Coelacanth DNA sequenced

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Coelacanth DNA sequenced

April 22, 2013 - 15:58
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Scientists have decoded the DNA of a celebrated "living fossil" fish, gaining new insights into how today's mammals, amphibians, reptiles and birds evolved from a fish ancestor.

The African coelacanth is a close relative of the first fishes to venture onto land.

The coelacanth is closely related to the fish lineage that started to move toward a major evolutionary transformation. Analysis shows its genes have been remarkably slow to change, an international team of researchers reported Wednesday in the journal Nature.

Maybe that's because the sea caves where the coelacanth lives provide such a stable environment, said Kerstin Lindblad-Toh, senior author of the paper and a gene expert at the Broad Institute in Cambridge, Mass.

Like lungfish, the other surviving lineage of lobe-finned fishes, coelacanths are actually more closely related to humans and other mammals than to ray-finned fishes such as tuna and trout. Ancient lobe fins were the first vertebrates to brave the land, and the coelacanth genome is expected to reveal much about the origins of tetrapods, the evolutionary line that gave rise to amphibians, reptiles, birds and mammals, says lead author Chris Amemiya, a biologist at the University of Washington in Seattle. “The coelacanth is a cornerstone for our attempt to understand tetrapod evolution,” he says.

Further study of the genome may give more insights into the transition to living on land, they said. Their analysis concluded that a different creature, the lungfish, is the closest living fish relative of animals with limbs, like mammals, but they said the lungfish genome is too big to decode.

The water-to-land transition took tens of millions of years, with limbs developing in primarily aquatic animals as long as nearly 400 million years ago, by some accounts, and a true switchover to life on land by maybe 340 million years ago, said researcher Ted Daeschler, curator of vertebrate zoology at the Academy of Natural Sciences of Drexel University in Philadelphia,

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