Physiological aspects of NaCl movements in the gills of the euryhaline crab, Eriocheir sinensis, acclimated to fresh water

1.1. Transepithelial inward active transport of Na+ and Cl− are found in the posterior gills but not in the anterior ones.2.2. The posterior gills further show transepithelial passive movements of Cl− but not of Na+ while the anterior ones show transepithelial passive movements of Na+ and not of Cl−.3.3. In the anterior gills, the PD can be accounted for by diffusive Na+ fluxes at the aplcal side and Na+/K+ pump and leak system at the serosal one.4.4. In the posterior gills, the PD can be related to diffusive fluxes of Cl− at the aplcal side and diffusive outward movements of K+ and Cl− at the serosal one.5.5. In these gills, the transepithelial inward active movement of Na+ would be essentially related to the operations of aplcal Na+/H+ and serosal Na+/K+ pumps. Cl− would be moved IN at the aplcal side by a Cl−/HCO3− antiporter and driven OUT at the serosal one through Cl− channels following the K − diffusion potential generated by the Na+/K+ pump and leak system.