# Octopus vs Squid: Eight Arms, Ten Limbs and Two Very Different Lives

*Worldwide oceans · JUL 25 2026*

> Octopuses have eight arms, no internal shell and live on the seabed; squid have eight arms plus two longer feeding tentacles, a stiff internal pen, fins and a streamlined body built for open-water swimming.

Arms versus tentacles, reef-crawler versus open-ocean swimmer, internal shell versus none. How to tell octopus and squid apart.

## What are the key takeaways from this briefing?
- Octopuses have eight arms; squid have eight arms plus two longer feeding tentacles.
- Squid are streamlined with fins for open-water swimming; octopuses are soft-bodied seabed dwellers.
- Squid keep a stiff internal shell remnant (the pen); octopuses have none.
- Many squid suckers carry hardened rings or hooks; octopus suckers are simple cups.
- Both are short-lived, but female octopuses brood their eggs and die after hatching.

## Octopus vs squid: how to tell them apart

Both are cephalopods, both are molluscs, and they solve completely different problems. See the [octopus guide](/wildlife-guides/octopus/) and [squid guide](/wildlife-guides/squid/).

### Count the limbs

Octopuses have eight arms, all the same. Squid have eight arms plus two much longer feeding tentacles that shoot out to seize prey and retract — ten limbs in total, of two distinct types.

### Body shape says where they live

Squid are streamlined torpedoes with fins along the mantle, built for sustained open-water swimming. Octopuses are soft, rounded and finless, built for crawling, squeezing and hiding on the seabed.

### The internal shell

Squid retain a stiff internal remnant of the ancestral shell — the pen or gladius — that stiffens the body against swimming forces. Octopuses have lost it entirely, which is why they can pour themselves through a gap the size of their beak.

### Suckers

Octopus suckers are simple muscular cups. Many squid have suckers reinforced with hardened rings, sometimes toothed or modified into hooks — gear for gripping struggling fish in open water.

### Lifestyle and social behaviour

Octopuses are largely solitary ambush hunters and den-dwellers. Many squid species shoal, hunt in open water and communicate with rapid body-pattern changes visible to neighbours.

### Lifespan and reproduction

Both are short-lived, typically one to two years. Female octopuses brood a single egg clutch, stop feeding and die after hatching. Squid generally spawn and die shortly afterwards without extended brooding.

### Quick field test

Two limbs noticeably longer than the rest, fins on the body and a rigid torpedo shape means squid. Eight equal arms, no fins and a soft bag-like body means octopus.

**[Read the full squid wildlife guide](/wildlife-guides/squid/)** for IUCN status, population context and sources — or **[donate to WARN](/donate/)** to help fund the partner teams protecting wildlife on the ground.

## What do people ask about this briefing?
### What is the difference between an octopus and a squid?
Octopuses have eight equal arms, a soft finless body and no internal shell, and live on the seabed. Squid have eight arms plus two longer feeding tentacles, fins, a streamlined body and a stiff internal pen, and swim in open water.

### How many tentacles does an octopus have?
Strictly, none. Octopuses have eight arms. 'Tentacle' properly refers to the two longer, specialised feeding limbs that squid and cuttlefish have and octopuses lack.

### Can a squid squeeze through small gaps like an octopus?
No. A squid's stiff internal pen and rigid body prevent it. An octopus has no hard part except its beak, so it can pass through any gap the beak fits through.

### Are octopuses and squid related?
Yes, both are cephalopod molluscs, along with cuttlefish and nautiluses. They diverged a long time ago and specialised in opposite directions — one for the seabed, the other for open water.

## Which sources does this briefing use?
- [Smithsonian Ocean — Cephalopods](https://ocean.si.edu/ocean-life/invertebrates/octopuses-and-relatives)
- [IUCN Red List](https://www.iucnredlist.org/)

Human-readable page: https://worldanimalrescuenetwork.org/newsroom/octopus-vs-squid-key-differences/