How an octopus changes its skin pattern
Octopuses can rapidly alter visible skin colour by expanding and contracting pigment-containing structures called chromatophores. Muscles spread each pigment sac to make its colour more visible, then allow it to shrink. Other skin structures reflect light, helping create patterns used in camouflage and signalling.
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Muscles reveal and conceal pigment
An octopus's chromatophores contain pigment sacs surrounded by muscles. When those muscles contract, the sac spreads over a larger area, increasing how much of its colour is visible.
When it retracts, less pigment shows. Coordinated activity across many chromatophores creates changing patches, stripes and other patterns.
Rapid colour change is not the same as manufacturing new pigment each time. Much of the effect comes from changing the visible area of pigment already present.
- Chromatophores control visible pigment coverage.
- Reflective structures contribute additional optical effects.
- Some skin muscles also alter surface texture.
The pattern need not be a literal copy of the surroundings. Camouflage can work by disrupting an outline, matching broad visual features or making the animal resemble a different kind of object.