The elongated body is horizontally lengthened. Most bony fishes have a fusiform body shape. Others may have a compressed, depressed, or elongated body shape. Most fish species have pigmentation. Pigment is mostly contained in cells called chromatophores.
Most fishes can contract and expand their chromatophores to change colors.
Reflective cells called iridocytes can change color rapidly. Since different wavelengths of light are absorbed at different depths, fishes may appear a different color underwater than they do at the surface. Coloration may serve as camouflage. Most species of fishes are countershaded. The dorsal side of a countershaded fish blends in with the dark ocean depths or ocean bottom when viewed from above.