Morphological changes in the oesophageal epithelium during adaptation to salinities in Oreochromis mossambicus, O. niloticus and their hybrid

Morphological changes in the oesophageal epithelium of Oreochromis mossambicus, O. niloticus, and O. mossambicus x O. niloticus hybrids were studied during adaptation to sea water. In fresh water, the epithelium is stratified and rich with mucous cells. In salt water, modifications occur in the oesophagus of O. mossambicus and of the hybrid: mucosa folds are more vascularized and covered with a monolayered epithelium, alternating with a multilayered one. The oesophagus of O. niloticus does not seem to be affected by salinity but this species survives only for brief periods in sea water. These observations underline the close relationship between the oesophagus morphology and salinity tolerance in tilapias.