Animal testing in Panama

international | environment | other press Wednesday April 05, 2006 16:08 by Dawn Jewell

American scientists are regularly visiting the jungles of Panama where they carry out animal testing, including pulling the limbs of animals. This story first appeared in the New york times

The New York Times
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April 4, 2006
Wingless Gliders May Reveal the Origins of Insect Flight
By ELIZABETH SVOBODA

When Stephen Yanoviak visited the jungles of Panama in 1998 to study
how ants forage, he found himself with some unexpected downtime. "Out
of boredom, I started flicking some ants off of a tree," he said.

And he saw something extraordinary. Some of the ants fell straight,
but others swerved at near-right angles and landed on tree trunks feet
from the ground.

Dr. Yanoviak, a University of Florida entomologist, forgot about the
bizarre insect gliders until several years later, when he was
assaulted by the same ant species, Cephalotes atratus, during a
mosquito-collecting trip to the Peruvian rainforest.

"I was sitting on a branch and they were crawling all over me, so I
tried to push them off," he said. "They fell, but immediately turned
around and glided right back to the tree trunk. That's when I realized
this was something worth investigating."

After returning from his trip, Dr. Yanoviak mentioned the gliding ant
sighting to his colleague Robert Dudley, an animal flight expert at
the University of California, Berkeley. "I thought it was the most
exciting thing I'd ever heard," Dr. Dudley said, and he decided to
join Dr. Yanoviak in exploring this uncharted biological territory.
Since then, their research has shed light on the airborne survival
strategies many wingless insect species have, and on the question of
how insect flight originated.

With the entomologist Michael Kaspari of the University of Oklahoma,
the two took video of the ants' descents, looking for clues about how
their structure and movements enabled complex aerial maneuvers.

The ants' hang time was impressive not because their bodies were
particularly aerodynamic, but because they knew how to move their long
limbs around to reduce drag. They moved their left hind legs outward
and rotated them, an off-kilter motion that allowed them to maintain
altitude.

"Any object can generate lift if it's asymmetric to the air stream,"
Dr. Dudley said. "If you put your hand out the window of a car and
rotate it, you'll feel it being lifted. Hands aren't that aerodynamic,
and neither are the ants, but you'll get this effect just the same."
The legs' increased distance from the ants' center of mass also
creates torque, spinning their bodies around — and accounting for the
spectacular swerves they often display before coming in for a landing.

The scientists' hunch that the ants' movements, not their body shapes,
chiefly dictated their gliding paths was confirmed when they started
chopping off appendages to see if the insects could still soar.

The ants showed remarkable resilience. They coasted to controlled
landings after multiple leg amputations and even after removal of
their abdomens, which ordinarily comprise 30 percent of their body
weight. When the researchers covered the insects' eyes with dots of
white nail polish, however, they sank to the forest floor like stones.

To isolate the visual cues so critical to successful gliding, Dr.
Dudley and Dr. Yanoviak returned to the Panamanian jungle last
November to carry out what they called their "Christo experiments."

They hung fabric swaths in an array of rainbow colors high in the
forest, then perched in the treetops and dropped hundreds of ants.
Light colors, especially white, elicited the most consistent gliding
behavior, with the insects veering acutely toward the banners and
landing on them.

These results hinted at gliding's importance as an evolutionary
adaptation. The ants have a vested interest in staying near their home
tree, since they are likely to be trampled or eaten on the forest
floor. White lichen that grows on trunks of rainforest trees serves as
a useful signpost, pointing them toward safe territory.

"There's lots of wind up in the canopy, and ants can easily get blown
off course," Dr. Dudley said. "A worker has to be able to find its way
home again." A paper detailing these findings will be published in a
coming issue of the Journal of Experimental Biology.

The scientists' most recent rainforest trips also yielded
high-resolution video showing that several other ant species glide, as
do the larvae of insects like grasshoppers and praying mantises.

"In their immature stages when they don't have wings, a lot of these
insects can glide back to the trunk, and they do it really well," Dr.
Yanoviak said. "That suggests it's a pretty pervasive behavior among
insects."

There are very few similarities between insect gliders and other
gliders. While the ants direct their descent with calibrated movements
of their limbs, flying squirrels sport epic flaps of skin between
their front and hind legs. These flaps act like the wings of the
Wright brothers' first gliders — their broad and relatively
streamlined shape produces lift and minimizes drag, allowing the
animals to stay aloft longer.

A rare species of Malaysian spotted lizard catches air by thrusting
out its rib cage to create rudderlike projections on either side of
its body. "There really aren't many common structures that are
necessary for gliding," Dr. Dudley said. "It seems to be something
that had multiple independent origins."

Understanding the mechanics of insect gliding could eventually help
engineers develop techniques like controlled parachuting and
pallet-dropping. For now, Dr. Dudley and Yanoviak are most
enthusiastic about tracking down the missing evolutionary link between
flightless and flying insects.

Ants previously had wings and lost them, making them less than ideal
to demonstrate this link, but the researchers have started zeroing in
on silverfish, which never developed wings but can still glide.

"This could be how the first flight began—insects just jumped off
branches and started gliding," said Brian Fisher, an insect behavior
specialist at the California Academy of Sciences. The best way to
assess where gliders fit on the evolutionary continuum between land-
and air-dwelling insects, he added, would be to study the
characteristics that allow silverfish to glide and compare them to
those of the earliest known flying insects.

"There's a big gap in the fossil record between insects that look like
they might be able to glide and insects that have wings," Dr. Dudley
said. "The insect equivalent of Archaeopteryx has not yet been found.
Locating that would be huge