The octopus is one of the strangest creatures in nature. It has a spongy body that can be compressed into small cracks, 8 arms that can grow again if injured, and 3 hearts that pump blue, copper-rich blood through its veins.
The octopus also has huge donut-shaped brains that give it superior intelligence compared to other invertebrates, but the most amazing feature of the octopus is its ability to change its color quickly, blend in with its surroundings, and camouflage itself as it pleases despite being color blind.
A report, published on the “Live Science” website, stated that the octopus’s mastery of camouflage has confused researchers since the beginning of science itself. About 2,400 years ago, the ancient Greek philosopher Aristotle, often considered one of the founding fathers of modern science, made detailed observations of octopus camouflage. He is the first known person to do so.
Although octopus camouflage has been studied and monitored for centuries, it is only in the past few decades that advanced technology has enabled researchers to deconstruct individual components of cephalopod camouflage such as octopuses, squid, and others and are now beginning to understand how they work.
Knowing that researchers are not allowed to experiment with cephalopods while they are alive because of their intelligence, they can solve complex problems, they use tools and feel pain. Octopuses and squid have been proposed as sentient beings in the UK.
How does it change colour?
Octopuses can change color tones because they have chromatophores, which are small, color-changing organs, Laila Deravi, a biochemist at Northeastern University in Massachusetts who studies the mechanics of octopus camouflage, tells Live Science. They are spread all over the skin of the octopus.
At the heart of each chromatophore are small bags filled with nanoparticles of a pigment called xanthommatin. These sacs are surrounded by an elastic matrix that in turn attaches to the muscle cells that surround the sac in the form of a pointed star.
When these muscle cells contract, the pigment sac expands, allowing more light to enter the cell and reflect back onto the xanthomatin molecules. Because xanthomatin absorbs certain wavelengths or colors of visible light, the light that is reflected back from the chromatophore is a different color compared to the light that first entered the cell.
There are 3 layers of chromatophores in the skin of an octopus, each layer containing xanthomatin molecules that reflect a different color, where the upper layer produces a yellow color, the middle layer reflects a red color, and the lower layer produces a brown color. Octopuses can incorporate these colors into each layer, enabling cephalopods to create a wide range of shapes.
Each chromatophore is individually controlled, with the knowledge that there may be tens of thousands or even millions depending on the species’ size, through nerve signals directly from the octopus’ brain that cause the muscles surrounding the sac to contract or relax, thus changing its shape.
Not the only structures
Chromatophores aren’t the only structures involved in changing color. Additional organs, known as iridophores and leucophores, found in the skin of certain octopuses can help improve or change the colors they produce.
While iridophores are slightly larger than chromatophores and help create the brighter, metallic colors of octopuses, leucophores are similar in size to chromatophores, but contain specialized white pigments instead of xanthomatins, which scatter or refract light and help control contrast and brightness.
Octopuses also have machines in their skin that help them change its texture, adding another layer of camouflage. It has small bumps called papillae, the relaxation of which can make the skin smooth like seaweed, or contraction making the skin lumpy and rough like rocks, and these papillae are also controlled by nerve signals from the brain.
Fastest to change color
Many animals rely on camouflage, but the octopus has a particularly distinguished position, due to the speed and precision with which it can switch between different colours. And it does so within a split second or faster than the blink of an eye. In contrast, chameleons can take several seconds to over a minute to completely change their color.
Deravi says octopuses can make rapid changes in color because “their brain is deeply attached to the surface of the skin”; They have rapid signaling mechanisms that enable them to say “turn on here” and “off there” throughout the body.
The main reason for this interconnection between the brain and the skin is that the octopus brain, unlike most brains of other animals, is not confined to a single region such as the head. It has “cerebral pockets” or nodes throughout its body and throughout its arms. The researchers believe this enables individual octopus arms to have a brain of their own, which can play a role in changing color.
Deravi also says that octopuses also have more chromatophores per square inch of skin than, say, squid, which helps them create ultra-fine patterns compared to other cephalopods.
Unsolved mystery yet
There is still one major unresolved mystery surrounding cephalopod camouflage, which is how they manage to match the color of their skin to the color of their surroundings even though the majority of octopuses and other cephalopods are color blind.
According to a research paper published in 2020 in the journal Frontiers in Physiology, octopus eyes have only one type of photoreceptor, and cells convert light into nerve signals, which means they can only detect differences in light intensity, while Human eyes, for example, contain 4 types of photoreceptors.
One possible explanation is that octopus eyes are able to see color without photoreceptors. A study published in 2016 – in the journal Biophysics and Computational Biology – hypothesized that there are additional types of receptors in the eyes of an octopus that we are not familiar with, which may enable cephalopods to see colors differently from humans and other animals. .
There are also theories that photoreceptors in the skin could help octopuses match the colors around them. Previous studies have also shown that octopuses’ arms can react to changes in light intensity when the octopus can’t see. However, there is no evidence yet that this helps her see colors.
Deravi says understanding more about how octopuses change color is very difficult; Because researchers are not allowed to experiment with cephalopods while they are alive.
Why does an octopus need camouflage?
Although octopus camouflage mechanisms are still being researched, scientists have a much better understanding of why these fascinating animals change color.
“Octopuses have no external protection and for any predator, the octopus is an unprotected bundle of protein, which means that Every creature in the ocean seeks it.” So God enabled the octopus to develop camouflage methods that make it invisible.
In addition to being unnoticed by their prey, octopuses can also use their amazing displays of color to hunt their prey, after they break camouflage and stun their prey with rapid and drastic shifts in color before quickly trapping them.
In 2019, scientists captured video footage of an octopus named Heidi changing colors while she slept, sparking speculation that the octopus might also change color when dreaming. Researchers have identified octopus-like sleep cycles, but not all researchers are convinced that the color changes can certainly be described as a dream, as it is absolutely impossible to know how octopuses dream.