Saturday, August 19, 2017


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Heterocyathus (Caryophyllidae)

Welcome to the Heterocyathus genus landing page. In this section, you will find general information about this genus and tips on how to identify it. If you are looking to confirm an observation made with the Coral Finder, use the image browser below to verify what you saw underwater. Then click on the following link for further comparison with a similar genus: Heteropsammia.

The symbiotic relationship between scleractinian corals and the algae zooxanthellae is well known, but symbioses between scleractinians and other organisms are less recognised.  To cope with burial while inhabiting soft sediments, Heterocyathus houses a sipunculid worm which moves the coral when it becomes covered in sediment.  Often a parasitic mussel may also join the party.  Both creatures live in a small hole in the lower surface of the coral.  For more information on this relationship check out Hoeksema & Borel-Best (1991) in the Suggested Reading list below.

Vital Statistics

  • 1 zooxanthellate species
  • Coral Finder p. 26
  • COTW – Vol 2 p. 412-213


Zooxanthellate species found in the Indo-Pacific.

ID Tips

Heterocyathus forms small, free-living colonies, and are found on soft substrates.  The corallites are generally solitary, although some may form small colonies with multiple corallites.

The septa running out from the centre of the corallite lead into prominent costal ribs that lead down the flanks of the coral.

(slide show with photos of hole in base of coral and costal ribs)

Similar Genera

The Coral Finder lists Heterocyathus in one key group with Heteropsammia being a possible candidate for confusion.

Similar genera to Heterocyathus (Coral Finder p26)

Free-living Heterocyathus may be confused with Heteropsammia.  They can however be easily separated by the prominent costal ribs that run down the flanks of Heterocyathus colonies.  The smooth flanks of Heteropsammia lack these ribs.


Similar genus: Heteropsammia


Taxonomic Changes

Learning Resources

Coral Hub

  • Caryophyllidae family page


Suggested Reading – Identification Tools

  • Davie, P. J., & Phillips, J. A. (2009). 13th International Marine Biological Workshop, The Marine Fauna and Flora of Moreton Bay, Queensland. Memoirs of the Queensland Museum, 54(2), 1-118.
  • Hoeksema, B. W., & Borel-Best, M. (1991). New observations on scleractinian corals from Indonesia.  2. Sipunculan associated species belonging to the genera Heterocyathus and Heteropsammia. Zoologische Mededelingen, 65, 221-245.
  • Veron, J. E. N. (1985). Corals of Australia and the Indo-Pacific. Sydney: Angus and Robertson.
  • Veron, J. E. N. (2000). Corals of the World. Melbourne: Australian Institute of Marine Science.

Suggested Reading – Other Topics