An octopus is a soft-bodied, eight-limbed mollusc of the order Octopoda. The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like other cephalopods, an octopus is bilaterally symmetric with two eyes and a beaked mouth at the centre point of the eight limbs. The soft body can radically alter its shape, enabling octopuses to squeeze through small gaps. They trail their eight appendages behind them as they swim. The siphon is used both for respiration and for locomotion, by expelling a jet of water. Octopuses have a complex nervous system and excellent sight, and are among the most intelligent and behaviourally diverse of all invertebrates.
Blue-ringed octopuses, comprising the genus Hapalochlaena, are four extremely venomous species of octopus that are found in tide pools and coral reefs in the Pacific and Indian oceans, from Japan to Australia. They can be identified by their yellowish skin and characteristic blue and black rings that can change color dramatically when the animal is threatened. They eat small crustaceans, including crabs, hermit crabs, shrimp, and other small sea animals.
Ocythoe tuberculata, also known as the tuberculate pelagic octopus or football octopus, is a pelagic octopus. It is the only known species in the family Ocythoidae.
Opisthoteuthis californiana, also known as the flapjack octopus, or flapjack devilfish is a species of umbrella octopus.
The giant Pacific octopus, also known as the North Pacific giant octopus, is a large marine cephalopod belonging to the genus Enteroctopus and Enteroctopodidae family. Its spatial distribution encompasses much of the coastal North Pacific, from the Mexican state of Baja California, north along the United States' West Coast, and British Columbia, Canada; across the northern Pacific to the Russian Far East, south to the East China Sea, the Yellow Sea, the Sea of Japan, Japan's Pacific east coast, and around the Korean Peninsula. It can be found from the intertidal zone down to 2,000 m (6,600 ft), and is best-adapted to colder, oxygen- and nutrient-rich waters. It is the largest octopus species on earth and can often be found in aquariums and research facilities in addition to the ocean. E. dofleini play an important role in maintaining the health and biodiversity of deep sea ecosystems, cognitive research, and the fishing industry.
Amphioctopus marginatus, also known as the coconut octopus and veined octopus, is a medium-sized cephalopod belonging to the genus Amphioctopus. It is found in tropical waters of the western Pacific Ocean. It commonly preys upon shrimp, crabs, and clams, and displays unusual behavior including bipedal and quadrupedal walking as well as tool use.
Octopus cyanea, also known as the big blue octopus or day octopus, is an octopus in the family Octopodidae. It occurs in both the Pacific and Indian Oceans, from Hawaii to the eastern coast of Africa. O. cyanea grows to 16 cm in mantle length with arms to at least 80 cm. This octopus was described initially by the British zoologist John Edward Gray in 1849; the type specimen was collected off Australia and is at the Natural History Museum in London.
Callistoctopus macropus, also known as the Atlantic white-spotted octopus, white-spotted octopus, grass octopus or grass scuttle, is a species of octopus found in shallow areas of the Mediterranean Sea, the warmer parts of the eastern and western Atlantic Ocean, the Caribbean Sea, and the Indo-Pacific region. This octopus feeds on small organisms which lurk among the branches of corals.
Eledone schultzei, the brush-tipped octopus, is a rare species of octopus. It has previously been known by other taxonomic names (synonyms) including Eledone thysanophora and Aphrodoctopus schultzei.
Callistoctopus ornatus is a tropical species of octopus native to the Indo-Pacific region. Other common names include white-striped octopus and night octopus, in reference to its nocturnal habits. It was previously known as Polypus ornatus. C. ornatus is edible and was recorded in a Hawaiian market in 1914 by S. S. Berry.
Eledone gaucha is a species of octopus from the southern Atlantic Ocean. It is a predator of fish, crabs, lobsters and molluscs.
Grimpoteuthis bathynectes is a deepwater species of Grimpoteuthis (Dumbo) octopus first described in 1990. It is known from 13 specimens.
Grimpoteuthis innominata, commonly known as the small jellyhead, is a species of small, pelagic octopus described by Steve O'Shea in 1999 from two specimens, however several further specimens have since been identified. The genus Enigmateuthis was described to contain this species when described, but Martin Collins placed the species in the genus Grimpoteuthis due to uncertainty regarding the type specimen of Grimpoteuthis.
Octopus bimaculatus, commonly referred to as Verrill's two-spot octopus, is a similar species to the Octopus bimaculoides, a species it is often mistaken for. The two can be distinguished by the difference in the blue and black chain-like pattern of the ocelli. O. bimaculatus hunt and feed on a diverse number of benthic organisms that also reside off the coast of Southern California. Once the octopus reaches sexual maturity, it shortly dies after mating, which is approximately 12–18 months after hatching. Embryonic development tends to be rapid due to this short lifespan of these organisms.
Opisthoteuthis agassizii is a lesser-known, deep-sea octopus first described in 1883 by Addison E. Verrill.
Opisthoteuthis albatrossi is a cirrate octopus originally found off Kinkasan in Japan. This species was described from only four specimens. It is similar to Opisthoteuthis californiana; the two may be the same species. It is also similar to Opisthoteuthis japonica.
Opisthoteuthis bruuni is a species of finned cirrate octopus found along the western coast of South America. Their tissue is almost jelly-like, and they have short, round bodies.
Opisthoteuthis depressa, also known as the Japanese flapjack octopus, is an octopus found in waters near Japan.
Opisthoteuthis dongshaensis is a species of octopus located in the South China Sea.
Opisthoteuthis grimaldii is an octopus found near the Azores.
