Monday, October 24, 2005

Wasps Used as Scent Detectors

A team in Georgia has built a tiny device that uses trained wasps to detect specific odors -- a prototype "biological sensor" capable of sniffing out anything from chemical warfare agents to corpses.

Five fly-size parasitic wasps -- which don't sting -- are placed in a disk-shaped chamber about the size of two stacked checkers, with a hole in the bottom and a tiny fan that sucks air into the disk. If the wasps detect the suspect odor, they gather around the hole, creating a cluster of pixels for a tiny webcam that sends an alarm signal.

Entomologist W. Joe Lewis of the Agriculture Department's Agricultural Research Service said he and colleagues have known for nearly 20 years that, with a reward of sugar water, wasps can be trained in as little as five minutes to respond to almost any odor.

"But this is the first packaged system," Lewis said from his lab in Tifton, Ga. Ultimately, the "Wasp Hound" will be "like a small BlackBerry" that can be operated robotically or by hand, he added. The disk would be swapped out after a few passes. Lewis and Glen C. Rains, a biological engineer at the University of Georgia, are publishing their latest research in the January-February issue of the journal Biotechnology Progress.

"The wasps are cheap and reliable, and you can breed thousands of them," Lewis said. Other researchers are showing that insects besides wasps can also be trained.

"What we once thought of as instinct is, in fact, learning," Lewis said. "And once you know that, you have a whole new emerging technology."

-- Guy Gugliotta

A New Natural Antifreeze

Canadian scientists studying tiny insects known as snow fleas have discovered two new frost-busting compounds that apparently keep the bugs from becoming six-legged ice cubes in subfreezing temperatures.

The natural antifreeze molecules are distinct from those previously found in other animals, suggesting that antifreeze compounds arose independently on many occasions through evolution, the team reported in Friday's issue of the journal Science.

Snow fleas, also known as springtails, are not really fleas. Just a millimeter or so in length, each sports a pair of stiff tail bristles that fold forward beneath the body, where they are held in place with a tiny hook. When the bristles are suddenly released, the insect flips through the air in a flealike acrobatic jump.

The critters munch on fungi and other organic debris but are most easily spotted when there is snow on the ground, where they appear as brown specks that move.

Wondering why the bugs seem unfazed by frost, Laurie Graham and Peter Davies of Queen's University in Ontario analyzed compounds in snow fleas' bodies. They isolated two proteins that attach specifically to developing ice crystals, which stops the crystals from growing even when temperatures get as low as 21 degrees Fahrenheit -- 11 degrees below freezing.

The researchers also identified the snow flea genes that code for the two proteins. When they stuck those genes into bacteria, the bacteria produced the ice-inhibiting compounds.

Many organisms, including some bacteria, plants, fish, moths and beetles, produce antifreezes. Most are structurally unrelated to one another, suggesting they arose independently after those organisms diversified millions of years ago, the team concludes.

-- Rick Weiss

Measuring Amazon Logging

Human activities are degrading the Amazonian forest twice as fast as was previously thought, according to a new study that examines the impact of logging as well as clear-cutting for farming.

Until now, satellite technology detected only clear-cut land, where crews had removed all the trees to make room for farming and grazing. But working with his colleagues, Gregory Asner at the Carnegie Institution of Washington has developed a satellite imaging method that can identify where selective logging has thinned out trees.

The researchers -- who published their findings Friday in the journal Science -- were able to examine each pixel of a satellite image to determine what portion of an area had been deforested. They found that between 1999 and 2002, selective logging accounted for between 60 and 123 percent more damaged area in the Amazon than was reported when researchers were evaluating deforestation.

"This method gives us an incredible map of the ubiquitous but very diffuse types of disturbances that exist in Brazil or in any tropical forest," Asner said. "Logged forests are areas of extraordinary damage. . . . When you knock down a tree, it causes a lot of damage in the understory. It's a debris field down there."

Asner and his coauthors determined that the region's tree harvest is equal to removing between 10 metric tons and 15 metric tons of carbon from the ecosystem, which represents a 25 percent increase in the amount of carbon released into the atmosphere.

-- Juliet Eilperin

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