Sector urchin

Scientific name : Tripneustes gratilla

Urchin with white banded or orange spines, arranged on 10 sectors and separated by 10 other sectors with only pedicellaria, blue or black coloured. The overall colour pattern is variable. Test diameter 10 cm.
One of the commonest species in the Indo-Pacific, it lives in bay and lagoon, on sand, rubble or seagrass covered bottoms. It likes to cover itself with various object, like rubble and detritus.
Difficult to confound for the general aspect. When it has no orange spines, it could be confused with Salmacis belli (thinner spines), or with Mespilia globulus for the general spine pattern.

Associated organisms
Host of the commensal shrimp Gnatophilloides mineri.