| Range: |
Indian and Pacific Oceans |
| Habitat: |
Reefs |
| Conservation Status: |
Not listed by IUCN |
| Scientific Name: |
Heterocentrotus mammillatus |
The pencil urchin gets its name for two reasons. Its blunt, solid spines not only resemble pencil stubs, but they were used by ancient Egyptians to write on slate or stone tablets! (Today, pencil urchins' spines are often used to make the wind chimes you see in seaside gift shops - one reason the species is being over-hunted in the wild.)
The pencil urchin is one of the more than 700 species of sea urchins that live in the world's oceans. As with other urchins, its hollow spines provide a fearsome defense against attackers. They contain an irritant that can inflict a very painful wound when a predator touches them.
Urchins often spend the day hiding in crevices on the ocean floor. They come out at night to graze on marine algae and grasses. They move very slowly by creeping along on the tips of their spines, aided by threadlike tentacles that have tiny suction disks on their ends.
Along with sea stars, sea cucumbers, and sand dollars, sea urchins are among the many types of echinoderms that live in the world's oceans. Echinoderm means "spine skin" and describes the way many of these animals look and feel. All adults are radially symmetric, with a body pattern that repeats itself five times, typically a star-like pattern with five arms - like a "sea star". Each of the five arms acts independently, with no central control; echinoderms have no head or brain.
Echinoderms are an ancient phylum, and used to be far more common then they are today; there are 20 extinct classes of echinoderms and only five living ones. Surprisingly, echinoderms are our closest relatives. Their phylum is nearest to our own!
|
