The mysterious octopus species is actually most similar to humans?

Leviathan: Compared to the soft body of the octopus (there is no need for "bone shrinking" because there are no bones), I may be more concerned about the intelligence of the octopus. The size and organization of the octopus's nervous system are very different from those of other animals: they have a very complex nervous system, but the brain only occupies a part of it, and two-thirds are located in its arms, which allows the octopus' arms to have many complex spontaneous movements. This actually means that many of the octopus's limb movements are planned, calculated, and executed by the claws themselves.

Many studies in the laboratory have shown that if one of the criteria for measuring intelligence is memory and learning, octopuses are obviously smart enough: in addition to their amazing adaptability, they can play games with people, give them tasks, and octopuses can also learn various skills through observation... They are simply mysterious octopuses!

Twisting, morphing, disguising themselves—often in an instant—octopuses are fascinating in their variety and variety. These six species offer their own unique charm.

You sit on the sea floor off the coast of Lembeh Island, Indonesia. You're not deep (about 20 feet) and there's plenty of light. The water is warm, as expected, near this tropical island. Looking around, you see ripples in fine gray-black sand and the occasional green duckweed floating on the waves. As you look around, you spot a conch shell. It's hard, with six spikes sticking out. Its owner may be inside the shell; or it may be dead and now belong to a hermit crab. You poke it curiously. A row of suction cups. A pair of eyes.

An octopus. More specifically, the striped octopus (Amphioctopus marginatus), or more commonly known as the coconut octopus, so called because they like to hide in abandoned coconut shells (sometimes they pick up coconut shells and carry them with them for emergency shelter). Really, any large shell will do - like a conch shell.

The octopus uses a few suckers to hold the two halves of the clam shell on its body. You watch quietly as it puts the clam shell down and slowly lifts itself up a little. It acts as if it is assessing the situation. You pretend to be a statue at this time. After a while, the octopus climbs out of the shell. Its body is the size of your thumb, and its claws are about three times its body. As it moves toward the sand, it becomes a dark gray shadow. Is it gone? No. Some of its claws are waving above the sand, and the rest are above the shell. With just a slight lift, it flips the shell over and swims in.

This female octopus - a species that has not been studied scientifically - is nursing her eggs. She will hatch them and then die soon after. Most female octopus species lay eggs only once in their lifetime. This means that the young octopuses must fend for themselves from an early age.

You don't want to bother it anymore, and just as you're about to swim away, you notice a small movement. The creature spurts a stream of liquid, clearing the sand from the bottom of the shell. Now there's a small gap between the shell and the seabed. In the gap, the eyes reappear. You bring the mask a little closer, and you stare at each other for a while. Of all the invertebrates, octopuses are probably the most human-like. In part, it's the way they respond to our gaze, as if they're examining us (which also sets them apart from vertebrates: most fish don't seem to stare at people). In part, it's their agility. Their eight claws are connected to hundreds of suction cup holes; this makes them better at manipulating objects, whether it's opening a clam shell, removing the filter system in an aquarium, or unscrewing the lid of a can. It's also different from many mammals, such as dolphins, who, although they are also very smart, have a hard time unscrewing anything due to their skeletal structure.

The octopus's arms allow them to easily twist off the lid and escape.

And, like any alien we could imagine, octopuses are just as weird. For starters, they have three hearts and blue blood. When they sense a threat, they squirt a cloud of ink and flee in the other direction. They have no bones. The only hard parts are a parrot-like beak and a small patch of cartilage around their heads. This allows them to slip through narrow gaps with ease—a skill that helps them escape, Houdini-like, from all but the most carefully designed aquariums. Not only are the two rows of suction cups on each claw all independently movable, each of the holes in the cup has a taste receptor—imagine having hundreds of tongues all over our bodies. Their skin contains many cells that can sense light. And the weirdest part of all—but more on that later. First, let's look at another type of octopus.

The pale octopus (Octopus pallidus) is a sturdy octopus with a large body and small claws. It lives in the waters southeast of Australia. It is active at night and feeds on shellfish.

You are standing in a small, windowless office at London's Natural History Museum. In front of you, on a desk piled with papers, sits a large block of dark, fine-grained rock. Next to you, Jakob Vinther, a sturdy Dane with blond hair and a ginger beard, is pointing at the rock.

