How squid power their amazing camouflage abilities

When it comes to blending into their surroundings, nature has produced many masters of disguise. From the chameleon’s shifting hues to the arctic hare’s seasonal coat change, camouflage is an essential survival tool in the wild. But one of the most remarkable camouflage experts might not be the first to come to mind – the squid.

Along with their cephalopod relatives like octopuses and cuttlefish, squid have an extraordinary ability to alter their skin color almost instantly. This unique trait has helped them evade predators and hunt effectively for millions of years, dating back to the age of the dinosaurs. 

However, despite their long evolutionary history, much about the mechanisms behind this ability remains a mystery.

New details about squid camouflage 

Leila Deravi, an associate professor of chemistry and chemical biology at Northeastern University, is working to change that. Her recently published study reveals new insights into how squid camouflage operates. 

The research demonstrates that squid possess specialized organs that function similarly to solar cells, generating energy that powers their remarkable skin transformations. 

The findings not only advance the understanding of these fascinating creatures but could also influence the development of new materials and technology for human use.

The science of squid camouflage

Deravi has spent years studying cephalopods, captivated by their unique biological abilities. Her Biomaterials Design Group at Northeastern focuses on uncovering the mechanics of squid camouflage, with the goal of applying these natural processes to innovative materials.

More recently, her team has concentrated on chromatophores, the specialized pigmented structures responsible for a squid’s ability to change color. This focus led to a groundbreaking discovery.

Chromatophores are tiny, pigmented organs embedded in the squid’s skin. These structures are surrounded by muscle fibers controlled by neurons, allowing the animal to open and close pigment sacs in response to its environment.

Working alongside another type of skin cell, called iridophores, chromatophores produce a broad range of colors. While chromatophores contain red, yellow, and brown pigments, iridophores reflect greens and blues, giving squid the ability to create a full spectrum of colors in a fraction of a second.

“To have something sense the colors around it and distribute [them] within hundreds of milliseconds is really insane,” Deravi said. “It’s not something that’s easy to do, especially in a living system that’s under water.”

Scientists have long believed that chromatophores function much like pixels on a digital display, simply reflecting colors as needed. But Deravi’s latest research shows that these structures do much more than act as mere colorants – they actually sense and generate energy from light.

Squid’s organic solar cells

Her study reveals that chromatophores operate as light-sensitive energy converters, much like solar cells. This capability allows squid to harness external light and transform it into energy that assists in their camouflage process.

“It can see whatever light is on the outside and convert that light into energy and then harvest that energy to help distribute camouflage,” Deravi explained.

To test this theory, her research team constructed a squid-powered solar cell. Using conductive glass, semiconductors, electrolytes, and pigmented nanoparticles extracted from squid chromatophores, they created a circuit capable of responding to light. 

By exposing the circuit to simulated sunlight, they measured the energy output to determine whether the chromatophores could genuinely generate electrical current.

“We found that the more granules you put into there, the higher the photocurrent response is,” Deravi said. 

“It’s a direct indication that the pieces of the chromatophore are actually converting the light from the sun’s simulated light to the voltage, which can complete the circuit and then be harvested, potentially, for a power supply in the animal.”

This marks the first time that scientists have directly linked the chromatophores of a cephalopod to an energy-generating function.

Secrets of squid camouflage 

Understanding how cephalopods achieve their dynamic camouflage could have broad applications beyond marine biology. 

Deravi’s lab has already translated their discoveries into practical uses, such as developing wearable UV sensors to help prevent skin cancer. Her startup, Seaspire, is also exploring how these findings could lead to more environmentally friendly and effective sunscreens.

Squid’s ability to distribute color efficiently with minimal energy consumption could also inspire advancements in wearable technology. 

Today’s wearable electronics must balance size, weight, and power usage. Studying how squid utilize their natural solar cells might provide clues for designing more energy-efficient, interactive materials.

“The squid might be the key to developing a truly ‘living digital skin,’” Deravi suggested.

She envisions a future where wearable technology mimics the adaptability of squid skin, seamlessly responding to environmental changes without relying on bulky batteries or complicated circuitry.

“If you think about fully wearable stuff, you just have to think about how to make it the most energetically favorable in order to be fully interactive with the surroundings,” Deravi said. “We’re trying to tap into what the blueprint is that the animal uses to do this and how that correlates to adapting to the environment as well.”

As scientists continue to unlock the secrets of squid camouflage, their discoveries may lead to transformative new technologies – taking inspiration from nature’s own evolutionary genius.

The study is published in the Journal of Materials Chemistry C.

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