Fifteen days old Oreochromis niloticus and 0. mossambicus juveniles were gradually adapted to 10,20,30
and 35 ppt sea water. Kidney morphology was observed after transfer to higher salinities and compared with
freshwater controls. Despite differences in salinity tolerance, both species have similar transformations
when transferred at high salinity, particularly reduction of the glomerular area after 2 months adaptation to
sea water, and change in tubule morphology.