A very special protein found in the cephalopod's skin

Dec 19, 2006 16:36 GMT  ·  By

People have always tried to find the secret of invisibility...

The world's oldest tales speaks about an invisibility cloak ...

But clues to achieve super-reflective materials may be found in the skin of the cephalopods (octopuses, squids, cuttlefish). Cephalopods have developed an extremely sophisticated skin that renders them almost invisible to predators.

A team at the Marine Biological Laboratory, Woods Hole, Massachusetts has identified a new group of proteins with remarkable properties in the skin of the cephalopods. The bottom layer of octopus skin, made up of cells called leucophores, is composed of a translucent, colorless, reflecting protein. "Protein reflectors are very odd in the animal kingdom," said Roger Hanlon, a zoologist. "What's even more odd is just how reflective these proteins are they reflect all wavelengths of light that hit at any angle. This is beautiful broadband reflection," Hanlon told.

Due to these properties, the material looks startlingly white in white light, and blue in the bluish light found beneath the waves. "These cells also match the intensity of the prevalent light", said research associate Lydia Mathger. This trait helps the animal to "get lost" into their environment.

In the cuttlefish (photos) some skin regions have increased the reflective properties due to flat cells called iridophores situated in the layer on top of the leucophores. In the brightest spots, there are equal numbers of iridophores and leucophores. "The flat platelets (iridiphores) are enhancing the brightness of the whiteness," Hanlon says, even if the precise mechanism is not known. "These are very complex 3-D cells," Hanlon says. "They require further investigation," he says.

Ryan Kramer, at the Air Force Research Laboratory in Ohio, is investigating reflectin, the only known reflective protein that has been fully genetically sequenced.

"Hanlon's work does show that leucophores are proteins," says Kramer. "Perhaps they are themselves a type of reflectin."

"Once the proteins involved and their optical properties are fully understood, there could be applications far more diverse than simply mimicking an octopus's camouflage," says Hanlon. "Better optical fibers could be made, for example, with super-reflective compounds."

Scientists could discover applications for this finding. "After all, the military is always interested in playing with light." added Hanlon.

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