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Primitive fish may shed light on evolution of limbs

Once thought to be extinct, the coelacanth (through its DNA) is aiding scientists in their growing understanding of evolution. When inserted into mice, the fish's DNA causes the mammals to grow limbs. In the fish the same DNA codes for fins, not limbs. 

Scientists have sequenced the genome of the coelacanth, a primitive "living fossil" that has evolved little over the past 400 million years. DNA from the coelacanth can make limbs sprout in mice.

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The genome of a primitive fish that was once thought to have died when the dinosaurs did has now been sequenced by scientists — and when put into mice, some of the fish DNA caused mice to sprout limbs.

The new analysis, described today (April 17) in the journal Nature, could help to reveal how primitive fish swapped their fins for limbs when they moved from land to sea.

The fish, called a coelacanth, seems to carry snippets of DNA that can turn on genes that code for forelimbs and hind limbs in mice. The new discovery could shed light on how four-legged creatures, called tetrapods, evolved. [Image Gallery: The Freakiest Fish]

"It really is a cornerstone from which we can view tetrapod evolution," said study co-author Chris Amemiya, a geneticist at the Benaroya Research Institute in Seattle, Wash.

Living fossil

The coelacanth was once thought to have gone extinct about 70 million years ago, roughly around the time dinosaurs vanished. But in 1938, a fish trawler brought a bluish-purple, 3.3-foot-long (1 meter) fish with fleshy fins to the South African naturalist Marjorie Courtenay-Latimer. It turned out to be an African coelacanth.

Over the next several decades, scientists unearthed a few hundred of the elusive creatures living around the Comoros Islands in the Indian Ocean, as well as off parts of Indonesia.


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