SEA URCHINS MAY LOOK AS IF THEY ARE STUCK IN ONE PLACE but in fact they creep around on little tubular feet. These green sea urchins (Strongylocentrotus droebachiensis), photographed at Cape Ann in Massachusetts, have crept into a crevice in the granite boulders that are so abundant New England waters. Presumably, it’s a protective strategy.
They eat algae. Presumably they creep out to do so. Strongylocentrotus droebachiensis are the most abundant sea urchins found north of Cape Cod, and their roe is considered to be a delicacy in Japan.
Principal Sources: Personal observation (the creeping part, it’s actually pretty neat to watch), Marine Life of the North Atlantic, Andrew Martinez.