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 & environment

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

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