1 of 2 | A new study finds the hogfish, which lives in the western Atlantic Ocean, can “see with its skin” in order to camouflage itself with its surroundings. Photo by Lori Schweikert/Duke University
Aug. 23 (UPI) -- A new study has found that a common fish in the western Atlantic Ocean can "see with its skin" in order to quickly camouflage itself with its surroundings.
Researchers at Duke University have determined that the hogfish, a pointy-snouted reef fish found between North Carolina and Brazil, has a sensory feedback mechanism in its skin to quickly change from pearly white to brown to red within milliseconds to adapt to shifting surroundings, according to the study published Tuesday in the journal Nature Communications.
Hogfish skin contains a light-sensitive protein called opsin, which acts like an "internal Polaroid film," according to researchers who discovered the light-sensitive protein can even detect changes shortly after death when the eyesight is gone.
"The animals can literally take a photo of their own skin from inside," Duke biologist Sönke Johnsen said. "In a way they can tell the animal what it's skin looks like, since it can't really bend over to look."
The study found hogfish skin senses light differently from its eyes and that its "skin vision" or "dermal photoreceptor" could apply to other animals -- such as octopuses and geckos -- that can also change colors quickly.
"If you didn't have a mirror, and you couldn't bend your neck, how would you know if you're dressed appropriately?" Duke biologist Lori Schweikert queried. "For us it may not matter, but it could be life or death" for creatures that use their color-changing abilities to hide from predators or woo mates.
To study their theory, researchers took pieces of a female hogfish's skin and retina and examined them under a microscope. They found specialized cells called chromatophore, which contain granules of pigment that can be red, yellow or black.
Researchers say the movement of the pigment granules determines the color of the skin. Clustered together, the cell becomes more transparent, while spread out the color becomes darker.
The light sensitive layer of opsin protein, which is different from the opsin genes found in eyes, lies just below the color-changing chromatophore and captures changes in the environment's color and light.
"Just to be clear, we're not arguing that hogfish skin functions like an eye," Schweikert said, adding that eyes do more than detect light by forming images.
Instead, Schweikert said hogfish skin contains a sensory feedback mechanism that allows the fish to monitor its skin as it changes color and then to match its skin to what it sees with its eyes.
"They appear to be watching their own color change."
