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Gallery: Sea Urchins

Purple urchins

Purple urchins

(Image credit: Jackie Sones)

Purple urchins, or Strongylocentrotus purpuratus, live in tidepools along the West Coast of North America.

Urchin spines

An adult purple sea urchin.

(Image credit: Claire Fackler, NOAA National Marine Sanctuaries)

The urchin's spines help it skewer food and protect itself against predators.

Spawning female urchin

Spawning female urchin

(Image credit: Dan Griffin)

The urchins breed annually around January, February and March.

Urchin larva

sea urchin larva

(Image credit: Elizabeth Lenz)

The urchins start out as free-floating larvae that may swim and feed for several months.

Urchin metamorphs

Urchin metamorphs

(Image credit: Eric Sanford)

Urchins undergo metamorphosis from a larval form to an adult form.

Inside-out urchin

sea urchin larvae

(Image credit: Andreas Heyland)

Sea urchin larvae turn inside-out as the larvae metamorphose to adults.

Sea urchin genome

(Image credit: Mount Desert Island Biological Laboratory)

Scientists recently sequenced the genome of the purple sea urchin.