Electric Skin

The squid is known for it's remarkable ability to camouflage at speeds unmatched by many in the animal kingdom.   Squids have the ability to camouflage at these speeds due to two different mechanisms to produce color and patterns.  Using pigmented organs call chromatophores they can produce yellow, red, and brown color patterns.  Located under these pigments are iridophores, which reflect light and add blue, green, and pink colors to the appearance of skin.   How squids have the ability to be able to control their skins iridescence had remained unknown.   This study looks at the squids ability to change color using iridophores. A video of the pencil squid, Loliginidae, can be seen rapidly changing colors. 

Researchers, Paloma Gonzalez Bellido and Trevor Wardill from the Marine Biological Laboratory (MBL), studied the squid Doryteuthis pealeii to learn more about control over their color change.  By stimulating with different electrical frequencies they found different color shifts. They also found that electrical stimulation of neurons in the squids skin shifted the reflection of light to shorter wavelengths. 

By tracing their nervous network and stimulating them electrically they found that they can shift from red and orange to yellow, green and blue in 15 seconds.   They traced the nerves by tagging them with Dylight 633 and traced them through different axons through different chromatophores.  They also found the the neurotransmitter acetylcholine (ACh) was found in the iridophore layer of skin on the squid.  The concentration of ACh is related to the color shift which supports that the quick change in color is under neuronal control, because of this complete neuronal control researches say it is safe to say that these squids have "electric skin".  

The mechanism responsible for the rapid color change, by iridophores, of squid, cuttle fish, and octopi still remains unknown.  This research will help provide future research with a better understanding of how theses sea creatures are able to change their color at such rapid rates.  Future research on their ability to camouflage could also help the military with their camouflage technology.  Researchers have already removed a protein from bacteria and transferred it to a biofilm that looks similar to a squids skin.  Military researchers say that this is the first step in developing a material that will responds to an external signal.

References:

http://www.sciencedaily.com/releases/2012/08/120827113355.htm
T.J. Wardill, P.T. Gonzalez-Bellido, R. J. Crook, R. T. Hanlon. Neural control of tuneable skin iridescense in squid.

http://www.sciencedaily.com/releases/2013/09/130909172215.htm