Biology/Natural History: Species is omnivorius but prefers encrusting bryozoans. Extends its mantle extremely when it encounters a seastar predator (such as Pycnopidia, Leptasterias, Pisaster, or Orthasterias) so that the shell is largely covered and the seastar has no place to grab onto the shell. Often contains a symbiotic polychaete worm Arctonoe vittata (picture) in its mantle cavity which may bite the seastar as well. Diodora's blood contains hemocyanin, has a low pH (7.1) and no Bohr effect.