Banded Sea Urchin

Overview

The Banded Sea Urchin is a widespread echinoderm found throughout tropical Indo-Pacific waters. It is easily recognized by its distinct dual-spine system and a prominent, often colorful anal papilla located on its upper surface.

Appearance

This species features a slightly oval test (shell) and two distinct types of spines. The longer, thicker primary spines are hollow and often display light and dark banding, though they can also appear solid white or black. Interspersed among these are shorter, thinner, and extremely sharp secondary spines that can deliver a painful sting. The test itself often exhibits five naked, star-shaped zones known as iridophores, which frequently shimmer with a blue hue. A large, translucent anal papilla is typically visible on the top of the urchin, often speckled with dots and surrounded by light-sensitive receptors.

Distribution & habitat

Banded Sea Urchins are common across the Indo-Pacific, ranging from the Red Sea and East Africa to French Polynesia and southern Japan. They inhabit a variety of reef environments, including lagoons, external reef slopes, and channels, typically residing in rocky crevices or under coral during the day.

Biology & behavior

Primarily nocturnal, this urchin remains hidden in sheltered areas during the day and emerges at night to forage. It is known to host commensal organisms, such as small crabs, which may reside near its anal papilla. While generally non-aggressive, the shorter spines are brittle and venomous, capable of penetrating skin and causing significant discomfort if handled.