Fine structure of the midgut epithelium in the millipede Telodeinopus aoutii (Myriapoda, Diplopoda) with special emphasis on epithelial regeneration

The midgut of millipedes is composed of a simple epithelium that rests on a basal lamina, which is surrounded by visceral muscles and hepatic cells. As the material for our studies, we chose Telodeinopus aoutii (Demange, 1971) (Kenyan millipede) (Diplopoda, Spirostreptida), which lives in the rain forests of Central Africa. This commonly reared species is easy to obtain from local breeders and easy to culture in the laboratory. During our studies, we used transmission and scanning electron microscopes and light and fluorescent microscopes. The midgut epithelium of the species examined here shares similarities to the structure of the millipedes analyzed to date. The midgut epithelium is composed of three types of cells—digestive, secretory, and regenerative cells. Evidence of three types of secretion have been observed in the midgut epithelium: merocrine, apocrine, and microapocrine secretion. The regenerative cells of the midgut epithelium in millipedes fulfill the role of midgut stem cells because of their main functions: self-renewal (the ability to divide mitotically and to maintain in an undifferentiated state) and potency (ability to differentiate into digestive cells). We also confirmed that spot desmosomes are common intercellular junctions between the regenerative and digestive cells in millipedes.