Red Sea Fire Urchin

Overview

The Red Sea Fire Urchin (Asthenosoma marisrubri) is a distinctive, venomous sea urchin endemic to the Red Sea. Known for its flexible, leather-like test and vibrant coloration, it is a regular inhabitant of tropical reef environments where it plays a unique role in the local ecosystem.

Appearance

This species typically reaches up to 20–25 cm in diameter. Its test is not fused, providing a remarkable flexibility that has earned it the nickname "leather urchin." The body is generally red to brown, often featuring a star-like pattern. It possesses two distinct types of spines: long, flexible oral spines used for movement and exploration, and shorter, defensive aboral spines. These defensive spines are equipped with potent venom glands, often topped with large, white, bulbous sacs.

Distribution & habitat

Asthenosoma marisrubri is primarily found in the northern Red Sea, including the Gulf of Aqaba and the Suez Canal. It inhabits a variety of environments, including coral reefs, lagoons, seagrass beds, and sandy or stony bottoms, typically at depths ranging from shallow waters down to approximately 150 meters.

Biology & behavior

Primarily nocturnal, this urchin often hides in caves or under rock ledges during the day. It is a highly venomous species capable of inflicting intense pain, requiring caution from divers and observers. Despite its toxicity, it serves as a host for various commensal organisms, such as specific species of shrimp and parasitic gastropods, which find shelter among its spines. It is a gonochoric species that reproduces via external fertilization, releasing gametes into the water column.