Structural modifications of the esophagus linked to osmoregulation in eels.

In comparison with the fresh-water Eel (Anguilla anguilla L.), the oesophagus of the sea-water Eel displays an almost complete regression of the multilayered epithelium and consequently the disappearance of mucous cells. In contrast, a large development of a columnaŕ epithelium is associated with a tremendous proliferation of the subepithelial vascularization. These modifications enable one to interpret the changes in ionic permeability of the oesophagus during transfer from freshwater to seawater.