One eye 'migrates' up and over the top of the head before coming to rest in the adult position on the opposite side of the skull. This remarkable arrangement arises during the youth of every flatfish, where the symmetrical larva undergoes a metamorphosis to produce an asymmetrical juvenile. Because these fish lay on their sides at the ocean bottom, this arrangement enhances their vision, with both eyes constantly in play, peering up into the water.
No such fish - fossil or living - had ever been discovered, until now.Īll adult flatfishes-including the gastronomically familiar flounder, plaice, sole, turbot, and halibut-have asymmetrical skulls, with both eyes located on one side of the head. A slightly asymmetrical skull offers no advantage. Opponents of evolution have insisted that adult flatfishes, which have both eyes on one side of the head, could not have evolved gradually. Hidden away in museums for more that 100 years, some recently rediscovered flatfish fossils have filled a puzzling gap in the story of evolution and answered a question that initially stumped even Charles Darwin. įlatfish Fossils Fill In Evolutionary Missing Link Until this discovery of these fossil fishes!. Opponents of evolution have insisted that adult flatfishes could not have evolved gradually. While being lopsided certain serves the flatfish well, scientists have long pondered how this came about. There are also changes in the fin arrangement, skeleton and digestive system.
One eye moves to what becomes the upper side.
As the larva matures, it starts to swim on one side of its body. Indeed when it first hatches, a flatfish larva looks like the larva of other ‘normal’ fish, with eyes on both sides of the head. The flatfish is a fish that swims on its side. Like an animated leaf, this fish slithers over the sea bottom, with both googly eyes on top and a crooked mouth to slurp up yummy worms and other tasty titbits. The flatfish is well and truly cock-eyed.
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