Researchers
have found that the scaly appearance of crocodiles' heads is actually
due to physical cracking rather than genetically-controlled development.
Reptile scales, including the crocodile's body armour, each form from a
single unit. This unit is known as the scale primordium and is
genetically controlled, growing to the shape and colour specified in the
crocodile's DNA. As a result, the pa
ttern
of reptile scales is often symmetrical. But the scales on the
crocodile's head have no regular pattern - the left and right sides of a
crocodile's face and jaws vary, and are different again from other
crocodiles.
To investigate this appearance, Michel Milinkovitch
(University of Geneva, Switzerland) and his team took high-resolution
shots of the heads of 15 young Nile crocodiles and using computer
modelling to recreate their heads. After removing all details except the
lines, pattern recognition techniques confirmed their placement was
random.
The next step was to study crocodile embryonic
development. While scale primordia developed as expected on the bodies,
they did not appear on the heads. Thicker skin developed first,
containing the vibration receptors. It was only during late development
that lines began to appear, beginning tiny but gradually spreading and
interlocking. The team concluded that due to the crocodile's rapid
embryonic growth puts its extremely stiff skin under a lot of stress and
actually cracks it. This results in the random "scales" we see, and
also means that crocodiles don't have scales on their heads in the
conventional sense (it's just a scale-like pattern rather than scales
developing from single units).
These findings highlight some of
the fascinating interplay between genetics and the physical/chemical
processes involved in development. "It is likely that with all the
attention to genetic determinism, we have underestimated this kind of
physical process," Milinkovitch commented.
Photo credit: Michel C. Milinkovitch and Adrien Debry.
For a video, see: http://bit.ly/Vd1QYn
http://www.bbc.co.uk/nature/
http://news.sciencemag.org/
http://www.eurekalert.org/
http://phys.org/news/
Researchers
have found that the scaly appearance of crocodiles' heads is actually
due to physical cracking rather than genetically-controlled development.
Reptile scales, including the crocodile's body armour, each form from a single unit. This unit is known as the scale primordium and is genetically controlled, growing to the shape and colour specified in the crocodile's DNA. As a result, the pa
Reptile scales, including the crocodile's body armour, each form from a single unit. This unit is known as the scale primordium and is genetically controlled, growing to the shape and colour specified in the crocodile's DNA. As a result, the pa
ttern
of reptile scales is often symmetrical. But the scales on the
crocodile's head have no regular pattern - the left and right sides of a
crocodile's face and jaws vary, and are different again from other
crocodiles.
To investigate this appearance, Michel Milinkovitch (University of Geneva, Switzerland) and his team took high-resolution shots of the heads of 15 young Nile crocodiles and using computer modelling to recreate their heads. After removing all details except the lines, pattern recognition techniques confirmed their placement was random.
The next step was to study crocodile embryonic development. While scale primordia developed as expected on the bodies, they did not appear on the heads. Thicker skin developed first, containing the vibration receptors. It was only during late development that lines began to appear, beginning tiny but gradually spreading and interlocking. The team concluded that due to the crocodile's rapid embryonic growth puts its extremely stiff skin under a lot of stress and actually cracks it. This results in the random "scales" we see, and also means that crocodiles don't have scales on their heads in the conventional sense (it's just a scale-like pattern rather than scales developing from single units).
These findings highlight some of the fascinating interplay between genetics and the physical/chemical processes involved in development. "It is likely that with all the attention to genetic determinism, we have underestimated this kind of physical process," Milinkovitch commented.
Photo credit: Michel C. Milinkovitch and Adrien Debry.
For a video, see: http://bit.ly/Vd1QYn
http://www.bbc.co.uk/nature/
http://news.sciencemag.org/
http://www.eurekalert.org/
http://phys.org/news/
To investigate this appearance, Michel Milinkovitch (University of Geneva, Switzerland) and his team took high-resolution shots of the heads of 15 young Nile crocodiles and using computer modelling to recreate their heads. After removing all details except the lines, pattern recognition techniques confirmed their placement was random.
The next step was to study crocodile embryonic development. While scale primordia developed as expected on the bodies, they did not appear on the heads. Thicker skin developed first, containing the vibration receptors. It was only during late development that lines began to appear, beginning tiny but gradually spreading and interlocking. The team concluded that due to the crocodile's rapid embryonic growth puts its extremely stiff skin under a lot of stress and actually cracks it. This results in the random "scales" we see, and also means that crocodiles don't have scales on their heads in the conventional sense (it's just a scale-like pattern rather than scales developing from single units).
These findings highlight some of the fascinating interplay between genetics and the physical/chemical processes involved in development. "It is likely that with all the attention to genetic determinism, we have underestimated this kind of physical process," Milinkovitch commented.
Photo credit: Michel C. Milinkovitch and Adrien Debry.
For a video, see: http://bit.ly/Vd1QYn
http://www.bbc.co.uk/nature/
http://news.sciencemag.org/
http://www.eurekalert.org/
http://phys.org/news/
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