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Pot-hole urchin

Pot-hole urchin

This is a large, round urchin with medium length spines that can reach about half its diameter in length. Its body is black, and its spines are purple with a metallic sheen, rarely greenish at the tips.  They are easily distinguished from similar species, eg. Needle urchins, by the presence of 5 grey zig-zagging sutures on their upper surface.

Multiple generations of pot-hole urchin slowly excavate caves for themselves – hence their name. This multi-generational behaviour has resulted in pot-hole urchins having a patch distribution, occurring in huge numbers where they have been able to dig these excavations, eg. The Philippines and Sri Lanka, but rarer in other parts of the Indo-Pacific.

They emerge from these hiding spots at night to catch scraps of floating algae.

Also known as a black sea urchin or long-spined sea urchin.
Grows up to 10cm wide.
Digging caves is important for their survival, as wave action reduces the size of their spines.