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Walter Leal has a nose for insects' sense of smell

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Walter Leal, professor of entomology at the University of California, Davis, is searching for safer alternatives to insecticides by studying the nuances of mosquito sensibilities. (Photo: UC Davis)

Even when he settles into his office, Walter Leal is unstoppable. Into an already compact space, Leal has crammed a stationary bicycle, so he can keep moving while reading research papers. He likes to compare his time on the bike to writing grant proposals. You work and work, he says, and get nowhere.

When Leal works and works, however, he usually gets somewhere.

Leal is a chemical ecologist, a professor of entomology at the University of California, Davis, who tries to understand at the molecular level exactly what an insect is smelling, and how it relies on scent to interact with the world.

He is slim and intense, with graying hair and clipped sentences jagged with inflections from his years in Brazil and Japan. And he does not, perhaps cannot, quit.

At 29, Leal didn't let a complete lack of Japanese stop him from leaving his native Brazil to accept a graduate scholarship in Japan. Instead, he threw himself into an immersion course with such enthusiasm that he regularly accosted strangers on the bus, asking them to help with his flashcards.

Years later, he once told a reporter that his quest for a particularly elusive beetle pheromone was "a matter of honor." Leal was so determined to puzzle out the mysteries of that 10-lined June beetle that he cut short a trip to Paris so he could collect more beetles during their prime mating time in California.

"He's one of the most dynamic people in the field," said John Hildebrand, a neurobiology professor at the University of Arizona in Tucson.

"He's a remarkably energetic and passionate person about his work ... and notorious almost for the rapid-fire way he speaks. He loves to joke that he can say twice as much in a lecture as anyone else because he only says half of each word."

Today, Leal and his lab members, about a dozen people including undergraduates and postdoctoral fellows, are working with moths, mosquitoes, and fruit flies, using tools ranging from gene silencing to olfaction mazes.

Projects include trying to identify segments of genes involved in olfaction and studying the molecules that respond to pheromones in moths, in hopes of pinpointing the active site on the molecule that grasps and binds the pheromone.

The bulk of their time is devoted to exploring the nuances of mosquito sensibilities. What sort of chemical duo might be laced through standing water so that one compound would encourage a female to lay her eggs there, and another would kill the larvae when they emerge? Which receptor molecules are interacting with DEET, the broadly effective insect repellant with the chemical name N,N-diethyl-meta-toluamide?

"This is one area where lots of competition is going on, so I'd better not talk too much," Leal confides with a smile just self-deprecating enough to take the edge off its calculation. "We go to these meetings and everyone is trying to steal information from each other."

Although DEET has been used for decades, researchers don't fully understand its mechanisms or how it repels so many different kinds of insects, even those with widely different needs and appetites. Leal's team has identified specific neurons in the antennae of Southern house mosquitoes that respond to DEET, and done other work suggesting the insect can smell the chemical and will avoid it.

DEET is a flawed tool, a chemical that needs to be used at high doses, can affect human biology, and isn't recommended for very young infants, according to Leal and others who have studied it. The point is finding something better than DEET, something more targeted to the most problematic insects and less dangerous for everything else, including people.

To search for safer alternatives to DEET and other insecticides, Leal said, researchers need to better understand the mechanisms of scent detection and chemical communication.

"Always my research has some applied component. I am very loyal to that," he said. "We can't have the pleasure of just entertaining ourselves."

That philosophy has long driven Leal's creativity, and has led to him holding more than 30 patents in the United States and Japan.

At UC Davis, Leal meets at least weekly with members of his lab, hunkered in a room dominated by heavy, gray concrete beams. On one of California's seductively mild fall days, when his group is mostly in shorts or jeans, Leal retains a hint of formality, three pens lined straight as sentinels in the pocket of a pin-striped shirt.

He leans forward when he listens, and gestures swiftly when he speaks, peppering his team with questions or prodding them to try new strategies.

"We are not that big a group," Leal said of his lab. He likes to remind each lab member: "The only thing we can beat up the competition with is ideas. You come with ideas."