This gregarious creature that feeds on algae is often found in groups, particularly during the day.
The urchin can be recognized by its long spines (up to 15 cm) and the orange-red ring around its anus on its posterior. Hatpin urchins are usually black, but their spines can also be lighter in colour (grey, white or purple) or even striped in juveniles.
Like all sea urchins, these spines are mobile, allowing the animal to point them toward any danger that may be threatening it. It is sometimes used as a refuge by shrimp and small fish.
The hatpin urchin's long, thin spines are covered with tiny barbs. These are not venomous but can easily slip into the skin, breaking off and becoming embedded only to later cause infection.
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