Wikipedia:Reference desk/Archives/Science/2017 January 6

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January 6

Chameleon colour change

Chameleon says that they change colour by adjusting the spacing between guanine crystals. Is it known how much energy that process takes, is it conscious or unconscious, and does it "hurt"? -- SGBailey (talk) 07:51, 6 January 2017 (UTC)

I looked at the reference in that article in National Geographic, which mentioned Michel Milinkovitch; searching PubMed I found relevant papers at [1] and [2]. Part of this pathway is familiar - the red and yellow pigments are pteridine (biopterin and sepiapterin) which occur widely in nature. Pterins are named for being isolated from butterfly wings, but they are chemically related to guanine which forms the other part of the system and forms part of DNA's structure. The way that the red and yellow pigments are distributed within cells is also familiar - we have much the same in melanocytes when getting a suntan, though not so quickly. Redistributing granules in cells is familiar from neurons, which are distantly related to melanocytes, e.g. retrograde transport. It's not something normally at the level of physical sensation, I would say. The change in structural color was induced in the lab by mechanical pressure or osmotic pressure, but I didn't quickly notice an explanation of control by the nervous system. It's probably something moderately interesting.

The first paper explains though that there are two species of chameleon, one of which redistributes granules to create green color by a combination of yellow + structural blue; the other uses structural green for the same shade. I think you could make an argument that if this were an exceptionally tiresome or painful process, you wouldn't have one species circumventing some of the shade changes and the other not (well, that's sort of weak). And of course you can make an ad hoc argument that a well evolved species shouldn't feel pain from doing what it's designed to do. (human childbirth is a notorious exception from that, but I take it to mean that humans are not a well evolved species, but something relatively new with massive increases in head size) Neither of these are really very persuasive though; ultimately you would need to do more studies. Wnt (talk) 12:54, 6 January 2017 (UTC)

Clarification please When the OP asks is it "conscious or unconscious", did they perhaps mean "voluntary or involuntary"? DrChrissy ^(talk) 20:17, 6 January 2017 (UTC)

I have not been able to find a direct study on the energetics of colour change but it appears that up until 2009, this had not been studied - see here[3]"Whether there are significant costs of colour change remains to be demonstrated but could be tested by, for example, comparing physiological performance or fitness of individuals exposed to uniform backgrounds (minimal colour change) with those repeatedly exposed to diverse backgrounds (frequent colour change)." DrChrissy ^(talk) 21:00, 6 January 2017 (UTC)

So nothing really conclusive, but I thank you for your insights. -- SGBailey (talk) 22:29, 6 January 2017 (UTC)

If, as it says here they use it to signal their intentions to other chameleons, I would presume it would be under their conscious control for that purpose. Richerman (talk) 16:38, 8 January 2017 (UTC)