Few creatures stir the imagination like the coelacanth. Scientists thought it had been extinct for millions of years, and then in the 1930s, a specimen seemed to have swum from the Devonian right into a fisherman’s net.
Now scientists have finally sequenced the genome of this elusive, primitive looking creature to find out how slowly it’s really evolved, and to discern its relationship to those fish that dragged themselves onto land and became our ancestors. The news was announced in a paper in Nature.
At the LA Times, Eryn Brown covered the advance in this story, which told us that it was difficult to get DNA from this highly endangered fish but not how they finally did it. How does one go about getting a DNA sample from a five-foot-long endangered fish that spends most of its time 500 feet deep?
The LA Times story also noted that the scientists determined the coelacanth evolved more slowly than other creatures – but did not explain how this was determined.
At the New York Times, Nicholas Wade’s story offered interesting background on the unlikely deep sea habitat of the modern-day coelacanth and noted that it’s very different from the shallow estuaries where its ancestors lurked.
Wade also gave readers the noteworthy fact that the coelacanth is more closely related to people than it is to other fish.
However, the Times story had a lot of confusing material near the beginning, discussing “pre-adaptations” without explaining the term, and at one point saying that a sequence was present in the coelacanth and other animals but not in ordinary fish. Where it says animals he must have meant mammals or perhaps land animals. In another place in discussing genes associated with the placenta, the story says animals when it would make more sense as mammals.
None of the stories helped me understand how scientists were able to claim that the coelacanth was not as closely related to us as the lungfish. It wasn’t clear the lungfish has been sequences and Wade’s story says it’s proven difficult because the lungfish has an improbable 100 billion base pairs of DNA (compared to about 3 billion for humans and coelacanths).
In about the same amount of space, Amy Maxmen of ScienceNow produced a more interesting and clearer story. Her version of the tale had a fascinating account of how one of the researchers managed to turn African fishermen into amateur scientists:
One of the 91 members of the coelacanth genome team, cell biologist Rosemary Dorrington of Rhodes University in Grahamstown, South Africa, showed fishermen in the Comoros archipelago off South Africa's coast how to collect coelacanth tissue in case they accidentally caught one again. She handed out kits including scalpels and glass vials filled with a solution to preserve the genetic material for a few days until it could be shipped to a laboratory and refrigerated.
Dorrington helped convince the fishermen that the genome project was worth their effort. "For these fishermen, fossils and evolution don't have significance," she says, "but they understand that this creature makes the world a richer place." Her efforts paid off: Fishermen collected samples for the project in 2003.
The story also explains the comparative approach that led the researchers to determine that the coelacanth’s DNA really has been in the evolutionary slow lane. And it gives a more detailed treatment of an interesting experiment glossed over in the newspapers, in which a segment of coelacanth DNA was transferred to a mouse, showing that in mammals it’s involved in limb development.
When reporters go beyond the facts presented in a paper, the result reads a lot more like a story – and this one was no fish tale.
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