Wildlife · Species comparisons
What is the difference between an octopus and a squid?
Octopuses have eight arms; squids have eight arms plus two longer feeding tentacles — both intelligent cephalopods with very different lifestyles.
In brief
Octopuses have eight arms and no shell; squids have eight arms plus two longer feeding tentacles and an internal pen (shell remnant). Octopuses are solitary benthic crawlers; squids are active open-water swimmers often found in schools.
By the WARN Research & Conservation TeamChecked against IUCN Red List & CITES sourcesLast updated
Octopuses and squids are cephalopod molluscs — jet-propelled, colour-changing predators with large brains relative to body size. Octopuses have eight arms, no internal shell and solitary benthic habits — crawling reefs and seabeds. Squids have eight arms plus two longer tentacles for striking prey, an internal pen (shell remnant) and open-water schooling behaviour in many species. Both live fast, die young — most species survive one to two years, breeding once before death.
8
Octopus arms — no tentacles
10
Squid limbs — 8 arms + 2 tentacles
500+
Cephalopod species worldwide
3 yrs
Typical maximum lifespan — most species shorter
Quick facts
| Octopus body | Soft, no shell — may squeeze through tiny gaps |
|---|---|
| Squid body | Internal chitinous pen supports mantle |
| Octopus habitat | Benthic — reefs, rock pools, seabed dens |
| Squid habitat | Open water — active swimmers, often in schools |
| Intelligence | Both solve puzzles; octopus farming raises welfare concerns |
| Giants | Giant Pacific octopus; giant and colossal squid |
Key takeaways
- Octopuses: eight arms, no shell, solitary benthic crawlers.
- Squids: eight arms plus two tentacles, internal pen, open-water swimmers.
- Both cephalopods — jet propulsion, colour change, large brains.
- Short lifespans — most breed once then die.
- Octopus intelligence raises welfare concerns about farming proposals.
- See WARN comparison for limb count, habitat and fishing pressure.
Limbs and hunting method
Octopuses capture prey with all eight arms — enveloping crabs, molluscs and fish in a web of suckers lined with chemoreceptors. Squids strike with two elongated tentacles equipped with hooks or suckers on clubs — grabbing prey and retracting it to the beak while the eight shorter arms hold and manipulate. Tentacles retract into pockets beside the eyes when not in use. This ten-limb arrangement is the quickest field distinction. Cuttlefish — a third common cephalopod group — have eight arms plus two tentacles like squids but with a cuttlebone and different swimming posture.
Body plan and movement
Octopuses lack an internal skeleton — boneless bodies squeeze through gaps an inch wide. They crawl on arms or expel water through siphons for jet propulsion over short distances. Squids have a stiff internal pen supporting the mantle — streamlined for sustained swimming in open ocean. Many squid species form schools — Humboldt squid hunt cooperatively in massive aggregations. Octopuses are solitary — meeting mainly to mate, often with cannibalistic risk. Colour change via chromatophores serves camouflage and communication in both groups.
Intelligence and lifespan
Octopuses demonstrate tool use — carrying coconut shells as portable shelters — and solve maze and puzzle tasks in laboratory settings. Squid cognition is less studied but schooling species show coordinated behaviour. Both have short lifespans: most breed once in semelparous death — females guarding eggs until starvation in many octopus species. Giant Pacific octopuses live three to five years; smaller species often one year. Proposed octopus farms raise welfare concerns given demonstrated problem-solving ability and solitary nature — unlike herd animals adapted to confinement.
Fisheries and conservation
Both groups support major commercial fisheries — calamari squid worldwide; octopus in Mediterranean and East Asian markets. Bycatch and overfishing pressure varies by species — many lack detailed stock assessments. Deep-water giant and colossal squids are rarely caught alive — most knowledge from washed-up specimens and sperm whale stomach contents. Climate change shifts distribution ranges — some squid species expand into warming waters while octopus populations respond to reef degradation. WARN’s marine hub links cephalopod guides to broader ocean fishing pressure context.