By far the most interesting item I've read this week is at Not Exactly Rocket Science:
When Domenico Fulgione placed Moorish geckos on dark surfaces, he saw what he had seen for years. These spiny, hand-sized lizards changed colour. Within an hour, their typical creamy white complexions transformed into blacker hues that better matched their environment.Fascinating. More details at Not Exactly Rocket Science.
And then Fulgione blindfolded the geckos.
They still changed colour. How does an animal adjust its colour to match its environment, when it can’t see that environment at all?...
These bizarre results started to make more sense when the team analysed the gecko’s skin. They found that the skin is rife with opsins—light-sensitive proteins that are the basis of animal vision. When light enters your eyes, opsins in your retinas respond by triggering chemical reactions that send signals to your brain. That’s how you see. The Moorish gecko has plenty of opsins in its eyes too, but the team also found these proteins all over the skin of its torso. It’s especially common in the lizard’s flanks, and in cells called melanophores that are filled with dark pigments.
The researchers think that the flank opsins can respond to surrounding light levels and automatically adjust the gecko’s colour. If they’re right, the lizard has a kind of distributed vision that is independent of its eyes, and perhaps its brain. In other words, it can “see” with its skin.
I found the video of an octopus several months ago at 22 Words.