For histological purposes, 1 cm2 of the skin from the dorsal anterior region of the body from 16 fish per dietary treatment was dissected (n= 4 fish per tank) and fixed in 4% buffered formaldehyde (pH = 7.4), dehydrated in a graded series of ethanol, cleared with xylene, embedded in paraffin and cut in serial sections (3–5 μm thick). Sections were stained with hematoxylin-esosin (HE) for general histological descriptions, whereas slides were stained with Periodic Acid Schiff for goblet cell identification (neutral mucins produced by mucous cells stain in magenta). All sections were observed under a light microscope (Leica DM LB; Leica Microsystems) and photographed (Olympus DP70 Digital Camera; Olympus Imaging Europa GmbH). Digital images (600 dpi) were processed and analyzed using an image analysis software package (ANALYSIS; Soft Imaging Systems GmbH). Measurements of the thickness of different skin regions (epidermis and dermis), as well as mucous cell number (full and empty) were based on the analysis of three to five randomly chosen fields from the skin per fish. The number of epidermal mucous cells was expressed over a length of 100 μm.