West Indian Keyhole Limpet (also known as the Measled Keyhole Limpet)
Phylum: Mollusca, Class: Gastropoda, Order: Vetigastropoda, Family: Fissurellidae, Genus: Fissurella, Species: Fissurella barbadensis · Fissurellidae (Keyhole Limpet family) · Gastropod (univalve), whole shell, cap-shaped or oval cone shape with an apical aperture
Species
Fissurella barbadensis
Shell Type
Gastropod (univalve), whole shell, cap-shaped or oval cone shape with an apical aperture
Family
Fissurellidae (Keyhole Limpet family)
Size
Approximately 1.5 to 2 inches in length, which is average to large for this species. Adults typically range from 1 to 2.5 inches.
Color & Pattern
The exterior features a mottled pattern of brownish-purple to grayish spots and chevrons arranged in radiating ribs against a lighter tan or cream base. The colors appear natural and well-preserved. The interior is glossy and white with a distinct green-rimmed keyhole aperture.
Rarity
Common, frequently found by dedicated beachcombers searching rocky intertidal areas in its native range.
Habitat
Found in intertidal and shallow subtidal zones, typically clinging firmly to hard substrates such as rocky shores, limestone formations, and coral reefs where wave action is moderate to high.
Geographic Range
Western Atlantic Ocean, specifically from southern Florida through the Caribbean Sea, the Gulf of Mexico, and down to Brazil.
Description
An attractive, robust cap-shaped shell featuring a distinctive oval keyhole-like opening near the apex. The exterior exhibits prominent radial ribs and concentric growth lines that create a textured, scaly appearance. The margin is finely crenulated, and the interior displays a characteristic green ring surrounding the internal callus of the apical pore.
Key Features
The presence of a sub-central apical perforation (the keyhole), strong radial costae (ribs), and the diagnostic greenish-teal interior border surrounding the keyhole aperture distinguish this species from other limpets.
Collector Value
Modest collector value. While very common and generally inexpensive (often selling for a few dollars), high-grade specimens with exceptionally vibrant patterns or pristine margins are prized by specialized shell enthusiasts.
Condition Notes
Very good to fine condition. The shell is intact with strong structural integrity, minimal wear on the radiating ribs, excellent preservation of the natural mottled color pattern, and a clean interior aperture.
Interesting Facts
Keyhole limpets use their apical pore not just for waste elimination and respiration, but also to expel gametes directly into the water column during broadcast spawning. The 'keyhole' is actually the remnants of the larval shell's slit that closed up as the animal grew.
Ecological Role
As herbivorous grazers, keyhole limpets feed on microalgae and encrusting algae on rocks, helping to control algal overgrowth and maintain space for other intertidal organisms. They serve as prey for various predatory gastropods, fish, and shorebirds.
Similar Species
Lottia alveus (Tortoiseshell Limpet) and other Fissurella species such as Fissurella nodosa. They can be distinguished by differences in the radial ribbing, the shape of the aperture, and the absence of the signature green interior ring.
Beach Finding Tips
Search rocky shorelines, tide pools, and limestone outcroppings at extremely low tide. Look tightly adhered to rocks in high-energy surf zones, or inspect wrack lines and shell debris washed up after storms.