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.
Compiled by Aquairi from published sources · Published · Updated
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.
Diadema antillarum Breeding Guide: Caribbean Urchin & Restoration
Overview
Diadema antillarum, the Caribbean long-spined sea urchin, belongs to the family Diadematidae. It inhabits the tropical Western Atlantic, including the Caribbean Sea, Gulf of Mexico and South American coasts to Brazil, with populations in the East Atlantic and Indian Ocean. Spines are typically 10-12 cm and can reach 30 cm in large individuals. It is the primary herbivore on Caribbean reefs, grazing algae that would otherwise smother corals.
Reproductive Mode
The species is a highly fecund broadcast spawner, with individuals producing over a million eggs per spawning event. Spawning relies on chemical signalling between males and females to synchronise gamete release.
Sexual Reproduction
Gametes are released into the water for external fertilisation, and the embryos develop into planktonic larvae that drift before settling on the reef and metamorphosing into juveniles. Dedicated nurseries in Jamaica and Puerto Rico now culture juveniles for relocation, with promising reef-recovery results in some regions, but this is aquaculture for restoration rather than home breeding.
Common Challenges
More than 97% of urchins died in the 1983 Caribbean mass die-off from an unknown disease, causing macroalgal overgrowth that inhibited coral recovery and reduced reef resilience; populations are recovering slowly. The planktonic larval cycle cannot be completed in home aquaria, and urchins do not reproduce asexually.