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Squid, octopus, cuttlefish: Ultimate shapeshifters

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Cuttlefish
A cuttlefish in the Red Sea.
Ratha Grimes | Creative Commons via Flickr 2014

When you think of camouflage in the animal world, you might immediately think of chameleons — but it's really cephalopods that should get your attention.

"This is an animal group that has probably the most beautiful and complicated and changeable skin on earth," said Roger Hanlon, senior scientist at at the Marine Biological Laboratory in Woods Hole, Massachusetts. "And we all know the chameleon, we love the chameleon, I think they are very cool. But they are dead boring in comparison."

Cephalopods include octopuses, squids and cuttlefish. They can change both their color and their shape.

Cephalopods have millions of tiny colored organs in their skin called chromatophores. They're like tiny sacks filled with color. On the skin's surface, they resemble tiny, colorful freckles that come in three shades: yellow, brown and red.  

  These chromatophores are attached to muscles that can pull on the organs to stretch them out or shrink them. If the cephalopod stretches out all the yellow ones, it can appear yellow. They can even mix the reds and yellows and browns to get a variety of shades and patterns.

But in order to blend into their surroundings underwater, they also need to be able to mimic blues and greens. For that, cephalopods use a different layer of the skin, which contains proteins that can reflect light.

  Cephalopods can manipulate those proteins in order to reflect back the blues and greens and even purple coming from the light underwater.

  So: One layer of skin has reflectors that can give off a blue or green or purple color. The layer above that can change to look red or yellow or brown. Combining all that, the cephalopods can create almost any color.

  In addition to changing colors and patterns, cephalopods can also change the texture of their skin to help blend in.  

In order to appear spiky or smooth — so they can mimic algae or coral, for instance — they use little lumps on their skin called papillae. Hanlon calls them "ultimate goose bumps."

The papillae can change shape in a way that's very similar to the way our tongues do. We can stick out our tongues and make them point, or we can flatten them out.

  It's as though cephalopods are covered in lots of little super-shifty tongues that can almost instantly get really pointy or flat or round or bumpy.

To Hanlon, who has been studying cephalopods for 40 years, one of the most amazing things is how quickly they can change appearance to match their environment — it takes just 300 milliseconds. How they are able to do it so fast is still a mystery.

  "So what is their secret? Is the octopus smarter than a human? Well, in this case it is," Hanlon said. "It makes you think about the visual perception. You are going to look around you as the octopus does, there is a tremendous amount of color and pattern information falling on your retina — but you don't have time to process all of that, because you'd require a brain the size of a Volkswagen. And to do it in 300 milliseconds — a third of a second — it is that shortcut that has fascinated us."  

Southern California Public Radio's Sanden Totten contributed to this report.

For more from Brains On, our science podcast for kids and curious adults, you can subscribe in iTunes or wherever you listen to podcasts.