Arctic Green Sea Urchin
Strongylocentrotus droebachiensis
Long-spined sea urchin
Diadema antillarum
About
The long-spined sea urchin is a reef grazer known for its dramatic crown of black spines. It plays an outsized role on Caribbean reefs, keeping algae in check so coral can keep growing.
- Depth
- up to 400 m
How to tell it apart
Several dark urchins share Caribbean reefs, but this one stands out by spine length alone: its spines are far longer than those of any other urchin nearby, often several times the length of its own body.
Appearance
This urchin has a round, dark test, the hard shell-like body common to sea urchins, bristling with thin black spines that are unusually long compared with other reef urchins. The spines radiate outward in every direction, giving the whole animal a spiky, dark silhouette.
Habitat
It lives on coral reefs and rocky bottoms across the tropical western Atlantic and Caribbean, usually wedged into crevices with only its spines showing. It is most common in shallow reef water but can be found down to 400 m. It avoids bright, open light and prefers shaded ledges and cracks.
Did you know?
In 1983 a disease swept through the Caribbean and wiped out almost the entire population of this urchin within a year, one of the most severe die-offs ever recorded in a marine invertebrate.
Log it in Into the Blue
Describe what you saw and we name it, then keep every species you find in your Oceandex.
