Difference between Octopus and Jellyfish

Key Difference: Octopus and Jellyfish are both invertebrates. Octopus belongs to the group of cephalopods. Cephalopod means feet around the head. Jellyfish belongs to the Phylum Cnidaria and Class Scyphozoa. Both differ in many aspects like anatomy, diet, etc. Unlike an octopus, a jellyfish does not have any heart, brain or blood.

An octopus is an aquatic animal which belongs to the group of cephalopods of Phylum Mollusca. Cephalopod means feet around the head. Octopuses belong to the family Octopodidae and group Octopoda. The most apparent characteristic of an octopus is its eight arms which usually bear suction cups. They do not have a protective outer shell. It contains a beak which is the only hard part present in the body of the octopus.

They have a short life span; for some species it even ranges to only six months. Octopus has three hearts. Due to the presence of copper rich protein hemocyanin present in the blood of the octopus, it is of blue color. An octopus defends itself by using mechanisms like ink sacs, camouflage and automising limbs. They are considered to be of high intelligence than any of the other invertebrates. The mobility of octopus is defined by crawling and swimming types of motions.

Jellyfish belongs to the Phylum Cnidaria and Class Scyphozoa. Jellyfish (Jellies or sea jellies) are the ones which are found floating freely in the oceans. They are usually transparent. They do not contain any bones. They vary in shapes and sizes. Most of the people consider it to be a fish due to its name, however it is not a fish. It belongs to a group of its own which is different from other animals. They lack backbones, heart, blood, brain, or gills.

The body of jellyfish is composed of mesoglea which is a non- living jellyfish substance. This body is coated by a layer of skin. Body of jellyfish is mainly composed of water, which tends to form around 90 percent of its body. They also have tentacles placed around their mouths. These are used for getting hold of prey. It is a carnivorous animal. Jellyfish and Octopus are different in many ways. Unlike an octopus, a jellyfish does not have any heart, brain or blood. Jellyfish are carnivores, whereas Octopus are omnivores.

Comparison between Octopus and Jellyfish:

	Octopus	Jellyfish
Classification	Phylum Mulusca, Class Cephalopoda, Order Octopoda, Superorder Octopodiformes, Kingdom Animalia	Phylum Cnidaria, Class Scyphozoa, Octopoda, Semaeostomeae, Kingdom Animalia
Found in	Shallow coastal waters. However, some can be found at great depts too.	Shallow and deep ocean. Few even inhabit freshwater.
Live in	Not in groups	Group
Example	Paroctopus bimaculatus., Octopus apollyoll	Common Jellyfish (Aurelia aurita), Compass Jellyfish (Chrysaora hysoscella)
Lifespan	1 to 3 years	Have a short lifespan with longest living species having life span to two to six months
Body type	Rounded, have eight long arms, lack a shell. Bite the prey with a pair of break like jaws	Bell shaped body with 90 percent of water content. They also have tentacles placed around their mouths. They lack backbones, heart, blood, brain, or gills
Diet	Omnivore	Carnivore
Attack on prey	They use piercing technique on the shells of the prey. Then they inject some poison which causes paralysis. Salivary enzymes released by them helps in getting the meet from the inner shell	Jellyfish stings the prey with its tentacles. It releases a venom which paralyses the prey.
Size	Ranges from 1 cm to 5 m in length	Most jellies range from less than half an inch (1 cm) wide to about 16 inches (40 cm)
Special Features	Eight arms with suckers and ink sack	Jelly-like body and long stinging tentacles
Color	Tan, Brown, Red, Orange, Blue, Purple	White, Blue, Pink, Yellow, Green, Purple, Red, Orange