Investigation of different ontogenetic stages of Raillietiella sp. (Pentastomida: Cephalobaenida): the midgut in nutrition and digestion.

The midgut of Raillietiella sp. was investigated ultrastructurally in different ontogenetic stages from the intermediate (cockroach) and the final host (small lizards). In the embryo the midgut anlage is an accumulation of cells filled with glycogen granules. During embryogenesis the cells organize and form a narrow tube. During postembryogenesis the contribution of the midgut to the alimentary tract rises considerably from the first larva to the adult parasites. In all stages the midgut is not divided into zones; however, two cell types (crystal and noncrystal cells) are distinguishable. Digestion takes place extracellularly. The main storage product of the midgut cells and the surrounding muscle cells is glycogen. A slight cyclic course of the digestive process is discernible.