Difference Between Squid and Octopus

Main Difference

Squid and Octopus both are aquatic animals that live in oceanic waters. They belong to same species, family, and genus. Both of them are cephalopods. The basic difference between a squid and octopus is that a squid lives in the open oceans and prefer to live on the upper surface of the water, whereas octopus lives in the dens in the oceans and prefer to live under deep dark water. Both of them have eight arms each as they both are cephalopods. Squids have two additional tentacles for catching and killing the prey whereas octopus does the same thing with the eight sucker-lined arms.

Comparison Chart

	Squid	Octopus
What are they?	Squid is head-footed aquatic cephalopod animal that has eight arms and two tentacles.	Octopus is aquatic cephalopod that is also head-footed. It has eight sucker-lined arms.
Class	Cephalopoda	Cephalopoda
Phylum	Mollusca	Mollusca
Order	Teuthida	Octopoda
Kingdom	Animalia	Animalia
Anatomy	Squids have a flexible bone called pen. They have two fins on their head. They also have eight arms that have hooks and sucker rings on them. Other than that they have two long tentacles on the front.	Octopi have round mantle like heads that has eyes on them. They are provided with eight arms that has rows of suckers on them. No hooks and rings are present.
Shell	Squids have a solid structure inside their body which is only flexible bone inside them. This shell type structure is called pen.	Octopi does not have any bone, shell or any solid bone like structure in their body. They represent the pure Mollusca phylum instead.
Fins	Along with the long tentacles in front, squids have two fins on their head too.	Usually normal kind of octopi does not have fins on them. But some rare species living deep inside the dens may possess.
Size	Squids are larger in size than Octopus. Their average size range from 60cm to 13m. Some giant one were also found more than 20meters.	Their average size ranges from 1cm to maximum 5meters.
Diet	Squid eats fishes and shrimp as their permanent and favorite food.	Octopi eat the small sea creatures that are found near corals in deep sea like crustaceans.
Life Span	The average life span of squid is nine months to 5 years.	The average life span of octopus is 1 to 3 years.
Hunting	Squid, unlike octopus, does not use their arms for catching the prey. They catch and kill their prey by using their two tentacles that are long enough. They eat their prey in chunks.	Octopuses use their eight sucker-lined arms for catching and killing their prey. Octopus injects venom through the shell of their prey and paralyzes it. The flesh of the prey is dissolved with saliva.
Geographical Distribution	Squids are found in salty waters and ocean. Temperate water is best for their dwelling.	Octopuses are also found in temperate and salty waters. They more specifically prefer to live in deep oceans.

What is Squid?

Squid is an aquatic cephalopod animal that lives in the salty oceans. Squid prefer to live in the temperate regions and oceans where the water is warm enough. Often squids are mixed with octopi and are considered to be same or thought as kind of octopus. This concept is totally wrong as squids are very much different from octopus and possess their identity, Although squids belong to the same family like octopus and possess the same phylum Mollusca and Class Cephalopoda. But they order is different from octopi. They belong to the order of Teuthida unlike of octopus. Squids, unlike octopi, have a solid structure inside their body, which acts as a flexible bone. It is also referred as the shell of the squids, but it does not have a proper shape that shell usually possesses. Due to its shape that bone structure is termed as a pen. Unlike octopi, squids have two fins on their head, which help them to swim and most probably help them in coming to the surface of water quickly. Squids have eight arms that are sucker lined similarly to the octopi arms, but unlike octopus the squids possess hooks and sucker rings present on them. The squid also possesses two long tentacles on their front that are not present in the octopus. Squid, unlike octopus, use these two long tentacles to catch and kill its prey. Squid eat its food in chunks. Squid prefer to eat fishes and shrimp. Squids like to live in open water spaces and can be found in the surface layer of the ocean as well.

What is Octopus?

Octopus is cephalopod aquatic animals that live in the salty waters and temperate oceans. Octopus prefer to live in the dark deep dens in the oceans. Octopus does not have any shell in their body. They do not have fins and tentacles, unlike squids. Octopus has a round mantle head and eight arms that possess two rows of suckers on them. Octopus catch their prey with their arms and kill it by injecting venom into their body that paralyzes them. The average lifespan of an octopus is 1 to 3 years. Octopi normally range from 1cm to 5m in size.

Squid vs. Octopus

Squid is the cephalopod aquatic animal that lives in the salty oceans and prefers to live in open water spaces.
Octopus is the cephalopod aquatic animal that also lives in the salty oceans but prefers to live inside the dark dens and deep, dense water.
Squids have shell known as a pen, which is more like a flexible bone.
Octopi does not have any shell or any bony structure inside their body.
Squids belong to the order of Teuthida.
Octopus belongs to the order of Octopoda.
Squids have two fins on their head.
Octopi does not have fins, but some rare kind could possess
Octopi have eight arms lined up with two rows of a sucker.
Squids have eight arms that possess sucker rings and hooks on them.
Squids have two long tentacles.
Octopi does not have tentacles.
Squids have eaten fishes and shrimps.
Octopi eat crustaceans and other smaller organism living with corals.
Squids catch and kill their prey by their tentacles.
Octopi catch their prey by arms and kill it by injecting venom into their body.

Comparison Video