AbstractThe euryhaline crab Eriocheir sinensis adapted to freshwater shows an ion transporting‐type epithelium in the three posterior gills and a respiratory‐type epithelium in the three anterior gills. When they are perfused in freshwater conditions, there is an increased transport of ions principally in the posterior gills.We also measure an increased degradation of the branchial glycogen. This polysaccharide is present in an extraepithelial lamina located in the hemal space of the lamellae. Its localization outside the ion‐transporting epithelium and its higher consumption by the posterior gills submitted to hypo‐osmotic conditions suggest a well‐suited glucose transport mechanism through their epithelial membrane. Accordingly, the uptake of glucose by the epithelial cells is slightly higher in the posterior gills as compared with the anterior.