"This is the ink sac," said Vinther, an expert on fossil invertebrates at the University of Bristol in the United Kingdom. "Inside it is actual pigment—chemically preserved melanin."

You lean over to observe. The stone bears clear marks of an octopus. It's not big: an octopus might only be 25 centimeters long in its lifetime. You can follow the soft membrane, which is structured like a bag and contains the octopus's gills, three hearts, and other major organs. Oh, and that dark spot in the middle—that's the ink sac. Its claws hang down, sparsely spaced, and each claw has rows of circles. "Those little round structures," Vinther says, "are the suction cups."

Octopus fossils are rare; soft-bodied creatures don’t usually leave much behind. This one, about 90 million years old, is one of the oldest known. That puts the octopus at 25 million years before the dinosaurs went extinct. “It came from a site in Lebanon where you find all kinds of really well-preserved soft-bodied creatures,” Vinther said. Lampreys, fireflies, everything was buried long ago beneath a fine-grained seafloor that was covered by a long-gone seawater.

The common octopus (Octopus vulgaris) has a nervous system far larger and more complex than that of most invertebrates. Can it think? Is it conscious, as some scientists and philosophers have suggested? How can we know?

While humans are classified as mammals, octopuses are cephalopods. The word means "head-foot" in Greek, referring to their weird anatomy, as their claws are directly attached to one end of their head, while their "trunk" - a soft, bag-like membrane - is attached to the other end. Cephalopods, in turn, are a type of mollusk - a group that also includes snakes, slugs, and clams and oysters.

Of all the predators that hunted in the ancient oceans, cephalopods were at the top. Evolving more than 500 million years ago—long before fish—these little guys first had shells that looked like witches’ hats. Yes, if you go back 450 million years, many of the fiercest predators in the oceans were shelled cephalopods. Many of them were enormous: the long-extinct giant nautilus (Endoceras giganteum) might have had a shell that was 5.5 meters long.

Giant Nautilus Imaginary Picture

There are more than 750 known species of cephalopods living on Earth today. Of these, octopuses make up about 300 species, along with various squids and cuttlefish (both of which have 10 arms) and several species of nautilus, a bizarre species with 90 tentacles and a shell.

Of all the invertebrates, octopuses seem to be the species most similar to humans, in a way that they respond to our gaze, as if they are observing us too.

Octopuses are a diverse group of creatures in our modern world. The giant North Pacific octopus (Enterocs dofleintopui), as its name suggests, is gigantic. A giant North Pacific octopus can have arms that are up to 1.9 meters long, and the whole thing can weigh more than 200 pounds. The smaller Octopus (Octopus wolfi), for example, weighs less than an ounce (28 grams). Some octopuses have tiny soft membranes but huge arms; others are more symmetrical. Most octopuses crawl around coral or sand, swimming only when they need to get from one place to another or escape from predators, but some prefer to swim with the currents. From tropical to polar regions, from coral reefs to sand flats, from tide pools to canyons, we find octopuses everywhere. At least if you can recognize them, they are everywhere.

Giant North Pacific octopus walking

Back in Lembeh, you're swimming across a shallow reef on a sunny morning. Your guide, a man named Amba, gestures to you that he's spotted an octopus. A big one. Where is it? You look around. No octopus. Just some rocks with corals and colorful sponges clinging to them. Amba gestures: Big octopus! You look where he's pointing. No, there's nothing. Wait. Look again. Look at that smooth, soft black coral, right there. Ah, that's not coral. It's a daytime octopus called Octopus cyanea. You almost miss it: It's the size of a dinner plate.

Octopuses and cuttlefish, which live in shallow water and prefer to hunt during the day, are world champions at disguise. Of course, disguise is not rare: many creatures have evolved from times when they were very different from what they are now. For example, that orange sponge over there is not a sponge but a frogfish, lurking in wait for a blind little fish to take its bait. That leaf you see drifting across the sand is not a leaf but a fish that has evolved to look like a leaf. Look at that leaf again—that thing over there, zipping across the sand—that is indeed a leaf, but it is also zipping across. A crab is holding it, holding it in its shell. That little anemone over there is actually a sea cucumber that has evolved to be able to pass for an anemone. And everywhere you look, the sand pile may suddenly stand up and walk around (that's a group of little crabs with shells the same color as the sand) or swim away (that's a flatfish, the same color as the sand).

