Bee-havior

Neuroscientist Susan Fahrbach has found a perfect partner for her research: the predictable, reliable honeybee.

Sometimes the simplest questions are the hardest to answer. Here's one for you: why do animals do what they do? How come their behavior matches so appropriately with each stage of their lives? Sometimes they reproduce; other times they don't. Sometimes they store food; other times they don't. How do they know what to do, and when?

Susan Fahrbach

Many of us might respond with a shrug or a tautology — they know because they know. Not Susan Fahrbach. She approaches the question as if it were a Russian doll or an onion — going in and in, patiently prying open or peeling back each successive chamber or layer until the core is exposed.

And she has found the perfect partner for that probe: the honeybee.

Fahrbach, the Reynolds Professor of Developmental Neuroscience who is in her second year at Wake Forest, investigates connections between hormones and behavior and between learning and memory. Bees, by virtue of their life cycles, behavior patterns, and brain structures, are ideal subjects.

"The honeybee has fewer than a million nerve cells in its brain," she notes. (By comparison, humans have billions upon billions.) "And yet, they do the right thing at the right time — predictably, consistently, and reliably. Scientific inquiry is an ever-smaller series of black boxes you keep unlocking. I want to go down to the cellular and molecular levels and bring it back to behavior."

Fahrbach has been fascinated with animal behavior ever since she was an undergraduate at the University of Pennsylvania. Neuroscience had not yet emerged as an independent field, so she majored in psychology. To acquire the neuroanatomical knowledge she would need for a research career, she spent two years after graduation at Oxford University in England earning a second bachelor's degree in physiology.

As a doctoral student at Rockefeller University in New York City, Fahrbach concentrated on hormonal regulation of behavior — specifically, the factors that trigger maternal behavior in female rats. "Something happens at birth that changes their attitude toward the young," she notes. "They're afraid of pups one day, and nurturing the next."

The researcher knew that estrogen's action on the brain prepares the way for another hormone, oxytocin, which causes the uterus to contract and milk to flow in pregnant mammals. She wondered whether oxytocin might also have some behavioral function. Sure enough: by injecting oxytocin into virgin rats, she induced motherly behavior in them, thus identifying oxytocin as a sort of "love hormone" that engenders feelings of affiliation.

Fahrbach soon found that even a rat's brain has far too many cells, and thus "too much that's going on," to draw the hormone-behavior correlations she was after. So she turned to insects in her postdoctoral research position at the University of Washington in Seattle.

"It was a complete switch, and I had to learn the basics of the insect nervous system," she says. "I loved it, so it stuck. It's important to have many different approaches to neuroscience. Working with insects — at Washington, it was big green caterpillars — gives me a chance to ask questions that would be unethical to pursue in vertebrates."

In 1988 Fahrbach landed a faculty position in the Department of Entymology at the University of Illinois in Champaign-Urbana. The next faculty member hired by the department the following year, Gene Robinson, specialized in bee research. "Gene was a bee person but not a neuroscientist," Fahrbach notes. "I was exactly the opposite. It was an ideal match." Their collaborative studies of bee behavior have yielded voluminous publications over the years.

"It's impossible to have a successful life as a bee if you can't remember where the flowers are or where your hive is," Fahrbach says in explaining her choice of research subject. "So she [all worker bees are female] absolutely depends on learning and memory. Also, until she is three weeks old, a worker bee spends all her time in the hive doing various tasks. Then, all of a sudden, she leaves the hive, goes to flowers and gathers pollen and nectar, and never does hive work again.

"What makes a bee decide it's time to change? It's a complicated question," she continues. "But what we have discovered is that bees who forage have a larger section of the brain, called the mushroom body, than hive bees do. All sensory information converges there."

Since she and Robinson published a short but influential article on the bee brain in the scientific journal Nature in 1993, Fahrbach has focused on three topics: the mechanism of brain growth; the process by which the bee's outside experiences connect to, or "couple" with, its brain cells; and the implications, or outcomes, of a larger brain.

"If a part of the brain gets bigger, is that better?" she asks. "Are you a better rat if your cortex is bigger? What's the impact? The answer might seem obvious, but this is the hardest question to answer. Bees are so good at navigation and odor recognition that it's hard to make subtle distinctions that could correlate behavior with brain size. One of the things we're working on here is devising tasks that bees don't do so well.

"For example, bees are very good at nest-mate recognition through odor," Fahrbach explains. "They'll post the equivalent of a bar bouncer outside the entrance to the hive to prevent any non-resident from entering. We're trying to find ways to make the task of recognition harder and harder — for example, by positioning hives next to each other. Will it be the bees with bigger brains that will make the distinction between a bee that is one of their own and one that is not?"

Fahrbach, whose research is funded by the National Science Foundation and two additional project grants involving other researchers, has one full-time research assistant and supervises the work of two graduate students at Illinois and three or four undergraduates at Wake Forest. To supply her lab with bees, she keeps five hives at Professor of Biology Peter Weigl's farm off Yadkinville Road in Pfafftown.

What prompted Fahrbach to foresake a tenured full professorship at Illinois after sixteen years? "I thought I'd never leave," she says. "But when you reach a certain stage of your career, they start to drop hints about how right you'd be for a particular administrative job. What I want to do is teach and do research; I do my best work one on one with students. Also, as state universities look for ways to cope with tighter budgets, they increase class sizes. Some semesters I'd find myself standing on a stage in front of 500 freshmen. That has value in its own way, but I didn't feel I could really reach out and shape students by doing that.

"The offer from Wake Forest was an opportunity to come to a first-rate research university and teach in paradise," she continues. "Last fall I taught my favorite course, hormones and behavior, which I never was able to do in my previous position. I had fourteen students, and it was the equivalent of teaching a graduate course at Illinois, with reading of primary literature and critical writing."

An added benefit of her move is the supportive environment she's found. "North Carolina is one of the best states for beekeeping," she notes. "It's far enough north so that its bees haven't been Africanized and far enough south to have longer summers and extended hive activity. There is a long tradition of beekeeping here, and in the short time I've been at Wake Forest I've made some wonderful connections with bee researchers at other universities in the state. We've formed a consortium for possible collaborations; one researcher in Greensboro is studying aging through the queen bee, which lives for years as opposed to the few months that worker bees live. With probably not more than fifty honeybee labs in the world, it's fun to have other folks in the field within driving distance."

In one sense, Fahrbach could not be described as a "bee person"; she doesn't keep bees recreationally or have a lot of bee paraphernalia around the house. But in another sense, she is the quintessential bee person in her appreciation for their special qualities.

"The greatest bee researcher who ever lived, Karl von Frisch, once described bees as a 'magic well' because he could dip into them endlessly and bring up new phenomena," she says. "That's how I would describe them too: a magic well to which I can keep going back."

— David Fyten

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