Wildlife

“Fossil fish” not the fossil we thought it was

The ancient looking coelacanth gained more than 60 genes in relatively recent history
  • Mar 05, 2021
  • 383 words
  • 2 minutes
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The coelacanth — also known as the “living fossil” fish — was thought to have been extinct since the time of the dinosaurs and was rediscovered in 1938 off the coast of South Africa. But it turns out it’s not the 65 million-year-old “living fossil” we once thought it was. According to new research out of the University of Toronto, the fish gained 62 new DNA-binding protein genes a mere 10 million years ago. Most other genomes — like humans and birds — have either none or just one gene from this family. 

“It was purely coincidental,” says senior study author Tim Hughes about the discovery. “My lab works primarily on human DNA and genes. We look at how proteins, and the sequences they bind, evolve over time.”

In comparing human DNA to other proteins, the researchers came across the protein that appears in the coelacanth, called ‘CGGBP1.’ But they were surprised by just how many of them the coelacanth had.

“We started looking at the evolutionary conservation of proteins and found they had this remarkable pattern,” says Hughes. “Most lineages don’t have [these proteins] at all. Some are present in fish or a few fungi.”

The researchers suspect that the proteins are derived from “transposons,” also known as “jumping genes.” These are genes that “jump” from one part of the genome to another. They are also known as “selfish genes,” as their sole purpose is to self-replicate. It appears that the coelacanth gained the new genes through gene transfer between species.  

While Hughes says they “hit the jackpot” with the discovery, the team is not quite sure what can be done with this new information. 

“We’ve been hemming and hawing about how to make it work for us in a couple years — even a review of the paper pointed out there’s no way to functionally analyze these,” says Hughes. “Almost by coincidence, we can’t even do the experiments on them — you can’t even cultivate them.”

Coelacanths are rarely studied, due to the depths at which they live: more than 700 metres below the surface. Estimates put their life spans at about 60 years, growing to almost two metres long and weighing almost 200 pounds. There are believed to be two separate species of the fish. 

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