This algae octopus (Abdopus aculeatus) has just squirted ink. Octopuses release ink when threatened, creating a jet of jet-black ink that effectively obscures the vision of predators. The trait has an ancient history: Ink sacs have been found in fossils of octopus ancestors that are more than 300 million years old.

So, what's so special about the camouflage of octopuses and cuttlefish (and slightly smaller squids) is that they can disguise themselves while swimming, sometimes pretending to be coral, sometimes turning into a clump of seaweed, and sometimes looking like a pile of sand. It's like they use their bodies to present a three-dimensional version of the background environment. How do they do this?

The mimic octopus (Thaumoctopus mimicus) is known for its extraordinary mimicry abilities, and can disguise itself as sea snakes, lionfish, brittle stars, flatfish, croakers, anemones, jellyfish, lionfish, and mantis shrimp.

There are three main elements to the octopus's camouflage. The first is color. The octopus produces its colors through a system of pigments and reflectors in its body. The pigments of an octopus - usually in shades of yellow, brown and red - are stored in thousands of ink sacs in the top layer of its skin. When the sacs are closed, they look like tiny spots. When the octopus is ready to spray, it contracts the muscles around the sacs, which in turn open the sacs and release the pigment. By opening and closing the sacs in different combinations, the octopus can continuously release different shapes of ink, such as ribbons, strips and dots. The reflectors in the octopus' body have two states. In the first state, they reflect incoming light back - so an octopus' skin appears white in white light, red in red light, and so on. In the second state, the octopus is a bit like a living soap bubble, and it appears different colors at different angles. With reflectors and pigment organs in both states, the octopus can create a wide variety of colors and patterns.

The second key to camouflage is the texture of the skin. Octopuses can change their skin from smooth to spiky through the movement of muscles in certain areas. The effect can be dramatic. The algae octopus (Algae octopus) can create wispy structures for a short period of time, often mistaking it for a plant of seaweed. The hairy octopus is a creature that has not been studied by science, but has permanently evolved a wispy form that looks like a mass of red seaweed.

A Pacific red octopus, Octopus rubescenes, shows its suckers. Octopuses can independently manipulate each sucker to bend and twist. The suckers not only help with adhesion, but also give the octopus great strength and amazing agility.

A Capricorn night octopus swims by, using muscles in its soft membrane to push water through a visible tube-like passage just below its eye.

Many young octopuses, such as this juvenile blue octopus (Octopus cyanea), grow very quickly.

Octopus species vary dramatically from tropical to polar regions. The zebra octopus (Wunderpus photogenicus, also called the wunderpus) lives in the warm, shallow waters of the Indo-Pacific.

The third key point is shape. The way an octopus holds its shape can make it stand out more or less in the environment. For example, some octopuses will curl up their bodies, leaving only two claws to slowly crawl on the seabed, looking like a piece of coral. (No, no, don't look at me - I'm just a rock...)

How did the octopus become so good at camouflage? The simple answer is evolution. Over tens of millions of years, the best-camouflaged species have been able to evade capture and thrive. So many animals—including eels, dolphins, mantis shrimp, cormorants, many fish, and even other octopuses—are eager prey on octopuses. Because octopuses have no skeletons, predators can swallow them whole. As Mark Norman, a world expert on living cephalopods at Museums Victoria in Melbourne, Australia, puts it, "These animals are just walking fat—they're like filet mignon."

Now let's talk about the octopus's nervous system. A common snail has only 10,000 nerve cells; a lobster has about 100,000; a jumping spider might have 600,000. Bees and cockroaches are the invertebrates with the richest nervous systems in the world, except for cephalopods, with about a million nerve cells. So the true octopus, with 500 million nerve cells, is completely unique. In terms of the number of nerve cells, the octopus is well-equipped to surpass the house mouse (80 million) and rat (200 million), and is almost as many as the cat (about 700 million). Most of the nerve cells in vertebrates are concentrated in the head, but two-thirds of the nerve cells in an octopus are in its claws. In addition, the nervous system requires a lot of energy to operate, and cells will only grow when the energy intake is greater than the energy consumption. What's going on?

