Friday, 10 August 2018

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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