Limpet
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 Patella vulgata limpets in their natural habitat (here northwestern Galicia). One animal was separated from the rock and turned over for the photograph to have a view of the underside and muscular foot.
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Limpets are marine gastropod molluscs in the order Patellogastropoda. They have flattened, cone-shaped shells. They live throughout the intertidal zone, from the high zone (upper littoral) to the shallow subtidal on the rocky coasts of most oceans. Limpets can be commonly found attached to rocks, looking like little disks or bumps on the rock surface. They attach themselves to the substratum using pedal mucus and a muscular "foot", which enables them to remain attached through dangerous wave action and which also seals against the rock to protect from desiccation during low tide. Limpets forage by grazing on algae found on rock surfaces. They scrape films of algae from the rock with a radula, a ribbon-like tongue with rows of teeth. Limpets move by rippling the muscles of their foot in a wave-like motion.
Some limpets have a hole at the top, through which gaseous exchange can occur. Most limpets are less than 3 in (8 cm) long, but a West Mexican Limpet grows to be 8 in (20 cm).
[change] Homing behaviour
Some species of limpets return to the same spot on the rock known as a "home scar" just before the tide recedes.[needs proving] In such species, the shape of their shell often grows to precisely match the contours of the rock surrounding the scar. This behaviour presumably allows them to form a better seal to the rock and may help protect from either predation or desiccation. It is still unclear how limpets find their way back to the same spot each time. It is thought that they follow a mucus trail left as they move. Other species, notably Lottia gigantea seem to "garden" a patch of algae around their home scar. They will aggressively push other organisms out of this patch by ramming with their shell, thereby allowing their patch of algae to grow for their own grazing. Also, where the limpets eat the algae, off bare rocks, it causes places where other organisms can grow and thrive.
[change] Predators and threats
Limpets are prey for variety of organisms including starfish, shore-birds, fish, seals, and humans. Limpets have a variety of defenses, such as fleeing or clamping their shells against the substratum. The defense response can be determined by the type of predator, which can often be detected chemically by the limpet.
Limpets can be long lived, with tagged specimens surviving for more than 10 years. If the limpet lives on bare rock, it grows at a slower rate but can live for up to 20 years.[needs proving]
Limpets found on sheltered shores (limpets that are less frequently in contact with wave action, and thus less frequently in contact with water) have a greater risk of desiccation because of the effects of sunlight, water evaporation and the wind. To avoid drying out they will clamp to the rock they inhabit, minimizing water-loss from the rim around their base. As this occurs chemicals are released that promote the vertical growth of the limpet's shell.
Limpets are being researched to see if the chemicals it releases are cancer preventing chemicals.[needs proving]
[change] References
- University of Hawaii Educational page from Christopher F. Bird, Dep't of Botany. Photos and detailed information distinguishing the different varieties.
- Acmaeidae at the NCBI taxonmy website
