Six-rayed sea stars are very small, reaching sizes of only two- to three-inch arm spans, living in the inter-tidal zone in the Pacific from British Columbia to Southern California. They are the only sea stars with six arms. The bodies of most echinoderms, which include sea stars, sea cucumbers, and sea urchins, are based on pentamerous radial symmetry with arms and sections in multiples of fives. Six-rayed sea stars eat small snails, limpets, mussels, chitons, barnacles, and other species. Most sea stars breed by releasing egg and sperm into the ocean, but female six-rayed sea stars brood their young until they are old enough to fend for themselves.