Here we are with episode three of our article series, where we discuss majestic organs found in extraordinary animals. In the first article, we explored the giraffe’s elongated neck, which scientists believe underwent such evolution to avoid competition with other grazing animals over food.
We also discussed the cat‘s very sensitive whiskers which enable the pet animal to do many vital functions to survive. Then we finally addressed the rabbit’s long ears and how they are used to save it from predation and help it regulate its internal body temperature.
In episode two, we discussed the elephant‘s robust trunk, which resulted from joining the long nose with the upper lip. Being an entirely muscular, boneless structure, the trunk enables the elephant to breathe, smell, eat, drink, shower, snorkel and even wrestle.
In the second part of episode two, we looked into the kangaroo’s mighty pouch. We learned how it works like a neonatal intensive care unit where the tiny foetus grows, for eight months, into a fully developed (and furred) little kangaroo.
In today’s article, we are going to explore two other majestic organs, the octopus’ eight limbs and the great white shark’s razor-sharp teeth.
So let’s hop into it.
1. The octopus’ eight limbs
Many animals are known for having four legs. Birds only have two legs, while kangaroos are said to have five legs, including their very robust muscular tail, which is used for balancing and standing.
But many other animals as well have more than just five limbs, on top of which is the famous marine animal, the octopus, our subject of matter in this section.
The octopus is not just one animal. In fact, over 300 octopus species live in the world’s oceans. Although they possess many physical differences that set each as an independent species, they have many primary things in common.
One relatively unknown yet common trait among all octopuses is their ability to change colour based on their environment or mood. Yes, that is precisely what chameleon the lizard does. Octopuses can change from grey and brown to pink, blue and green. If an octopus turns red, that means the poor guy is terrified.
Another well-known and familiar thing among all octopuses is having eight limbs covered with hundreds of suckers. These two organs are what we are elaborating on here.
But why did octopuses grow these eight limbs?
Modern-day octopuses descended from a differently-looking ancestor that appeared on Earth some 530 million years ago. Throughout its entire history of evolution, it underwent a huge transformation which eventually resulted in the current octopuses.
Now the question is, what did this ancestor look like?
Well, that is a challenging thing for scientists to figure out. Modern-day octopuses have no bones. If their ancestors did not have any bones either, it would be super hard for scientists to find fossils since everything inside the body must have dissolved over this long period of time, leaving behind no evidence whatsoever of its existence.
Luckily, scientists found several old octopus fossils preserved in limestone. Yet, they just made things more complicated. One fossil revealed an octopus ancestor had 10 limbs.
Other findings led to the assumption that the octopus’ ancestor once had a shell. Then around 270 million years ago, it started incorporating, say swallowing, the shell inside. The shell was then replaced by a soft tissue that covered the entire body. As you can see, that does not explain in any way how octopuses grew eight limbs.
Scientists are still figuring out how octopuses evolved and grew to their current shape and body composition. But for the time being, we know that there are 300 different octopus species, all of which have eight limbs.
These 300 different octopus species range widely in size, thanks to having different limb lengths. The largest species is the giant Pacific octopus. It weighs about 15 kg and has an arm span of 4.3 metres. The arm span is the distance from the tip of one arm to the tip of another. The most giant octopus ever recorded had an arm span of nine metres.
Every octopus’ eight limbs are divided into four groups of two. They extend from the head, all attached to one another at the base. They surround the octopus’ mouth and branch out in an inverted triangular shape in all directions, covering 360°.
The octopus uses its two back limbs to walk on the ocean floor. That is why they are called legs. The remaining six limbs are used to look for food and grab things, so they work like arms. To ease things up, we will just call them all arms.
Most octopuses have their arms covered with suckers, mainly arranged in two rows from base to tip. Looking like little cups, these suckers have a tremendous holding/sucking ability. But this arrangement does not necessarily apply to all octopus species. The glass octopus, for instance, has only one row of suckers on each arm. Some other species do not have any suckers at all.
The total number of suckers per octopus varies based on the species. The giant Pacific octopus, for instance, has a sum of 2240 suckers on all arms. Assuming that each arm has an equal number of suckers, then there are 280 suckers on each arm! Is that not just magnificent?
Suckers on each arm also have different sizes. Since arms have a triangular shape, wide at the base and narrow at the tip, suckers near the base are large compared to those near the tip.
Now let’s explore how mighty these suckers are.
Suckers are exceptionally vital for the octopus to survive. They are used for positioning, exploring the environment, foraging and holding food.
Every sucker consists of two main parts. The first is what we see on the outside, a shallow socket which we commonly call the cup, while scientists call it the infundibulum. Under the cup is a hollow socket called the acetabulum. Both parts are strong muscles, covered with a thick skin-like substance and connected through an opening.
As the substance covering every sucker used for sucking, it is constantly shed and renewed.
Every sucker is also connected to a different muscle. This means the octopus can control each of them independently from the others. It, the octopus, can rotate its suckers in any direction at the same time. It can even increase the suckers’ lengths to twice as much.
When a sucker touches an object, the opening between its two parts closes, and the cup flattens, taking the shape of that object. As the sucker is supported by powerful muscles, it does not allow any water to get in between it and the object, so it firmly sticks to it.
With this tremendous power, the octopus can hold and pull the object.
Suckers are so powerful that they can stick to any kind of surface with any sort of texture. It does not matter if it is rigid, smooth or uneven. They can also hold objects weighing up to 16 kilograms. Besides, the octopus uses them to break the hard shell of clams and crabs to eat what is inside them.
Interestingly, suckers do not stick to the upper surface of the arm. Scientists found that the skin of the octopus, the soft tissue that covers the entire body, produces a particular chemical material that disables the suction of the suckers.
