Tripneustes gratilla is not especially common at Kwajalein. We see it occasionally in lagoon Halimeda patches where it is invariably covered with rocks, algae or debris it holds over itself for camouflage. The urchins vary in color, but a typical coloration is dark with orange spines and white tube feet.
Tube feet with mostly white spines over on the left side.
A striking color form is mostly white with small purple pedicellariae.
Underside and mouth of the previous animal.
They are usually covered with debris.
Like other urchins, this species possesses pedicellariae, jaw-like structures on the ends of stalks extending from the urchin body. Like their relativeToxopneustes pileolus, the pedicellariae of this species contain a rather virulent venom. However, the pedicellariae jaws are too small in Tripneustes to get a bite onto human flesh.
Created 16 June 2018