The world is full of attractive colorful things. Among many plants and species there are many creatures. Besides to chameleon, what else do we know? You certainly will be curious to know that there are three other creatures in the Pacific Ocean !
They are, cuttlefish! Squid! octopus! The three creatures are so different and colorful with lot of long like paws. They are really amazing and one can not believe after watching them. Let us take a look at them here.
What changes the color of animals?
Before understanding this, we should know how our vision is formed. If an object reflects blue light, we see blue. If an object reflects all light, we see white. If you absorb all the light, that is black. Our color vision is like this.
In fact, many animals have the ability to change color. Mostly animals can change color on the whole. For example, mammalian can change their hair too. Birds can change their colors of feathers. Some animals due to their specific hair, can change with the environment, such as some wolves.
The process of changing color is very slow. In the day time they are able to change quickly. Some creatures slowly change their color in accordance with the seasonal changes. Depending upon their ability of rapid discoloration, they are devided into reptiles, amphibians, fish, insects, and marine molluscs.
Reptiles are the most familiar to everyone, such as the chameleon, there are some snakes can change color. Amphibians mainly refers to some frogs. And some fish can really change color, such as flounder, puffer fish can do.
We have seen people doing mimicry. Some such type of phenomena is seen in the three softkeys: octopus, cuttlefish (squid), squid. These animals, also known as cephalopods, are tentacles that grow on top of their heads.
Molluscs can change their color
Cuttlefish (squid)
First, let's talk about octopus. Octopus can not only change color, but also do some sort of mimicry. For example, mimic octopus, can simulate at least 15 kinds of animal appearance. They can transform many colors such as red, yellow, brown, blue, green, and many more.
Not only do they have plain, monochromatic cells on the surface of the skin, they also have a rainbow of cells beneath the monochromatic cells. The color change mechanism of this cell is different from that of monochromatic cells. Can change the color of more similar metals.
Cephalopod mollusks are mainly divided into three kinds of discoloration. Monochrome camouflage discoloration, variegated camouflage discoloration and intermittent camouflage discoloration.
Monochrome is the same general color, mainly in order to adapt to a smooth background, such as the sand of the sea.
Variegated is to adapt to the more complex environment, such as rocks. The intermittent color change is mainly to get rid of the overall sense of the whole body so that they do not look like themselves.
Why Molluscs change color?
Any animal, if any, has only two goals. Either survive or multiply. This ability to change color not only improves survivability but also increases productivity.
In the case of lizards and snakes, they are generally discolored for three purposes: camouflage, communication and thermoregulation.
And lizards can change their color, depending on their predator, such as a snake or a bird. The communication is to convey information among them, such as when the courtship will appear bright color, the failure will be dim.
The purpose of changing molluscs is much the same. On the one hand, discoloration is to create a protective color, so that natural enemies find difficult to locate themselves.
On the other hand, discoloration also helps them capture their favorite foods, so they choose to blend in with the environment.
Many predators of molluscs, of which mainly whales belong to their largest natural enemies. Because these molluscs are long! 3-5% daily weight gain with no pressure! So only the general predator can endure.
The general predatory fish is not so good, during the day molluscs are in the sea, birds can not eat them. And they have mucus body, slippery in autumn.
So there are only those toothed whales that have big mouths. Such as sperm whales, full of belly.
However, many whales can not see well. Because the sea water may not help them with their sight. Sometimes discoloration is a warning to predators, "do not touch me!"
Another purpose is communication. Or to convey information and express emotions. After all, molluscs can not speak. Then discoloration has become a natural language.
Squid becomes white or transparent when it is scared. In the battle for courtship, the beginning is also a mutual transformation of stripes and plaque to express information. Battles peakes as body colors became gorgeous. When communicating with females, males also use body color changes.
Moreover, the three softballs can change the color to make them similar with the opposite sex. In particular, males are good at this. For example, octopus, as the male octopus semen is limited, if after a mating, it will take a long time to come back again.
