Monday, March 19, 2007

Chromatophores and Blending In

Discover Magazine has opened its archives for free. That's great news for people interested in popular science and science-based fiction. I've been browsing around and found some neat science-fiction related articles.

For example, in April 2006 Discover published an article, "What cephalopods can teach us about language" about special chromatophores, or pigment-containing cells, which are found in octopuses (octopi?), squid and other cephalopods. Muscles change the shape of the chromatophores, which causes the cells to change color.

Morphing in cephalopods works somewhat similarly to how it works in computer graphics. Two components are involved: a change in the image or texture visible on a shape's surface and a change in the underlying shape itself. The "pixels" in the skin of a cephalopod are organs called chromatophores. These can expand and contract quickly, and each is filled with a pigment of a particular color. When a nerve signal causes a red chromatophore to expand, the "pixel" turns red. A pattern of nerve firings causes a shifting image—an animation—to appear on the cephalopod's skin. As for shapes, an octopus can quickly arrange its arms to form a wide variety of them, like a fish or a piece of coral, and can even raise welts on its skin to add texture.

To see what that looks like, watch this great National Geographic video of an octopus changing colors. The color change appears to be under visual control, but the exact mechanism is a bit of a mystery, because cephalopods do not appear to have color vision.

In the interactive companion to the article, "Why Not Morph?", Discover issues a challenge to write a story using the science of chromatophores:
Suppose humans had chromatophores that could alter body appearance allowing it to blend perfectly with the background. Think about it. Then, write a science fiction story about a genetically modified individual who has been given this camouflage ability. Remember that good science fiction is based upon science fact.
I'm not aware of any stories in which humans have color-changing skin. However a example of color-changing humanoids are the genetically-enhanced Suliban of the Enterprise universe, who can blend into their surroundings using subcutaneously-implanted pigment sacs. According to creator Brannon Braga the modification was indeed inspired by octopus skin.

If you know of any other examples, please share them in the comments!

Tags:, ,
Image from the Ocean Planet Exhibition at the Smithsonian.


  1. Anonymous9:36 AM

    In Greg Bear's novel Darwin's Radio, a new species of humans arises with chromatophores on their faces, which they use as a channel of non-verbal communication.

  2. Amy Thomson set her novel, The Color of Distance, on a planet that was inhabited by aliens that communicated by changing patterns on their skin. I suppose that was through chromatophores. The plot of the novel centered on a human who was genetically modified by the aliens in order to live on the planet, as a result she learned to communicate the same way.

  3. Anonymous10:44 AM

    Stephen Baxter's Manifold: Time had a subplot dealing with genetically-altered sentient squids who communicated through their chromatophores via symbols and signs on their skin. It was intensely interesting, and I'd recommend reading it.

  4. Anonymous10:49 AM

    Great blog, but "word verification" to post comments doesn't seem to work in Firefox, just Internet Explorer.

  5. Great suggestions! I didn't think of Darwin's Radio and I'm putting both Thomson and Baxter on my list of authors to check out.

    Anonymous: I was having the same problem with CAPTCHAs in Firefox (it would work in Safari for me). This is a known problem in Blogger and the official suggestion is to quit and restart your browser - that permanently fixed the problem for me. If that doesn't work, apparently clearing the cache and resetting your blogger cookies should fix it (directions here).

  6. How about an alien society that telegraphs their emotions or speech unconsciously by means of their chromatophores?

    A person who found a way to consciously morph in such a society could be bloody dangerous.

    Interesting stuff.

    I feel a story coming on...

  7. Thanks for the link to Discover mag - another place for me to waste my writing time day after day ;-)

    I don't put a lot of science into my novels, but a few legit details here and there can help make an author sound like they know what they're doing, and I need a lot of that sort of help ...

  8. Anonymous1:05 PM

    Cuttlefish are similar. Why is it claimed that they communicate with language if they are colour blind? One of these two must be incorrect.

    My feeling, from having seen them use language in mating rituals, is that the colours seem very much to be about communication. Perhaps they see colour in a different way from vertebrates. They can sense the polarization of light: is it possible that the same skin changes which produce the colour changes which we see produce polarization changes which they see?

  9. Sorry to comment so long after the original post but the late Charles Sheffield's Sight of Proteus had aliens who communicated using their chromatophores.


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