ACCLIMATION TRIAL OF MUGIL CEPHALUS JUVENILES TO FRESH-WATER - 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 i n 48 h. The adaptation capabilities of M. cephalus were evaluated usin g de scriptors such as tissue osmolality, chloride cell number, Na+-K ATPase activity and morphological aspects of oesophagus and gills. Th e high survival rate and tissue osmolality regulation demonstrate the adaptation ability of striped mullet of this size. Chloride cell numbe r and osmolality proved to be good markers of functional adaptation. T he morphological and biochemical aspects of oesophagus and gills in ju veniles are similar to those of the adult, suggesting that osmotic reg ulatory mechanisms are precociously developed to allow the colonizatio n of eutrophic inland waters.