June 2022, ScientificAmerican.com 15Arun Roisri/Getty ImagesG E N E T I C SFlying Frogs
Analysis and flight test probe
how “parachute frogs” glideA few frog species in the jungles of
East Asia take hopping to the extreme.
These daredevil amphibians, dubbed para-
chute frogs, leap from treetops and soar
through the rain-forest canopy to evade
predators. Some can cover more than 50
feet in a single glide.
Although they lack the true wings of
birds and bats, these frogs use extensive
webbing between their toes as a winglike
surface to slow their descent. They also
have oversized feet, as well as flaps of
loose skin along their limbs and sticky toe
pads to help them safely land.
University of Texas at Austin evolution-
ary biologist David Hillis and his colleagues
at China’s Chengdu Institute of Biology
collected several specimens of black-
webbed tree frogs—a lime-green para-
chute frog species with black and yellow
webbing—from rain forests in southern
China to pick apart the genetics behind the
impressive adaptations.
The researchers compiled the tree frog’s
genome and compared it with a closely
related frog incapable of gliding. For a study
in the Proceedings of the National Academy
of Sciences USA, they pinpointed 455 modi-
fied genes. “Many of the genes we identi-
fied are associated with various aspects of
webbing, foot and limb development,” Hillis
says. “All are consistent with the strong
morphological adaptation of flying frogs forgliding behavior.” The researchers found
some genes produced longer limbs and
stickier toe pads for climbing. They also
identified the network of genes likely
responsible for extra webbing by tracking
foot development in each species’ tadpoles.
To observe these differences in action,
the researchers conducted a controlled
flight test. They placed frogs from each
species on perches and recorded any
jumps and subsequent glides—positioning
soft sponges below in case frogs fared
badly in the air. This proved important for
the nongliding frogs, which plummeted
into the sponges. But the parachute frogs
splayed their heavily webbed toes to glide
horizontally before touching down.
According to biomechanist Mimi Koehl of
the University of California, Berkeley, who
has studied flying frogs’ biodynamics and
was not involved in the work, the extra web-
bing both slows their fall and helps them
steer through the rain-forest canopy. The
frogs dodge trees by using oversized back
feet like rudders as they descend toward
puddles on the forest floor, congregating to
mate and lay eggs. “If they can’t maneuver
through this complicated environment,
they’re going to miss the orgy,” Koehl says.
The researchers say understanding
these frogs’ adaptations may help illumi-
nate how other animals—such as flying
squirrels and flying lizards—took to the sky.
Koehl and her colleagues have even used
flying frogs to help model dinosaur flight.
Flying dinosaurs “had feathered tails and
feathers on their hind legs,” she says.
“They had the same maneuverable body
design as flying frogs.” — Jack TamisieaParachute frog
Arun Roisri/Getty ImagesG E N E T I C SFlying Frogs
Analysis and flight test probe
how “parachute frogs” glideA few frog species in the jungles of
East Asia take hopping to the extreme.
These daredevil amphibians, dubbed para-
chute frogs, leap from treetops and soar
through the rain-forest canopy to evade
predators. Some can cover more than 50
feet in a single glide.
Although they lack the true wings of
birds and bats, these frogs use extensive
webbing between their toes as a winglike
surface to slow their descent. They also
have oversized feet, as well as flaps of
loose skin along their limbs and sticky toe
pads to help them safely land.
University of Texas at Austin evolution-
ary biologist David Hillis and his colleagues
at China’s Chengdu Institute of Biology
collected several specimens of black-
webbed tree frogs—a lime-green para-
chute frog species with black and yellow
webbing—from rain forests in southern
China to pick apart the genetics behind the
impressive adaptations.
The researchers compiled the tree frog’s
genome and compared it with a closely
related frog incapable of gliding. For a study
in the Proceedings of the National Academy
of Sciences USA, they pinpointed 455 modi-
fied genes. “Many of the genes we identi-
fied are associated with various aspects of
webbing, foot and limb development,” Hillis
says. “All are consistent with the strong
morphological adaptation of flying frogs forgliding behavior.” The researchers found
some genes produced longer limbs and
stickier toe pads for climbing. They also
identified the network of genes likely
responsible for extra webbing by tracking
foot development in each species’ tadpoles.
To observe these differences in action,
the researchers conducted a controlled
flight test. They placed frogs from each
species on perches and recorded any
jumps and subsequent glides—positioning
soft sponges below in case frogs fared
badly in the air. This proved important for
the nongliding frogs, which plummeted
into the sponges. But the parachute frogs
splayed their heavily webbed toes to glide
horizontally before touching down.
According to biomechanist Mimi Koehl of
the University of California, Berkeley, who
has studied flying frogs’ biodynamics and
was not involved in the work, the extra web-
bing both slows their fall and helps them
steer through the rain-forest canopy. The
frogs dodge trees by using oversized back
feet like rudders as they descend toward
puddles on the forest floor, congregating to
mate and lay eggs. “If they can’t maneuver
through this complicated environment,
they’re going to miss the orgy,” Koehl says.
The researchers say understanding
these frogs’ adaptations may help illumi-
nate how other animals—such as flying
squirrels and flying lizards—took to the sky.
Koehl and her colleagues have even used
flying frogs to help model dinosaur flight.
Flying dinosaurs “had feathered tails and
feathers on their hind legs,” she says.
“They had the same maneuverable body
design as flying frogs.” — Jack TamisieaParachute frogsad0622Adva3p.indd 15sad0622Adva3p.indd 15 4/20/22 7:01 PM4/20/22 7:01 PM
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