Species group · Sea urchins

Urchins

WAnimals has 4 species of urchin, spread across 4 families (Diadematidae, Echinidae, Spatangidae, Strongylocentrotidae).

4 species

4 families

146 countries

77 parks

Ranges calculated from the profiles that record the figure, not from all 4.

All 4 species of urchins on WAnimals

Each one has its own full profile. This group does not replace them: it brings them together.

3 Not Evaluated1 Near Threatened

No species documented in this group is genuinely at risk according to the IUCN, with the data available today.

Recorded in 146 countries. The ones with the most species in the group:

It scrapes algae off rocks with its Aristotle's lantern, made up of five calcareous teeth.
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A large female can release as many as 20 million eggs.
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It is the only sea urchin listed as Near Threatened by the IUCN.
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Its long hollow spines break off easily inside the skin on contact and release a toxin that causes intense, lasting pain.
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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.
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In 2022 a further mass mortality, attributed to a ciliate protozoan, struck the recovering populations again.
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It has lost the radial symmetry typical of echinoderms and regained a bilateral one, with a front and a back, an adaptation to a buried and mobile life.
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