Pencil sea urchin
Heterocentrotus mammillatus
- Scientific name
- Heterocentrotus mammillatus
- Group
- Echinoderms (starfish, urchins...)
- Rarity
- Common
- Where to see it
- Indo-Pacific & Red Sea
- Conservation status (IUCN)
- Not evaluated
Did you know?
The pencil sea urchin gets its name from its thick, blunt spines, quite different from the thin, sharp spikes of most sea urchins. It feeds on algae, grazing across the reef at night.
What defines this group — Echinoderms (starfish, urchins...)
Starfish, urchins and sea cucumbers: a five-fold symmetry found nowhere else in the animal kingdom.
- The body is arranged in fives around a centre: no head, no front, no back.
- They move on hundreds of tube feet driven by water under pressure.
- Many regrow a lost arm; some starfish can rebuild themselves from a single one.