Biologists unravel DNA of ‘living fossil’

coelacanth

The coelacanth was considered to have been extinct for approximately 65 million years until a specimen was caught off the coast of Africa in 1938. Evidence of how far science has progressed was demonstrated Wednesday when biologists announced they had unraveled the rare fish’s DNA.

Scientists are hopeful that the genetic blueprint of the coelacanth, called the “living fossil” fish, can shed light on how life in the sea crept onto land hundreds of millions of years ago, according to Agence France-Presse.

Analysis of the coelacanth genome shows three billion “letters” of DNA code, making it roughly the same size as a human’s, biologists said.

“The genetic blueprint appears to have changed astonishingly little over the eons, pointing to one of the most successful species ever investigated,” according to the wire service.

“We found that the genes overall are evolving significantly slower than in every other fish and land vertebrate that we looked at,” said Jessica Alfoeldi of the Broad Institute of the Massachusetts Institute of Technology and Harvard.

Coelacanths are an exceedingly rare order of fish – only 308 have ever been caught – that include two living species: the West Indian Ocean coelacanth and the Indonesian coelacanth

The grey-brown fish can grow up to 6.5 feet in length and weigh as much as 200 pounds.

Questions about the ancient-looking fish have long loomed large in scientific circles.

Fossil of prehistoric coelacanth.

Fossil of prehistoric coelacanth.

“Modern coelacanths closely resemble the fossilized skeletons of their ancestors of more than 300 million years ago and the genome confirms what has long been suspected: coelacanth genes are evolving more slowly than other organisms,” according to the website RedOrbit.

The slow rate of evolutionary change might be because the coelacanths have not needed to adapt.

For the most part, both species live at ocean depths where relatively little has changed over the millennia, RedOrbit added.

“We often talk about how species have changed over time,” said researcher Kerstin Lindblad-Toh, also of the Broad Institute.

“But there are still a few places on Earth where organisms don’t have to change, and this one of them,” she added. “Coelacanths are likely very specialized to such a specific, non-changing extreme environment – it is ideally suited to the deep sea just the way it is.”

A fossilized skull described by Chinese paleontologists dates the first coelacanth to 375 million years ago.

Perhaps it’s not surprisingly then that coelacanths were thought to have gone extinct in the Late Cretaceous period until they were rediscovered 75 years ago off the coast of South Africa.

One of the big interests in coelacanths is in their lobe-shaped fins, according to the Agence France-Presse report

“These have sparked speculation that coelacanths were part of a group of fishes that used stubby appendages to ease their way out of water and eventually crawl onto land,” the wire service reported.

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