Limpet

Limpets
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.
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Order:	Patellogastropoda Lindberg, 1986
Suborders
See text.

Limpets are marine gastropod mollusks in the order Patellogastropoda with flattened, cone-shaped shells. They live throughout the intertidal zone, from the high zone (upper littoral zone) 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.

Most limpets are less than 3 in (8 cm) long, but a West Mexican Limpet grows to be 8 in (20 cm).

In Hawaii, limpets are commonly known as 'opihi, and are considered a delicacy.

Homing behaviour

Some species of limpets return to the same spot on the rock known as a "home scar" just before the tide recedes. 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, but 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 are one of the few invertebrates to exhibit territoriality and 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 creates places where other organisms can grow and thrive.

Predators and threats

Limpets are preyed upon by a variety of organisms including starfish, shore-birds, fish, seals, and humans. Limpets exhibit 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.

Limpets found on exposed shores, that have fewer rock pools than sheltered shores and are thus in less frequent contact with water, have a greater risk of desiccation due to the effects of increased sunlight, water evaporation and the increased wind speed. 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 they release have cancer-preventing qualities.

Taxonomy

• Suborder Lepetopsina
  • Superfamily Lepetopsoidea
    • Family † Damilinidae
    • Family Lepetopsidae
    • Family Neolepetopsidae
• Suborder Nacellina
  • Superfamily Acmaeoidea
    • Family Acmaeidae
      • Genus Acmaea
      • Genus Notoacmea
      • Genus Pectinodonta
      • Genus Problacmaea
    • Family Lepetidae
      • Genus Bathylepeta Moskalay, 1977
      • Genus Cryptobranchia Middendorff, 1851
      • Genus Iothia Forbes, 1849
      • Genus Lepeta J. E. Gray, 1842
      • Genus Limalepta Moskalev, 1978
      • Genus Propilidium Forbes and Hanley, 1849
      • Genus Sagamilepeta Okutani, 1987
    • Family Lottiidae
      • Genus Lottia Gray, 1833
        • • Lottia gigantea Sowerby, 1834
          • †Lottia alveus, Eelgrass limpet
  • Superfamily Nacelloidea
    • Family Nacellidae
      • Genus Macklintockia
      • Genus Naccula
      • Genus Nacella
        • • Nacella kerguelenensis (E. A. Smith, 1877
          • Nacella macquariensis Finlay, 1927
          • Nacella terroris (Filhol, 1880)
• Suborder Patellina
  • Superfamily Patelloidea
    • Family Patellidae
      • Genus Cellana
        • • Cellana ampla
          • Cellana ardosioea Hombron & Jacquinot, 1841
          • Cellana capensis Gmelin, 1791
          • Cellana craticulata Suter, 1905
          • Cellana conciliata Rainbow limpet
          • Cellana denticulata Martyn, 1784
          • Cellana eucosmia Pilsbry, 1891
          • Cellana exarata Hawaiian blackfoot ‘opihi
          • Cellana flava Hutton, 1873
          • Cellana grata Gould, 1859
          • Cellana melanostoma Pilsbry, 1891
          • Cellana nigrolineata Reeve, 1854
          • Cellana ornata Dillwyn, 1817
          • Cellana radians (Gmelin, 1791)
          • Cellana rota
          • Cellana sandwicensis
          • Cellana stellifera Gmelin, 1791
          • Cellana strigilis Powell, 1955
            • Cellana strigilis strigilis Hombron & Jacquinot, 1841
            • Cellana strigilis bollonsi Powell, 1955
            • Cellana strigilis chathanensis (Pilsbry, 1891
            • Cellana strigilis flemingi Powell, 1955
            • Cellana strigilis oliveri Powell, 1955
            • Cellana strigilis redimiculum (Reeve, 1854)
          • Cellana talcosa Gould, 1846
          • Cellana testudinaria Linnaeus, 1758
          • Cellana toreuma Reeve, 1855
          • Cellana tramoserica Holten, 1802
      • Genus Helcion
        • Subgenus Ansates
          • Helcion pellucidus
          • Helcion tella
        • Subgenus Helcion
          • Helcion pectunculus
        • Subgenus Patinastra
          • Helcion dunkeri
          • Helcion pruinosus
      • Genus Helioniscus
        • • Helcion tella
      • Genus Patella
        • Subgenus Olana
          • Patella cochlear
        • Subgenus Patella
          • Patella baudonii
          • Patella caerulea
          • Patella candei
            • Patella (candei) gomesii
          • Patella compressa
          • Patella depressa
          • Patella ferruginea
          • Patella lowei
          • Patella miniata
          • Patella moreleti
          • Patella piperata
          • Patella rustica
          • Patella ulyssiponensis
          • Patella variabilis
          • Patella vulgata
          • Patellida
          • Patella granularis
          • Patellona
          • Patella adansonii
          • Patella canescens
          • Patella granatina
          • Patella lugubris
          • Patella oculus
          • Patella plumbea
          • Scutellastra
          • Patella argenvillei
          • Patella barbara
          • Patella chapmani
          • Patella exusta
          • Patella flexuosa
          • Patella kermadecensis
          • Patella laticostata
          • Patella longicosta
          • Patella peronii
          • Patella tabularis
          • Patella tucopiana
      • Genus Rhodopetala
        • • Rhodopetala rosea

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