In a research study just recently published in the journal Nature Communications, Schweikert, Johnsen, and colleagues teamed up to take a better look at hogfish skin.
Up close, a hogfishs skin looks like a pointillist painting. Seen through a microscopic lense, a hogfishs skin looks like a pointillist painting. The scientists estimate that the opsin molecules in hogfish skin are most sensitive to blue light.” Just to be clear, were not arguing that hogfish skin functions like an eye,” Schweikert added.
Scientist discovered that hogfish possess a special light-sensitive protein in their skin, enabling them to alter colors. The research study suggests that these fish can monitor their own skin color modifications, perhaps permitting them to adjust to their environment more efficiently.
Now scientists think they know why.
Several years back, during a fishing expedition in the Florida Keys, biologist Lori Schweikert came face to face with an unusual quick-change act. She caught a pointy-snouted reef fish referred to as a hogfish and placed it on her boats deck. When she later on meant to move it to a cooler, she observed a strange phenomenon: its skin had actually taken on the same color and pattern as the deck of the boat.
A typical fish in the western Atlantic Ocean from North Carolina to Brazil, the hogfish is understood for its color-changing skin. The species can change from white to mottled to reddish-brown in a matter of milliseconds to mix in with corals, sand, or rocks.
Still, Schweikert was surprised due to the fact that this hogfish had actually continued its camouflage despite the fact that it was no longer alive. This got her wondering: Can hogfish find light using just their skin, separately of their eyes and brain?
” That opened up this entire field for me,” Schweikert stated.
In the years that followed, Schweikert began researching the physiology of “skin vision” as a postdoctoral fellow at Duke University and Florida International University. In 2018, Schweikert and Duke biologist Sönke Johnsen published a research study revealing that hogfish bring a gene for a light-sensitive protein called opsin that is triggered in their skin which this gene is various from the opsin genes discovered in their eyes.
A pointy-snouted reef fish called the hogfish can alter from white to spotted brown to reddish depending upon its environments. Credit: Photos courtesy of Dean Kimberly and Lori Schweikert
Other color-changing animals from octopuses to geckos have actually been discovered to make light-sensing opsins in their skin, too. But exactly how they utilize them to assist change color is unclear.
” When we discovered it in hogfish, I took a look at Sönke and stated: Why have a light detector in the skin?” said Schweikert, now an assistant professor at the University of North Carolina Wilmington
One hypothesis is that light-sensing skin assists animals take in their environments. Brand-new findings suggest another possibility– “that they might be utilizing it to see themselves,” Schweikert said. In a study recently published in the journal Nature Communications, Schweikert, Johnsen, and colleagues collaborated to take a closer look at hogfish skin.
The scientists took pieces of skin from various parts of the fishs body and took photos of them under a microscopic lense.
Up close, a hogfishs skin looks like a pointillist painting. Its the motion of these pigment granules that changes the skin color.
Next, the scientists utilized a technique called immunolabeling to find the opsin proteins within the skin. They discovered that in the hogfish, opsins arent produced in the color-changing chromatophore cells. Rather, the opsins live in other cells straight underneath them.
Images taken with a transmission electron microscope exposed a previously unknown cell type, just below the chromatophores, loaded with opsin protein. This implies that light striking the skin needs to pass through the pigment-filled chromatophores first before it reaches the light-sensitive layer, Schweikert stated.
Seen through a microscope, a hogfishs skin looks like a pointillist painting. Each dot of color is a specialized cell including pigment granules that can be red, yellow, or black. The pigment granules can expand or cluster tightly together within the cell, making the color appear darker or more transparent. Credit: Lori Schweikert, University of North Carolina Wilmington.
The researchers approximate that the opsin particles in hogfish skin are most sensitive to blue light. This takes place to be the wavelength of light that the pigment granules in the fishs chromatophores absorb finest. The findings suggest that fishs light-sensitive opsins act rather like internal Polaroid film, capturing modifications in the light that are able to filter through the pigment-filled cells above as the pigment granules lot up or fan out.
” The animals can literally take a photo of their own skin from the within,” Johnsen stated. “In a way, they can inform the animal what its skin appears like, since it cant truly bend over to look.”
” Just to be clear, were not arguing that hogfish skin functions like an eye,” Schweikert included. Eyes do more than simply discover light– they form images. “We do not have any evidence to recommend thats whats taking place in their skin,” Schweikert said.
Rather, its a sensory feedback mechanism that lets the hogfish monitor its own skin as it alters color, and fine-tune it to fit what it sees with its eyes.
” They seem seeing their own color change,” Schweikert said.
The scientists say the work is necessary because it could pave the method to new sensory feedback strategies for devices such as robotic limbs and self-driving cars that should fine-tune their efficiency without relying entirely on vision or camera feeds.
” Sensory feedback is one of the techniques that innovation is still trying to find out,” Johnsen stated. “This study is a nice dissection of a brand-new sensory feedback system.”
Schweikert stated. For creatures that utilize their color-changing capabilities to conceal from predators, warn competitors, or woo mates, “it could be life or death.”
Recommendation: “Dynamic light filtering over dermal opsin as a sensory feedback system in fish color modification” by Lorian E. Schweikert, Laura E. Bagge, Lydia F. Naughton, Jacob R. Bolin, Benjamin R. Wheeler, Michael S. Grace, Heather D. Bracken-Grissom and Sönke Johnsen, 22 August 2023, Nature Communications.DOI: 10.1038/ s41467-023-40166-4.
The study was co-authored by researchers from the Florida Institute of Technology, Florida International University, and the Air Force Research Laboratory. Financial backing came from Duke University, Florida International University, the Marine Biological Laboratory and the National Science Foundation.