These urchins are very common, usually seen with just their spines extending from holes they have bored into the hard reef, although they can also be found regularly in patches of algae and not in holes. Although pointy, the spines do not easily enter flesh or break off in the wound.
Oral side (bottom) showing the mouth and a bit of the jaws, called Aristotle's lantern.
Hole bored into live coral.
Loose in Halimeda algae.
In hole in rock covered by a layer of Palythoa.
In live Montipora coral.
Created 15 June 2018