2012: Advent Biology: A shrimp can change its spots

by on December 3, 2012

Among the animals which can change their colour to match their background in an attempt to camouflage themselves is the common shrimp, Crangon crangon. This crustacean can detect the levels of light above and below itself and change colour accordingly in what is known as an albedo response.

The change itself is a secondary response, not caused directly by the detection of light but by the release of hormones from a gland in the eye stalk. This sinus gland releases chemicals called ‘pigmentary effector hormones’ which act when they reach specialised cells on the shrimp’s hide called chromatophores. The two main chemicals involved have opposite effects: one causing the pigments in the chromatophores to spread out, making the shrimp darker, and the other causing them to collect in much smaller areas, making the shrimp lighter. It’s a reaction in minutes rather than seconds, but will make the shrimp much better matched to the background it needs to hide against.

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