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Imagine a creature that can grow its own spear and helmet when threatened by an attacker. There is one and the federal government was intrigued enough to fund a major effort to investigate this fierce little creature's genetics. NPR's Joe Palca reports.

JOE PALCA: Anything that can grow its own armor sounds pretty scary. But it's hard to be afraid of a creature named Daphnia.

Dr. JOHN COLBOURNE (Associate Director, Center for Genomics and Bioinformatics, Indiana University): Daphnia are small crustacea, about the size of an equal sign on your keyboard.

PALCA: Or about the size of a grain of rice, says John Colbourne. He's at the Center for Genomics and Bioinformatics at Indiana University, Bloomington.

Other crustaceans you might be familiar with are shrimps and lobsters. Daphnia are a bit different.

Dr. COLBOURNE: They are transparent.

PALCA: Well, so are a lot of us. But in Daphnia's case it's literally true you can see right through them. That transparency also led the first scientists who saw Daphnia to think it was a flea.

Dr. COLBOURNE: When they first noticed this organism, sometimes they would be found to be bright red.

PALCA: So, scientists thought they were bloodsuckers and called them water fleas. Turns out, they're not bloodsuckers, they're blood makers. Daphnia have genes that make hemoglobin. So, when the animal is stressed out, these genes switch on and Daphnia looks red. In fact, Daphnia have an astonishingly large number of genes.

Dr. COLBOURNE: The genome measures only 200 million bases and yet within this region we count over 31,000 genes.

PALCA: For comparison, the human genome has more like 23,000 genes. If Guinness tracks such things, Daphnia would hold the record for the most genes of any animal studied to date. And Colbourne says Daphnia has another surprise.

Dr. COLBOURNE: Many of those genes - we estimate around 35 percent of them -are brand new to science.

PALCA: Colbourne and his colleagues are publishing their findings in today's issue of the journal Science.

Now, if you're like me, you might be wondering something: Why does a simple organism like Daphnia need more genes than a human being?

Dr. COLBOURNE: It's hard to say need more genes, because that would mean evolution has a goal. In this case it's obviously found some way to use more genes.

PALCA: And apparently it uses these genes to cope with its environment. Low oxygen, switch on the hemoglobin genes; predators around, switch on the armor-making genes and on and on and on.

Jeff Dudycha of the University of South Carolina says knowing the DNA sequence of Daphnia is particularly useful because many of the animals used for genetic research have only been studied in the lab.

Dr. JEFF DUDYCHA (Assistant Professor, Biological Science, University of South Carolina): It's virtually impossible to figure out much about their ecology in nature.

PALCA: But ecologists have been studying Daphnia for years. Now, they think they can link all that ecological research with the new genetic research.

Saran Twombly is a program officer at the National Science Foundation, one of the federal agencies that supported the investigation of Daphnia's genetics. She agrees that Daphnia provides some unique research opportunities.

Ms. SARAN TWOMBLY (Program Officer, Division of Environmental Biology, National Science Foundation): What is it about the genome that allows an organism to be so flexible in response to its environment?

PALCA: Twombly says you shouldn't be surprised that it's possible to learn something fundamentally important about life on Earth from a critter about the size of a grain of rice.

Ms. TWOMBLY: Most of what we know about biology comes from decidedly uncharismatic organisms: worms, flies, bugs. We can grow them easily, we know what to feed them, we can do experiments with them. Can't do any of that stuff with lions and tigers and bears.

PALCA: Oh my, no. That would make the laboratory a pretty scary place to work.

Joe Palca, NPR News, Washington.

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