Octopuses look rather weird: they have soft bodies, 8 renewable tentacles, and 3 hearts. Compared to other invertebrates, huge brains give them higher intelligence. But the most admirable thing about octopuses is their ability to change color, they can quickly change color according to their surroundings, and camouflage themselves at will.
Written by | Harry Baker
Compile the | spruce
Edit | Poplar/Kapok
Image source | pexels/pixabay
Camouflage is a common skill of almost all cephalopods,a marine invertebrate, including squid and cuttlefish, but octopus takes this skill to a whole new level. So far, scientists have found about 300 species of octopuses, but not every octopus can change color, and the camouflage mechanisms they use may be different.
Scientists have long been confused about the camouflage mechanism of octopuses. About 2400 years ago, the ancient Greek philosopher Aristotle observed the camouflage of octopuses in detail. Leila Deravi, a biologist at Northeastern University in Massachusetts, said: "Although the camouflage mechanism of octopus has been studied for centuries, progress has only recently been made. ”
The color change of cephalopods is a complex process that involves many different mechanisms. This makes octopus camouflage mechanisms "almost impossible" to be thoroughly studied, Dravan said: "Over the past few decades, technological developments have allowed scientists to gradually 'tease' the various mechanisms of cephalopod camouflage to understand how they work." ”
The skin contains pigment cells
Octopuses can change color because they have tiny discoloration organs on their skin that contain pigment cells.
"The core of each pigment cell is a tiny sac filled with pigments, which are surrounded by an elastic matrix that is connected to the muscle cells that surround the sac," Dravan said. When these muscle cells contract, the pigment sac stretches, allowing more light to enter the cell and reflect the color. Because pigments absorb certain colors of visible light, the light reflected from the pigment cells is different in color from the light that initially enters the cell. ”
The skin of the octopus has 3 layers of pigment cells, each layer contains yellow pigments, which can reflect different colors, the top layer of cells reflect yellow, the middle layer reflects red, and the bottom layer reflects brown. Octopuses can combine these colors by contracting their muscles and changing the shape of their pigment cells, creating a wide variety of shades.
Can change the texture of the skin
But pigment cells aren't the only structures involved in discoloration. Some octopus skin also contains iris cells and white cells that can help enhance color.
Iris cells are slightly larger than pigment cells and help create brighter and more metallic colors. According to a 2018 study, iris cells contain a protein called a reflectin that has an effect similar to that of a mirror. "White cells are similar in size to pigment cells and can scatter or refract light and control the contrast and brightness of colors," Dravan said. "These two types of cells are also controlled by the octopus's brain like pigment cells.
In addition, octopuses can change the texture of their skin, which is one of the reasons why their camouflage ability is super. The octopus has tiny bumps on its skin called papillae that can make the skin smooth like seaweed when loose and rough like a rock when it contracts. Dravan says the mastoids are also controlled by the brain, but this texture change is harder to understand than the color change.
Why is it always integrated into the environment?
Many animals rely on camouflage to survive, but octopuses are special, mainly because they can quickly switch between very different colors. "It only takes 1 second," Dravan said, "and I think the fastest conversion is probably less than 0.1 seconds, faster than blinking." "In contrast, a chameleon can take a few seconds to 1 minute to completely change color.
"Octopuses are able to change color quickly because their brains are tightly connected to the surface of their skin." Dravan said. Unlike most animals, octopuses have 9 brains, and in addition to the brain of their head, they have a parabrain on each of their tentacles. Scientists believe that each tentacle has its own mind, which may play a role in color changes.
Dravan said the octopus has more pigment cells on its skin than squid and cuttlefish, and octopuses are able to create higher-resolution patterns compared to other cephalopods.
However, there is still an unsolved mystery about the camouflage of cephalopods: how do they change their skin color to match their surroundings? Despite their ability to produce multiple colors, most octopuses and other cephalopods are actually color blind: octopuses have only one type of sensor, meaning they can only detect differences in light and cannot recognize colors.
One possible explanation is that the octopus's eyes are able to see colors without photoreceptors. A 2016 study hypothesized that the presence of structures unknown to us in octopus eyes could allow cephalopods to see colors in different ways than humans and other animals.
There are also theories that photoreceptors in the skin can help octopuses match the colors around them. Previous studies have shown that when an octopus can't see, the octopus's tentacles respond to changes in the intensity of light. However, there is currently no evidence that this helps them see color.
[Science of the Singularity is the copyright partner of Science Illustrated, a classic European popular science magazine, focusing on reporting exciting cutting-edge technological advances and allowing readers to see the future in advance.] 】
Resources
[1]https://www.livescience.com/how-do-octopuses-change-color
[2]https://baike.baidu.com/item/%E7%AB%A0%E9%B1%BC/77798?fr=aladdin#1