Echinothrix calamaris
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| Echinothrix calamaris Pallas, 1774 |
The Double spined urchin (Echinothrix calamaris) is a urchin, with a test (shell) diameter of about 5 cm. It has two sets of spines, shorter closed spines which are dark in colour and can deliver a nasty sting, and longer open ended spines that are often striped.
It is found in the Indo-Pacific region, in back reef. It is active at night, hiding in crevices or under rocks at night.
Many juvenile fish of the family Apogonidae (cardinal fish) may hide in the spines for protection.
The difference with Echinothrix diadema is that spines of E. diadema are not banded, there is only one layer, and they are darker. The more similar species is Diadema savignyi, having stiped spines, the distinguishing feature being that the striped spines of D. savignyi are closed at their ends.
