Cuttlefish have the ability to change colour very rapidly, making them extremely good at natural camouflage. They can change colour in less than a second.
Embedded in the skin of a cuttlefish are numerous elastic pigment sacs called chromatophores, which are surrounded by circular muscles. When the muscles contract, these sacs are stretched out into flat discs of dense pigment and when the muscles relax, the sacs fold down into small dots of colour.
Chromatophores produce the orange to red, brown to black and yellow colours of the skin. Reflecting cells that provide the cuttlefish with blue and green colouration are called Iridophores and Leucophores form white spots.
Cuttlefish can also change the texture of their skin for natural camouflage. By contracting certain muscles, the cuttlefish can sprout spiky-looking projections called papillae. They can use skin textural and colour changes to disguise themselves as a patch of swaying kelp, a cluster of coral or even a chunk of rock.
If natural camouflage fails, the cuttlefish shoots ink out at the pursurer. The sepia ink may be produced as a mucus-bound blob or as a large cloud. It is secreted from a sac near the anus and discharge through the siphon. Sepia ink ejection is usually followed by a rapid colour change to confuse the pursuer. Sepia ink, once widely used in printing, art and photography, was originally prepared from the 'sepia ink' of cuttlefish.
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