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By Barbados Field Guide   Published: May 17, 2025  
These tiny candy-colored animals protect coral reefs. But they need protection too.These tiny candy-colored animals protect coral reefs. But they need protection too.
Beneath the bristly armor of sea urchins lies an interesting striking natural sculpture. This piece of art is called the test, a delicate, rounded skeleton known for its textures and perfect symmetry. They are hundreds of species spread across every ocean and can be found in shallow tidepools or deep in the open ocean. They are an extraordinary presence in Barbados and oceans around the world.

Barbados is home to a variety of sea urchin species, each playing a vital role in the island’s marine ecosystems. Among the most common is the Black Sea Urchin (Diadema antillarum). This species is known for its long, sharp spines. It is important in keeping coral reefs healthy by grazing on algae. You’ll also find the West Indian Sea Egg (Tripneustes ventricosus), a round, short spiny urchin. This species has a larger test than the Black Sea Urchin, but have shorter spines. They are also traditionally harvested by some locals for its edible roe. 

Other species include the Slate Pencil Urchin (Eucidaris tribuloides), recognized by its thick, blunt spines, and the Reef Urchin (Echinometra viridis), which is smaller and often hides in rock crevices. These urchins are found in various coastal habitats, from rocky shorelines to coral reefs.

Together, these species support reef biodiversity and indicate the overall health of the marine environment, making their conservation increasingly important. Since 2022, the species has faced a devastating threat: a scuticociliate parasite—tiny, single-celled organisms that attack their soft tissue, causing their iconic spines to fall off. This outbreak began in the Caribbean and has rapidly spread eastward. In many regions, researchers have encountered mass die-offs, finding thousands of lifeless urchins.

Black Sea Urchin - Diadema antillarum

Sea urchins are crucial to coral reef ecosystems. By feeding on algae that can otherwise overwhelm coral, they play a vital role in maintaining ecological balance.

Photographs of the test often highlight the creatures’ radial symmetry from a top-down perspective. On their underside lies a powerful feeding mechanism: a mouth equipped with five self-sharpening teeth capable of consuming algae, kelp, and plankton—or even chiseling small shelters into rock to avoid predators.


Sea Urchin Tests
Tests of the Black Sea Urchin - Diadema antillarum and West Indian Sea Egg - Tripneustes ventricosus


The term urchin traces back to the 14th-century word for hedgehog, a fitting comparison given their spiny defense system. These spines aren’t just for show—they’re essential for movement, protection, and environmental sensing.

Read more about the Sea Urchins found in Barbados in the book Seashells of Barbados


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