Acclimation trial of Mugil cephalus juveniles to freshwater: morphological and biochemical aspects

Acclimation trials of Mugil cephalus juveniles (SL = mean 28.05, sd = 3.54 mm) were performed by means of a gradual transfer to freshwater in 48 h. The adaptation capabilities of M. cephalus were evaluated using descriptors such as tissue osmolality, chloride cell number, Na+-K+ ATPase activity and morphological aspects of oesophagus and gills. The high survival rate and tissue osmolality regulation demonstrate the adaptation ability of striped mullet of this size. Chloride cell number and osmolality proved to be good markers of functional adaptation. The morphological and biochemical aspects of oesophagus and gills in juveniles are similar to those of the adult, suggesting that osmotic regulatory mechanisms are precociously developed to allow the colonization of eutrophic inland waters.