Fish's DNA Holds Clues to Evolution: Scientists

Scientists find DNA for placenta, limbs in ancient fish

By Mark Russell,  Newser Staff

Posted Apr 18, 2013 11:13 AM CDT

(Newser) – The coelacanth doesn't just look like a prehistoric fish, it was believed to be one, extinct for some 70 million years—until one turned up at a South African fish market in 1938. Now, scientists have decoded the endangered species' genome, and they say they've found some clues as to how today's land animals evolved from a fish ancestor, reports the New York Times. First, some fascinating backstory: The Times explains that the coelacanth and lung fish—both "lobe-finned fish"—have been duking it out for the title of the closet relative to that first ancestral fish that used its fins to walk on land.

Post-decoding, the lungfish emerges as the closer relative, but in the Times' telling, the "coelacanth may have the last laugh"—that's because the lungfish genome is too long to decode using current technology. What scientists learned from the coelacanths' DNA:

  • Even though coelacanths don't have a placenta, they have a gene related to one that allows land animals to grow a placenta.
  • A DNA sequence found in coelacanths, but not ordinary fish, bolsters the genes that helps an embryo grow limbs. Researchers actually injected the coelacanth's sequence into mice; "it lit up right away and made an almost normal limb," says one.
You can check out the original article at Nature.

This 2008 image made available by the Smithsonian's National Museum of Natural History shows an African coelacanth (Latimeria chalumnae).
This 2008 image made available by the Smithsonian's National Museum of Natural History shows an African coelacanth (Latimeria chalumnae).   (AP Photo/Smithsonian, Chip Clark)
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