Species profile
Giant Keyhole Limpet
Megathura crenulata
At a glance
Giant Keyhole Limpet (Megathura crenulata) is a limpet present across the CatchRules coverage area but without species-specific bag, size, or season rules tracked in our regulatory dataset.
Confirmed by 4,379 research-grade iNaturalist observations, concentrated in California.
Notable details
- The shell reaches up to 4 inches across, nearly hidden beneath a large black mantle.
- Its blue blood contains a protein called KLH, widely used in cancer vaccine research.
- The 'keyhole' slot channels exhaust water out after the gills extract oxygen.
- Found only along the Pacific coast from Baja California to Monterey Bay.
- It grazes algae and encrusting organisms using a long, ribbon-like radula.
Where Giant Keyhole Limpet are seen
Background
Megathura crenulata is a northeastern Pacific Ocean species of limpet in the family Fissurellidae known commonly as the great keyhole limpet or giant keyhole limpet. Megathura is a monotypic genus; in other words, this is the only species in that genus. This species occurs along the rocky coast of western North America, its distribution extending from Southern California to the Baja California…
Background excerpt adapted from Wikipedia's Giant Keyhole Limpet article (CC BY-SA). Visit Wikipedia for the full entry.
Other limpets on CatchRules
Photo credit: iNaturalist / Wikipedia. Identification reference only — verify regulations with the issuing wildlife agency before retaining a catch.