A shoal of jellyfish in the Pacific Ocean


Cnidaria are a phylum of aquatic animals that includes jellyfish and corals. They have two body shapes: the medusa (a jellyfish-like swimming form) and the polyp (a sea anemone-like sessile or static form). During their life cycle they may transform themselves from one shape to the other. All cnidarians possess stinging cells, which they use to kill or paralyse prey.

Scientific name: Cnidaria

Rank: Phylum

Common names:

  • Cnidarians,
  • corals and allies,
  • Jellyfish

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  1. Life
  2. Animals
  3. Cnidaria