Beauty Skin Deep - How Do Octopuses Change Color?
After watching octopuses rapidly change their color several times each second, everyone has the same question: how do they do it? How dynamic is their skin? Can I get some octo skin for myself? Okay, that may be more than one question, but the amazement and wonder regarding their pixelated displays is surely genuine. As far as how they do it, there are actually a few different layers of their skin that all come together to make them even more incredible than we can sense.
Octopus Skin
Photo credit Leslie Sherlin
The most basal layer of octopus skin includes leucophores, which reflect any wavelength of light. This basically means that they are white, so we’ll skip to the topmost layer, which is responsible for all of the brilliance we actually see: the chromatophores. Essentially, these cells are sacks of pigment attached to some muscles spiking outward like the spokes of a wheel. These muscles control the size of that sack, making them wide and bold or shrink away to a minuscule dot. They can change their color at the speed of thought, which explains the lightning speed with which they disappear into coral or a rocky background. These pigments are generally red, yellow and brown, and provide an assortment of warm, dull colors to their repertoire.
Photo credit Leslie Sherlin
But wait, you may be thinking, I’ve seen blue rings on an octopus before! This chic hue comes from a far more interesting set of cells, the iridophores. These, like the leucophores, reflect light very well, but only at particular wavelengths, including silvers, golds, and greens. The wavelength they reflect also depends on the angle of the light, meaning that the octopus may be a different color depending on where the viewer, or camera, happens to be. As if this were not already enough, these cells also add a dimension to their displays that we cannot see: they can adjust how their skin interacts with polarized light. All light is composed of electromagnetic waves, but normally these waves vibrate haphazardly in every direction. Polarized light, however, oscillates only in a single plane, a nuance that we humans cannot observe. These can also be altered or adjusted, but they are under hormonal control, and are thus much slower.
All of these layers serve to create the dazzling displays we see simulated on viral octopus videos or, if you may be so lucky, in the ocean itself. While some of the greatest mysteries in science may be the most difficult to notice, cephalopods do not pretend that their biology is dull in any sense of the term.
Further Reading:
https://www.nature.com/scitable/topicpage/cephalopod-camouflage-cells-and-organs-of-the-144048968
http://www.thecephalopodpage.org/cephschool/HowCephalopodsChangeColor.pdf
Contributing Author: Cody Miner