultrastructure of the midgut epithelial cells of the eutardigrade Xerobiotus pseudohufelandi and to determine if there are any differences in the ultrastructure of midgut epithelial cells between males and females. The analysis was performed with the use of the light and transmission electron microscopes. In X. pseudohufelandi the midgut epithelium is composed of digestive cells, but in the anterior portion of the midgut a group of cells with different ultrastructure has been observed. Histochemical staining showed the accumulation of reserve material in the cytoplasm of digestive cells. We suggest that some of them fulfil the role of regenerative cells (crescent-like cells, midgut stem cells), whereas others are differentiating cells which form new digestive cells. No differences in the ultrastructure of the midgut epithelium between males and females were distinguished except in the amount of multivesicular bodies.