Learn through this article all about the octopuses (order Octopoda), which are cephalopod molluscs, of which there are approximately 300 known species. Some of these creatures are consumed by humans, and their main feature is their eight arms.
It is important to mention that their scientific name is Octopoda, which is derived from the ancient Greek ὀκτώπους or ὀκτά-, a compound form of ὀκτώ (okto, «eight») and πούς (pous, «foot»).
Table Of Content
- 1 Main Characteristics.
- 2 Are the Octopus Smart?
- 3 Life Cycle
- 4 How do Octopuses Reproduce?
- 5 Octopuses’ Habitat and Distribution
- 6 What do Octopuses Feed On?
- 7 How is the Octopuses’ Camouflage?
- 8 Octopuses’ Defense Mechanism
- 9 Main Threats
- 10 The Octopuses and Science
- 11 Some Octopuses’ Curiosities
- 12 The Vampire Squid
Octopuses are solitary creatures, which depend on their eyes to survive in nature. They aren’t able to hear or make sounds. They are considered to be one of the most fascinating creatures of aquatic life due to their very different body. They have a skull, where the brain is located, but interestingly it doesn´t contain any bone. Apart from that they have 3 hearts which is also an interesting and outstanding aspect of their anatomy.
The octopods can move through the water with speed and grace. When they move, their eight arms move behind them. If they lose one of their arms due to an injury, in a very short time a new one replaces it.
The lack of a skeleton allows them to squeeze through places that are too small compared to their size. They usually hide in slits and tiny holes to avoid predators and not being detected in the water.
The head of an octopus is very large, has a very strong beak in the mouth that is sometimes difficult to notice and each of the eight arms has small suction cups at the ends. If the body of an octopus is cut in half, it would be perfectly symmetrical on both sides.
Octopuses have three hearts, two of which pump blood through the gills to each side of the body. The third is responsible for pumping the blood through the rest of the body. Their gills aren´t noticed unless we observe their body carefully. These organs help them with breathing as water circulates through them.
The food they eat must be the size of a bite to pass through the esophagus, and then pass through the digestive tract and into the stomach. Another gland allows them to create and maintain the venom they inject in their prey to immobilize them, without which they would have difficulties to hunt and feed themselves. Many times they rely on their powerful beak to break the shells of their prey, but when they can’t , they have a very powerful suction capacity to remove them from the shell.
The octopuses’ nervous system is controlled by the brain and is very complex. The interesting thing is that they lack of hearing organs that is, the octopuses are deaf. They have a sack where the ink they release is produced to escape from any danger. Actually, the responsible for producing the ink is a gland and the amount of ink depends on the species of octopus and size.
The octopuses can perform different movements thanks to their general anatomy. They are often seen walking at a leisurely pace, dragging themselves by bending their arms at different angles, swimming quickly to avoid danger or to capture their prey, or moving away extremely quickly thanks to their jet propulsion system.
The vision of an octopus is very good and they use it to move better through the water or realize when they have a predator nearby.
Let’s learn more about them
The giant Pacific octopus (Enteroctopus dofleini) is often cited as the largest octopus species in the world. Adults generally weigh around 15 kg, with an arm of up to 4.3 m. The largest specimen of this species that was scientifically documented was an animal of 71 kgms.
Octopuses with bigger size than the giant pacific octopus have been also reported: a specimen was registered with a weight of 272 kg and with an arm of 9 m. On the other hand, the smallest octopus in the world is the wolfi Octopus, which measures around 2.5 cm and weighs less than 1 g.
The Octopuses’ Ink Bag
The ink back of an octopus is located below its digestive gland. A gland attached to the sac produces the ink and the sac stores it. The bag is close enough to the funnel for the octopus to shoot the ink with a jet of water. Before it exits the funnel, the ink passes through the glands that mix it with mucus, creating a thick, dark spot that allows the animal to escape from a predator. The main pigment in the ink is melanin, which gives it its black color.
Are the Octopus Smart?
The octopuses are very intelligent, but the scope of their intelligence and capacity for instruction are not well defined. Labyrinth exams and problem solving have shown evidence of a memory system that can store both the short and long term retentive.
It is not known precisely what provides the learning skills to the adult octopuses’ behavior. Young octopuses don’t learn anything from their parents, since adults don’t provide parental care beyond attending to their eggs until young octopuses are born. In laboratory’s experiments octopuses can easily be trained to distinguish between different shapes and patterns.
It has been reported that they practice observational learning, although the validity of these findings is controversial. Octopuses have also been observed in what has been described as a game, which is to drop some bottles or toys repeatedly in a circular current in their aquariums and then catch them.
Octopuses have a relatively short life expectancy; some species live only six months. The Pacific giant octopus which is one of the two largest species of octopus, can live up to five years. The life of an octopus is limited by reproduction: males can only live a few months after mating and females die shortly after they lay their eggs.
How do Octopuses Reproduce?
