Scientists discover Color-changing sharks

In July 2025, scientists at the City University of Hong Kong made a surprising discovery: blue sharks can change color.

These sleek and stunning creatures are known for their vivid blue appearance. But how they can achieve this brilliant shade has been something of a mystery until now. Researchers found that the secret of the unique color lies in the sharks’ skin, specifically in their tooth-like scales, which are covered in tiny nanostructures. Together, they work to create the vibrant blue hue we see.

According to Professor Dean from the City University of Hong Kong, it’s like the skin contains “bags filled with mirrors” and “bags with black absorbers.” The skin is all packed closely together, so they work as a team to produce that signature blue color. Something that makes the discovery even more fascinating is that these structures allow blue sharks to change shades based on their environment. Some changes in things like water pressure, humidity, or swimming depth can slightly shift how the nanostructures behave. For example, as a shark dives deeper into the ocean, pressure increases and pushes the guanine crystals closer together, which makes the shark appear a darker and deeper blue. This natural shift of their blue color might help the shark better blend in with its surroundings, which is a clever camouflage tactic for survival.

To understand all this, the team studied a shark’s fin under powerful microscopes and used computer simulations to see how these nanostructures respond to different conditions. Their work suggests this kind of color-changing mechanism is unlike anything previously seen in sharks, or really, in any animal.

Therefore, blue sharks aren’t just unique, they’re also wonders of natural design and camouflage tactics. Their remarkable ability to shift color, combined with the microscopic complexity of their skin, shows just how mysterious and adaptable marine life can be.