Peter Godfrey-Smith, a former philosopher and now a biologist who specializes in octopuses at City University of New York and the University of Sydney in Australia, believes that many factors contributed to the octopus's complex nervous system. First, its limbs. After all, the nervous system evolves in coordination with the limbs, and the octopus's limbs have evolved to be extremely complex. Although it has no bones, the octopus's arms can extend in any direction and at any position; unlike you and me, its arms are not restricted to the shoulder, elbow, or wrist. This gives the octopus a lot of freedom of movement; of course, each arm can make different movements at the same time. So the octopus in action is a sight to behold. All the arms are stretched out on the sand dunes, searching, inspecting, exploring the burrows of prey. If one arm startles a shrimp, the two arms next to it can quickly arrive and grab the prey. The octopus not only has suction cups that can move independently, but also has body structures and mechanisms that can control the color and texture of its skin. In addition, they have evolved an ability to receive and process a large amount of sensory information: suction cups for sensing taste and touch, structured statocysts for sensing gravity, and complex eye structures that can capture a variety of information.

On top of that, many octopuses live in relatively complex environments—they have to navigate up and down, side to side, and back and forth between reefs. Without a carapace to protect them, they need to appear menacing to predators, and they need to know where to hide if camouflage isn’t enough. As a result, octopuses are fast, agile predators that eat a wide range of animals, from oysters to crabs to fish. The lack of a skeleton, the complexity of the environment, the rich and varied diet, the need to avoid being eaten—all of these factors, Godfrey Smith believes, contributed to the evolution of intelligence in octopuses.

Even if there is no doubt that octopuses have complex nervous systems, are they really smart? Assessing the intelligence of other animals is tricky at the best of times, and sometimes experiments teach us less about the animal than about ourselves. Markers of intelligence in birds and mammals, such as the ability to use tools, don’t usually apply to octopuses: their entire bodies are tools. They don’t need tools to squeeze into rocks—they can do it themselves—or to crack open an oyster.

The spots on this Callistoctopus alpheus are pigment-filled cells that, when fully opened, turn the octopus red with white dots.

That said, a series of experiments dating back to the 1950s and 1960s have shown that octopuses are good at many skills, including learning and memory—two attributes thought to be associated with intelligence. Indeed, octopuses have a part of their brains dedicated to carrying out these commands, the vertical lobes. I’m focusing on octopuses here because they’ve been the most studied so far. Different species of octopuses have slightly different brain structures, and because only a few have been studied scientifically, we don’t know if all octopuses have the same talents. “Some of the octopuses I’ve worked with in the lab seem to be really dumb,” says Roy Caldwell, an octopus researcher at the University of California, Berkeley. Example? “Octopus bocki, a very small octopus.” Why is it so dumb? “It doesn’t seem to move much.”

Octopus bocki

But whether they are smart or dull—whether they often ponder philosophical questions or lunch problems, or nothing at all—seems less important than the fact that they are enough to amaze and fascinate people just by swimming around.

Let's take one last dive. It's dusk in Lembeh Island. You kneel beside a rocky slope. In front of you, a pair of small fish swim side by side, laying eggs. An eel curls up in a hole. A large hermit crab clatters past in a borrowed shell. And over there, sitting on the rock, is a tiny seaweed octopus.

As you wish, it begins to move. Sometimes it seems to float, like an eight-armed yogi ascending slowly. Sometimes it slides down. Now it begins to crawl over the rocks—but whether it pulls itself over with the front paws or pushes itself over with the back paws, you can't tell. As it moves down the slope, one paw finds a small hole, and then, one by one, the other paws go in. It disappears. No—not quite. The tip of one paw reaches out of the hole, gropes around, grabs a few small rocks and piles them at the mouth of the hole. All right, it'll be all right tonight.

By Olivia Judson

Photo by David Liittschwager

Translated by Xixi

Proofreading/Rabbit's Light Footsteps

Original article/www.nationalgeographic.com/magazine/2016/11/octopus-anatomy-cephalopod-disguise-evolution/