Male Caribbean reef squid Sepioteuthis sepioidea turn red to attract females and white to repel other males—and can even split the coloration of their bodies down the middle to attract a female on one side and repel a male on the other!
This flashing is suspected to be a means of communication—but no one knows what the squid are trying to say. Skip to main content. The blue-lined octopus may be small, growing to at most 15 cm, but it can be deadly: its venom can cause breathing failure in humans as well as other animals. Tony Brown, Flickr. This day octopus Octopus cyanea has shaped itself like algae or some coral so hide from predators or stalk prey.
In addition to color control, many of the squid can produce light and control its intensity. Biologically produced light is called bioluminescence, and it is used for a wide variety of purposes by marine organisms. Some creatures are believed to use bioluminescence to confuse or startle predators, others may stun their prey, and some use it as a decoy to facilitate escape or as a lure to attract the unwary.
Bioluminescence may also offer a means of communication in the dim midwater or twilight region of the sea. Squid and other marine creatures create light by mixing two substances into a third that gives off light, similar to the mechanism by which a common firefly lights up or the way the popular plastic green glow-sticks work. To get a glow-stick to "glow," it is bent. This causes the two chemicals inside to mix and react, yielding a third substance that gives off light. Within an organisms special light-producing cells photocytes or organs photophores , essentially the same thing happens.
A substance called luciferin reacts with oxygen in the presence of an enzyme, luciferase. These reflecting surfaces are also responsible for adding shades of blue and green to the octopus' colouration, as its pigments are unable to produce these colours. A final structure in the skin of an octopus is the leucophore , another reflective structure that lies beneath the blue-green iridophores.
Unlike the mirror-like reflectiveness of the iridophores, the leucophores are covered in tens of thousands of jagged stalks that scatter light. On the surface, this scattered light always appears white, but in deeper waters it allows the octopus to passively scatter light in whatever wavelengths are present in its environment - providing passive camouflage if the octopus is caught off-guard.
The intensity of this reflective layer is controlled by the upper chromatophores, providing the octopus with additional colour options, including disruptive camouflage if desired. Apart from all those reflectors and pigments, octopus skin also have the ability to rapidly change its texture using small muscle bundles called papillae.
Muscles in these bundles form a network, with some running radially and others in circles, allowing areas of skin to be quickly smoothed out or raised as needed - a bit like goosebumps just way more useful. The abovementioned abilities are made even more remarkable by the fine control that octopuses have over these individual elements. You probably already know that octopuses are one of the smartest animals on Earth, so these abilities might not surprise you. But, what if we told you that octopuses are actually colourblind?
It's true. Octopuses only have one type of receptor in their eyes, which means they are completely colourblind, only seeing the world in shades of grey. Fortunately, octopuses have two really awesome tricks up their eight sleeves to deal with this.
To change the color of their skin, octopuses will make the color cells bigger or smaller by stretching or relaxing their muscles. So, by changing the sizes of all the different color cells, the octopus can very rapidly create complex patterns that allow it to better blend in with its surroundings.
Thus, by changing its shape, behavior and color, the octopus has an array of different camouflage techniques that allow it to successfully hide from even the most the most observant animal or human.
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