How to Tell the Difference Between a Squid and an Octopus

Squid and octopuses both belong to the molluscan group Cephalopoda, which literally means "head footed." Because neither possess a shell like other mollusks and they both have eight legs they can often be difficult to tell apart. This article should help you distinguish between squid and octopuses.

Instructions

1. Appearance. Octopuses have eight sucker-lined tentacles. Squids have eight arms with suckers and in addition possess two specialized tentacles that reach out and capture prey. The head of a squid is generally longer and less round than that of an octopus.

2. Habitat. Octopuses live on the sea floor in dens and eat crustaceans that dwell there. Squid have no such dens and live in the open water, capturing fish and crustaceans that are freely swimming.

3. Size. Both octopuses and squids can be as small as one centimeter. While the largest octopus known is not more than 5 meters long, the largest squid can be upwards of 20 meters.

4. Behavior. Octopuses are solitary creatures, while squid can live in large schools.

Tips & Warnings

• Neither octopuses nor squids pose much of a danger to humans. Tales of giant human-eating squids are unfounded.