Octopus, a cold-blooded mollusk belonging to the Cephalopoda class, grouped with cuttlefish, nautiloid, and squids, has around 300 species. These giant-sized invertebrates, with their unique appearance, have been immensely popular as sea monsters in mythology, also being a part of several literary works.

Scientific Classification


Scientific Classification


Types of Octopus

List of Common Types of Octopus Species

  • Blue-ringed octopus
  • Atlantic Pygmy octopus
  • California Two-Spot Octopus
  • Caribbean Reef Octopus
  • East Pacific Red Octopus
  • Mimic Octopus
  • North Pacific Giant Octopus
  • Seven-Arm Octopus
  • Dumbo octopus
  • Smoothskin octopus
  • Blanket octopus
  • Flapjack octopus
  • Giant Pacific octopus
  •  Coconut octopus
  • Day Octopus


Appearance and Physical Description

Size: Most of them have an arm span of about 14 ft. while for species like the Giant Pacific octopus, it can be as much as 32 ft.

Weight: The adults approximately weigh 33 pounds, with the giant Pacific weighing about 110 pounds on an average.

Color: They can be found in a wide range of colors because their skin has specialized cells called chromatophores containing pigments of red, yellow, brown, black, and orange pigments. Most of them possess three of these colors, while some may have two or four.

Heart: It has three hearts. One is a systematic heart assisting in blood circulation throughout its body, while the other two are branchial hearts helping to pump blood into both its gills

Head: It is large, also containing the brain and mouth.

Mouth: The mouth is situated underneath its arms, also having a sharp and hard beak.

Octopus Mouth

Eyes: It has two big eyes situated on top of its head. The eye pattern is just like that of a fish, remaining enclosed within a cartilaginous membrane, joined to the cranium.

Mantle: It is a muscular structure with a hollow, bulbous shape, attached behind its head, having a majority of the crucial organs.

Gills: Octopuses have two gills contained in the muscular walls of the mantle cavity, through which they breathe. However, they do not have lungs.

Limbs: According to the recent studies, scientists have concluded that out of their eight limbs, two are legs, and the remaining six are arms. They swim and move about on the seafloor using their legs. On the other hand, their hands help them with eating and holding objects.

Teeth: They have tiny teeth arranged in multiple rows, placed within their radula, which is a spiked, muscular organ similar to a tongue.

Octopus Teeth

Skin: Their skin indeed has an interesting texture, with the presence of several cells helping in color change, as mentioned above. The skin’s muscles help to change the mantle’s texture, assisting them in camouflaging in a better way.  

For instance, in certain species, the skin can attain a spiky look, resembling algae. Diurnal octopuses dwelling in shallow water possess a complex skin structure than the nocturnal species inhabiting deep waters.

Nervous System: The nervous system is extremely complex, with only a portion of it confined to the brain, contained within a cartilaginous capsule. 2/3rds of its neurons are present in its arm’s nerve cords, helping them perform a host of reflex actions even when the brain provides no input at all.  


They may be found in every ocean worldwide like the East Atlantic, Pacific as well as the Mediterranean Sea. 

Where Do Octopus Live

Different species of octopus adapt well to several marine habitats. For instance, the Common octopus dwells in shallow tide pools when they are juveniles. The Hawaiian Day Octopus thrives on coral reefs. The Spoon arm octopus, on the other hand, dwells in abyssal plains at a depth of approximately 1000m, while the Cirrate octopuses thrive in deep-water regions. However, no species live in freshwater areas.

How Long Do They Live 

Octopuses have a relatively short lifespan, with certain species living for just six months. On average most of them do not survive for more than one or two years. The Giant Pacific Octopus is said to have the longest life expectancy, living for approximately five years. Reproduction is said to limit their lifespan as the males die postmating, while the females pass away shortly after the eggs are hatched.

What Do They Eat

The diet varies from one species to the other, though they commonly eat polychaete worms, crustaceans clams, whelks, fish, prawn, crabs, scallops, and spider crabs.

Octopus Tentacles

Behavioral Characteristics

  • They are generally solitary, mostly remaining confined in their dens, comprising of crevices located in hard terrains.
  • On capturing their prey, they mostly bring it to their den, where they can have it privately. Some tend to catch a higher amount of prey than what they can consume. Hence decayed or uneaten food could often be found lying around their dwelling places.
  • Though not territorial, they prefer living within the domains of their range that they may leave while searching for food. Their navigation skills assist them in returning to their den without even retracing the route.
  • They have a high level of intelligence, and several laboratory experiments show that they can adeptly differentiate between various patterns and shapes when trained to do so.
  • These species have slow locomotion, mostly crawling around along soft or solid surfaces when not in a hurry. Their fastest ways of moving around involve backward swimming or jet propulsion.


  • Their soft body helps them in altering their shape. Hence they can squeeze through small gaps flexibly, with ease, a perfect way to protect themselves against predators.
  • Because of the presence of chromatophores, they camouflage by changing their skin color for which they may stretch or relax the muscles to increase or decrease the size of their color cells.

