Short, sharp spines cover the disc and arms of this prickly creature. They embed in leathery skin, running from base to tip. The texture is rough. A fish attempting to swallow it will regret the decision immediately. The spines deter predators effectively. Under rocks and in crevices, it hides during daylight hours. This brittle star is nocturnal. It emerges only after dark to feed. It wedges itself into gaps where predators cannot reach. During the day, it remains still and silent. Its arms tuck close to the body. At night, it unfolds. The arms stretch into the water column. The arms are long and slender. They can span twenty centimetres. Flexible and coiling, they wrap around rocks and kelp stalks. Movement involves writhing like snakes. The disc is small, measuring only two to three centimetres across. Yet the arms keep going. They search for food in the dark. When threatened, the arms break. This is a defence mechanism. If a predator grabs an arm, the animal sheds it. The captured limb writhes in the attacker's grasp. The rest of the animal escapes. Regeneration occurs within weeks. It is a costly defence, but it works. Rocky reefs and kelp forests provide preferred habitat. It lives from the low tide mark down to fifty metres depth. Reefs, harbours, and estuaries all host populations. It is most common in areas with complex rocky structure. These places offer plenty of crevices for hiding. Night divers often spot it. The Māori name Pēwhā refers to its sinuous, snake-like movement. The arms twist and coil. They move with a grace that seems impossible for an animal with no obvious muscles. It is a fitting name for a creature that appears to flow rather than crawl. Climate change may affect it indirectly. Warming waters and ocean acidification may impact the planktonic larvae that drift before settling. The spiny brittle star is resilient, but it has limits. For now, it remains common on rocky reefs. It hides under rocks during the day. It unfurls its spiny arms at night. No one told it otherwise.