What Is a Crustacean?

Sally Lightfoot crab (Grapsus grapsus)
G&M Therin-Weise/Robert Harding World Imagery/Getty Images

Question: What Is a Crustacean?

Crustaceans are animals in the Phylum Arthropoda and Subphylum Crustacea. The word crustacean comes from the Latin word crusta, which means shell.


Crustaceans are a very diverse group of invertebrate animals which includes active animals such as the crabs, lobsters, shrimp, krill, copepods, amphipods and more sessile creatures like barnacles.

Characteristics of Crustaceans

All crustaceans have:

  • A hard, but flexible exoskeleton or shell
  • Two pairs of antennae
  • A pair of mandibles (which are appendages used for eating)
  • Two pairs of maxillae on their heads (additional mouth parts located after the mandibles)
  • Two compound eyes, often on stalks
  • Segmented bodies with appendages on each body segment
  • Gills

Crustaceans are animals in the Phylum Arthropoda, and Subphylum Crustacea.

Classes, or broad groups of crustaceans, include the Branchiopoda (branchiopods), Cephalocarida (horseshoe shrimp), Malacostraca (the class that is probably most important to humans, and includes crabs, lobsters, and shrimps), Maxillopoda (which includes copepods and barnacles), Ostracoda (seed shrimp), Remipedia (remipedes, and Pentastomida (tongue worms).

Crustaceans are diverse in form and live around the world in a variety of habitats - even on land. Marine crustaceans live anywhere from shallow intertidal areas to the deep sea.

Crustaceans and Humans

Crustaceans are some of the most important marine life to humans - crabs, lobsters and shrimp are widely fished and consumed around the world. They may also be used in other ways - crustaceans like land hermit crabs may also be used as pets, and marine crustaceans may be used in aquariums.

In addition, crustaceans are very important to other marine life, with krill, shrimp, crabs and other crustaceans serving as prey for marine animals such as whales, pinnipeds, and fish.

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Kennedy, Jennifer. "What Is a Crustacean?" ThoughtCo, Aug. 26, 2020, thoughtco.com/what-is-a-crustacean-2291790. Kennedy, Jennifer. (2020, August 26). What Is a Crustacean? Retrieved from https://www.thoughtco.com/what-is-a-crustacean-2291790 Kennedy, Jennifer. "What Is a Crustacean?" ThoughtCo. https://www.thoughtco.com/what-is-a-crustacean-2291790 (accessed March 21, 2023).