Caribbean Long Spine Urchin Care Guide
Diadema antillarum is the Caribbean long-spine urchin, a key reef herbivore that suffered a 1983 mass die-off. It is a highly effective algae grazer.
Overview
Diadema antillarum, the Caribbean long-spine urchin, is an echinoid of the family Diadematidae and the western Atlantic counterpart of the Indo-Pacific D. setosum. It is defined by exceptionally long black spines, commonly 10–12 cm and reaching up to 30 cm. Historically it was the most abundant and important herbivore on western Atlantic and Caribbean reefs, and it remains a highly effective algae grazer.
Taxonomy
- Class: Echinoidea
- Order: Diadematoida
- Family: Diadematidae
- Genus: Diadema
- Scientific name: Diadema antillarum (Philippi, 1845)
Habitat
The species occurs in the tropical western Atlantic, including the Caribbean and Gulf of Mexico south to Brazil, with records also from the eastern Atlantic Canary Islands. It typically lives at depths of about 1–10 m on coral reefs, sheltering in crevices by day and roaming roughly a metre from its shelter to feed at night.
Tank requirements
- Minimum tank volume: 200 L
- Temperature: 24–26 °C (75–79 °F)
- pH: 8.1–8.4
- Carbonate hardness (dKH): 8–11
- Specific gravity: 1.024–1.026
- Spine length: commonly 10–12 cm, up to 30 cm
- Lifespan: roughly 4–10 years
Provide a large, established tank with plenty of live rock for grazing and daytime refuge, and supplement with dried algae if natural growth is insufficient.
Diet
Diadema antillarum is primarily a herbivore feeding on algae and occasionally seagrass; starving individuals may turn carnivorous. As a nocturnal grazer it plays an outsized role in suppressing algae that would otherwise overgrow corals.
Compatibility
It is reef compatible as a grazer but needs space because of its long spines, and it should not be kept with urchin predators such as triggerfish and pufferfish.
Conservation status
A Caribbean-wide mass mortality in 1983 killed more than 97% of the urchins, triggering widespread algal overgrowth and reduced reef resilience. Populations have recovered unevenly, with denser numbers in the eastern Caribbean by 2015, while a further die-off was recorded in 2022 in the U.S. Virgin Islands, Saba and St. Eustatius.