Flatfish

Flatfish are a group of ray-finned fish belonging to the suborder Pleuronectoidei of the order Carangiformes. Their collective common name is due to their habit of lying on one side of their laterally-compressed body (flattened side-to-side) upon the seafloor; in this position, both eyes lie on the side of the head facing upwards, while the other side of the head and body (the "blind side") lies on the substrate. This loss of symmetry, a unique adaptation in vertebrates, stems from one eye "migrating" towards the other during the juvenile's metamorphosis. Due to interspecific variation, some species tend to face their left side upward, some their right side, and others face either side upward; members of Pleuronectidae lie on their left side, with eyes on the right, Paralichthyidae lie on their right side, with eyes on the left, while the "primitive" genus Psettodes may develop into "right-facing" or "left-facing" individuals. They are one of the most diverse groups of demersal fish. Their cryptic coloration and habits, a form of camouflage, conceals them from potential predators. Many species are of interest for fisheries.