Tripneustes gratilla (Linnaeus, 1758)
Common throughout the Solitary Islands Marine Park. Widespread distribution through the Indian Ocean from South Africa to Australia, western Pacific region to Hawaiian Islands. In Australia recorded from Perth in Western Australia north to the Timor Sea, the Coral Sea and Great Barrier Reef in Queensland, south to eastern Victoria and including Lord Howe and Norfolk Islands.
Frequents shallow reefs and lagoons where it feeds on algae and sea grasses. Often found with algae or shell fragments adhering to dorsal surface, possibly as camouflage. Depth to 75 m.
May be variable colouration - white or reddish spines with black, purple, brown or green body spaces between the spines. See colour variations in photographs below. Grows to a test diameter of 150 mm with a spine length of around 15 mm.
Graham J. Edgar. Australian Marine Life, 2nd Edition, 2008. Reed New Holland Publishers. pp.418-9.
Davie, Peter. Wild Guide to Moreton Bay and Adjacent Coasts. Second Edition. Published by Queensland Museum. Vol 2, p.275.
Atlas of Living Australia website at https://bie.ala.org.au/search?q=tripneustes+gratilla. Accessed 14/10/2018.