Purple sea urchin using tiny tube like feet to glide across an ocean tidepool habitat in the wild

purple sea urchin animal feelers tubes feet moving feeling rock rocky seashore sea water underwater creatures prickly movement 4k discovery nature science biology marine ocean habitat ecosystem poop diet spiny globular round echinoderms species tide pool crawling tube anatomy muskuloskeletal test pores anus echinoderm shell organisms wild wildlife venomous toxic stings