Dari ayam ke dinosaurus : Para ilmuwan ber eksperimental ' evolusi reverse’ dari kaki bertengger --T-REC-komunitas reptil-semarang--KSE-komunitas satwa eksotik

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Dari ayam ke dinosaurus : Para ilmuwan ber eksperimental ' evolusi  reverse’ dari kaki bertengger 

Date:

May 22, 2015

Source:

Universidad de Chile

Summary:

Sebuah adaptasi yang unik di kaki burung adalah adanya kaki saling berlawanan seperti ibu jari , yang memungkinkan mereka untuk  bertengger . Namun, dalam nenek moyang dinosaurus mereka , kaki ini kecil dan tidak  saling berlawanan , dan bahkan tidak menyentuh tanah , menyerupai dewclaws pada  anjing dan kucing . Hebatnya, perkembangan embrio burung menyediakan paralel sejarah evolusi ini : toe mulai keluar seperti nenek moyang dinosaurus mereka, tapi kemudian basis ( metatarsal ) menjadi tidak normal , sehingga saling berlawanan ....read more

From chicken to dinosaur: Scientists
experimentally 'reverse evolution' of perching toe

Date:

May 22, 2015

Source:

Universidad de Chile

Summary:

A unique adaptation in the foot of birds is the presence of a thumb-like
opposable toe, which allows them to grasp and perch.  However, in their
dinosaur ancestors, this toe was small and non- opposable, and did not even
touch the ground, resembling the dewclaws of dogs and cats. Remarkably, the
embryonic development of birds provides a parallel of this evolutionary
history: The toe starts out like their dinosaur ancestors, but then its base
(the metatarsal) becomes twisted, making it opposable.

......................

A unique adaptation in the foot of birds is the presence of a thumb-like
opposable toe, which allows them to grasp and perch. However, in their dinosaur
ancestors, this toe was small and non- opposable, and did not even touch the
ground, resembling the dewclaws of dogs and cats. Remarkably, the embryonic
development of birds provides a parallel of this evolutionary history: The toe
starts out like their dinosaur ancestors, but then its base (the metatarsal)
becomes twisted, making it opposable. Brazilian researcher Joâo Botelho,
working at the lab of Alexander Vargas at the University of Chile, decided to
study the underlying mechanisms. Botelho observed that the twisting occurred
shortly after the embryonic musculature of this toe was in place.

"This is one of the clearest examples of how indirect the
morphological consequences of genetic change are mediated," Gunter Wagner,
evolutionary geneticist and professor at Yale.

Bird embryos move a lot inside the egg during development, and the onset of
movement at this toe coincided with the twisting of its base. Botelho also
demonstrated that in this toe, genes of cartilage maturation were expressed at
a much later stage than other digits: It retains many rapidly dividing stem
cells for a much longer period. Such immature cartilage is highly plastic and
easily transformed by muscular activity.

These observations suggested the toe is twisted as a result of mechanical
forces imposed on it by the embryonic musculature. Definitive proof, however,
would come from experiments. When Botelho applied Decamethonium bromide, a
pharmacological agent capable of paralyzing embryonic musculature, the result
was a non-opposable toe with a straight, non-twisted base identical to that of
their dinosaur ancestors. Only a few experiments are known to recover dinosaur
traits in birds (such as a dinosaur-like shank and tooth-like structures). The
undoing of the perching digit is thus an important new addition, and the
results have now been published in Scientific Reports, an open-access journal
of the Nature Publishing Group.

The significance of this experiment, however, goes beyond the fact that a
dinosaur-like toe is being retrieved. Evolutionary research often centers on
mutations, but the development and evolution of the perching toe cannot be
understood without the forces of embryonic muscular activity. The study is
described as "true developmental mechanics" by Gunter Wagner, an
evolutionary geneticist and professor at Yale. "This is one of the
clearest examples of how indirect the morphological consequences of genetic
change are mediated. The experiments prove that interactions about organ
systems channel the directions of organismal evolution."










Story Source:

The above story is based on materials provided byUniversidad
de Chile. Note: Materials may be edited for content and length.










Journal Reference:

1.   
João Francisco Botelho, Daniel Smith-Paredes, Sergio Soto-Acuña, Jorge
Mpodozis, Verónica Palma, Alexander O. Vargas. Skeletal plasticity in
response to embryonic muscular activity underlies the development and evolution
of the perching digit of birds. Scientific Reports, 2015; 5:
9840 DOI: 10.1038/srep09840

http://www.sciencedaily.com/releases/2015/05/150522174534.htm

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