Giant Keyhole Limpet

Aquarium Inhabitant Bio

Megathura crenulata


A large and uniquely-shaped sea snail. Can be identified by its fleshy, oval-shaped body that typically covers its volcano-shaped shell with a hole on top. Color ranges from black to tan with dark blotches.

Habitat and distribution

Most commonly found in rocky reefs and kelp beds. Ranges from southern California into Baja California.


A grazer and scavenger, Giant Keyhole Limpet primarily consumes algae and decaying organisms on the seafloor.

Fun Fact

A blood protein found in the Giant Keyhole Limpet called hemocyanin is used as an ingredient in human vaccines.