Blue Sharks Use Nanotech To Shift Color Underwater, Scientists Discover
Blue sharks are known for their glorious shimmer and glow with one of the rarest colors found in nature. Scientists have now discovered how the shark’s bodies are able to pull this off, and it involves microscopic crystals and pigments hidden within their skin.
A new study on the blue shark has shown that intricate nanostructures within their skin created the animal’s blue hue and allows for its subtle shifts in color, according to Sci Tech Daily.
“Blue is one of the rarest colors in the animal kingdom, and animals have developed a variety of unique strategies through evolution to produce it, making these processes especially fascinating,” says Dr. Viktoriia Kamska, a post-doctoral researcher in the lab of Professor Mason Dean at City University of Hong Kong.
More specifically, the researchers found that the vivid blue appearance is from structures located inside the pulp cavities of dermal denticles, which are tiny, tooth-like scales that form a layer of protection over the shark’s skin.
The cavities contain what are known as guanine crystals which reflect blue light. They also have melanin-filled vesicles called melanosomes that absorb other wavelengths.
“These components are packed into separate cells, reminiscent of bags filled with mirrors and bags with black absorbers, but kept in close association so they work together,” explains Dr. Kamska.
“When you combine these materials together, you also create a powerful ability to produce and change color,” says Professor Dean.
“What’s fascinating is that we can observe tiny changes in the cells containing the crystals and see and model how they influence the color of the whole organism.”
“We started looking at color at the organismal level, on the scale of meters and centimeters, but structural color is achieved at the nanometer scale, so we have to use a range of different approaches,” he stated.
Dr. Kamska and her collaborators used simulations to confirm which architectural parameters the nanostructures within the sharks are credited for the specific wavelengths.
“It’s challenging to manually manipulate structures at such a small scale, so these simulations are incredibly useful for understanding what color palette is available,” says Dr. Kamska, who added that certain environmental conditions can also impact how the shark shifts its color.
“In this way, very fine scale alterations resulting from something as simple as humidity or water pressure changes could alter body color, which then shapes how the animal camouflages or counter-shades in its natural environment,” says Professor Dean.
Dr. Kamska added that as the sharks swim deeper, the increase in pressure causes the guanine crystals to get tighter and closer together, so the color darkens to better suit their surroundings.
“The next step is to see how this mechanism really functions in sharks living in their natural environment,” says Dr. Kamska.
“Not only do these denticles provide sharks with hydrodynamic and antifouling benefits, but we’ve now found that they also have a role in producing and maybe changing color too,” says Professor Dean.
“Such a multi-functional structural design —a marine surface combining features for high-speed hydrodynamics and camouflaging optics— as far as we know, hasn’t been seen before.”
“A major benefit of structural coloration over chemical coloration is that it reduces the toxicity of materials and reduces environmental pollution,” says Dr. Kamska.
“Structural color is a tool that could help a lot, especially in marine environments, where dynamic blue camouflage would be useful.”
“As nanofabrication tools get better, this creates a playground to study how structures lead to new functions. We know a lot about how other fishes make colors, but sharks and rays diverged from bony fishes hundreds of millions of years ago – so this represents a completely different evolutionary path for making color,” said Professor Dean.
Eric Mastrota is a Contributing Editor at The National Digest based in New York. A graduate of SUNY New Paltz, he reports on world news, culture, and lifestyle. You can reach him at eric.mastrota@thenationaldigest.com.
