NEW YORK — 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 (SEE-lah-kanth) is closely related to the fish lineage that started to move toward a major evolutionary transformation, living on land And it hasn't changed much from its ancestors of even 300 million years ago, researchers said.
At one time, scientists thought coelacanths died out some 70 million years ago. But in a startling discovery in 1938, a South African fish trawler caught a living specimen. Its close resemblance to its ancient ancestors earned it the "living fossil" nickname.
And in line with that, analysis shows its genes have been remarkably slow to change, an international team of researchers reported Wednesday in the journal Nature.
Modern coelacanths make up two endangered species that live off the east coast of Africa and off Indonesia. They grow to more than 5 feet long and have fleshy fins.
The coelacanth's DNA code, called its genome, is slightly smaller than a human's. Using it as a starting point, the researchers found evidence of changes in genes and in gene-controlling "switches" that evidently aided the move onto land. They involve such things as sense of smell, the immune system and limb development.
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.