  • They have an ink sac below their digestive gland, where an ink-like substance is stored. When in danger, the octopus ejects a dark, black, watery substance to distract their predator and flee away.
  • Their flexible bodies give them the ability to perform the moving rock trick, where they assume the shape of a rock and go at a slow pace to capture their prey.
  • They can even use their agile body stature to mimic sea snakes, eels, and lionfish to stay away from their predators.
  • The presence of a siphon, a moveable tube, facilitates respiration and locomotion. During breathing, the water gets into their mantle cavity, passes through the gills, and ejects out through their siphon. While moving about, expelling water through this tube again helps them to propel about conveniently.
  • Statocysts are sensory receptors, helping them to maintain balance and also hear any sound.
  • The suction cups or suckers present on their arms (also considered as one of their unique physical traits) possess chemoreceptors (specialized sensory receptors), aiding in tasting what they touch.
  • The tension sensors in its arms help it know when they are stretched out.
  • The presence of longitudinal, circular, and transverse muscles in its arms makes it easy for the octopuses to extend, contract, bend and twist their body in any direction or even keep it rigid if they wish.

Reproduction and Mating

There are more males than females; hence, the former may be at a tussle with each other to get hold of their prospective partner. The males often warn their competitors to stay away by flashing colors, and in case this does not work, they battle it out to win their mate.

During reproduction, the males use the hectocotylus (a specialized arm) that has a length of about 3 feet, to hold the sperms. The transfer mechanism varies from one species to the other. The male could come in contact with its mate and insert the sperm into her oviduct.  He may even give the arm to the female directly so that she could store it for the future in her mantle.

The female further fertilizes the eggs by spreading the sperm over them. In species like the Giant Pacific Octopus, the male changes the texture and color of its skin during courtship.

She is highly protective of her eggs, guarding them rigorously for approximately five months against any predators, as they take that long to hatch. During this time, the mother stops eating and hardly goes out of her den. She ensures the cleanliness of her eggs by aerating them well, as most of them may not hatch if proper care is not taken. Since they lose their parents early, most octopuses get on their own from the time they hatch.

Octopus Fish


1. How many brains does an octopus have?

It has nine brains in total. The entire nervous system is controlled by a central brain, while each of its eight arms has a small brain each, helping them in functioning independently.

2.  Does octopus have bones?

No, they do not have bones but a hydrostatic skeleton, giving them a flexible motion.

3. Is an octopus a mammal?

No, it is an invertebrate animal, lacking a spinal cord.

4. What is a baby octopus called?

When newly hatched, they are known as larvae, while the young ones are referred to as fry or hatchlings.

5. What is a group of octopus called?

A consortium

6. Where do octopuses come from?

The class of cephalopods to which the octopus belong were said to have originated from the nautiloid, which evolved 500 million years back. However, there are different theories regarding the evolution of these creatures.  

7. How fast can octopus swim?

They can swim at a speed of 25 miles/hour.

8. What eats the octopus?

Some of its predators include birds, large fish, certain species of whales, dolphins, and eels.

9. What color is the blood of an octopus?

Octopus has blue blood, mainly because of the presence of hemocyanin, a protein-rich copper, helping in the transportation of oxygen.

10. Can octopus live out of water?

They can, but for a couple of minutes, as staying out of water for a prolonged period could cause damage to their gills.

11. What sound does an octopus make?

They hunt silently, hardly making any sound, except that of their movement through the waters as they pass by.

12. Can an octopus eat itself?

There is specific evidence of octopuses suffering from self-cannibalism where they end up eating their arms, stress being the main reason.

13. What type of an immune system does the octopus have?

Their immune system is innate. The hemocyte responds to infection through encapsulation, phagocytosis, and infiltration.

14. How many tentacles does octopus have?

They do not have tentacles, and this term refers to their limbs.

15. What is the plural of octopus?

Octopuses; the forms octopodes (used in ancient history), and octopi are considered incorrect.

Interesting Facts

  • The Common Octopus can hear sounds ranging from 400 Hz to 1000 Hz, and hears 600 Hz sounds the best.
  • Their reputation as sea monsters has been famous in every mythology like Norway’s Kraken, Ainu’s Akkorokamui, and ancient Greece’s Gorgon.
  • These mighty creatures have appeared in shunga, Japan’s erotic art.
  • They have been used as the subject in a host of literary works like Toilers of the Sea by Victorian Hugo, and Octopussy by Ian Fleming.
  • People, particularly around the Mediterranean and coastal areas of Asia, consume octopus as a delicacy.
  • Their name is derived from the Greek words okto and pous translating to eight and foot, respectively.
  • Octopuses are the only acceptable plural form, while octopi and octopodes are not considered correct.
  • All of them are venomous, with the Blue-ringed octopus being the most dangerous, and their bite proving fatal to humans.
  • Because of their intelligence, in certain countries, they have been considered in the category of experimental animals.

Subscribe our newsletter

Enter your email here to stay updated with the animal kingdom