Northern Sea Star, Acadia National Park, Maine

Sea star moving over coralline crust past periwinkles.

Sea stars are boneless echinoderms; spiny skinned animals who depend of their tough skin, made up of calcium carbonate, and plates for protection like a coat of armor. They use their rubbery tube feet to move around. Sea stars also use their feet to collect food, for example, pulling open mussels.