| Popis: |
The ultrastructure, in particular, the cell junctions and the electrophysiological properties of the larval midgut ofTenebrio molitor (Insecta, Coleoptera) are described. Gap junctions were not detected by thin-section or freeze-fracture in this tissue. Neither were low-resistance ion pathways between the cells, found in other epithelia, detected electrophysiologically or by intracellular injection of fluorescent tracers under several physiological conditionsin vitro. However, the hindgut epithelium which is continuous with the midgut epithelium is ionically coupled and the tracers pass from cell to cell. In comparison, the midgut of a weevil larva (a related beetle) has gap junctions, is ionically coupled, and tracer movement occurs under the same physiological conditions. The absence of ionic coupling in some insect midgut epithelia appears to be unique to this tissue type. |
