Slate pencil urchin

Heterocentrotus mamillatus · The slate pencil urchin is a large, spiky sea urchin native to tropical Indo-Pacific reefs and especially common in Hawai‘i.

Also called Red slate pencil urchin, Red pencil urchin.

Slate pencil urchin
Photo: U.S. Fish & Wildlife Service - Pacific Region's, CC BY 2.0
Slate pencil urchin
Photo: Kora27, CC BY-SA 4.0
Slate pencil urchin
Photo: Brocken Inaglory, CC BY-SA 3.0

Taxonomy

KingdomAnimalia
PhylumEchinodermata
ClassEchinoidea
OrderCamarodonta
FamilyEchinometridae
GenusHeterocentrotus
SpeciesHeterocentrotus mamillatus

Where it lives

Tropical Indo-Pacific reefs, 8 to 25 m deep, and especially common around Hawaii.

Fun facts

  • Its body can span over 8 cm across, with thick spines reaching up to 10 cm long.
  • At night, its bright red spines surprisingly fade to a chalky pink color.
  • It can wander up to 600 cm from its starting spot, averaging about 96 cm of travel per day.
  • Unlike most bilaterally symmetrical animals, it has no fixed front end, so it moves equally well in any direction.

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Facts and taxonomy adapted from Wikipedia (CC BY-SA 4.0).