Bryan McAllister’s personal reference notebook
July 30, 2026Short & citedBlog
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Field Notes • Biology

Squid

Squid are a diverse group of marine cephalopod molluscs, usually with elongated bodies, eight arms, and two longer tentacles used for catching prey.

Updated July 30, 20261 min readCited sources

Squid are marine cephalopods with eight arms and two longer tentacles. Over 300 species inhabit oceans worldwide, including Canadian waters.

What it is

Squid belong to the class Cephalopoda, closely related to octopuses and cuttlefish. They have a soft, elongated body, large eyes, and muscular arms with suckers. Most species are fast swimmers and can change colour or release ink to escape predators.

Key details

Squid live in coastal waters and the open ocean around the globe. They are highly adapted for rapid swimming and camouflage. Their two longer tentacles are used to catch prey, which includes fish, crustaceans, and shellfish.

Why it matters

Squid are a crucial link in marine food webs, serving as prey for whales, seabirds, and other predators. In Canada, squid species occur in the Atlantic, Pacific, and Arctic waters, contributing to both ecological balance and commercial fisheries.

In short

  • Squid are marine molluscs with eight arms and two tentacles.
  • They are found worldwide in coastal and open-ocean waters.
  • Squid are carnivorous predators that use camouflage and ink.
  • Over 300 species exist, ranging from tiny to giant forms.
Canadian angle

Squid are relevant to Canadian readers through Canada’s Atlantic, Pacific, and Arctic marine ecosystems, where several squid species occur and some are part of commercial or ecological food webs.

Quick questions

What is a squid?
A squid is a marine cephalopod mollusc with a soft body, eight arms, and usually two longer tentacles.
How many species of squid are there?
There are more than 300 known species of squid.
Where do squid live?
Squid live in marine waters worldwide, including coastal areas and the open ocean.

Sources

  1. Encyclopaedia Britannicahttps://www.britannica.com/animal/squid
    Supports: General definition, cephalopod classification, species count, and habitat
  2. National Geographichttps://www.nationalgeographic.com/animals/invertebrates/facts/squids
    Supports: Species count, global distribution, body form, and diet
  3. Britannica Kidshttps://kids.britannica.com/kids/article/squid/353804
    Supports: Body plan, behaviour, diet, size range, and reproduction
  4. Australian Antarctic Programhttps://www.antarctica.gov.au/about-antarctica/animals/squid/
    Supports: Size range and broad biological description
  5. Encyclopedia.comhttps://www.encyclopedia.com/plants-and-animals/animals/zoology-invertebrates/squid
    Supports: Body structure, tentacles, and marine mollusc description