Keyhole Limpet (also known as Shield Limpet or Owl Limpet depending on exact species)
Phylum: Mollusca, Class: Gastropoda, Order: Lepetellida, Family: Fissurellidae/Lottiidae, Genus: Fissurella/Lottia, Species: barbadensis/gigantea · Fissurellidae (Keyhole Limpet family) and Lottiidae (True Limpet family) · Gastropod (univalve), whole shells, low-conical and cap-shaped morphology
Species
Fissurella barbadensis (Barbados Keyhole Limpet) and Lottia gigantea (Owl Limpet)
Shell Type
Gastropod (univalve), whole shells, low-conical and cap-shaped morphology
Family
Fissurellidae (Keyhole Limpet family) and Lottiidae (True Limpet family)
Size
Approximately 1 to 2.5 inches in length, which is average for adult keyhole and true limpets in these genera
Color & Pattern
Mottled patterns of brown, cream, white, and greyish-blue. Exteriors often show concentric growth rings and radial ribs. Interiors vary from porcelain white to dark brown with translucent central areas.
Rarity
Common to Very Common, frequently encountered by beachcombers exploring rocky intertidal areas
Habitat
Intertidal and shallow subtidal zones, firmly attached to rocky substrates, wave-swept shores, and tide pools where they graze on algae
Geographic Range
Widely distributed globally, with specific species found in the Western Atlantic, Caribbean, Pacific coast of North America, and tropical intertidal zones worldwide
Description
These cap-shaped univalve shells display a low, flattened profile designed to withstand crashing waves. They feature fine radial ribbing and concentric growth lines. Keyhole limpets distinctively feature a small aperture or 'keyhole' at the apex for water expulsion, while true limpets maintain a solid apex.
Key Features
Low conical or cap-shaped profile, oval aperture footprint, absence of a traditional spiral spire in adults, and the diagnostic apical perforation present in the keyhole limpet specimens
Collector Value
Low to Moderate commercial value, highly valued by beginner and intermediate beachcombers and educational display collectors rather than high-end investors
Condition Notes
Mixed condition ranging from Good to Fair. Some specimens exhibit weathering, slight fading, and minor encrustations from their marine environment, typical of beach-cast or rocky-shore finds
Interesting Facts
Limpets possess a remarkable homing instinct, returning to the exact same 'scar' on a rock after foraging. Their radula (feeding ribbon) is lined with teeth made of goethite, one of the strongest biological materials known to science
Ecological Role
Limpets are vital primary consumers in rocky intertidal ecosystems, controlling algae populations and maintaining bare rock spaces that allow other marine organisms to settle
Similar Species
Slipper shells (Crepidula) and other true limpets like Acmaea, distinguished primarily by interior shelf structures or lack of an apical keyhole
Beach Finding Tips
Search rocky shorelines, jetties, and tide pools during extreme low tide. Look closely at rocks where limpets graze on microalgae, or scan the high-tide driftline for washed-up specimens