The ancient armor of fish—scales—provide clues to hair, feather development

July 17, 2018, University of Virginia

When sea creatures first began crawling and slithering onto land about 385 million years ago, they carried with them their body armor: scales. Fossil evidence shows that the earliest land animals retained scales as a protective feature as they evolved to flourish on terra firma.

But as time passed, and species diversified, animals began to shed the heavy scales from their ocean heritage and replace them with fur, hair and feathers.

Today the molecular mechanisms of scale development in fish remain remarkably similar to the mechanisms that also produce feathers on birds, fur on dogs and hair on humans—suggesting a common evolutionary origin for countless vastly different skin appendages.

A new study, scheduled for online publication Tuesday in the journal eLife, examines the process as it occurs in a common laboratory genetics model, the zebrafish.

"We've found that the molecular pathways that underlie development of scales, hairs and feathers are strikingly similar," said the study's lead author, Andrew Aman, a postdoctoral researcher in biology at the University of Virginia.

Aman and his co-authors, including UVA undergraduate researcher Alexis Fulbright, now a Ph.D. candidate at the University of Utah, used molecular tools to manipulate and visualize scale development in zebrafish and tease out the details of how it works. It turns out, as the researchers suspected, skin appendages seen today originated hundreds of millions of years ago in primitive vertebrate ancestors, prior to the origin of limbs, jaws, teeth or even the internal skeleton.

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T. Rex skin was covered in scales, not feathers

June 7, 2017

by Chuck Bednar 

Although its ancestors probably did have feathers, as recent research has suggested, a new study published this week in the journal Biology Letters has concluded that the Tyrannosaurus rex did not, and was in fact covered in scales similar to those found on modern-day lizards.

In the new study, Phil R. Bell, a paleontologist from the University of New England in Australia, and his colleagues analyzed skin impressions from a T.rex skeleton found in Montana, as well as from four related species (Albertosaurus, Daspletosaurus, Gorgosaurus and Tarbosaurus) late in the tyrannosaur’s history, according to BBC News and the Washington Post.

While recent studies had found that two tyrannosauroids that preceded the T. rex by around 50 million years (Dilong and Yutyrannus) were covered in feathers, the new analysis of the T. rex itself revealed that the creature’s abdomen, chest, pelvis, neck, and tail were covered exclusively in scales. If it had feathers, they were limited to its back or spines, the authors said.

“With all the hype about feathered theropods, it's easy to forget that actually, most dinosaurs had scaly, reptilian-like skin,” Bell told the Post via email. However, he noted, the new study “shows without question that  had scaly skin.” The reasons for this trait remain a mystery, although size may have played a role.

“Big animals have trouble shedding excess heat, so being covered in feathers is not a good idea unless you live somewhere cold,” he explained. However, while Dilong was much smaller than the T. rex, Yutyrannus was closer to the size of the larger dinosaur, lived in similar climates and still had feathers. “So what's the reason for this difference? We really don't know.”

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Hong Kong intercepts 2 tons of pangolin scales

Posted on March 20, 2015 by Kevin Heath

Hong Kong customs department has announced that on Tuesday its officials intercepted and confiscated 2 tons of pangolin scales. The scales have been valued at over USD 1.2 million and originated from Nigeria.

Customs officials at the Kwai Chung Customhouse Cargo Examination Compound became suspicious of the container as it arrived in Hong Kong and on further examinations they found nearly 2,000kg of pangolin scales.

With an adult pangolin provide approx. 1 kg of scales the seized shipment represents the death of 2,000 pangolins also known as scaly ant-eaters.

All 4 species of pangolins found in Africa are classed a vulnerable in the IUCN Red list and are also on the CITES Appendix II lists to control international trade which has surged in recent years as asian pangolin species have crashed in number die to poaching activities.

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Snakes' Scales Propel Them Up Tree Trunks

Without legs, snakes must get creative to slither up trees, and new research suggests they use the scales covering their bodies to make such climbs.

Their scales and body muscles work together to push against the bark on the tree as they inch upward, the researchers said.

"An important and surprising finding of our study was that snakes can double their friction coefficients … by active control of their scales," the researchers write in their research paper, published in the June 13 issue of the journal Royal Society Interface.

Holding on tight
Friction is the glue that holds the world together. For example: Imagine the difference between a regular slide and a water slide. The slide slick with water has much less friction than a dry slide, so you move faster down the water slide. Also, a small child slides quicker and easier than a 200-pound man, because the weight pushing against the surface increases the friction.


Continued:  http://www.livescience.com/20915-embargoed-snakes-scales-propel-tree-trunks.html

Snakes on an inclined plane control scales to climb (via Herp Digest)

March 2012 by Lisa Grossman

Whether a serpent tempted Eve to eat apples from the Tree of Knowledge is up for debate, but now we understand better how it could have climbed the tree in the first place. It seems snakes can control each of their scales individually to grip rough surfaces and fight gravity.

Biologists have long known that snakes' scales are good for gripping. Their scallop-shaped geometry and the way they lie over each other like Venetian blinds help stop them sliding backwards.

Now Hamid Marvi of the Georgia Institute of Technology in Atlanta and colleagues have found that snakes can also control each scale. "[Biologists] knew about the passive mechanism, not the active one," he says.

"I'm not aware of previous published research showing active control of individual scales," agrees zoologist Harry Greene of Cornell University in Ithaca, New York.

Marvi and fellow researchers sedated an albino corn snake and let it slip, unconscious, down a ramp. They measured the angle at which they had to tilt the ramp to get the snake to slide, which revealed the coefficient of friction between the snake and the ramp.

Awake snake

They repeated the experiment with an alert snake and found that the coefficient of friction was twice as large as when it was asleep. That suggested it could do something to improve its grip.

"When the snake is unconscious, there is no control, no feedback, no sensory system," Marvi said at a press briefing at this week's American Physical Society conference in Boston. "But when the snake is conscious it can sense, 'I'm sliding, so I should do something.' There's an active mechanism involved."

Indeed, when the team took close-up videos of the snakes' soft underbellies, they found the snakes can control the angle of each scale to most effectively stick to a surface. "By controlling the initial angle of attack of the scale, snakes can increase their friction," Marvi says.

Armed with this knowledge, Marvi and colleagues built a climbing robot called Scalybot, which could be used for search and rescue work, he suggests.