Long-spined Urchin

• defensaIts long hollow spines break off easily inside the skin on contact and release a toxin that causes intense, lasting pain.
• In 1983 and 1984 a disease of unknown origin killed more than 95% of the Caribbean population in little over a year, and without its grazing many reefs shifted from being dominated by coral to being dominated by algae, a change they have still not recovered from.
• In 2022 a further mass mortality, attributed to a ciliate protozoan, struck the recovering populations again.
• Its spines reach 30 cm, are hollow, brittle and venomous, and break off inside the skin once embedded.
• It was the great herbivore of Caribbean reefs. In 1983 and 1984 a die-off of unknown cause killed 98% of the population across the whole Caribbean.
• Without its grazing, algae took over the reefs and prevented new coral from settling. It is one of the main causes of the shift from coral-dominated to algae-dominated reefs, and thirty years later the population was still around 12% of the original.
• In January 2022 another mass die-off began, this time with the culprit identified: a ciliate of the genus Philaster. Koch's postulates were satisfied and the disease was named Diadema scuticociliatosis.
• At one site off Saba, 99% of the population was lost in a single month.
• The parasite has not stayed in the Caribbean: in 2022 Diadema setosum died en masse in the Mediterranean, and in 2023 off the coast of Oman.

Habitat and environment

Coral reefs and rocky bottoms of the Caribbean and the tropical Atlantic

Sources consulted: https://es.wikipedia.org/wiki/Diadema_antillarum