Like all cephalopods, octopuses are dioic creatures, that is, their individuals belong to one of both sexes. Although it is difficult to distinguish a male from a female during their juvenile stage, in adulthood they show a clear sexual dimorphism. In the males, of smaller size, the third right arm is transformed in its final section and works like a penis known as hectocotylus. Two of their arms have one or two pairs of enlarged suckers, characteristics all of which adult females lack.
During copulation, the male introduces the hectocotylus into the female’s paleal cavity and deposits its sperm into it. The octopuses are promiscuous and, as in other cephalopod species, there is probably sperm competition: the sperm of one male can be removed by that of another that copulates later. After fecundation, the female looks for a place to lay her eggs, a cave or rock of sufficient amplitude, hidden and easy to defend.
The female places the eggs in strings attached to the ceiling of the cave at one end, forming clusters. The embryonic development lasts from one to four months, depending on the water’s temperature. During this time the female remains quartered in her lair, aerating, cleaning and protecting the laying. She doesn’t feed, but she uses her reserve substances to survive. When the embryo reaches the appropriate size inside the egg and the yolk sac has been almost completely consumed, hatching occurs. Then, the mother, exhausted and worn out, dies.
A newborn octopus is morphologically similar to an adult. The embryonic development is direct, there is no metamorphosis with different larval stages, as in the other mollusks. This phase of an octopus’ biological cycle is called paralarvae. After a more or less prolonged period of planktonic life in deep waters, the paralarvae approaches the coast and settle to the bottom. The young octopuses have a huge capacity to hunt live prey, as well as a wide repertoire of chromatic and postural responses that help them hide from their predators.
The octopuses’ reproductive organs mature due to the hormonal influence of the optic gland, but cause the inactivation of their digestive glands, which causes the octopus to die of starvation. It has been confirmed that by means of the experimental extirpation of both optical glands after the spawning, the upbringing ceases and the feeding, the growing, and longer lives are resumed.
Let’s watch them mating
Octopuses’ Habitat and Distribution
Octopuses only live in the oceans because of their need for salt water. They can adapt to different places although coral reefs are their most common habitats. They create dens where they commonly live which can be cracks or even under rocks.
They are able to live in different water temperatures. What is very interesting is that the species that live in the warmer bodies of water are much smaller than those that live where it is colder. The fact that they can be so adaptable to different areas of water is one of the reasons why the various species have been able to survive for millions of years.
While it is true that most octopus species live on the ocean floor, some of them also live very close to the surface. The offspring of most octopus species live on the surface of the water when they first emerge from their shell, which makes them very vulnerable to different predators.
What do Octopuses Feed On?
At the ends of their arms, octopuses have suckers, which are structures that contain sensors to taste their food. These animals are very particular in terms of the taste they want in their meals, and they even pass on a food that is readily available, if they are not interested in its taste, even if they need to eat desperately to survive.
The octopuses have a very strong and powerful beak in their mouths, which they use to get the prey and dismember them. They swallow the pieces of whole food and what they consume mainly are mollusks and crustaceans, although they also eat several types of fish and snails. Sometimes they feed on smaller species of octopus they find around, especially when they can’t find other sources of enough food to survive.
Many of the foods that octopuses consume have shells. Surprisingly when they are unable to remove food from their shell, they release a type of toxin that quickly dissolves the tissues that connect the prey to its shell. This behavior may seem simple, but researchers have observed how complex it can be to carry it out in nature. The octopuses know when they should release the toxin and in what quantity. With some prey they make two holes and introduce the toxin into each of them, with others they only make a hole. It is believed that they have some instinctive connection that allows them to differentiate what they have to do in each case to obtain food.
The octopuses almost always feed duringnight since they are able to see well in the dark, in fact the turbid waters give them the advantage over their prey. They can hunt during the day, although this happens when they are very hungry or have a good chance. They are incredible predators that can mix very well in their environment to approach their prey without being recognized.
The suckers in their arms also help in capturing the prey because they have a sticky residue from which it is very difficult to escape. The food they eat passes through the esophagus and goes directly to the brain area. Then they are taken back to the digestive system.
How is the Octopuses’ Camouflage?
The octopuses use camouflage to hunt and to avoid predators. They employ specialized cells of their skin that change its appearance by adjusting its color or opacity. They can also adjust its reflectivity which contains yellow, orange, red, brown, or black pigments; most species have three of these colors, while some other species have two or four.
Other cells that change their colors are the reflecting iridophores and the white leucophores. This ability to change color is also used to communicate with each other or notice the presence of other octopuses. Octopuses can create distracting patterns with waves of dark coloration throughout the body, which is known as the «passing cloud.» The muscles of the skin change the texture of the layer to achieve a camouflage, in some species, the mantle can take the appearance of algae tip among others.
Octopuses’ Defense Mechanism
Besides humans, octopuses can be prey to some fish such as sea otters , pinnipeds, cetaceans and other cephalopods. For this reason they usually hide by means of camouflage and mimicry.
The blue rings octopus is considered the most poisonous octopus in the world. This animal uses its poison when it is threatened; the exposure of this poison is shown through an iridescent warning.
