Octopuses, along with squids and cuttlefishes, can change the color and pattern of their skin in an instant, faster than almost any other animal. The transformation is driven by the nervous system and happens without the animal moving at all. How Coral Reefs Form.

The main tools are thousands of tiny color-changing cells called chromatophores, sitting just below the surface of the skin. At the center of each chromatophore is an elastic sac filled with pigment, in shades such as black, brown, orange, red, or yellow. A ring of muscle surrounds each sac. When the muscles pull the sac wide, the pigment spreads out and the color shows; when the muscles relax, the sac shrinks to a dot and the color nearly vanishes. Because nerves control each cell individually, an octopus can switch on complex patterns, not just a single overall shade.

Chromatophores are not the whole story. Some cephalopods also carry iridophores, cells stacked with reflecting plates that produce shimmering greens, blues, silvers, and golds, and leucophores, which mirror back the colors of the surrounding environment and help the animal blend in. Many octopuses can also change the texture of their skin by raising or flattening small projections called papillae, turning a smooth body into a bumpy, rock-like surface.

This living display serves several purposes. Camouflage is the most obvious: by matching the colors and textures of rocks, coral, or sand, an octopus can hide from predators and sneak up on its own prey. Color change also sends signals. Some octopuses flash bold patterns to threaten rivals or warn attackers, and they use shifts in color to communicate with one another. The small but highly venomous blue-ringed octopus, for example, flashes vivid blue rings when provoked, a clear signal to stay away.

The short answer

Octopuses change color by expanding and contracting thousands of pigment-filled skin cells called chromatophores, with help from reflective iridophores and leucophores and texture-changing papillae. The system delivers fast camouflage, warning displays, and communication.

Sources

  1. National Geographic Kids, "Octopus." β€” https://kids.nationalgeographic.com/animals/invertebrates/facts/octopus
  2. Monterey Bay Aquarium, "Giant Pacific Octopus." β€” https://www.montereybayaquarium.org/animals/animals-a-to-z/giant-pacific-octopus
  3. Smithsonian Ocean Portal, "How Octopuses and Squids Change Color." β€” https://ocean.si.edu/ocean-life/invertebrates/how-octopuses-and-squids-change-color

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