Keyhole Limpet
Phylum: Mollusca, Class: Gastropoda, Order: Lepetellida, Family: Fissurellidae, Genus: Fissurella, Species: Fissurella barbadensis · Fissurellidae (Keyhole limpet family) · Gastropod (univalve), whole shell, cap-shaped or cone-shaped.
Species
Fissurella barbadensis
Shell Type
Gastropod (univalve), whole shell, cap-shaped or cone-shaped.
Family
Fissurellidae (Keyhole limpet family)
Size
Approximately 1 inch in length, which is average for this species. Adults typically range from 0.75 to 1.5 inches.
Color & Pattern
Whitish to cream base color with fine radial ribs alternating in shades of brown and grey, creating a speckled or rayed pattern. The interior is white and glossy with a distinct dark green or greyish border around the keyhole aperture.
Rarity
Common
Habitat
Found in the intertidal and shallow subtidal zones on rocky shores, adhering tightly to rocks, tide pools, and wave-swept ledges. Marine species.
Geographic Range
Western Atlantic, including the Caribbean Sea, Gulf of Mexico, Florida Keys, and south to Brazil.
Description
A charming and uniquely structured cap-shaped shell featuring prominent radial ribs and concentric growth lines that give it a textured, star-burst appearance. The most defining feature is the apical opening, or 'keyhole', located near the apex of the shell, which allows for water circulation and waste elimination.
Key Features
The presence of a distinct apical perforation (keyhole) near the apex, combined with strong radial ribs and a scalloped margin matching the exterior ribbing.
Collector Value
Low to moderate value. While very popular among beachcombers and beginner collectors for their unique keyhole feature, they are common enough that individual specimens have modest monetary value, typically sold for a few dollars.
Condition Notes
Good condition. The shell is intact with clearly defined radial ribs and a visible aperture structure, though it shows minor natural wear consistent with wave action in the intertidal zone.
Interesting Facts
Keyhole limpets are not true limpets despite their appearance; they are more closely related to abalones. The keyhole is used to expel water after it has passed over the gills, as well as waste products. They graze on microscopic algae using a ribbon-like tongue called a radula.
Ecological Role
Keyhole limpets play an important ecological role as herbivores, grazing on microalgae and keeping rock surfaces clear, which provides settlement space for other marine organisms.
Similar Species
True limpets (family Lottiidae), which lack the apical keyhole perforation and have a solid apex.
Beach Finding Tips
Look along rocky coastlines, limestone shelves, and tide pools during extreme low tide. Search among drift lines of shell fragments washed up on rocky beaches.