Double spined urchin

Scientific name : Echinothrix calamaris

Diadematid sea urchin, with an obvious double order of spines. Long and thin spines, capable of painful stings, are alternate on 5 rows with larger, tubular spines with open distal tip. The latter are often banded. Dark and light banded anal sac. Test diameter 5 cm.
Normally found on the back reef, during daytime under stones and corals. Active at night.
The banded tubular spines are unique. Diadema savignyihas banded spines, but pointed. Also the colour of anal sac is different.
The thin spines can inflict very painful stings.

Associated organisms
Many juvenile Apogonidae (cardinal fishes) look for shelter among the spines.

Double spined urchin Author FEDERICO BETTI Place: Indonesia, Manado Id: 1