If it consumes its sperm cheek pouch, it will lose the mating ability. Some male octopus will imitate the female to fake mating.
And male squid can also disguise itself as a female, pretend to be a female squid girlfriends and go to mating. After all, big squid can occupy multiple wives. This steal ability is very important for them.
The sea water temperature almost does not change. So mollusc discoloration is proportional to body temperature is not difficult.
In fact, said these, the most special thing about them is, whether octopus or squid, they are color-blind! There is only one pigment in their eyes, where as there are three in humans and four in birds.
So they can only see these colors black and white or in gray shades. Others are unable to distinguish. But is not it strange that they are able to integrate exactly with the environment?
Some studies suggest that this is because squid eyes can distinguish brightness. So molluscs change color because they distinguish the brightness and contrast of the surrounding environment. Instead of seeing the color.
The mechanism of discoloration of molluscs
The reason for the discoloration of molluscs is due to the morphological changes of the pigment cells in their skin. Their skin has a layer of pigments , which have a lot of pigment cells. Pigment cells within these pigments, we can see are red, yellow, brown, black and other different colors.
Mollusca's skin, the inside of the point is the pigment cell pigment capsule
Mollusc pigment cells compared to other forms, are stored in the pigment capsule. The entire cell around the muscle fiber can stretch. While sending nerve signals, these muscle fibers can shrink or relax, making the pigment cells swell or shrink.
As the cells are stretched, these plain bladders are also stretched, so that the color of the pigment increases in area and, as a whole, the mollusc's body discolors.
Mollusc pigment cell structure map
Cephalopod skin pigment cell size changes caused by skin color changes
However, in addition to the above-mentioned discoloration methods, some molluscs are distinguished with the class of discoloration.
In the lower layer of pigment cells there is a layer of cells, so that cuttlefish presents yellow, green, blue and other metallic luster (the first figure can be seen), this layer of cells is called rainbow cells.
The interior of the rainbow cell has a replicated stack that reflects and refracts light to create that metallic color. The nervous system can also control the arrangement of the internal stacks of these rainbow cells, thereby refracting and reflecting light of different wavelengths, making their skin colors more variable.
Different stacks of rainbow cells have different reflection patterns.
Mollusc skin layers of cells, together to create its changing body color. The bottom layer is the reflective layer, giving the white skin color.
Finally, as these cells are controlled by the nervous system, molluscs change their body color in a very short period of time.
And, different color structures can represent different emotions. For example, the problem of pigment cells shrink and appear white, for the mollusks generally represent the extreme stress emotions.
Scientists have found that the body squid is actually covered with light-sensitive cells, so without the vision also they can change their color according to the environment.
Some studies have found that there are many opsin proteins in the cephalopods, which are the same as opsins in the retina. To some extent, it is fair to say that they are all eyes.
But in fact the mechanism of mollusc discoloration is not very clear. These are just some theories, discoveries and conjectures.
A recent study may help scientists identify their color change mechanism. Scientists found that squid managed to accomplish discoloration by sending instructions from the brain through the nerve center around the stellate ganglion to the skin.
Specifically, through the axon system. Axons are nerve fibers that serve as the main conduction line of the nervous system. They are usually about 1 micron wide and in some mammals the axons can reach 20 microns. But in squid these huge axons can be up to 1 millimeter in diameter, some large enough to be seen with the naked eye.
This finding provides scientists some more clues , perhaps in the near future, they can confirm this mechanisms of color change.
References for Text and Images:
- https://thescinder.com/2016/07/25/through-the-strange-eyes-of-a-cuttlefish/
- http://www.this-magic-sea.com/COMWEB.HTM
- https://www.asianscientist.com/2011/05/in-the-lab/how-cuttlefish-camouflage-predators/
- https://www.pulseheadlines.com/squid-octopus-populations-growing-fast-sea/32280/
- https://laughingsquid.com/color-changing-pfeffers-flamboyant-cuttlefish-at-the-monterey-bay-aquarium-in-california/
Support 
project - curating and supporting quality STEM
related content on Steemit