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Jellyfish, anemones, corals and other cnidarians

Jellyfish, anemones, corals and hydroids are collectively known as cnidarians (Ancient Greek: knide = nettle, named after a type of plant with stinging hairs). With over 10,000 known species, they all have soft, hollow bodies, live in water and generally have tentacles.

Many sea anemones form important mutualistic relationships with plants and animals. For example, some species of sea anemones harbour single-celled algae. Most commonly known is the mutualistic relationship between the sea anemone and clownfish, famously portrayed in the film Finding Nemo. Sea anemones can also live on the shell of hermit crabs or snails and on top of the claws of a boxing crab.

All cnidarians can regenerate, although some more than others. Some species of jellyfish, such as the Moon Jelly, are capable of reverting to its earlier, polyp stage and regrow into an adult over and over again. Besides ageing backwards, Moon Jellies can also regenerate lost body parts. To a lesser extent, corals can regenerate by regrowing small body parts and cells. The Great Barrier reef is the world’s largest coral reef and provides complex habitats for a large variety of other organisms.

Learn more about these fascinating sea animals and the research underway at the Australian Museum Lizard Island Research Station to understand the impacts of a changing climate on these complex marine habitats.

Jellyfish, anemones and corals factsheets

19 Fact Sheets in this section