Last week our oldest octopus, Mayhem, thrilled visitors with a display that demonstrated the characteristic chromatic control typical of the giant Pacific octopus. For about 10 minutes, most of the right side of her body was patterned with a mottled brick red, which contrasted vividly with the pale gray-white of her left side.
Enteroctopus dofleini have very fine control over the expression of their chromatophores, the tiny sacs of pigment that make them camouflage experts. These chromatophores are located in the outer layer of skin but are almost invisible when they are relaxed, allowing the deeper reflective layer of skin to show through as a gray-white. Each chromatophore is surrounded by muscles that are enervated by nerves controlled by the central brain. When those nerves are triggered, these muscles pull the tiny round chromatophores, flattening them like Frisbees.
When thousands or millions of these chromatophores are stretched like this, they will touch and produce the patterns or areas of solid brick red that we see. The pigment inside the chromatophores is basically a very concentrated melanin, the same basic material that colors human skin and hair. In the photo at top, many of the chromatophores on the right half of Mayhem’s body were partially flattened and stretched out by their respective muscles, while almost none were on the left, allowing us to see the underlying white layer.
Come visit our two giant Pacific octopuses, Mayhem and Oreo at the Aquarium!