Connecting the dots

Curious about the strange bumps on an alligator's face, a UM researcher sheds new light on a 200-million-year-old species

July 08, 2002|By Gary Dorsey | Gary Dorsey,SUN STAFF

Some people have a way of stating the obvious.

"Gee," said Daphne Soares, "what are these little dots on the face?"

She was not being rude. It was not the pimply face of a little friend or the stubbled chin of an old grandfather. It wasn't even human at all. Soares was staring at an alligator.

Sitting atop the 8-foot-long creature in the back of a pickup truck roaring along a Louisiana backwater -- just graduate student and gator -- Soares finally asked the right question about a species that, after 200 million years of belly-scraping in the bayous, no one else had bothered to become quite so intimate with.

Looking down that long, gnarly snout, she simply couldn't help herself.

So what are those little dots on the face?

Well, nobody knew. Not even a clue.

Investigating the neuronal paths of bird brains, which has been Soares' specialty at the University of Maryland at College Park, was one thing. The side trip to the swampy backwaters of Louisiana in 1999 to study Crocodilia was only supposed to enhance what she knew about birds. Since, as everybody knows, alligators and crocodiles are the closest living relatives to birds ("The way their auditory brain stems are put together are almost identical," she says), Soares only wanted a little insight into how gators hear. She thought it might tell her more about how birds make sense of sound.

But those weird bumps ...

"So I thought, this is a good side project," she said. "I called and e-mailed everyone I could think of and asked, you know, `What is this?' People thought they were maybe salt detectors, so if alligators were going out into the ocean they would think about coming back. Or taste buds. Or signal detectors. But no one had ever actually researched it."

Before you knew it, she had eight baby gators in her biology lab at College Park. Her work was about to take a startling turn.

The "little dots" that speckle an alligator's face are not cosmetic blemishes or taste buds or anything of the kind, as Soares found out. The tiny domed structures, which she discovered through fossil records had been evident since the Early Jurassic period 200 million years ago, actually were pressure sensors. Big, important stuff.

"The first time I dissected one, I was amazed at how big the nerves were," she said. "They are the biggest things around. I thought they were muscles at first."

Examining alligator skulls, Soares found thousands of nerves threading through holes in the facial bone, wrapping into a larger nerve that connected directly into the brain. Although an alligator has a fairly small brain, about the size of a peach pit, Soares discovered by injecting a chemical tracer into the receptors and dissecting the brain to see where the chemical ended up that a huge portion of the brain was devoted to responding to the "little dots" on alligators' faces.

What could be that important?

Easy does it

That a graduate student, at the cusp of her career, might make a significant finding that experts had overlooked would be unusual. So Soares proceeded carefully.

She had ideas developing into a major hypothesis. She kept a very low profile.

"You don't want to make a silly person out of yourself by saying, `Hey, look what I found!' and then have someone turn around and say, `Yeah, we've known that forever.' Oh, I really wanted to make sure I was right."

So she went slowly.

For the first year, she traveled around the country to look at old bones, tracking the natural history of pressure sensors on the faces of alligators and crocodiles and lizards. She searched the world's scientific literature, hoping to find out who else had ever noticed the little dots. She came across a few old German manuscripts from the 1800s and then a paper by a Harvard scientist in 1986. That was it. A few scientists had noticed the dots and even gave them an impressive name, "integumentary sensory organs," which Soares thought awfully dull. But behind the fancy name, there was little else to report.

Soares was on an adventure.

She was onto something big.

Could those little dots, she wondered, be one of the defining characteristics in the evolution of the species?

For two years, as she pursued a Ph.D. on the neurobiology of bird brains, she kept getting acquainted with the eight little alligators in her lab. She traveled to Louisiana and brought back alligator eggs. You should have seen her slipping through the X-ray machine at a Houston airport with her box of fragile eggs.

"The security guy was saying, `What's this?' and I thought, `Uh oh,' because the embryos looked pretty far along," she said. "So I got on the plane and put them in my lap and started reading a magazine. Next thing I knew I hear, `eeek, eeek, eeek!' And the lady next to me is looking over, and my heart sank because that's the noise they make when they hatch.

"So every time they started to `eeek, eeek!' I coughed. Hack, hack, hack! I spent an hour and a half coughing. I'm sure the lady didn't buy it, but she was polite enough not to call the stewardess."

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