A black urchin with an iridescent sheen and no banding on the spines - which is what separates it from the two long-spined urchins it shares the reef with.
The trio is worth learning as a group. The true Diadema has very long, needle-thin spines and blue spots on the test; the banded Echinothrix has two clearly different spine types, long and banded plus short and fine; this one has a single set of uniform dark spines with a metallic gloss. All three are nocturnal grazers, all three are venomous, and all three shelter other animals.
Grazing is what they are for. Urchins are the reef's other lawnmower alongside the herbivorous fish, and where fish are overfished, urchins take over the job entirely - which works until something happens to the urchins.
Spines break off in a wound and dissolve slowly. Hot water helps the pain; a fragment near a joint or deep in a hand is a matter for a doctor.
- uniformly dark spines with no banding, often with a green or purple sheen
- spines all much the same length, unlike its banded relative
- blue-green iridescent spots on the dark test
- spines to 20 cm
