Novel nanostructures in blue sharks reveal their remarkable potential for dynamic color-change

New research into the anatomy of blue sharks (Prionace glauca) reveals a unique nanostructure in their skin that produces their iconic blue coloration, but intriguingly, also suggests a potential capacity for color change.

"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.

The team revealed that the secret to the shark's color lies in the pulp cavities of the tooth-like scales – known as dermal denticles – that armor the shark's skin. The key features of this color-producing mechanism inside the pulp cavity are guanine crystals, which act as blue reflectors, alongside melanin-containing vesicles called melanosomes, which act as absorbers of other wavelengths.

While this research provides important new insights into shark anatomy and evolution, it also has a strong potential for bio-inspired engineering applications. "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."

Image source: Viktoriia Kamska.