ULTRASTRUCTURAL-STUDY OF THE ESOPHAGUS OF SEAWATER-ACCLIMATED AND FRESH-WATER-ACCLIMATED MUGIL-CEPHALUS (PERCIFORMES, MUGILIDAE), EURYHALINE MARINE FISH

The esophagus of the common grey mullet Mugil cephalus shows a single mode of organization that is common to both seawater- and freshwater-a cclimated specimens. A short anterior segment is lined by a stratified epithelium with mucous cells; posteriorly, this is progressively repl aced by single-layered columnar epithelium. Ultrastructural features o f the columnar epithelium are quite similar in the seawater- and fresh water-acclimated specimens. Apical microvillous projections, lamellar structures, and dilated intercellular spaces are observed. The present study suggests that the mullet esophagus is involved in active ion tr ansport and water permeability, both in seawater and in freshwater env ironments. (C) 1993 Wiley-Liss, Inc.