Lance urchin

Scientific name : Phyllacanthus imperialis

Large urchin, with few, long and thick spines, whose surfaces have longitudinal grooves. Brown colour, the spines are lighter. Test diameter 8 cm, spine lenght 10 cm.
Encountered in the back reef, during the day inside crevices. Active at night.
Distinguished from Prionocidaris verticillata for the spines with longitudinal grooves, from Hetrocentrotus mammillatus for the round section of the spines.

Associated organisms
We observed on this urchin the commensal shrimp Periclimenes imperator. The spines are normally covered with epibiotic organisms.