Cell types in the esophageal epithelium of Anguilla anguilla (Pisces, Teleostei). Cytochemical and ultrastructural characteristics

The esophagus is an important osmoregulatory organ in euryhaline teleost fishes; however, its histochemical and ultrastructural characteristics have been studied in few species. The structure of the esophageal mucosa was analyzed in the European eel (Anguilla anguilla L.) and compared to the findings reported for other species. The histological features of the esophageal mucosa, the histochemical characteristics of mucosecretory cells in the epithelial layer and the ultrastructural features of the different cell types in this layer in animals caught in fresh water and raised in the laboratory were analyzed. The role of mucus as a protective covering and its role in ion transport an the esophagus are discussed. In addition, comments on the role of tonofilament-rich epithelial cells in ion transport are made.