Key to Australian Freshwater and Terrestrial Invertebrates



Phylum Cnidaria


Key to the Families of Cnidaria

Common names: jellyfish, sea anemones, corals, hydroids

Cnidarians are radially symmetrical, soft-bodied animals that only live in aquatic environments. They include the jellyfish, sea anemones, corals and hydroids. The body of a cnidarian consists of an internal cavity used for respiration and a gastrovascular cavity (functioning like a stomach) with a mouth, but they do not have an anus. Almost all cnidarians are predatory, using tentacles covered in stinging cells called nematocysts to paralyse and kill prey. Australia is home to over 2,000 species of cnidarian, but the vast majority of these live in marine habitats. The freshwater cnidarians are all found within the class Hydrozoa, and in Australia these can take either �hydroid form� (families Hydridae & Oceaniidae), or �hydromedusae form�(families Oliniidae & Austromedusidae).

Cordylophora caspia
Oceaniidae - Cordylophora caspia
a cosmopolitan species occuring in both fresh and brackish waters
Image credit: Dr Horia R. Galea,
used under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License
Cordylophora caspia
Oceaniidae - Cordylophora caspia
a cosmopolitan species occuring in both fresh and brackish waters
Image credit: Dr Horia R. Galea,
used under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License
Craspedacusta sowerbii
Olindiidae - Craspedacusta sowerbii
Image credit: OpenCage,
used under a Creative Commons Attribution-ShareAlike license
Craspedacusta sowerbyi
Olindiidae - Craspedacusta sowerbii
Image credit: Stepanka Nemcova,
used under a Creative Commons Attribution-NonCommercial license




References and further information


ABRS Australian Faunal Directory: Cnidaria
Atlas of Living Australia: Cnidaria
Encyclopedia of Life: Cnidaria
Tree of Life: Cnidaria

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