Pencil Urchin

Heterocentrotus mamillatus

Pencil Urchin

Heterocentrotus mamillatus

Other Common Names
Slate Pencil Urchin, Red Slate Pencil Urchin, Red Pencil Urchin

Connected Coasts

Other Common Names

Slate Pencil Urchin, Red Slate Pencil Urchin, Red Pencil Urchin

At the Aquarium

Connected Coasts

Appearance

The pencil urchin has long (up to 10 cm) and thick (up to 2 cm) primary spines. The primary spines stick out like spikes and protect the urchin from predators. The spines are light or dark brown, dark purple or whitish in color. The tips of the spines are blunt and sometimes have a cream-colored band. The pencil urchin has secondary spines between the primary spines. These are short, flat and often dark brown. Sea urchin spines help them with defense, movement and food gathering. They can even repair their spines when damaged.

Habitat

Shallow reefs from 0-25 m.

Diet

Mainly algae. The pencil urchin’s mouth is on the underside of its body. It uses five sharp teeth to scrape algae off surfaces.

Life History

Like other urchins, they reproduce by broadcast spawning. This involves releasing eggs and sperm into the water. Once eggs hatch, the larvae float and are carried by ocean currents. They eventually return to the shoreline where they grow into adults. The pencil urchin is active at night and hides under rocks or corals during the day.

IUCN Status

Not Evaluated

Ecosystem & Cultural Importance

The spines are used for decoration purposes in some parts of the world. Because of this, the pencil urchin has become rare in most parts of the Philippines. Pencil urchins are important grazing animals as they keep coral reefs from becoming overgrown with algae. They are also a food source for predators.

Across most of the Indo-West Pacific, from the Red Sea and East Africa over the Malayan Archipelago to Hawaii. Not found around India.

This animal is not native to the Oregon Coast, however is found in the larger Pacific Ocean. It lives in the Aquarium as part of our Connected Coasts gallery.

The spines of the pencil urchin remain intact after the urchin dies and often wash up on beaches. The reproductive organs of several types of sea urchins are eaten by humans, but the pencil urchin is toxic when consumed and should not be eaten by humans.

Citations & Other Resources

Chetan-Welsh, H. (n.d.). Sea urchins: Strange and spiny wonders of the ocean. https://www.nhm.ac.uk/discover/sea-urchins-strange-and-spiny-wonders-of-the-ocean.html.

Colin, P. L. 1995. Tropical Pacific invertebrates: a field guide to the marine invertebrates occurring on tropical Pacific coral reefs, seagrass beds, and mangroves. Coral Reef Press, Beverly Hills, Calif.

Ebert, T. A. (n.d.). Growth, Regeneration, and Damage Repair of Spines of the Slate-Pencil Sea Urchin Heterocentrotus mammillatus (L.) (Echinodermata: Echinoidea)!

Lauer, C., T. B. Grun, I. Zutterkirch, R. Jemmali, J. H. Nebelsick, and K. G. Nickel. 2018. Morphology and porosity of the spines of the sea urchin Heterocentrotus mamillatus and their implications on the mechanical performance. Zoomorphology 137:139–154.

Schoppe, S. 2000. Echinoderms of the Philippines: a guide to common shallow water sea stars, brittle stars, sea urchins, sea cucumbers and feather stars. VISCA-GTZ Program on Applied Tropical Ecology, Visayas State College of Agriculture, Leyte, Philippines.

Schultz, H. 2005. Sea urchins. H. & P. Schultz Partner Scientific Publications, Hemdingen, Germany.

Pencil Urchin

Pencil Urchin

Other Common Names

At the Aquarium

Appearance

Habitat

Diet

Life History

IUCN Status

Ecosystem & Cultural Importance

Citations & Other Resources

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