The University of Arizona Alumnus / Winter 2008
Beehive of Activity
These linchpins of American agriculture are responsible for annually pollinating up to $20 billion worth of agricultural crops — including most of the nation’s livestock feed.
by Tim Vanderpool
Jacob Chinn photos
Consider the honeybee. With a brain the size of a rice grain, this insect nonetheless boasts the densest neuropile on earth — pure gray and white brain matter — small but tight, and stunningly dynamic.
Then consider that bee colonies can number nearly 50,000 residents by summer’s peak, and a hive’s foragers can cruise miles searching for food. Upon return, they communicate directions to juicy dining spots in an elaborate language known as the waggle dance.
The insects likewise boast incredible visual acuity, and a genetic hard-drive that separates workers and queens by complex chemical signals at birth. Finally, there’s the crucial fact that these tiny wunderkinds are the veritable linchpins of American agriculture, responsible for annually pollinating up to $20 billion worth of agricultural crops — including most of the nation’s livestock feed.
Enjoy cranberries, almonds, blueberries, or a juicy watermelon? Thank the honey bee. All of which goes a long way toward explaining why these insects have captured the attention and imaginations of University of Arizona researchers.
It also explains the buzz in the U.S.D.A. Carl Hayden Bee Research Center, nestled on the UA farm in the heart of Tucson. Sprawled across a couple of acres, the federal facility seamlessly cross-pollinates with the university, providing bees for campus scientists, and drawing knowledge from UA research.
Colony Collapse Disorder and Countermanding Mother Nature
Centers like Carl Hayden are ground-zero in learning how to manage the influx of Africanized bees from South America, fight the devastating Varroa mite now spreading among bees, and shed light on a very disturbing phenomenon known as colony collapse disorder. The disorder is wreaking havoc on the bee industry, and raising more questions than answers among biologists such as Gloria DeGrandi-Hoffman, the lab’s research leader.
“Our major problem right now is keeping colonies alive,” DeGrandi-Hoffman says. “We don’t know the causative agent for colony collapse disorder. There’s a virus that’s certainly a marker for it, but whether it’s the causative agent or not, we just don’t know.”
All of this comes at a time when the demand on bees for agriculture has reached unprecedented levels. As bees are trucked all over the country to pollinate crops, the demand creates new complications.
“We know we’re stressing colonies,” DeGrandi-Hoffman says, “that we’re asking colonies to do more now than we ever have.”
To demonstrate demand, consider that until recently, beekeepers were paid about $30 per colony for a pollination job. Now they’re commanding up to $120 a pop.
Meanwhile, the pollinating season has been stretched. “The year for a beekeeper, particularly in the Western United States, now begins with almond season in February,” says DeGrandi-Hoffman. “People are trying to build their colonies up by then, which is something that we’ve never had to do before. In February, colonies are usually at the lowest point in their population.” Typically, she says, hives weren’t expected to reach their peak until midsummer.
Cranking the season into motion six months early — and basically countermanding Mother Nature —forces researchers to chart new ground. “We’re seeing if we can stimulate those bees through better nutrition.”
The lab has moved closer to that goal with development of MegaBee: The Tucson Bee Diet, a pollen substitute for bees fashioned to boost their health and longevity.
Varroa mite
Conversely, labs at the Hayden center also are working to contain the Varroa mite, a homely, blood-sucking parasite that shortens bee life spans and causes larval deformities. “Varroa is a serious problem,” says DeGrandi-Hoffman. “It seems that the mite is getting resistant (to treatment) quicker, so we’re having to come up with new ways to control them now.”
In turn, these research tendrils reach beyond the UA Farm. DeGrandi-Hoffman says the center works hand-in-glove with campus scientists. “It goes both ways. There are things the University does that we can’t do here, such as in the molecular arena, the biochemical arena — they have expertise and equipment that we don’t have. So we just have this tradeoff — and we go with each other’s strengths.”
Queen Determination and Agriculture
For the UA’s Diana Wheeler, the Hayden center provides one more element critical to bee research: bees. A professor of entomology, she focuses on the caste differences in bees — what makes one destined to become a queen and another a worker. In the big picture, her research could help beekeepers manage their colonies better, and produce more of the European queens, used solely for American agriculture.
“In honeybees, it’s what the larvae are fed that determines what they’ll become,” Wheeler says. “They all start with the same genetic equipment.” But when needed, some are singled out for special treatment. “We know that when honeybees rear new queens, it either means that that their hive is getting very large and they’re ready to split the colony, or that the old queen has died.”
Either way, “At that point they build a (larval) cell that looks different than the typical hexagonal cell,” she says. “It’s shaped more like a bell.”
And then the colony bees start feeding the heck out of the anointed queen in her special cell, while giving less food to the worker larvae.
Wheeler hopes to learn how that triggers hormonal changes in the bee. “I want to understand the link between food and hormones,” she says. “For example, we know there’s a juvenile hormone that does a lot of things to insects developmentally. And we know that if we put that hormone on larvae, they’ll also develop as queens.”
During her postdoctoral research, Wheeler “had looked at genes that were expressed between larvae developed as workers and larvae developed as queens, to see which ones were different very early on.” “Those that were different were key in starting a chain of events that led them along the pathway to developing into queens,” she says.
Wheeler then played a game of musical cells, switching bees around that had been on one menu — worker or queen —for up to three days. She moved them into cells where they’d be fed opposite food, either the workers’ miserly dab of jelly, or the queen’s abundant “royal jelly.”
Then the bees are removed and frozen for DNA testing, to find out which genes are being expressed, relative to their diets.
Her conclusion? Once the die is cast, bees are very reluctant to veer from their assigned course — even if their diets are reversed. “This tells us about evolutionary biology,” she says, “about how these systems evolved. The bees are trying to stay on their pathway, because that’s the best outcome for the colony. It shows how the system has been tweaked to do that over time.”
It also “broadens our basic understanding of the process of queen determination,” she says. “And the (research) funding agencies consider this important to agricultural systems — that it’s something worth knowing more about.”
Visual Acuity and the Bee Brain
Meanwhile, the work of UA doctoral candidate Angelique Paulk focuses on the remarkable visual ability of bees — their startling knack for recognizing and recalling color and patterns — which may help scientists in developing facial recognition systems and robotics.
To do this, Paulk places extremely fine-honed glass tubes inside the bee’s brain, and tabulates the reactions of that dense little organ. “We record from individual cells in the bee brain and see how they respond to different visual cues,” she says.
“That’s how we’ve been able to understand how the visual process happens, whether it’s in bees, or cats, or humans.”
The ability of bees to relay what they’ve seen is nothing short of astounding.
Bees are believed to be the only insect with its own language — different movements in the waggle dance tell hivemates where food can be found, among other remarkable communications.
“Bees are amazing at visually learning things,” Paulk says. “So the next question is — what’s going on at their brain level to allow them to be able to do all these amazing things?”
Paulk’s research has shown that bees have certain properties — or certain aspects of the visual processing pathways — that are very similar to humans’. “And in some ways it’s even a little more complex than what’s going on in the human brain, or at least the vertebrate brain,” she says.
“We’re getting a feeling that if we can record from them — if we can actually end up understanding what’s going on in the bee brain — then we can predict what cells are both color and motion sensitive,” Paulk says. “This is possibly happening in the human brain as well. But are cells doing this with visual cues and very precisely timed spikes? Or do they just fire crazily to certain colors and not others?”
Big questions, centered around a noggin the size of a rice grain. There’s no longer any doubt that bees — and their brains — are well worth considering.
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