While they may be visually similar, squid and octopi are quite different from one another. They live different lives and have varied body structures. They are both quite remarkable animals to study.

That being said, they also share numerous features, such as the ability to produce ink, change colors, use their tentacles for hunting, and use their beaks for breaking up their food. 

Both creatures hold a special place in mythological history, appearing in numerous stories and myths throughout history, including in tales of the Kraken and of the Gorgon of Ancient Greece. 

Squid (left) vs. Octopus (right) – a visual comparison

The Main Differences Between a Squid and an Octopus

Here are the top six main differences between a squid and an octopus: 

  • Shape: Squid have tubluar bodies with ten tentacles, opposed to octopuses which with a more rounded head and eight tentacles. 
  • Catching prey: Squid use two of their longer tenticles to catch prey, whilst octopuses can use all of their arms to find prey. 
  • Swim: Squid swim through the water backward. Octopus do this too, but also tend to use two tentacles to walk along the seafloor (as their arms are more fliexble).
  • Size: Squid are generally bigger than octopi.
  • Intelligence: Squid are throught to be less intelligent that octopi, although they are still both intelligent animals.
  • Habitat: Squid tend to prefer open ocean to live in, whilst octoposes prefer the seafloor as their home.

We’ll explore these changes and interesting facts about each ocean creature more below.

What is a Squid? 

The term “squid” is used to describe a type of soft-bodied molluscs. They are cephalopods of the Decapodiformes superorder. Squid are known for their rapid swimming ability, use of jet propulsion, and ability to actively hunt prey. They are also quite intelligent. Their natural predators include sharks, seabirds, sperm whales, and seals. 

They are consumed by people around the world and are particularly valued in Japanese commercial fisheries and in the Mediterranean. 

Squid in blue water
A squid in blue water

Squid Appearance 

Squids have elongated tubular bodies, unlike most octopi, and shorter heads. There are eyes on either side and ten arms. Two of which are feeding tentacles and are longer and slimmer than the other eight. There have been examples in which a squid while using its feeding tentacles, has been able to strangle a shark. 

Squid range in length from two inches long all the way up to an incredible sixty-five feet in length. They use their beak in order to eat the prey they catch, tearing it up into smaller bites and making it easier to consume. 

Squid have the remarkable ability to change color in order to signal and camouflage themselves. Their active camouflage allows them to match backgrounds protect themselves against predators. Their skin is covered by chromatophores that they can control, creating different colors. Some, like the firefly squid, can use light to create countershading, allowing their undersides to appear lighter than their uppersides. 

Squid swim through the water backward, propelling themselves with the water itself. They also, like fish, use their gills for breathing underwater. Interesting, squid also has three hearts. It’s believed that the giant squid has the largest eyes of any animal. 

Squid Habitat, Diet, and Mating Practices 

Squid are found in marine environments all over the world, but not all species live all over the world. Some prefer warmer or colder environments. They feed on a variety of sea creatures, including other squid, shrimp, and fish. They can use their feeding tentacles to grasp and kill prey. 

One of the best-known abilities in a squid’s repertoire is the ability to produce ink. Their ink glands eject a cloud of ink, allowing them to distract and escape from predators. The ink itself is made of melanin particles. 

Squid mating practices are quite interesting. It takes place in open water. The male selects a female and transfers the spermatophores to her. Some squid, like the Caribbean reef squid, change colors during the courtship process. Others, like the female bobtail squid, eat the sperm packets of males that they’ve mated with, according to Monterey Bay Aquarium Research Institute. 

What is an Octopus? 

Octopi are soft-bodied molluscs, like squid. They belong to the order Octopoda. It is combined with the class Cephalopoda to which squid belong. They are known for their long appendages or tentacles, two of which are used for walking along the seafloor. They come in a variety of shapes and sizes, meaning that their prey and natural predators vary. 

A pink octopud
An octopus has eight legs, unlike a squid which has ten

Octopus Appearance

The octopus, like the squid, has a beaked mouth and long tentacles. But, octopuses have eight, where squid have a total of ten. Their soft bodies are easily malleable, allowing them to move through small gaps. They also move through the expulsion of jet water, like squid. Also, like squid, they are thought to be quite intelligent. The octopus has the interesting ability to walk on two rear appendages along the seafloor while the other six seek out food. Their beaks are located underwear their arms, and they’re used to tear up food into smaller bits and make it easier to consume. 

Their arms are also covered in suckers, circular in shape. It creates a seal when pressed against a surface. Their eyes are located at the top of their head. 

The largest known octopus species is the giant Pacific octopus that weighs in at around 33 pounds and with an arm span of fourteen feet. But, much larger specimens have been claimed to exist. They lack a skeletal structure, part of what allows them to squeeze through small spaces. Unlike the squid, there are a wide variety of body shapes among octopi. Some are quite small and rounded while others are longer and slimmer. For example, the Grimpothethis or dumbo octopus belongs to the former body shape category. 

Octopus Habitat, Diet, and Mating Practices 

Octopus live throughout the ocean but prefer areas of coral reefs and among the seed. Some live in deeper areas of the ocean, including abyssal depths. 

dark octopus
An solitary octopus in the dead dark sea

When reproducing, the male uses one arm, known as a hectocotylus, to move the packets of sperm into the female’s mantle cavity. Like with squid, there are a few species that change color while undergoing the courtship and reproduction process. With the giant Pacific octopus, the female lays strings of eggs in a crevice and guards them for months, around a total of 160 days. 


What is the difference between an octopus and a squid? 

Octopi (plural for octopus) have more varied body shapes, are generally smaller, have eight arms, and have rounded heads. Squid, on the other hand, have ten arms, have two fins on top of their heat, and a rigid backbone. 

Is calamari a squid or an octopus?

Calamari is squid but is often confused with octopus. The two animals are both eaten, although squid is more common. 

Which is bigger, squid or octopus?

Squid generally grow to be larger than octopi, between 60 centimeters to 20 meters long. Octopi, on the other hand, only reaches between one centimeter and nine meters long. 

What is the largest squid in the world?

The largest squid in the world is the giant squid which can grow up to forty-three feet or thirteen meters long. 

Who is smarter…squid or octopus?

Squid are generally believed to be the less intelligent of the two species. But that doesn’t mean that squid are unintelligent. The opposite is true, in fact.