Long arm octopus (Octopus minor)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Mollusca · Class: Cephalopoda · Order: Octopoda · Family: Octopodidae · Genus: Octopus.

Accepted name: Octopus minor · Authority: (M. Sasaki, 1920) · Taxonomic status: accepted · AphiaID: 342002.

Synonyms and superseded combinations recorded for this taxon: Octopus minor minor (M. Sasaki, 1920); Polypus macropus var. minor M. Sasaki, 1920; Polypus variabilis M. Sasaki, 1929; Polypus variabilis var. pardalis M. Sasaki, 1929; Polypus variabilis var. typicus M. Sasaki, 1929.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=342002 (CC BY 4.0). Accessed 2026-09-23.

Biology and life history (SeaLifeBase)

Measured values published by SeaLifeBase for Octopus minor. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Maximum length: 70 cm · Common length: 30 cm · Depth range: 0–200 m · Habitat zone: benthic · Vulnerability index: 48 of 100 · Fishery importance: commercial.

SeaLifeBase notes: The species is light to dark gray in color, but when in danger or stimulated, it turns to dark red (Ref. 83447). Its mantle length is 8 cm (Ref. 96968). Maximum depth from Ref. 106826. Benthic, littoral species to a depth of 200 (Ref. 106826). Found on mud and mud sand (Ref 112117). Feeds on crustaceans. Common bait are small live crabs (Ref. 112117).

Source: SeaLifeBase species summary (SpecCode 58008) — https://www.sealifebase.se/summary/Octopus-minor.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-23.

Distribution and occurrence records (GBIF)

170 georeferenced occurrence records for Octopus minor are published through GBIF from 3 countries or marine areas. The map above plots 28 distinct locations from a sample of 170 records, omitting 12 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: Korea, Republic of (164); Japan (4); China (2).

Marine regions with a valid WoRMS distribution record: West North Pacific.

Source: GBIF Occurrence Search (taxonKey 2289697) — https://www.gbif.org/occurrence/search?taxon_key=2289697&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=342002 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-23.

Conservation status (IUCN Red List)

The IUCN Red List assesses Octopus minor (Sasaki, 1920) as Data Deficient (code DD). No trend, population estimate or threat analysis is given here, because none is available from this source without the Red List API; follow the source link for the full assessment, including its date.

Source: IUCN Red List of Threatened Species (taxon 83457578) — https://www.iucnredlist.org/species/83457578/0; GBIF IUCN Red List category endpoint (taxonKey 2289697) — https://api.gbif.org/v1/species/2289697/iucnRedListCategory. Accessed 2026-09-23.

Description and natural history (Wikipedia)

O. minor carries cultural and economic value in the countries in which it is found. It is important commercially to the fishing communities in Korea, where it is known as nakji, and contributes to the $35 million octopus industry. It is a Korean seafood, commonly referred to as nakji (). The octopus is served both cooked and raw, and is often a snack during sporting events.

There have been multiple findings concerning the physiological makeup of O. minor. It has been shown to host a dangerous parasite, while also demonstrating the ability to adapt its morphology to a wide range of environmental conditions. These characteristics have increased interest in the species and its genome has been mapped.

This species was published as one subgroup of the species, Polypus macropus var. minor Sasaki, 1920 by Madoka Sasaki, Japanese Malacologist. Later, he moved it to another species, Polypus variabilis Sasaki, 1929 var. minor Sasaki, 1920, to distinguish it from P. macropus (=Callistoctopus macropus). In 1965, Iwao Taki transferred the name to Octopus minor (Sasaki, 1920). Sometimes referred as Octopus' minor, because genus Octopus is paraphyletic.

Kaneko et al. (2011) noted that O. minor is the member of genus Callistoctopus Taki, 1964 morphologically and phylogenetically based on mtDNA (COI and COIII); they subsequently renamed it into Callistoctopus minor''' (Sasaki, 1920). This relationship is supported by subsequent research teams in their own phylogenetic analyses. Several researchers still use the old name "Octopus minor", as the World Register of Marine Species still considers it a species of Octopus.

Their body surface is mostly smooth, with small pimples scattered on the dorsal surface. Live O. minor shows red-brown with light yellow spots on dorsal surfaces. It can be identified by its grey colouring which matches the sandy plains in which it is commonly found, however when it finds itself threatened or in danger, it will shift its coloration to a dark red.

Arms are thin and remarkably unequal in length. The first arm, the longest one, is about 80% of total length, which is twice length of third or fourth arms.

Funnel organ is VV-shaped.

Male has a hectocotylized arm to use for the mating. It is formed on right third arm, about half length of the left third arm. Ligula, the tip of the hectocotylized arm is large, spoon-shaped about 10–20% of the arm with about 42–48 suckers. Mature male also has enlarged suckers around level of 8th or 9th sucker pair, largest on the first arms.

The O. minor reaches a mantle size of 18 cm with arms of up to 65 cm. It is on the smaller side of its class, compared to colossal squids which can reach lengths of over 10 metres (33 feet).

Feeding O. minor, like other octopus populations, possesses predatory traits. O. minor's diet coincides with that of other bottom-dwelling octopuses, with over 50% of its prey being fish, 25% by shellfish such as whelks and clams, the remainder being made up of crustaceans such as crabs, along with annelids and nematodes, other commonly found species sharing their habitat with O. minor. The smaller size of the octopus means rejection of larger species including rock scallops and large fish.

The benthic nature of O. minor allows it to move between rocks and through crevices. Once it has identified its prey, it makes a sudden pounce, using its suckers to grip on and pull it in. The O. minor preys on smaller animals by trapping them in the web-like structure of its legs. The O. minor injects its prey with a paralyzing saliva, using miniature teeth at the end of its salivary papilla to dismember them. When targeting shelled molluscs, the O. minor creates a toxic saliva that enables the calcium carbonate of the shell to be broken down. Once the outer protection is penetrated, the prey's muscles relax, allowing the octopus to remove and eat its prey's soft tissues.

Feeding intensities differ between the males and females of the species. Different intensities revolve around the ovarian maturation calendar of the female octopus. From the months of April to July the intensity of feeding in females decreases, while in males it increases. While 10 different taxa have been identified within the stomach of the O. minor, the family Gobiidae was most prevalent during the female's ovarian maturation.

Different to other multi-limbed hydrostats such as crabs, the O. minor performs movements using all eight independent limbs. The arrangement of muscles within its arms allows for movement in any direction. Movements of the O. minor involve crawling between rocks and crevices, and swimming with its dorsal fin in a leading position. Jet propulsion is another form of locomotion also used by the O. minor. The process of crawling involves the use of the octopus's suckers. Some are used to grip to surrounding environments allowing the octopus to pull itself forward with its legs. Others push from behind. This process is repeated until a change of locomotion is performed.

Source: Wikipedia: Octopus minor — https://en.wikipedia.org/wiki/Octopus_minor (CC BY-SA 4.0). Accessed 2026-09-23.

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