Hatpin Urchin

Overview

The Hatpin Urchin (Centrostephanus longispinus) is a distinctive sea urchin found in the Mediterranean Sea and the Atlantic Ocean. It is recognized as a sentinel species for coralligenous habitats, where it plays a vital role in maintaining ecological balance by regulating algal growth.

Appearance

This species features a small central test surrounded by exceptionally long, mobile spines that can reach up to 30 centimeters in length. These spines are typically reddish-brown, often tipped with purple or pink, though coloration can vary; some individuals exhibit banded patterns on a paler background. A unique characteristic of this species is the presence of specialized club-shaped spines on its lower surface. Additionally, the urchin possesses light-sensitive pigment cells, or chromatophores, which allow it to shift its overall body color from a dark, nocturnal black to a lighter, grayish-brown during the day.

Biology & behavior

Primarily nocturnal, the Hatpin Urchin is typically solitary and tends to avoid direct sunlight. During daylight hours, it seeks shelter in rock crevices, cavities, and among hard substrates. Its long, toxic spines serve as a primary defense mechanism and are also utilized for locomotion. While generally sedentary, it is an active grazer that contributes to the health of its environment by feeding mainly on red algae and occasionally consuming small invertebrates.