All extant and extinct species are classified into five major kingdoms. The most common one of these is the Animalia Kingdom, whose millions of members, also known as species, live on land, in the air, and underwater. Those are also further classified into several other ranks to make their studying less intimidating and more approachable.
Why intimidating? Because no two animals are alike. Each and every animal is unique for possessing features, or shall we say superpowers, that enable them to survive and thrive in their natural habitats. Such superpowers can be in their body compositions and functions, behaviours, diet or how they respond to a threat or even a peer’s call.
On land, we have giraffes with their elongated necks that allow them to browse without competing with other animals over food. In the air, we have hawks whose vision is the best in the entire animal world. Underwear, we have the mighty, large-headed, eight-limbed octopus.
As we previously demonstrated giraffes and hawks, it is the octopus’s turn this time. In this article (and the following one), we will learn some jaw-dropping superpowers of this bizarre-looking marine animal that will just leave you astonished.
So let’s hop into it.
Octopuses have a super large oval-shaped head, branching from which are eight limbs with the animal’s sharp curved beak being their centre point. Every limb is covered from below with hundreds of differently-sized suckers, which are super vital for the octopuses’ survival.
Octopuses have no bones whatsoever. Their bodies are pure muscles covered with soft skin that has an incredible ability to change colour, pattern, and texture. Those boneless animals are called invertebrates. Sharks are also invertebrates.
Such a thing, having no bones, is very majestic, for sure. But it made it challenging for scientists to understand how octopuses evolved, why they developed so many limbs and whether or not their ancestors had eight limbs too. That is because octopuses leave behind no fossils which scientists can study. When they die, their bodies quickly dissolve in the water and never fossilise.
Speaking of the water, octopuses live in saltwater only, unlike dolphins which survive in salt, brackish, and fresh waters. Octopuses are found in every ocean on the planet, from the largest and deepest one, the Pacific Ocean, to the smallest one, the Arctic Ocean, around the north pole.
That said, octopuses are more concentrated in warm tropical waters, and only a small population lives in the Arctic and Southern oceans—the Southern Ocean is that one surrounding the southernmost frozen continent of Antarctica.
But octopuses are not just one animal but rather 300 species varying widely in size, colour, and habitat. The smallest species is the Octopus Wolfie which has nothing to do with the wolf, by the way. It lives in shallow waters and can perfectly fit on your fingertip, measuring less than 2.5 cm and weighing less than 1 g.
On the other hand, the largest octopus species is the giant Pacific octopus, living in the northern Pacific Ocean. It has an arm span of 4.3 metres—this is the length of two extended limbs, from tip to tip—and adults weigh 59 kilograms on average.
The most giant northern Pacific octopus ever reported weighed 136 kilograms and had an arm span of 9.8 metres!
But diversity does not end at size. It also extends to skin colour and pattern. The most beautiful combination of these is found in the four blue-ringed octopus species. They have yellow skin on which there are brown spots surrounded by blue rings. When these octopuses are provoked or hunted, their skin colours brighten up.
By the way, these blue-ringed octopuses are some of the deadliest marine animals. We will know why in Part Two of this article!
Another distinct species is the glass octopus. This one is completely transparent, making it easy to see through the skin. One can easily spot the organs located in the large head as well as the veins and arteries.
All 300 octopus species are famous for having relatively short lifespans, ranging between one and five years. This has to do with their reproduction, which we will get to discuss later on. How long an octopus lives is proportional to its size. As a result, the biggest species, the giant Pacific octopus, lives the longest, and vice versa.
Octopuses are backed with so many great things that would literally leave us gazing at those fantastic creatures without feeling even a tiny bit of boredom. Although we do not have enough room for all of those great things, we can still highlight the most majestic ones.
So grab a cup of hot chocolate and read on.
1. Octopuses have a body-like head.
While we call these creatures octopuses, scientists like to call them cephalopods, which basically means head-footed or feet that branch out of the head. There is no mention of a body whatsoever.
In humans and so many animals, the brain is found in the head, while the rest of the organs are scattered around the body. Since octopuses lack ‘bodies’ in common usage, their everything is located in their large heads. So yes, the octopuses’ heads pretty much function as their bodies. That is why scientists do not call them heads but rather mantles.
The mantle has a bulbous shape. It looks like a camel’s hump. All the important organs, such as the heart, brain, gills, kidneys, and the entire reproductive system, are found in the mantle. All such organs swim in a cavity that helps protect them.
Attached to the mantle is the funnel, or syphon. This is a large tube projecting outward and is used to help the octopus move and breathe.
2. They have blue blood.
Humans and most animals have red blood, but octopuses are different. They have blue blood—yes, blue! And it all goes back to the blood composition itself.
In general, blood is responsible for delivering oxygen and to the rest of the body. To do that, it must contain a particular protein which takes the oxygen from the lungs or gills and facilitates its delivery to the cells.
In the human blood, this protein is called haemoglobin. It contains iron, and iron is what gives our blood the red colour. On the other hand, the octopus’s blood has a protein called hemocyanin. Hemocyanin is rich in copper, which then makes the blood blue.
3. They have three hearts.
It seems like octopuses like to outnumber most other creatures. Just like they have eight limbs, instead of two or four, octopuses also have three hearts, and not just one. To understand why this is the case, we need to learn a little about the blood cycle in the body.
The human heart pumps blood to every organ in the body. When it reaches the lungs, the haemoglobin extracts oxygen from the air we breathe and, therefore, becomes oxygenated.
This oxygenated blood goes back to the heart, which, in turn, pumps it to the rest of the body. The oxygenated blood gives oxygen to the cells and takes carbon dioxide in return, which then makes it deoxygenated. After that, the deoxygenated blood goes back to the heart. The heart pumps it to the lungs, and we breathe out, releasing carbon dioxide.