All suckers have an enormous number of taste buds. In fact, they have more taste buds than there are in the human tongue. So they intensify the octopus’ sense of taste and allow it to find out about food without moving it to the mouth.
We can also think of the suckers as fingertips. Besides tasting, the octopus can learn so much about any object with only a little touch. Suckers have chemotactic sensors which activate the octopus’ sense of touch. Through that, it can get an idea about what kind of object it is touching and whether it is moving or still.
It is known that neurons are the nerve cells found in the brain. They are responsible for the brain activity and the way it controls the body. For the miraculous animal we have in hand today, things are a little different yet undoubtedly majestic.
Over 60% percent of the octopus’ neurons are found in the arms. Do you know what that means? That means the octopus does not have just one brain, that is found in the head. But it also has eight more little brains found in the arms.
Consequently, each arm can work independently, and each can do a completely different function. At the same time, the octopus’ primary brain can still focus on something completely different and much more critical.
Well, this is the mere definition of multitasking. While two arms are looking for food, another is recognising a piece of a shipwreck, and a third one is tasting some seaweed, the main brain can stay occupied by looking out for predators.
2. The great white shark’s teeth
“We are going to need a bigger boat.”
— Police Officer Martin Brody when he finally realised how giant the shark he was trying to kill was!
But this could not be further from the truth. Sharks are just notorious to us because of how we portray them in film. Almost everyone knows about the famous film franchise Jaws. It shows sharks as human-killing machines, doing nothing but waiting patiently for humans to go swimming or surfing to pull their legs and feed on them.
The truth is sharks do not even like to eat humans. Even their attacks on humans, despite being deadly due to the shark’s powerful bite, are very rare. Moreover, sharks do not intend to attack humans in the first place. They often mistake them for prey, especially when other fish are around.
So yes, sharks are no villains, only if lions and pandas are!
Like octopuses, sharks have many species found in different waters around the world. They are diverse, ranging in size from 17 cm to 12 metres.
The most common shark species is the great white shark. This is the one that appeared in the Jaws films and the one that usually comes to mind when most of us hear the word shark.
OK. Do you remember Bruce, the vegetarian shark from Disney’s epic film Finding Nemo (2003)? It was a great white shark. His friends, Anchor and Chum, are two other super distinct shark species, the hammerhead shark and the mako shark.
The great white shark is found around the coasts of all the world’s oceans, including the Pacific, the Indian, and the Atlantic Oceans. Males are notably smaller than females, measuring up to 4 metres in length. However, females range in length between 4.6 and 4.9 metres.
Although it is called white, this shark’s back and fins are grey. It is the underparts that are white. Besides its tremendous size, another thing the great white shark is famous for, the very thing that earned it the bad reputation, is its numerous razor-sharp teeth.
Sharks cannot be sharks without teeth. Interestingly, every species has a different type of teeth highly suitable for its diet. Since the great white shark feeds on dolphins, sea lions and small whales, it needs teeth that can bite and cut such large prey into smaller, swallowable pieces. That is why its teeth are triangle-shaped.
Like humans and all animals, the great white shark has teeth on its upper and lower jaws, yet it is their size and number that differ. The teeth on the upper jaw are triangular, while those on the lower jaw are pointed. The edges of all teeth are serrated, sawlike, which adds extra power to the bite.
What is even more fantastic about this shark’s teeth is their significant number as well as arrangement. The great white shark’s teeth are arranged in several lines. Those on the first line, the outermost teeth, are called functional teeth. These are the main ones that the shark uses to bite.
Each of these functional teeth accounts for a row, behind which is a series of teeth known as replacement teeth. Surprisingly, all these teeth are not fixed but movable. When a functional tooth is lost, it falls off, and the first replacement tooth in line immediately moves forward to replace it.
This is no magic. Tooth replacement is made easy because the shark teeth are not embedded in the jaw bones like ours. Instead, they are set in the gum, which makes it easy for the teeth to be replaced.
Tooth replacement happens pretty often because the great white sharks usually lose their teeth while attacking and biting prey. It happens every week because sharks lose at least one tooth per week. The process of replacement itself happens in only one day.
OK. If the great white shark loses, replaces, and grows new teeth all the time, how many does it have at a given moment? How many does it grow in a lifetime?
First of all, let’s count the number of teeth the great white shark has at any given moment.
Well, the upper jaw has 28 functional teeth. Each one of them has a series of five or six teeth. On the other hand, there are around 25 functional teeth on the lower jaw, with each having five or six replacement teeth as well. Doing the maths, a great white shark typically has an average of 292 teeth.
As the shark replaces its teeth on a regular basis, it ends up having up to 35,000 teeth during its lifetime—great white sharks live around 70 years and sometimes more.
Interestingly, the ocean floor is almost covered with shark teeth. As they are made of calcium phosphate, this super hard material allows the teeth to survive for thousands of years and fossilise. Conversely, sharks and their skeletons dissolve rapidly and disappear.
Here we come to the end of episode three, where we discussed two amazing organs found in two fantastic marine animals, the octopus’ eight arms and the great white shark’s teeth.
In the first section of this article, we learned some interesting information about the anatomy of the octopus’ arms and how they work like little brains, thanks to possessing the majority of the nerve cells. We also studied the octopus’ suckers that cover the arms. We understood the tremendous power of those suckers and how they are used to touch, taste, hold, and carry objects.
Then we moved to another famous yet notorious marine animal, the great white shark.
Besides its great size and iconic dorsal fin that has scared humans for decades, this mighty shark enjoys razor-sharp triangular and pointed teeth used for hunting and eating prey.
Thanks to an exceptional tooth-replacement system, the great white shark ends up having up to 35,000 teeth during its 70-something-year lifetime.
We hope you found this article interesting as much as we loved writing it for you. Make sure you check part one and part two of this article series to know more about many animals’ majestic organs.