Now you see the Cuttlefish, wait, now you don’t! Squid, octopus, cuttlefish and other members of the cephalopod family have organs in their skin, called chromatophores, that can create and change complicated body patterns. They use these body patterns as camouflage to blend into their surroundings, to attract mates, and to send warning signals.
This week, I wrote a story for Discovery News about engineering researchers who built a artificial chromatophores out of an elastic polymer than responds to electrical stimuli, basically an artificial muscle. You can read the story here.
In the process of researching that story, I spoke with a cephalopod expert, marine biologist Lydia Mathger, and she told me so many cool things about camouflage and chromatophores that I couldn’t fit it all into that story. They are just so fascinating that I needed to keep writing about them!
Here, watch this quick video on cephalopod camouflage:
Pretty cool, right? According to Mathger, cephalopods use several different mechanisms in their skin to create all of their body patterns. Chromatophores create the dark colors, usually browns, reds, and some yellows. Green and blue colors are created by light reflective cells called iridiphores. These mechanisms are found throughout the skin in complicated spatial arrangements, and requires a complicated neurological system for control.
Chromatophores are considered organs, made of one sac of dark granules, which is surrounded by muscles. When the muscles contract, they stretch the sac out into a large dark spot. Iridiphores are cells that contain lots of thin protein plates. Each plate reflects light of a particular wavelength, but they have no color themselves, only reflection, like soap bubble. No muscles are involved, instead, to change the display, the creature’s brain sends a neurotransmitter to the cells that causes the protein in the plates to go through a state change.
“They don’t just copy whatever they are sitting on,” Mathger said, explaining that each cephalopod species has a relatively set repertoire of body patterns; from just 2, light and dark, in some squid, to up to 30 in cuttlefish.
The cuttlefish looks around at the environment, to determine which of its camouflage pattern will work best in this specific area. For example, the cuttlefish will do a disruptive pattern, a mosaic of large white and dark spots, if it is in an environment with lots of white objects.
“They are pretty smart,” Mathger said, but she quickly clarified what she meant by smart. “Cephelopods have big brains for invertebrates. They process an enormous amount of information.”
Beyond camouflage, cephelopods use their body patterns for signaling. They can put on these patterns very quickly because they don’t need to look around the environment. The max speed scientists have recorded for body pattern change is 700 milliseconds.
Although they are famous for their color-changing skin, cuttlefish also have feeding tentacles, lots of arms, and the ability to use skin muscles to change the texture-appearance of their bodies, so they blend into the sand on the sea floor. Awesome. Watching them hunt is pretty cool: In the video below, you can check out how they eat shrimp: