A black urchin with very long thin spines. A disease killed most of the Caribbean population in 1983, algae took over the reefs it had been grazing, and a second die-off followed in 2022.
Test to about 10 cm with black spines several times that length, and a fifth of what it used to be in the Caribbean. It sits in reef crevices by day with the spines out and grazes at night.
A mass die-off in 1983 removed more than ninety per cent of the population across the whole region in about a year, and the algae it had been grazing took over reefs that had also lost their large herbivorous fish. It is one of the clearest single events in the decline of Caribbean reefs, and a second die-off in 2022 hit the recovering populations. Where it is common the reef around it is noticeably cleaner.
The spines are long, brittle and sharp enough to go through a glove or a wetsuit. They break off in the wound and are difficult to remove, and the injury is a puncture rather than an envenomation. Most of what it costs is a bad evening with tweezers.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.