Why Do Octopuses Change Color? How It Works and Why They Do It

Question: How (and why) do cephalopods change color?

Answer: These amazing animals can change color thanks to some fascinating biological adaptations, and they use this ability to help them in many different situations.

First of all, a quick note on the plural of octopus, because this comes up whenever I talk about these animals: in my professional opinion as a Ph.D. marine biologist and a published author, octopuses is fine. Merriam-Webster has a whole rant on how you can also use octopi or even octopodes if you want. I use octopuses. Feel free to send me angry letters about it.

But in this case, we’re discussing an amazing ability not just found in the octopus, but also in their cephalopod relatives which includes squid. To discuss it, I spoke to the internet’s favorite squid scientist, Dr. Sarah McAnutly, who drives the squid-mobile and runs a squid-facts hotline (in addition to her day job as the executive director of Skype-A-Scientist, a non-profit that puts public school science classrooms in touch with scientists).

Dr. McAnulty says there are two biological structures that cephalopods have that aid in their color change.

“On the top layer, they have chromatophores, tiny sacs of pigment surrounded by muscles,” Dr. McAnulty says. “When the muscles contract, the tiny pinprick of pigment is spread out into a big flat pancake, making the skin of the cephalopod appear that color.”

She points out that there are different chromatophores with different pigments, and that different species have various combinations of these available- and that contracting the muscles can be blink-and-you’ll-miss-it fast. Below that, she says, lots of species also have a structure called an iridophore, which can be sparkly in appearance, which have different colors and also change color more slowly than chromatophores.

Related Reading: Do Sharks Sleep? The Surprising Truth About Shark Rest Patterns

Why do they do it? There are many reasons that depend on the situation that a cephalopod finds itself in, including signaling mates, communication, blending in with their environment and trying to scare away potential predators. “Despite being colorblind, cephalopods are very good at coordinating their color patterns to blend in with their environment, and some are even able to incorporate texture thanks to a structure called papillae which can be thought of like extreme goosebumps,” Dr. McAnulty says.

Many species of fishes can also change color using similar biological structures, and for similar ecological reasons. (And yes, the plural when discussing more than one species of fish, is “fishes”.) However, the mechanism for the type of slower color change that occurs with growth—as in, when a baby of a species is a different color than an adult—works differently than color change in cephalopods.

Related Reading: What 50 Years of Shark Surveys Have Revealed

Ask a Marine Biologist is a monthly column where Dr. David Shiffman answers your questions about the underwater world. Topics are chosen from reader-submitted queries as well as data from common internet searches. If you have a question you’d like answered in a future Ask a Marine Biologist column, or if you have a question about the answer given in this column, email Shiffman at WhySharksMatter@gmail.com with subject line “Ask a Marine Biologist.”

Dr. David Shiffman is a marine conservation biologist specializing in the ecology and conservation of sharks. An award-winning public science educator, David has spoken to thousands of people around the world about marine biology and conservation and has bylines with the Washington Post, Scientific American, New Scientist, Gizmodo and more. Follow him on @WhySharksMatter on Twitter, Facebook and Instagram, where he’s always happy to answer any questions about sharks.

The views expressed in this article are those of David Shiffman, and not necessarily the views Scuba Diving magazine.