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Octopus Classification & Characteristics

Joanna Tatomir, Amanda Robb
  • Author
    Joanna Tatomir

    Joanna holds a PhD in Biology from the University of Michigan and is currently working towards a degree in Veterinary Medicine at Michigan State University. She has taught a combination of ESL and STEM courses to secondary and university students.

  • Instructor
    Amanda Robb

    Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts.

Discover what an octopus is and learn unique octopus characteristics. See what phylum includes octopuses, the octopus classification, and the octopus description. Updated: 10/21/2021

Table of Contents


What is an Octopus?

Earth's oceans are inhabited by a wide variety of fascinating creatures. From sharks and dolphins to jellyfish and crabs, different parts of the ocean are characterized by unique populations of animals. The octopus represents one interesting animal found in the ocean.

Although sometimes confused with the squid, octopuses constitute a distinct species with their own anatomy and life history.

What kind of animal is an octopus? Octopuses are invertebrate cephalopods characterized by a large head with eight attached arms. Approximately 300 species of octopus can be found in oceans throughout the world. While a majority of octopuses live on the ocean floor, some species can be found living closer to the ocean's surface. Octopuses use their arms to catch prey, like crab, shrimp, and mollusks.

Because their bodies are invertebrate, or lacking a backbone, octopuses are able to change their body shape to hide from prey and potential predators. This also enables octopuses to fit through small cracks and spaces. Some species of octopus are also able to camouflage themselves using special skin cells capable of producing a variety of colors and textures. An octopus is also able to use a special muscular tube, known as a siphon, to forcefully expel water in order to escape from predators.

An octopus in an aquarium.


Some more interesting information about octopuses will be covered below in this lesson.

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  • 0:04 What Are Octopuses?
  • 1:17 Octopus Body Structure
  • 2:24 Octopus Venom
  • 2:57 Octopus Camouflage
  • 3:45 Intelligence & Reproduction
  • 6:05 Lesson Summary
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Octopus Classification

So is an octopus a mammal or is an octopus an invertebrate? When classifying living organisms, we use taxonomy, or the scientific method of organizing creatures based on their relatedness. Based on taxonomy, the octopus classification is as follows:

  • Kingdom: Animalia
  • Phylum: Mollusca
  • Class: Cephalopoda
  • Order: Octopoda
  • Family: Octopodidae
  • Genus: Octopus

Using this taxonomy, the octopus represents an invertebrate cephalopod. Invertebrate refers to the fact that octopuses lack a backbone, while cephalopod comes from the Greek words for "head" (cephalo) and "foot" (poda). So the name octopus literally translates into "head-foot." This name is used in reference to their anatomy, which essentially consists of a large head and eight attached arms.

The scientific name for an octopus includes its genus and species designations. Some examples of octopus species include the Octopus Australis, Octopus Macropus, and Octopus Wolf.

Octopus Characteristics

Octopus characteristics are highly variable depending on the specific species. However, there are some traits that are commonly found in octopuses.

Octopuses are incredibly smart animals, with the ability to use tools and recognize individuals. In some species of octopus, for example, the animal will use shells or rocks to build shelters for itself. Other species will use the venom-containing tentacles of the Portuguese man o' war to protect themselves. Some octopus species will use tools for killing their prey and when eating.

The ability to recognize different individuals is related to the octopus eye, which is as complex as the human eye. The eyes of an octopus are large in size and capable of moving independently from one another. The octopus can change its visual field by withdrawing or extending the eyes out from the head, and even by rotating the eyes up to 80 degrees in either direction. These characteristics of the octopus eye enable this animal to have a high level of visual acuity.

The octopus eye.

Octopus eye

Octopuses, such as the Mimic Octopus (Thaumoctopus mimicus), also have the ability to camouflage their bodies from predators and prey. The octopus possesses a special adaptation that allows it to change its skin's color and texture. Embedded within its skin are specialized organs known as chromatophores. Chromatophores contain red, yellow, and brown pigments, as well as radial muscles, that produce bumps and color patterns mimicking the environment in which an octopus is found.

An octopus using camouflage to disguise itself.

Octopus camouflage

Some other characteristics of octopuses include:

  • Size: 1/2 inch to 30 feet in length
  • Weight: up to 600 pounds
  • Diet: carnivorous, consisting of mollusks, crabs, and shrimp
  • Venom: contains proteins similar to snake venom, but the venom of a majority of octopus species is not harmful to humans. The Blue Ringed Octopus (Hapalochlaena lunulata) represents one venomous species of octopus.
  • Lifespan: 1 to 5 years

Octopus Description

The octopus has unique anatomy that is characteristic of cephalopods. As their name implies, the octopus has a large head with big eyes and a beak-like jaw. Attached to the head are four pairs of arms covered in suckers, or suction cup-type structures, that aid in capturing prey and using tools.

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Frequently Asked Questions

Is an octopus a fish or a mammal?

An octopus is neither a fish nor a mammal. Instead, octopuses are cephalopods related to squid and cuttlefish. The octopus is classified as one branch of mollusks.

What is an octopus classified as?

An octopus is classified under the phylum Mollusca and class Cephalopoda. They are invertebrate cephalopods with a high degree of intelligence and excellent visual acuity.

Is an octopus a mollusk or a cephalopod?

An octopus is an invertebrate cephalopod. As suggested by the root words of their name- cephalo (head) and poda (foot), octopuses are characterized by a large head with eight attached arms. However, cephalopods like the octopus are part of the phylum Mollusca.

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