Fantastic Bloody Pigeon! (Or Hitchcock Nightmare)

Bloody pigeon (Photo: Wellcome Images/Scott Echols)

The Wellcome Trust presents an annual award for scientific imagery, and two of this year’s winners (above and below) caught my eye for the new ways in which they reveal the natural world.  Think of the one above as new insight into the cardiovascular system of living (and extinct) dinosaurs.  Or just a bloody pigeon.

Here’s how The Guardian‘s Nicola Davis describes it:

Open-beaked against a jet-black background, the image of a bird leaps forth, a frenzy of red-and-white squirming lines hinting at its form. It looks like a still from a Hitchcockian nightmare. “It looks so cross, sort of squawking at you,” says Catherine Draycott, head of Wellcome Images.

In fact, the eerie shot is the product of

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Getting Ruff with Pigeons

Richard Bailey photographed some of the pigeons breeds that fascinated Darwin

How do breeders develop such colorful and varied pigeons?  To find out,  the normally reclusive Charles Darwin immersed himself in the hobby, frequenting the taverns and other low abodes where fanciers met and becoming “hand & glove with … Spital-field weavers & all sorts of odd specimens of the Human species, who fancy pigeons.”

Now a University of Utah researcher has taken on the same question more directly, with genetic analysis.  He traced the efflorescence of spectacular pigeon head ornamentation to a change to a single gene.  Here’s part of the story, from Carl Zimmer’s account in today’s New York Times:

… pigeon breeders produced crests on the birds on five separate occasions. The scientists compared the genomes of the crested pigeons with one another, as well as with other pigeons and with chickens, turkeys and other species. They hunted for mutated genes unique to the crested breeds, and found that all of them shared precisely the same mutation in precisely the same gene, EphB2.

Bird embryos develop placodes, little disks of tissue on their skin from which feathers will grow. The scientists found that in ordinary pigeons without crests, EphB2 became active on the bottom edge of the placodes; in crested pigeons it was active on the top edge.

The experiment suggests that EphB2 tells the placode which way is up. In most pigeons, it instructs the feathers to grow down the neck; but the mutation changes the location where EphB2 switches on, effectively turning the feathers upside down and producing a crest.

“They grow the wrong way,” Dr. Shapiro said. “They’re even pointing the wrong way in the