X-ray microanalysis of freeze-dried digestive mucus in Anguilla anguilla L: modifications of ion content during the early steps of secretion

Digestive mucus of sea-water adapted eels has been observed and analyzed by the scanning electron microscope (SEM) after rapid freezing at liquid nitrogen temperature followed by freeze-drying. No chemical procedures were used in this technique. This allowed the maintenance of the mucous coating.Preliminary X-ray microanalysis carried out on freeze-fractured and freeze-dried samples of the oesophagus showed a decrease of K⁺ and an increase of Ca²⁺ and Cl⁻ from the basal part of the mucous cell towards its the apical part. This technique has proven to be satisfactory for it prevents translocation and loss of diffusible elements in situ and allows X-ray microanalysis in the SEM.