Why are bat wings so weird? Scientists
want to know
By Washington Post, adapted by Newsela staff
04.08.16
Grade Level 7 Word Count 821
A vampire bat is caught in a net in Aracy, in the northeastern Amazon state of Para, Brazil. Bat
wings are a weird genetic adaptation that don't exist in other mammals. Scientists are trying to
understand how a bat's wings grow so differently from its hind limbs. Photo: AP/Mario Quadros
Chiroptera is a Greek word meaning "hand wing." It is a fitting name for bats, which fly
using long, webbed fingers. The evolutionary history of the wings of bats — the only
mammals with powered flight — has not been studied thoroughly. Now, new research
provides the first comprehensive look at the genetic origins of their incredible wings.
Consider how crazy a bat in flight truly looks.
Try an experiment: Stick your arms out to the side, palms facing forward, thumbs pointing
up toward the ceiling. Now imagine that your fingers are long, arching down toward the
floor like impossibly dirty fingernails — but still made of bone, sturdy and spread apart.
Picture the sides of your body connecting to your hands. A rubbery membrane attaches to
your leg and main part of your body to those long fingers, binding you with strong, stretchy
skin. Finally, imagine using your muscles to flap those enormous hands.
Bats, man.
Shedding New Light On Bat Wings
But the genetic origins of their storied wings has remained murky. However, new findings
from an international team of researchers sheds new light on bat wings.
Researchers looked at bat genes, which help shape what they will look like. Some parts of
DNA turn genes on and off when we grow, working like switches. The switches, called
enhancers, help build an animal's body plan. Enhancers determine whether and when a gene
is turned on to make the stuff that does the stuff. The scientists found the enhancers that
turn genes on and off when the bats grow wings.
They not only found the switches that were used in the earliest development of wings, but at
what point during development the genes were turned on and off. They also examined what
elements in the genome were regulating the expression of these genes.
Scientists first sequenced the entire genome of a long-fingered bat found in eastern and
southern Africa. The genome refers not just to genes themselves, but to all of the genetic
information encoded in the DNA. That includes the parts not translated into protein, as
genes are, but those that play supporting roles as enhancers. Researchers then used the
information to study bats at specific stages of development. They looked at what parts of the
genome were used, and when, to grow those big, flying hands.
A Bat's Limbs Could Hardly Be More Different
Researchers also found there were major differences in development between forelimbs and
hind limbs.
So how different are patterns of forelimb and hind limb development in bats, as compared
with other mammals? The answer depends on how you look at the question.
"On one level, a bat is using the same basic set of genes in its wings and hind limbs that a
mouse [or person] uses. So on that level the two are very similar," said Stephen Schlebusch.
He is a PhD student at the University of Cape Town in South Africa, and a co-leader of the
research.
"On the other hand, there aren't many major differences between the forelimb and hind limb
of most mammals," Schlebusch said. "One might be larger or longer, but by and large they
are fairly similar and their development follows a similar process. In comparison, a bat's
limbs could hardly be more different." He was referring to why bats grow long, webbed
wings and why the unbalanced pattern of their wings differs from their balanced hind limbs.
Hind Limbs Stay Normal, But Front Limbs Go Crazy
So where did these differences start to appear during development?
Until a certain stage, bat forelimbs and hind limbs develop more typical of mammals. Then,
at specific points in development, the forelimbs go crazy and lose their balanced appearance.
But the hind limbs stay normal, said Nadav Ahituv, of the University of California at San
Francisco. He is another co-leader of the research.
Scientists can't quite figure out exactly what makes a bat wing go wacky.
"We have a nice genomic blueprint of all the different factors that could potentially be
causing the development of the wing," Ahutiv said. But testing their findings to determine
what factors cause the tweaks gets a little more complicated.
Scientists can remove some genetic information from a life form and see what results. In this
case, they might remove certain genes to see which were necessary for the key runaway
forelimb development.
A Link To Malformed Human Limbs?
That's not actually possible in bats, as they are not an animal model used in labs.
Researchers also plan to study bats more closely throughout the developmental process. They
might follow the functional changes that occur as certain genes are expressed.
The research could also help explain how human limbs become misformed.
Humans can present a variety of limb malformations. The include longer digits or webbing
between them. By learning about the development of bat wings, scientists now have new
tools to understand how some of these limb malformations occur.
Reproduced with permission. Copyright © 2016 Washington Post. All rights reserved.