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About Polychaetes
Worms that are not polychaetes

Echinodermata: Holothuroidea  -  sea cucumbers


Holothuroidea: Chirodotidae [photo: M.Marmach]

Holothurians are sausage-shaped echinoderms which are pentamerously symmetrical in cross-section, although this is often not obvious. Mouth with a circlet of oral tentacles which may be either bushy of digitate. Soft bodied except for isolated calcareous ossicles in the skin. Tube feet present or absent. Anus terminal.


Large holothurians, in particular tropical species, are not easily confused with polychaetes since their radial symmetry, tube feet and oral tentacles are sufficiently distinctive. However, small apodous holothurians (such as the one illustrated on this page) are widespread in temperate environments. Lacking tube feet, apodous holothurians may not be recognised initially as holothurains. However, the oral tentacles, if everted, are distinctive and unlike anything in the polychaetes. The soft, fragile body of apodous holothurians often has a "sticky" feel, due to the minute hook-shaped ossicles.

Over 1,400 species of holothurians are known world-wide. The Australian fauna, when catalogued in 1995, comprised fifteen families, 69 genera and 211 species, although additional cryptic species of small apodous holothurians continue to be recognised from temperate Australian environments. Accurate identification of echinoderms will require dissection, and examination of ossicles. Since the ossicles dissolve readily, holothurians which have been fixed in formalin are often unidentifiable.


Rowe and Gates (1995) exhaustively list the then known Australian fauna and its literature. Edgar (1997), Shephard & Thomas (1982) and the Marine Research Group's 1984 Coastal Atlas introduce the southern Australian holothurian fauna. Shephard & Thomas (1982) describe study methods.

Edgar, GJ. 1997. Australian Marine Life. Reed, Kew, Victoria.

Marine Research Group of Victoria. 1984. Coastal Invertebrates of Victoria - an atlas of selected species. Marine Research Group of Victoria and Museum of Victoria, Melbourne.

Rowe, FWE and Gates, J. 1995. Echinodermata. Zoological Catalogue of Australia. CSIRO Publishing, Melbourne.

Shepherd, SA and Thomas, IM. 1982. Marine Invertebrates of Southern Australia Part I. Handbooks Committee of the South Australian Government, Adelaide.