Cephalopods such as cuttlefish often use use adaptive camouflage to blend in with their surroundings. They are able to match colors and surface textures of their surrounding environments by adjusting the pigment and iridescence of their skin.
On the skin surface, chromatophores (tiny sacs filled with red, yellow, or brown pigment) absorb light of various wavelengths. Once visual input is processed, the cephalopod sends a signal to a nerve fiber, which is connected to a muscle. That muscle relaxes and contracts to change the size and shape of the chromatophore. Each color chromatophore is controlled by a different nerve, and when the attached muscle contracts, it flattens and stretches the pigment sack outward, expanding the color on the skin. When that muscle relaxes, the chromatophore closes back up, and the color disappears. As many as two hundred of these may fill a patch of skin the size of a pencil eraser, like a shimmering pixel display.
The innermost layer of skin, composed of leucophores, reflects ambient light. These broadband light reflectors give the cephalopods a ‘base coat’ that helps them match their surroundings.
Between the colorful chromatophores and the light-scattering leucophores is a reflective layer of skin made up of iridophores. These reflect light to create pink, yellow, green, blue, or silver coloration, while the reflector cells (found only in octopuses) reflect blue or green.
Watch this video from PBS Deep Look to learn more about how cephalopods use adaptive camouflage:
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Read more about the shape-shifting abilities of cephalopods, including the cuttlefish, in Tamsin Woolley-Barker’s “Learning from the Master Shape-Shifter: Cephalopod Technologies” in Zygote Quarterly:Edit Summary
“The cuttlefish, octopus, and squid are the undisputed champions of camouflage… They can instantly modulate their color, shading, patchiness, mottling or stippling, transparency, heat, and even bioluminescence, light-polarity, or iridescence…” (Woolley-Barker 2012: 12)
Learning from the Master Shape-Shifter: Cephalopod TechnologiesZygote Quarterly
The Design in NatureJanuary 17, 2002
“Cephalopods have such remarkable camouflage primarily because of their chromatophores – sacs of red, yellow or brown pigment in the skin made visible (or invisible) by muscles around their circumference. These muscles are under the direct control of neurons in the motor centres of the brain, which is why they can blend into the background so quickly. Another aid to camouflage is the changeable texture of cuttlefish skin, which contains papillae – bundles of muscles able to alter the surface of the animal from smooth to spiky. This comes in pretty useful if it needs to hide next to a barnacle-encrusted rock, for instance.
“The final part of the cuttlefish’s camouflage portfolio comes from leucophores and iridophores, essentially reflecting plates that sit underneath the chromatophores. Leucophores reflect light across a wide range of wavelengths so can reflect whatever light is available at the time – white light in shallow waters and blue light at depth, for example. Iridophores combine platelets of a protein called reflectin with layers of cytoplasm to produce iridescent reflections rather like those of butterfly wings. Iridophores in other species, like some fish and reptiles, produce optical interference effects that shift the light towards blue and green wavelengths. Cuttlefish can turn these reflectors on or off in seconds to minutes, controlling the spacing of the platelets to select the colour. They can also combine these iridescent hues with those of the chromatophores to make shimmering purples and oranges, for example.” (Brooks 2008:28)