A soft-bodied urchin that flattens into a cushion rather than holding the rigid globe shape of its relatives, reddish brown, up to 20 cm (8 in) across. The spines are short and blunt-looking, and many carry a swollen sac at the tip in blue or violet - the venom glands, and the reason this animal is worth recognising from a distance.
Contact drives the sac against the skin and injects its contents. The result is immediate, severe pain out of proportion to the small wound, and the spines break off easily in the flesh. On these reefs it lives on sand and rubble below the coral, mostly deeper than 5 m (16 ft), and moves onto open ground at night. Divers meet it when settling on the bottom in poor light, which is exactly the situation to avoid. The species was described in 2004 from this sea and is known only from here and the 🌊 Gulf of Aden, so the name is honest. A commensal shrimp of the genus Periclimenes often rides its surface, safe among the very spines that make it dangerous.
- flattened cushion-shaped body, soft rather than rigid
- short spines tipped with swollen blue or violet sacs
- reddish brown with pale banding on the spines
- diameter up to 20 cm
