Throughout the animal kingdom, the squid’s (and those of their fellow cephalopods) colour changing abilities are the most sophisticated. In the blink of an eye, squid can change from sandy brown to vibrant red or ripple with bright metallic rainbows.
Leila Deravi, an assistant professor of chemistry and chemical biology at the Northeastern University quoted that “People have been trying to build devices that can mimic cephalopod colour change for a long time by using off-the-shelf components”. However, nobody has come anywhere near the speed and sophistication of how they actually work.
The squid’s skin contains two types of structures that manipulate light to produce various colours. Organs near the surface, called chromatophores use elastic sacs of pigment that stretch rapidly into discs of colour when the muscles around the contract. When light strikes the pigment granules, they absorb the majority of the wavelengths and reflect back only a narrow band of colour. Deeper in the skin, cells called iridophores reflect all the light that hits them. By the method known as structural coloration, they bounce back a bright sheen of iridescence of scattering this light.
All available data had previously indicated that the above mentioned separate structures could only produce one type of coloration or the other: pigmented or structural. But when the researchers looked closely at the squid chromatophores, they spotted iridescence shimmering in perfect alignment with the pigment. This unexpected discovery, that the chromatophore is using both pigmented and structural colouration to create its dynamic effects, opens up new opportunities for biologists and chemists alike.
By copying the inner workings of cephalopod skin, researchers hope to find ways to improve camouflaging devices or design colour-changing materials and cosmetics. But that ultimate goal is still a long way off.
Radhika Boruah