Strongylocentrotus fransciscanus

Habitat: Red Sea Urchins are typically are found on rocky bottoms.

Average adult size: Adults can grow to be 10 inches across.

Natural history: The name echinoderm means "spiny-skinned," and these red urchins are about as spiny as you can get. Their shells or "tests" are covered with sharp spines. Urchins use their short spines on the bottom, like hundreds of tiny legs, to walk. The long upper spines are for protection, like an underwater porcupine. Spines also come in handy for burrowing and trapping food. Extending from between the spines are suction-cupped appendages called tube feet. Their lower feet grip the rock, while the upper ones grab at pieces of "drift" kelp floating by. Kelp is the red sea urchin's favorite food. Urchins also have pincher-tipped grabbing arms called pedicellariae. These look like miniature pliers and are used to keep the body surface free of debris. Their mouth is located underneath. The teeth come together like the beak of a bird and scrape off a seaweed snack. "Red" urchins can be red, purple or black in color. Urchins usually are found in crevices or rounded depressions in the rock created by years of chewing and grinding. Here they are protected from wave action and most predators. Sheephead wrasses and large sea stars, like the giant sun star, are major predators of the sea urchin. The larger urchins may live to be at least 10 years old and possibly 30 years old.

Range: From Alaska south to Baja, California.

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