|
 Researchers on Thursday said these animals, when navigating murky
freshwater environments like rivers and streams, can turn on an
enzyme in their eyes that supercharges their ability to see infrared
light, sharpening their vision in the muck and mire.
The enzyme, called Cyp27c1, is related to vitamin A, which was
already known to promote good vision, particularly in low light.
Vitamin A is a critical component of the visual pigment in eyes that
facilitates sight. With the enzyme, fish and amphibians can tune
their vision to match the environmental light.
Chemically, Cyp27c1 makes a small modification on the molecule of
the form of Vitamin A called Vitamin A1 to turn it into Vitamin A2,
shifting sensitivity of eye photoreceptors to longer wavelengths
such as red and infrared light.
 This explains how freshwater fish like salmon can smoothly adjust
their vision as they exit ocean waters, where the light environment
is blue-green, and enter inland waterways, where the light
environment veers to the red and infrared end of the spectrum.
This ability is also valuable for amphibians that switch from vision
on land to underwater.
"Fresh water tends to be more turbid or murkier than these other
environments. This murkiness filters out shorter wavelengths of
light - blue, greens, and yellows - leaving mainly longer
wavelengths - red and infrared light," said pathologist and vision
scientist Dr. Joseph Corbo of Washington University School of
Medicine in St. Louis.
[to top of second column] |
"We don't know when in the course of evolution the Cyp27c1 enzyme
first acquired the function it has today," Corbo said. "However, the
fact that the same enzyme is used by both fish and amphibians
suggests that this function originated hundreds of millions of years
ago."
The researchers first pinpointed the enzyme in a common laboratory
fish called the zebrafish, then found it in bullfrogs. Humans
possess a copy of the gene that controls this enzyme, but it is not
active in our eyes.
Corbo said the enzyme possibly could be used in conjunction with
optogenetic devices, which allow scientists to turn the activity of
neurons on and off with light, in a new approach to treat
neurological and blinding diseases.
The research was published in the journal Current Biology.
(Reporting by Will Dunham; Editing by Sandra Maler)
[© 2015 Thomson Reuters. All rights
reserved.]
Copyright 2015 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.
 |
