Purple sea urchin

What to look for

Adults usually have a rounded body covered with purple spines. Young animals may be paler and greenish, so color alone is not a complete identification.

What it eats

They collect drifting algae and scrape food from surfaces with a five-toothed feeding structure called Aristotle’s lantern. Giant kelp is an important food.

Life and behavior

Tube feet and spines help the animal move slowly and hold position. Large numbers can graze kelp, but the ecological effect depends on local conditions and food availability.

Field context

Low intertidal shores and kelp forests, particularly wave-exposed, well-aerated water.

Observing responsibly

Look in rock crevices and pools. Depths describe common viewing habitat, not the species’ full depth range.

When to look

The available records do not establish a reliable local viewing season. Use the map’s month filter to inspect dated observations; it does not predict an encounter.

Learn more about this species

• Monterey’s kelp forest puzzle: why sea otters leave some urchins uneaten