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.
A cephalopod is any member of the molluscan class Cephalopoda such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.
Bigfin squids are a group of rarely seen cephalopods with a distinctive morphology. They are placed in the genus Magnapinna and family Magnapinnidae. Although the family was described only from larval, paralarval, and juvenile specimens, numerous video observations of much larger squid with similar morphology are assumed to be adult specimens of the same family.
Grimpoteuthis is a genus of pelagic cirrate (finned) octopods known as the dumbo octopuses. The name "dumbo" originates from their resemblance to the title character of Disney's 1941 film Dumbo, having two prominent ear-like fins which extend from the mantle above each eye. There are 17 species recognized in the genus. Prey include crustaceans, bivalves, worms and copepods. The average life span of various Grimpoteuthis species is 3–5 years.
The Bolitaeninae are a subfamily, in the family Amphitretidae, of small, common pelagic octopuses found in all tropical and temperate oceans of the world. The taxonomy of this taxon is not entirely certain; recent research suggests just two genera exist, Bolitaena and Japetella, both of which are thought to be monotypic by some authorities and under this view, the family would represent two very similar species: Bolitaena pygmaea and Japetella diaphana. However, currently a second species of Bolitaena, B. massyae is also recognised.
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.
The California two-spot octopus, often simply called a "bimac", is an octopus species native to many parts of the Pacific Ocean including the coast of California. One can identify the species by the circular blue eyespots on each side of its head. Bimacs usually live to be about two years old. They are closely related to Verrill's two-spot octopus. In 2015, the genome was sequenced.
Kiwa is a genus of marine decapods living at deep-sea hydrothermal vents and cold seeps. The animals are commonly referred to as "yeti lobsters" or "yeti crabs”, after the legendary yeti, because of their "hairy" or bristly appearance. The genus is placed in its own family, Kiwaidae, in the superfamily Chirostyloidea. The genus Kiwa is named after the god of shellfish in Polynesian mythology.
Aggregata is a genus of parasitic alveolates belonging to the phylum Apicomplexa.
The curled octopus, also known as the horned octopus, lesser octopus or northern octopus, is a species of cephalopod found in the northeast Atlantic, ranging from Norway to the Mediterranean, including the British Isles. The total length of an adult is around 50 cm, but their arms are often tightly curled. It immobilises and eats large crustaceans by drilling a hole through their shell. It is mainly by-catch in commercial fisheries of the north eastern Atlantic and Mediterranean, where the common octopus is the preferred species.
Eledone gaucha is a species of octopus from the southern Atlantic Ocean. It is a predator of fish, crabs, lobsters and molluscs.
Thermarces cerberus is a species of ray-finned fish in the family Zoarcidae. This fish, commonly known as the pink vent fish, is associated with hydrothermal vents and cold seeps at bathypelagic depths in the East Pacific.
The larger Pacific striped octopus (LPSO), or Harlequin octopus, is a species of octopus known for its intelligence and gregarious nature. The species was first documented in the 1970s and, being fairly new to scientific observation, has yet to be scientifically described. Because of this, LPSO has no official scientific name. Unlike other octopus species which are normally solitary, the LPSO has been reported as forming groups of up to 40 individuals. While most octopuses are cannibalistic and have to exercise extreme caution while mating, these octopuses mate with their ventral sides touching, pressing their beaks and suckers together in an intimate embrace. The LPSO has presented many behaviors that differ from most species of octopus, including intimate mating behaviors, formation of social communities, unusual hunting behavior, and the ability to reproduce multiple times throughout their life. The LPSO has been found to favor the tropical waters of the Eastern Pacific.
Opisthoteuthis calypso or calypso flapjack octopus is a species of genus Opisthoteuthis, which are known as the cirrate octopuses. Octopuses in this genus are known as the flapjack octopuses and can be found in a variety of oceans across the world.
Octopus insularis is a species of octopus described in 2008 from individuals found off the coast of Brazil, with a potentially much larger range.
Opisthoteuthis agassizii is a lesser-known, deep-sea octopus first described in 1883 by Addison E. Verrill.
Opisthoteuthis grimaldii is an octopus found near the Azores.
Bathypolypus sponsalis, commonly called the globose octopus, is a deep sea cephalopod that can be found in both the eastern Atlantic Ocean and the Mediterranean Sea. It possesses many morphological traits adapted to a deep sea environment, including large eggs, reduced gills, no ink sac, and subgelatinous tissues. A distinguishing factor are the relatively large reproductive organs. Their diet consists of predominantly crustaceans and molluscs, but they sometimes consume fish as well. Bathypolypus sponsalis usually dies quickly after reproduction and only spawns once in their lifetime. Sexually mature females have a mantle length of at least 34 mm and sexually mature males have a mantle length of about 24 mm. Juveniles are white and transition to dark brown then to dark purple once maturity is reached.
Opisthoteuths massyae is an octopus living in the eastern Atlantic Ocean.
Opisthoteuthis robsoni, also known as the deep-water umbrella octopus, is a deep-sea octopus living off New Zealand on the Chatham Rise. It has been found from 1,178–1,723 m (3,865–5,653 ft) below the surface. Not much is known about the octopus' habitat or life cycle, as only four specimens have been found. It occupies the benthic zone, or the seafloor and the water directly above it. O. robsoni eats large amphipods.
