August 28, 2012
‘Electric Skin’ Helps Squid Camouflage Themselves
Watch the Video: Squid´s Remarkable Electric Skin
Lee Rannals for redOrbit.com - Your Universe Online
Squid and their relatives are notorious for being some of nature's best masters of disguise, but their trickery has, for the most part, remained a mystery until now.
Scientists report that squid control their skin's iridescence through their nerves, manipulating the animal's spectrum of hues, as well as their speed of change. This research is the first time neutral control of iridescence in an invertebrate species has been seen.
Squid skin is able to produce both color and pattern in two ways, including pigmented organs called chromatophores, and iridophores, which are located underneath the pigments.
The chromatophores create patterns with yellow, red, and brown, while the iridophores reflect light and add blue, green, and pink colors to the skin's appearance.
These two groups of skin elements can help create optical illusions, which enables the squid to blend in to its environment to help it both hunt prey, and keep from becoming prey.
“For 20 years we have been wondering how the dynamically changeable iridescence is controlled by the squid,” said Roger Hanlon, who co-authored the study published in the journal Biological Sciences. “At long last we have clean evidence that there are dedicated nerve fibers that turn on and tune the color and brightness of iridophores."
Hanlon calls this "electric skin" because the nerve network found throughout the skin instantly coordinates tens of thousands of chromatophores with iridescent reflectors, rapidly changing the illusion the squid wishes to produce.
During the study, the team traced a highly branched network of nerves on a longfin inshore squid, stimulating them with electricity. They found they could activate progressive color shifts from red and orange to yellow, green, and blue within 15 seconds.
The new findings suggest that the specific color of each iridophore is controlled by the nervous system.
How a squid chooses and holds skin colors remains a mystery, and is interesting to scientists because the animals are completely colorblind.
“One possibility is the animals do not care about the color of the iridophores, but shifting the color from red to blue will dramatically increase the relative brightness of iridophores,” Trevor Wardill, a Marine Biological Laboratory researcher on the project, said in a press release. “This is because squid see predominantly blue light. Blue light is especially important in the ocean as it penetrates best into deeper water.”