Giant Keyhole Limpet 7694963816 O
53Identifcation number on The Map®

Giant Keyhole Limpet

Megathura crenulata

Giant Keyhole LimpetDavid R. Andrew ~


  • Mantle usually covers most or all of the shell
  • Shell has a large oval opening in the center
  • Mantle color varies from black to mottled gray
  • Length of shell to about 6 inches


  • Mendocino County, California to Isla Asuncion. Baja California


  • Found on rocky substrate from low intertidal to about 110 feet


  • These large limpets feed on algae and tunicates

Interesting Facts

  • Play an integral role in cancer research including the manufacturing of a variety of cancer vaccines, including non-Hodgkins lymphoma, cutaneous melanoma, breast and bladder cancer