But octopuses breathe through gills, like most other fish, and not lungs. Yet, that does not make any difference for gills function the same as lungs. While the lungs pick up oxygen from the air, gills extract oxygen from the water. It is the blueness of the octopus’s blood that makes its cycle a little different.
While our haemoglobin is really efficient in transferring oxygen to the cells, hemocyanin is more viscous, thanks to its copper content. So to do its job as efficiently as haemoglobin, it must be pumped at a high pressure. One heart is not able to do this job. So the octopus is backed with three hearts.
The first and most vital of the octopus’s three hearts is called the systematic heart, while the other two are called the branchial hearts. The systematic heart takes the oxygenated blood from the gills, increases its pressure and pumps it to the rest of the body.
Instead of returning to the systematic heart, the deoxygenated blood goes to the branchial hearts located near the gills. They take this blood and pump it through the gills to release carbon dioxide into the water. As a result, the systematic heart continues to pump blood and provide the body with energy.
4. They have eight limbs that are not all legs.
Octopuses are distinct for their eight limbs, all extending from the head outward, covering 360°. All limbs can be curled and moved in different directions.
Those eight limbs are divided into four groups of two. The rear group functions as two legs which the octopus uses to walk on the ocean floor. The other groups are called arms because the octopus uses them to search for food and grab and hold things.
While octopuses do not have any bones, their bodies are mere muscles, lots and lots of muscles, most of which are concentrated in the limbs. This allows the fantastic movement of the octopus. As we will see in a bit, the octopus can move each arm in a different direction, just like how we can move our arms and fingers independently and spontaneously.
Furthermore, octopuses enjoy this fascinating ability to regrow their limbs if they ever lose them, for instance, in a fight with another animal. In fact, they do that more efficiently than lizards—lizards can regrow their tails. An octopus can regrow an entire arm in three months on average.
The octopuses’ eight limbs have always fascinated and confused scientists for they are unable to understand why or how they evolved them. As we mentioned earlier, octopuses do not fossilise due to having no bones. Instead, they dissolve in the water when they die.
On some rare occasions, researchers could find some fossils well preserved in limestone lying on the ocean floor. These fossils go back thousands and maybe millions of years and they revealed some interesting facts: some octopuses’ ancestors had ten limbs while others had six limbs.
Interestingly, scientists could identify one of the 300 extant octopus species, known in the scientific world as Haliphron atlanticus, that has seven limbs only!
5. They have hundreds of suckers.
Do you know what is more majestic than the octopus’s eight limbs? The suckers that cover them.
Every limb of the octopus has many, many suckers arranged in two rows. They have different sizes based on their location. Suckers near the base of the arm are typically larger than those found more toward the tip.
Given that octopuses vary widely in size, they do not have the same number of suckers. The bigger the octopus, the more suckers it has. Take, for example, the giant Pacific octopus, the largest octopus species in the ocean. It has around 280 suckers on each arm, making up a total of 2240 suckers on all arms.
That said, each octopus does have a number of suckers most suitable for its survival. That is true; those little cup-like organs perform many functions that allow the octopus to survive in its natural habitat.
So what are those suckers like anyways?
Every sucker has two parts, one is external, found on the outside of the arm, and the other is internal, located inside the arm. The outer part is the cup or the shallow socket, while the internal one is the hollow socket. Both sockets are covered with a thick, skin-like material and connected through an opening.
Interestingly, each and every sucker is connected to a different muscle. This means the octopus is able to move every sucker in a different direction, completely independently from other suckers. That is why they are used to perform several functions, all enabled by how suckers work in the first place.
When a sucker gets in contact with any object, the opening between the external and internal sockets closes. As a result, the shallow socket or the cup flattens. Thanks to the muscle it is connected to, the cup acquires tremendous power. It allows no water whatsoever to get between it and the object. As a result, it firmly sticks to it.
Besides sticking to objects, suckers can hold them. Thanks to their huge power, they can hold things as heavy as 16 kg.
Besides holding things, suckers also function as tongues and fingertips at the same time. Every sucker has a large number of taste buds, way larger than the taste buds found in our tongues. So when a sucker gets in contact with anything, it tastes it and decides whether it likes it or not without having to pull it toward its big mouth.
Besides the taste buds, suckers also have sensors called chemotactic sensors. These are responsible for the sense of touch. Once a sucker touches something, these tactic sensors tell the octopus a whole bunch of information about that thing.
Here we get to the end of Part One of this journey we are making to explore some fantastic superpowers the octopus has. While some are quite well known, others turned out to be a complete mystery to us.
Before we elaborated on those superpowers, we discussed some basic information about the octopus in terms of its classification, the different species, habitats, sizes, colours, and lifespans.
Then we moved to learn about the octopus’s amazing body, starting with its head. Lacking a body in common usage, the octopus has most of its vital organs located in its head or mantle, as scientists call it.
After that, we understood why the octopus has blue blood and how efficient this blood is in transferring oxygen to the rest of the body. This is one feature that forced the evolution of three hearts, one systemic and two branchial hearts. After we learned about the blood cycle in the body, we understood how those three hearts cooperate to help the octopus maintain good health and sustain its active lifestyle.
Last but not least, we looked, with a lot of detail, into the octopus’s eight limbs, which turned out to be two legs and six arms. Thanks to the hundreds of suckers those eight limbs have, the octopus is able to do many vital functions, such as touching, tasting, and grabbing and holding things.
We hope you enjoyed reading this article just like we loved writing it for you. While you wait for Part Two of this article, you can learn about sharks, which are not, in any way, less majestic than octopuses. But if sharks scare you, you can read about the school of fish or completely get out of the water, head to the north pole and learn about polar bears.
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