Purple Sea Urchin

The purple sea urchin (Strongylocentrotus purpuratus) is a spiny grazer of the Pacific coast of North America and one of the most important organisms in developmental biology. Its genome was sequenced in 2006.

🧬 Field Guide Specimen: Open Purple Sea Urchin in the CRV Science Field Guide to log the specimen, see its place among the Deuterostomia lineages in the Cladogram Explorer, and test your recall in the Red List conservation game.

Sea urchins are deuterostomes, distant cousins of vertebrates. Their genome contains many genes once thought to be vertebrate inventions and a large repertoire of immune genes, though they have no adaptive immune system like ours. See Gene.

Eggs are plentiful, transparent and fertilized in a dish, so cell divisions and early development can be watched under a microscope. Work by Hans Driesch and Theodor Boveri on sea urchin embryos in the late nineteenth century helped show how cells specify one another and that chromosomes carry heredity.

After a wasting disease killed sunflower sea stars along the Pacific coast beginning in 2013, and marine heatwaves stressed kelp, purple urchins multiplied and grazed down kelp forests in parts of northern California. See Giant Kelp.

• Giant Kelp — the forests urchins graze
• Sea Otter — an urchin predator
• Embryogenesis — early embryo studies