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Bagaimana
toepads lengket berkembang
dalam tokek gecko dan apa
artinya bagi teknologi perekat
Tokek dikenal dengan jari-jari lengket yang
memungkinkan mereka untuk memanjat dinding dan bahkan menggantung terbalik pada
langit-langit. Sebuah studi baru menunjukkan bahwa tokek batu telah memperoleh
dan kehilangan struktur perekat unik ini beberapa kali selama sejarah panjang
evolusi mereka dalam menanggapi perubahan habitat................
How sticky toepads evolved in geckos and what that means for adhesive
technologies
Date:
June 28,
2012
Source:
University of Minnesota
Summary:
Geckos are known for sticky toes
that allow them to climb up walls and even hang upside down on ceilings. A new
study shows that geckos have gained and lost these unique adhesive structures
multiple times over the course of their long evolutionary history in response
to habitat changes.
.....................
Geckos are known for sticky toes that allow them to climb up
walls and even hang upside down on ceilings. A new study shows that geckos have
gained and lost these unique adhesive structures multiple times over the course
of their long evolutionary history in response to habitat changes.
"Scientists
have long thought that adhesive toepads originated just once in geckos, twice
at the most," says University of Minnesota postdoctoral researcher Tony
Gamble, a coauthor of the study. "To discover that geckos evolved sticky
toepads again and again is amazing."
The findings
are published in the most recent edition of PLoS ONE. Gamble is a
researcher in the College of Biological Sciences' Department of Genetics, Cell
Biology and Development. Aaron Bauer, a professor at Villanova University, is
the study's senior author. The research is part of a long-standing
collaboration on gecko evolution among biologists at the University of
Minnesota, Villanova University and the University of Calgary.
Geckos, a
type of lizard, are found in tropical and semitropical regions around the
world. About 60 percent of the approximately 1,400 gecko species have adhesive
toepads. Remaining species lack the pads and are unable to climb smooth
surfaces. Geckos with these toepads are able to exploit vertical habitats on
rocks and boulders that many other kinds of lizards can't easily get to. This
advantage gives them access to food in these environments, such as moths and
spiders. Climbing also helps geckos avoid predators.
The
researchers found that sticky toes evolved independently in about 11 different
gecko groups. In addition, they were lost in at least nine different gecko
groups. The gain and subsequent loss of adhesive toepads seems associated with
habitat changes; e.g., living on boulders and in trees versus living on the
ground, often in sand dunes, where the feature could be a hindrance rather than
an advantage. "The loss of adhesive pads in dune-dwelling species is an
excellent example of natural selection in action," Bauer says.
Repeated
evolution is a key phenomenon in the study of evolutionary biology. A classic
example is the independent evolution of wings in birds, bats and pterosaurs. It
represents a shared solution that organisms arrived at separately to overcome
common problems.
In order to
understand how the toepads evolved, the research team produced the most
complete gecko family tree ever constructed, including representatives of more
than 100 genera (closely related groups of species) from around the world. This
family tree can serve as the basis for answering many other questions, such as
how and when did live birth, temperature-dependent sex determination, and night
color vision evolve in geckos? The family tree will also allow the authors to
revise gecko taxonomy to best reflect the group's evolutionary history.
Gecko toepads
adhere through a combination of weak intermolecular forces, called van der
Waals forces, and frictional adhesion. Hundreds to hundreds of thousands of
hair-like bristles, called setae, line the underside of a gecko's toes. The
large surface area created by this multitude of bristles generates enough weak
intermolecular forces to support the whole animal.
The amazing
clinging ability of Gecko toes has inspired engineers to develop biomimetic
technologies ranging from dry adhesive bandages to climbing robots.
"Gaining a better understanding of the complex evolutionary history of
gecko toepads allows bio-inspired engineers to learn from these natural designs
and develop new applications," says co-author Anthony Russell, of the
University of Calgary.
While scientists
have a good understanding of how geckos stick at the microscopic level, they
are just beginning to understand how geckos use their adhesive toepads to move
around complex environments in the wild. Learning how gecko toepads have
evolved to move in nature is an important step in developing robotic
technologies that can do similar things. "It's one thing to stick and
unstick a piece of 'gecko tape' to a smooth surface in a lab, but something
else altogether to get a robotic gecko to move across a complicated landscape
in the real world and stick to all the different shapes and textures it will
encounter," says Gamble. Examining the repeated evolution of gecko toepads
will let scientists find common ways natural selection solved these problems and
focus on the characteristics shared across different gecko species.
Story
Source:
The above
story is based on materials provided by University of Minnesota. The original article was written
by Deane Morrison. Note: Materials may be edited for content and length.
Journal
Reference:
- Tony Gamble, Eli Greenbaum, Todd R. Jackman, Anthony P. Russell, Aaron M. Bauer. Repeated Origin and Loss of Adhesive Toepads in Geckos. PLoS ONE, 2012; 7 (6): e39429 DOI: 10.1371/journal.pone.0039429