The talented octopus and the cuttlefish have clever ways to camouflage themselves, including changing the pattern and texture of their skin to mimic the rocks or coral where they’re hiding. The mimic octopus can actually make itself look like other animals. But squid are out in the open ocean, and need other tricks to hide from predators. So, they put on a special show of color, changing colors and patterns so quickly that it looks like a computer screen saver.
Many thousands of color-changing cells called chromatophores just below the surface of the skin are responsible for these remarkable transformations. The center of each chromatophore contains an elastic sac full of pigment, rather like a tiny balloon, which may be colored black, brown, orange, red or yellow. If you squeezed a dye-filled balloon, the color would be pushed to the top, stretching out the surface and making the color appear brighter—and this is the same way chromatophores work. A complex array of nerves and muscles controls whether the sac is expanded or contracted and, when the sac expands, the color is more visible. Besides chromatophores, some cephalopods also have iridophores and leucophores. Iridophores have stacks of reflecting plates that create iridescent greens, blues, silvers and golds, while leucophores reflect only the colors of the environment, making the animal less conspicuous.
The most obvious reason such a soft-bodied animal would change color is to hide from predators—and octopi are very good at this.
They can change not only their coloring, but also the texture of their skin to match rocks, corals and other objects in their surroundings. They do this by controlling the size of projections on their skin (called papillae), creating textures ranging from small bumps to tall spikes. The result is a disguise that makes them nearly invisible; can you even see the octopus in the video above? Color changing is just one tool in an octopus’s arsenal of defenses, however; it can also spray ink, and make a quick escape through any hole it can get its hidden bony beak through.