Purple urchins, or Strongylocentrotus purpuratus, live in tidepools along the West Coast of North America.
The urchin's spines help it skewer food and protect itself against predators.
Spawning female urchin
The urchins breed annually around January, February and March.
The urchins start out as free-floating larvae that may swim and feed for several months.
Urchins undergo metamorphosis from a larval form to an adult form.
Sea urchin larvae turn inside-out as the larvae metamorphose to adults.
Sea urchin genome
Scientists recently sequenced the genome of the purple sea urchin.