Cayenne Keyhole Limpet (Diodora cayenensis)

SHELL LENGTH: Approximately 1 inch (2.54 cm)

The Keyhole Limpet is a small, oval shell, growing up to two inches, with a keyhole shaped hole at the top, thus giving it its name. This hole begins as a slit near the edge of the shell in young limpets and migrates to the top as the animal grows, functioning to drain water after it has passed over the gills. Radial ribs run from the hole to the bottom edge of the shell, which is usually tan to brown in color, but can be covered by green algal slime if the specimen is fresh. Keyhole Limpets live on solid objects such as rocks, pilings, and jetties where they spend most of the day in small depressions that they carve out with their radula. At night, limpets crawl around on a large, suction-like foot in search of algae. At low tide, if the limpet happens to be out of the water, it shuts tight where it can survive for hours. They are also able to survive the crashing of waves without being washed away. The sexes are separate in limpets and eggs are laid on the solid objects where they live.