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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