Red Pencil Urchin

Overview

The Red Pencil Urchin is a distinctive tropical sea urchin widely distributed across the Indo-Pacific region. It is easily recognized by its robust, pencil-like spines, which provide significant mechanical protection and a unique appearance.

Distribution & habitat

This species inhabits tropical reefs throughout the Indo-Pacific, ranging from the Red Sea and East Africa to the Hawaiian Islands, southern Japan, and the Great Barrier Reef. It favors shallow, high-energy environments such as the tops of barrier reefs, where it uses its tube feet to anchor firmly to rocky or coral substrates to withstand wave action.

Appearance

The urchin features a spherical, solid test often hidden by its prominent primary spines, which can reach up to 10 cm in length. These spines are typically bright red, though brown and purple variations exist, and they often display a white ring at the base. The spines are rounded to triangular in cross-section and taper toward the tip. Interestingly, the spines may shift to a chalky pink color at night. In addition to the large primary spines, the body is covered in smaller, flattened secondary spines that act as a protective layer.

Biology & behavior

Primarily nocturnal, this urchin remains hidden in rock crevices or under ledges during the day to avoid predators. It is a relatively active grazer, moving across the reef at night to feed. It utilizes a specialized internal mouth structure known as Aristotle's lantern to scrape food from the substrate. Like other sea urchins, it reproduces through broadcast spawning, releasing eggs and sperm into the water column to produce pelagic larvae.