Skin camouflage is controlled by
chromatophores in the skin. The muscular
contraction and expansion of the chromatophores changes the apparent
concentration of the pigment, so when the muscles contract, the
chromatophore and pigment is concentrated in a smaller area, thus
becoming more apparent. All species have chromatophores with a
variety of pigments including, yellow, orange, red,
blue and black. This effect is then enhanced by layers of reflector
cells called iridocytes which differentially reflect light.
The chromatophores are controlled by the nervous system and are
triggered by hormones, while the initial stimulus seems
to by visual. Colour change varies greatly among species, some
such as the cuttlefish changing colour as the background changes.
Most changes, however, appear to
be behavioural, i.e. courtship or when alarmed. Many of the deep
and mid-water squid are also bioluminescent, with photophores arranged
in patterns over the body. This bioluminescence may be intrinsic, or
it may be produced by symbiotic bacteria.
Return to innovative designs
by students on the MSc
Palaeobiology programme in the Department
of Earth Sciences at the University of Bristol for academic