|Color Change Cells Working in Concert|
“Sustained patterns are like a chord of music played upon a keyboard. The single keys are the single components or banks of motor units.” (Packard 1995)
|One type of cell is not enough to produce an image or pattern on a cephalopod. Several cell types must work in concert to achieve this feat. There seem to be light sensing cells in the skin of cephalopods that allow them to match backgrounds without visual stimulus (Mathger et al 2010). Amazingly a recently deceased octopus can change color to match a background (Cousteau 1973). This certainly indicates the existence of senses beyond the eyes.|
This video shows chromatophores expanding and contracting in a dead squid.
|Neurological Control of Color Change|
The primary factor that distinguishes cephalopod color change from that of reptiles or amphibians is that cephalopod color change cells are directly controlled by the brain of the animal. This allows for astonishingly fast changes in color and pattern. An octopus can go from jet black to totally white in under a second. Different neurotransmitters allow for different signaling patterns. Acetalcholine, for instance, stimulates rapid pulsations, FaRP controls sustained signaling, and glutamate helps with transient signaling (Florey 1966, Loi et al 1997).
Nerve damage can cause loss of control to color change. This is most easily identified by white patches on cephalopods that do not change with the rest of the animal. This damage is mostly temporary because the nerves can regrow and restore almost all the previous function (Packard 1995).
The famous mimic octopus. While thier color change is not that impressive, they effectivly mimic dangerous sea animals in shape and behaviour to evade predation.
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