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.
Frequents shallow reefs and lagoons to a depth of at least 25m. Feeds on algae and sea grasses. Often found with algae or shell fragments adhering to dorsal surface, possibly as camouflage.
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 about 150mm dia.