Ultrastructure of the transporting epithelium of tubus ventralis in Tetrodontophora bielanensis Waga (Collembola).

The cells of the transporting epithelium of the tubus ventralis in Tetrodontophora bielanensis Waga (Collembola) are polarized, i.e. the major axis of the cell is determined by apical microvilli on one side and basal cell membrane infoldings on the other side. The involvement of this epithelium in fluid transport is indicated by the presence of PMC complexes, a large number of microtubules and glycogen in the middle and basal zones of the cells, and the arrangement of the endoplasmic reticulum, as well as by the presence of septate junctions and intercellular spaces. Typical features of this epithelium also include hemidesmosomes, and a well developed basement membrane to which they are attached. The cuticle covering the transporting epithelium is porous. It has a smooth surface, devoid of the wrinkles typical of other regions of the cuticle, which absorbs moisture and contributes to fluid transport.