Pencil Urchin (Eucidaris tribuloides)

The Pencil Urchin is part of the sea urchin family.   Some refer to them as slate pencil urchin, red slate pencil urchin, or red pencil urchin.   These creatures can be found throughout the tropical waters of the Indo-Pacific region, but is most abundant in Hawaii.   Specimens from Hawaii tend to have bright red spines, while specimens from other parts of the Pacific may have yellowish or brown spines.   As pencil urchins age, you will find many specimens have become covered in algae and coralline, since they do not move around very much.   They are most common at about 17 to 23 feet in depth.   When you first see one, you may think it is not alive.   Pencil urchins do have eyes or legs.   They move around like starfish and sand dollars…by means of hundreds of tiny, transparent, adhesive “tube feet.”

They are described as “sluggish echinoid” that leads a nocturnal, bottom dwelling existence. During daylight hours, the pencil urchin uses its large primary spines to anchor itself under or atop rocks or to lodge itself in crevices. Individuals rarely stray far from their locality.   At night, they will feed primarily on corals and sponges, among other things.

If you should run across a pencil urchin while swimming in the ocean, handle it carefully.   You should not try to pry it out of a hole or off the rock because you will break their spines before they will let go.



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