Genome of ancient-looking fish gives clues to first limbed landlubbers

Aquamarine Fukushima

An African coelacanth, photographed using a Remotely Operated Vehicle off the coast of Tanga, Tanzania.

By John Roach, Contributing Writer, NBC News

The genome of the coelacanth, an ancient-looking lobed-finned fish, has been sequenced and is already providing insight to the evolutionary changes that allowed the first four-limbed animals, called tetrapods, to crawl out of the water and on to land.

The sequence and preliminary analysis, reported Thursday in the journal Natureby a team spanning 40 research institutions and 12 countries,is a "massive piece of work," Xiaobo Xu, a paleontologist at Kean University who was not involved in the effort, told NBC News in an email.

"The paper really provides rare and valuable genomic data for offering heavy-weight opinions on issues bearing on the fish (to) tetrapod transition," he said.

It also settles a debate that has long raged amongst evolutionary biologists: what fish is the closest relative of tetrapods: the coelacanth or the equally odd-looking lobed-finned lungfish. The winner, according to analysis of the newly-published genome, is the lungfish.

"We think we have definitively shown it now," Jessica Alfldi, a research scientist at the Broad Institute of MIT and Harvard and co-first author of the paper, told NBC News. "They are very close, which is why it took so much data to figure it out."

Slow evolving genes Scientists thought coelacanths went extinct about 70 million years ago, during the Late Cretaceous period. That changed when a fish trawler off the South African coast delivered a fresh-caught coelacanth to a local natural history museum in 1938, proving that the fish are alive and well.

The coelacanths' odd, ancient-looking looks raised eyebrows and earned it the nickname "living fossil" much to the chagrin of evolutionary biologists, noted Alfldi. ("It makes people think there was no evolution," she explained.)

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Genome of ancient-looking fish gives clues to first limbed landlubbers