Psettodidae (spiny turbots)
Bothidae (lefteye flounders)
Pleuronectidae (righteye flounders)
Paralichthyidae (large-tooth flounders)
Achiropsettidae (southern flounders)
Soleidae (true soles)
Achiridae (American soles)
The flatfish are an order (Pleuronectiformes) of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. The name means "side-swimmers" in Greek. In many species, both eyes lie on one side of the head, one or the other migrating through and around the head during development. Some species face their left side upward, some face their right side upward, and others face either side upward.
Many important food fish are in this order, including the flounders, soles, turbot, plaice, and halibut. There are more than 400 species of this order. Some flatfish can camouflage themselves on the ocean floor.
The most obvious characteristic of the flatfish is their asymmetry, with both eyes lying on the same side of the head in the adult fish. In some families, the eyes are always on the right side of the body, and in others, they are always on the left. The primitive spiny turbots include equal numbers of right and left sided individuals, and are generally less asymmetrical than the other families. Other distinguishing features of the order are the presence of protrusible eyes, another adaptation to living on the seabed (benthos), and the extension of the dorsal fin onto the head.
The surface of the fish facing away from the sea floor is pigmented, often serving to camouflage the fish, but sometimes with striking coloured patterns. Some flatfish are also able to change their pigmentation to match the background, in a manner similar to a chameleon. The side of the body without the eyes, which faces the seabed, is usually colourless or very pale.
Full article ▸