Your body eventually absorbs this harmless dye. If a wana spine is in a joint or looks like it's getting infected, see a doctor. Not all sea urchins have sharp spines. The one called slate pencil has red, paddlelike blades. Another, the tough, wave-resistant shingle urchin, has broad spines that overlap like shingles.
Sea urchins eat drifting algae or scrape it off rocks.
They also catch drifting animals with pincers that, when alerted by an intruder, stand up from the surface of the urchin's body. They also provide another food source. The list of facts about sea urchins is so long, I will never know everything about them. But I do know that those round, spiny things in the ocean aren't plants. They're space aliens.