By Ian RandallEchinoderms are survivors. Many of the marine invertebrates—such as starfish and brittle stars—can regrow lost limbs, and some will even shed an arm or two to escape a predator.
Their spiky sea urchin cousins are known to replace lost spines. Now, seafloor images taken off the coast of Norway have revealed a new high-water mark for the tenacious sea urchin: Despite having a gaping hole where its anus and sexual organs used to be, one severely injured Strongylocentrotus kept moving for at least 43 hours and 20 minutes, at one point even dodging an attack from a hungry crab (above).The reason the tough little critter survived its fatal-looking wound, scientists say, is because sea urchins have no real brain.