Squid are famous quick-change artists. They, and their fellow cephalopods, can go from conspicuous sea creature to ordinary rock on the seafloor faster than you can say calamari. But just how they achieve this, and in particular, how they control their iridescence, is a real mystery
But now researchers at the Marine Biological Laboratory may have answered this old question. By electrically stimulating the nerves tied to the squid’s skin (see video below), they found they could stimulate progressive color shifts–and the skin could shift through the spectrum from red to blue in seconds.
It’s the sparkly part of the squid’s skin that allows these kinds of complex changes. Mirror-like structures called iridophores change the way light reflects off the skin, expanding the range and quality of colors the squid can take on, all coordinated by a subcutaneous nerve network. The squid is the first invertebrate found to have control of this ability.
Now the next mystery to solve is: how do squid decide what hue to be? As all squid are colorblind, this should be more challenging than the squid make it appear to be.
“The cool thing about it is that these animals are colorblind, and yet they are producing a color signal,” said Paloma Gonzalez Bellido, one of the authors of the study. “It’s puzzling to us … how do you know you’re doing this right? You can’t see color.”