They also use distraction as a defense system, using a cloud of ink injected from their bag, which is believed to reduce the efficiency of the olfactory organs of some predators as well as their prey.
Another one of its defenses is also its amputated arms, since they still move after being amputated and they use them to distract their predators while they escape. These mollusks are able to replace these arms as some lizards and crabs do.
Some species for example the Mimo octopus can combine the flexibility of its body with its ability to change color, to mimic other more dangerous animals such as lionfish, sea snakes and eels, which is why it is called the mimic octopus.
Some people’s common question is if the octopuses are in danger of extinction. Currently none of its species has this problem, so the biggest concern is the water’s quality because the octopuses are susceptible to pollution.
On the other hand, human beings use their flesh as food, and there are also other important predators of which we will know below.
Octopuses’ Main Predators
There are different types of predators that consider octopuses as an excellent food. Some of the predators that this mollusk has to battle are usually large fish, seabirds and some varieties of whales. In some areas, they also have to worry about eels and dolphins.
It seems that when the normal food sources for this type of animal are hard to find, they will become more dependent on the octopus. Given the reduction in the number of sharks and dolphins , these predators have become a minor problem for the octopuses. The bigger octopuses fight violently for their survival against this type of predators, and that is why they are often left alone unless there is nothing more that these predators can consume.
Octopuses can also bite, and when they do so they release a powerful poison in their bodies, which is also useful to consume their preys.
Parasites in the Octopuses?
Parasites that affect octopuses have been studied little, but these are known to be the middle and final hosts of various cestode parasites, some copepod nematodes and 150 species of protists and metazoans. Octopuses have an innate immune system, and their hemocytes respond to phagocytosis, encapsulation, infiltration or cytotoxic activities to destroy or isolate pathogens.
Haemocytes play an important role in the recognition and elimination of foreign bodies and for repairing wounds. Some animals in captivity have been found more susceptible to pathogens than wild specimens. Moreover, a bacterium called Vibrio lentus has been found in octopuses which causes skin lesions, exposes muscles, and octopus in extreme cases can die.
The Octopuses and Science
In ancient Greece, Aristotle commented on the octopuses’ abilities for changing color, both for camouflage and its signaling. In his story of Aristotle animalium, he observed that the octopus had a hectocotyl arm and suggested that it could be used in sexual reproduction.
The octopuses offer many possibilities for biological research, including their ability to regenerate limbs and to change their skin color. In addition, they also behave intelligently with a distributed nervous system, and make use of 168 types of protocaderins (humans have 58), which are the proteins that guide the neuron’s connections to each other.
The Californian octopus has a sequenced genome, which allows the exploration of its molecular adaptations, after having evolved, possessing an intelligence that is on par with that of mammals. These interesting creatures have been compared with hypothetical intelligent extraterrestrials. Their problem-solving skills, along with their mobility and lack of rigid structure allow them to escape from supposedly safe tanks in public laboratories and aquariums.
Thanks to their intelligence, octopuses are used in some countries as experimental animals in which surgery can’t be performed without anesthesia, a protection that generally extends only to vertebrates. In the United Kingdom, from 1993 to 2012, the common octopus was the only animal protected by the Animal Law of 1986. In 2012, this legislation was extended to include all cephalopods in accordance with a general directive of the European Union..
Some research on robotics explores the biomimetic of the octopuses’ characteristics. The octopuses’ arms can move autonomously without their central nervous intervention. In 2015, a team in Italy built soft-bodied robots capable of crawling and swimming, requiring only a minimal calculation.
In 2017, a German company made an arm with a pneumatically controlled soft silicone clamp equipped with two rows of suction cups, which can grab objects such as a metal tube, a magazine or a ball and fill a glass by pouring water from a bottle all this inspired by the octopuses.
Some Octopuses’ Curiosities
Octopuses are mysterious creatures that have very peculiar characteristics, of which we will learn below.
Are the Octopuses Old?
Octopuses are millenary creatures. The oldest octopus fossil known belongs to an animal that lived almost 300 million years ago, during the Carboniferous period.
That specimen belongs to a species called Pohlsepia and is on display at the Field Museum in Chicago. Harmon Courage describes it as a «flattened cow patty» or a «globular sprinkle».
Octopuses in Gastronomy
Most octopuses for human consumption come from North and West Africa. Octopuses have been a popular food in East Asia, Spain, Greece and other countries for centuries, and have recently gained popularity in the US. Today, Koreans consume more octopuses. But that popularity has had an impact on octopus populations in the oceans around the world. According to the Food and Agriculture Organization of the United Nations, around 270,000 tons of octopuses are imported by several countries around the world each year.
The Vampire Squid
The vampire squid is called squid but in fact, it is more related to the octopuses, and they are grouped in the Octopoda sub order. Like an octopus, it has eight arms with spines in the middle, which makes it look like it is wearing a cape. In conjunction, with this dark mantle, its eyes (which sometimes glow red) make it look like a vampire in the depths of the ocean. When threatened, the vampire squid has a special ability instead of shooting the ink, offering a light show, which dazzles its opponent.
Let’s have a final look of them