species: Echinothrix calamaris in Lizard Island Field Guide (Lizard Island Field Guide)
Echinothrix calamaris

©Anne Hoggett: Echinothrix calamaris about 10 cm test diameter at Lizard Island at night. 

©Anne Hoggett: Echinothrix calamaris about 7 cm test diameter at Lizard Island at night

©Lyle Vail and Anne Hoggett: Echinothrix calamaris at night
Kingdom Animalia
Phylum Echinodermata
Class Echinoidea
Order Diadematoida
Family Diadematidae
Genus Echinothrix
Species Echinothrix calamaris



Distinguishing features

A large urchin only seen exposed at night. Two types of spines: thick, often blunt-tipped ones that are slightly longer than the test is wide, and shorter, much finer spines. Conspicuously bare interambulacral areas on the test, often greenish.

There are two colour forms of this species and both occur at Lizard Island. The paler form is more common. Its longer spines are pale and often banded. The longer spines of the darker form are more uniformly dark. Both forms have a swollen periproctal cone with white flecks (Coppard and Campbell, 2006). This distinguishes the dark form from the related species Echinothrix diadema (Coppard and Campbell, 2006) which also occurs at Lizard Island.


  • Size data has not been obtained.

Depth range

  • Depth range data is not yet available.



©Atlas of Living Australia: Australian distribution

Distribution and habitat preferences

Echinothrix calamaris is never seen during the day as it is hidden deep within the reef. It is a common and conspicuous member of the nocturnal reef fauna at many localities around the island.

Local abundance

  • Lizard Island: Common, but only exposed at night.

Web resources


References that assist with identification

  • Coppard, S.E. and A.C. Campbell (2006). Taxonomic significance of test morphology in the echinoid genera Diadema Gray, 1825 and Echinothrix Peters, 1853 (Echinodermata). Zoosystema, 28(1): 93-112. LIRS catalog number 90419.

Other references

  • Young, M.A.L. and D.R. Bellwood (2011). Diel patterns in sea urchin activity and predation on sea urchins on the Great Barrier Reef. Coral Reefs, 30: 729-736. LIRS catalog number 1483.
  • Young, M.A.L. and D.R. Bellwood (2012). Fish predation on sea urchins on the Great Barrier Reef. Coral Reefs, 31: 731-738. LIRS catalog number 1541.