Scientists
from The Field Museum in Chicago and Argonne, using Advanced
Photon Source (APS) X-ray beams, discovered a surprising
new insect breathing mechanism that is similar to lung ventilation
in vertebrates.
“The
discovery of this fundamental aspect of respiratory biology for
insects
could revolutionize the field of insect physiology,” said
Mark Westneat, associate curator of zoology at The Field Museum.
Insects—the
most numerous and diverse group of animals—don’t
have lungs. Instead, they have a system of internal tubes called
tracheae that are known to exchange oxygen through slow, passive
mechanisms, including diffusion. But this new study demonstrates
that beetles, crickets, ants, butterflies, cockroaches, dragonflies
and other insects also breathe through the use of rapid cycles
of tracheal compression and expansion in their head and thorax.
Tracheal compression
was not found for all types of insects studied, but for those
where it was found, the compression
patterns varied
within individuals and between species. The three species
most closely studied—the wood beetle, house cricket and
carpenter ant—exchange up to 50 percent of the air
in their main tracheal tubes approximately every second.
This is similar to the
air exchange of a person doing moderate exercise.
Until now,
it has not been possible to see such movement inside living
insects. This problem has been solved by using
the brilliant
X-rays at the APS to obtain videos of living, breathing
insects.
“This
is the first time anyone has applied this technology to obtain
highly detailed, real-time video images of the internal
organs of living insects,” said Argonne physicist Wah-Keat
Lee.
One aspect
of the technique that makes the videos so revealing is edge enhancement,
which highlights the edges
of some
internal organs.
This effect
is due to the special properties of the APS’s
X-ray beams. “It’s almost as if parts
of the anatomy have been outlined in pencil, like
a drawing
in a coloring book,” Lee
explained. This work may lead to powerful new techniques
for studying how living animals function, he added.
Indeed, Westneat,
Lee and their collaborators are already aiming the synchrotron
at the jaws of insects
to see
how they chew. “Most
of the 12 moving parts in an insect’s jaw
mechanism are internal, so our inability to see
inside living,
moving insects has prevented
us from understanding how these parts work together,” Lee said.
Westneat envisions
using similar videos to study animal functions, biomechanics
and movements.
New
discoveries
about animal
function can have broad implications. For example,
active tracheal breathing
in the head and thorax among insects may have
played an important role in the evolution of terrestrial
locomotion and flight
in insects, and be a prerequisite for oxygen
delivery to
complex sensory systems
and the brain.
This research
could not only help scientists learn more about the animals studied
but could
also provide
insights
into
human health.
For example, studying how larval fish move
their backbones could shed light on how to treat spinal
cord injuries
in humans. Likewise,
studying the walls of blood vessels in mice
and the tiny hearts in beetles—each beetle
has eight to ten hearts—could
shed light on high blood pressure.
“Basic
principles of mammal, fish or insect physiology and function
could have important implications for health care,” Westneat
says. “We intend to develop this novel
technique for a range of applications that
will greatly improve our knowledge of how
tiny animals live and function.”
For more information,
please contact Catherine Foster.
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