Flatfish |
![19th c. engraving depicting several types of flatfish](./modules/Fish-MM/images/250px-BonyFlatfish.jpg)
19th c. engraving depicting several types
of flatfish
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Scientific classification |
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Families |
Suborder Psettodoidei
Psettodidae
Suborder Pleuronectoidei
Citharidae
Scophthalmidae (turbots)
Bothidae (lefteye flounders)
Pleuronectidae (righteye flounders)
Paralichthyidae (large-tooth flounders)
Achiropsettidae (southern flounders)
Samaridae
Suborder Soleoidei
Soleidae (soles)
Achiridae (American soles)
Cynoglossidae (tonguefishes) |
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. The other distinguishing features of the
order are the presence of protrusible eyes, another
adaptation to living on the sea-bed (benthos), and the
extension of the dorsal fin onto the head.
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.
Flatfish have been cited as dramatic
examples of evolutionary adaptation. For example, Richard
Dawkins in The Blind Watchmaker, explains the flatfish's
evolutionary history as:
... bony fish as a rule have a marked tendency to be
flattened in a vertical direction.... It was natural,
therefore, that when the ancestors of [flatfish] took to
the sea bottom, they should have lain on one side....
But this raised the problem that one eye was always
looking down into the sand and was effectively useless.
In evolution this problem was solved by the lower eye
'moving' round to the upper side.
The development of flatfish is thus considered to
recapitulate their evolutionary history.
The asymmetric geometry of flatfish has been likened to
the
cubist paintings of Pablo Picasso, and is often perceived as being
"imperfect", "grotesque", "strange", etc. It is likely that
the asymmetry contributes to their survival by helping to
disguise them on the ocean floor.
See also