Biologists Study Alaska Bugs' "Antifreeze"

Sonya Senkowsky
for National Geographic Today
May 8, 2003
In interior Alaska, the winter temperatures average slightly below 0°F (-18°C). Frequently they dip to 20° below zero F (-29°C), and can dive to 60° below zero F (-51°C). Yet insects not only survive but thrive there. How?

In Anchorage, Todd Sformo, a graduate student in biology and environmental physiology at the University of Alaska-Fairbanks, retrieves one answer after another as he digs through a thin layer of spring snow to layers of dead leaves below.

There he unearths dozens of small green stink bugs—shield-shaped, half-inch-long creatures. Under a warming blanket of leaf litter, they have waited out winter in a state of reduced metabolism, or diapause, as researchers call it.

A secret of the insects' overwintering strategy lies in the blood, known as hemolymph.

Last month Sformo and other researchers came to Alaska to harvest that blood and purify the protein within it that allows the insect to "supercool" by lowering its freezing temperature.

The protein operates by a process known as thermal hysteresis, first identified in Antarctic fish—lowering the freezing point of water in the hemolymph. Insects, however, may practice hysteresis even more effectively.

To get enough of the protein, the researchers will have to collect thousands of the bugs at a rate of 1 microliter (it would take 250,000 microliters to gather a cup) of hemolymph per insect.

"I wish they were bigger," says Jack Duman, a biologist at Notre Dame University, in South Bend, Ind. "It would be nice if there were a two-pound stink bug."

Creamier Ice Creams, Hardier Plants

Duman and Brian Barnes, a University of Alaska-Fairbanks animal physiologist and head of the Institute for Arctic Biology, are co-leaders of the study supported by the National Science Foundation.

Duman first studied a similar protein in fish with Art DeVries, a biologist from Stanford University in Palo Alto, Calif., and a pioneer in researching "antifreeze protein," or AFP.

DeVries had wondered how Antarctic fish stay alive in waters cold enough to freeze them. In 1967, he found a gene capable of inhibiting the formation of ice crystals in water.

"That has burgeoned into a large number of people around the world studying (the overwintering capabilities) of insects, fish and plants," Duman says.

The discovery has launched a flurry of patent applications for everything from creamier ice creams to hardier plants. Hopes for the antifreeze protein include better ways to preserve human organs for transplant as well as environmentally safer airplane de-icers.

For years Duman had studied AFP-containing insects that live in Indiana. In 1999, he teamed up with Barnes.

Neither was an insect expert. Barnes teaches a class on overwintering strategies among Alaskan animals, from ground squirrels to migrating birds. Barnes and his students began to study insects, too, and published research on Alaska yellow jackets and stink bugs.

Together Duman and Barnes conducted a brief survey of Alaska insects. The yellow jackets didn't use AFPs, says Barnes. But the survey turned up many others that do—seven of 12 species that the researchers tested.

Stink bugs attracted Duman's attention because they appear to contain a previously unknown version of AFP.

Tough Bugs

Duman's team is also looking into comparisons between AFP-containing insects that live in both Indiana and Alaska, like the beetle Cucujus clavipes. In Indiana, Duman says, the insect dies at minus 13°F (-25°C), but above the Arctic Circle, it can survive temperatures near 60° below zero F (-51°C).

This season's explorations have already raised more questions.

Since the Indiana insects show different levels of AFPs in their blood at different times of year, Duman assumed that in winter's coldest months, Alaska beetles would contain even more of the protein—perhaps a record amount.

As it happens, the Alaska insects don't use much more AFP than the Hoosier variety.

"I guess in retrospect, maybe we should have anticipated that these guys have got to get ready (for frigid temperatures) early," Duman says.

Another finding was that some of the Alaska insects also appear to lose most of their body's water in winter, practically desiccating, but somehow rehydrate and come back to life.

Alaska insect physiology pioneer Keith Miller, formerly of the University of Alaska and now retired in Central Point, Ore., says that this spring's research only increases his respect for Alaska's insects.

When he studied them, he says, "I was constantly being surprised" at the seemingly infinite list of strategies that insects use to inhabit one of the world's least hospitable climates.

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