Animals like chameleons and octopuses are renowned for their almost supernatural ability to change color and blend into their surroundings. Now, it turns out the blue shark (Prionace glauca) has some color-shifting powers of its own. Researchers at the University of Hong Kong have revealed just how the sharks obtain their striking blue hue and their capacity for changing color.
“Blue is one of the rarest colours in the animal kingdom, and animals have developed a variety of unique strategies through evolution to produce it, making these processes especially fascinating,” Viktoriia Kamska, a post-doctoral researcher in the lab of Professor Mason Dean at City University of Hong Kong, in a press release. Kamska presented the team’s research at the Society for Experimental Biology Annual Conference in Antwerp 2025, earlier this month.
Blue Shark Scales and Crystals
The vast majority of sharks are some shade of gray, but the blue shark stands out for its unusual coloring — blue on top, silver on the sides, and white on the abdomen. According to new research, the secret to its distinctive hue lies in its tooth-like scales, called dermal denticles, which contain guanine crystals and melanosomes that reflect and absorb wavelengths respectively.
“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,” said Kamska in a press release.
The size of these structures is so tiny — they occur on the nanometer level — that researchers used a combination of techniques ranging from fine-scale dissection to optical microscopy and electron microscopy to investigate the mechanism behind the shark’s color-shifting talent.
Read More: The Unique Traits and Behaviors of the Stunning Blue Shark
Blue Sharks, Chameleons of the Sea
The blue shark’s camouflaging abilities might not be as dramatic as an octopus, say, but the researchers found small tweaks to the formation of the guanine crystals can influence the animal’s coloring, turning it from blue to silver — and even to green and gold.
Using 3D segmenting, the researchers created a computer model of the cells, showing that even the smallest cell contains as many as 152 separate guanine crystals. Digital simulations revealed that changing the angles of the crystals transformed the animal’s color from blue to gray. Meanwhile, further experiments revealed that narrower spaces between the crystals were associated with a blue color. As those spaces increased, the color changed to green and then gold. This, the researchers say, suggests small environmental changes could impact the shark’s overall color.
“In this way, very fine scale alterations resulting from something as simple as humidity or water pressure changes could alter body colour, that then shape how the animal camouflages or counter-shades in its natural environment,” Mason Dean, a marine biologist, zoologist and anatomist at the University of Hong Kong, said in a press release.
Blue Sharks and Bioengineering
The researchers hope to understand how this color-changing mechanism works by looking at sharks in their natural habitat. But as well as offering interesting biological insights into the anatomy of some of the most feared creatures on the planet, the team hopes these findings will have practical applications — for example, in the field of nanofabrics and bioengineering.
“As nanofabrication tools get better, this creates a playground to study how structures lead to new functions,” said Dean in a press release. “We know a lot about how other fishes make colours, but sharks and rays diverged from bony fishes hundreds of millions of years ago – so this represents a completely different evolutionary path for making colour.”
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Rosie McCall is a freelance writer living in London. She has covered science and health topics for publications, including IFLScience, Newsweek, and Health.
