When it hunts, an octopus has the ability to change the colour of its skin as a way of camouflaging itself. Octopi have thousands of colour-changing cells, called chromatophores, that enable them to alter their appearance. Each chromatophore has a small elastic sack that contains colour pigment – either yellow, brown, red or black. An extensive network of nerves and muscles helps the octopus to activate the sacks, allowing them to expand and contract. Besides being able to transform the colour of their skin, octopi can also create new skin textures to match the surfaces of objects like rocks and coral.
Marine biologist David Scheel from Alaska Pacific University has been researching octopi for many years and recently observed an octopus change colour while it was sleeping. “It's a very unusual behavior to see the color come and go on her mantle like that, just to be able to see all the different color patterns flashing one after the other, you don't normally see that when an animal's sleeping.” Scheel has a theory as to why this happened – it could be evidence of the creature’s brain activity while it sleeps. In other words, he believes this may be an indication that octopi dream. Scheel admits more research is required before this phenomenon can be confirmed. He is looking forward to spending more time on this dream job.