Information about Limpet

Limpets
Four Patella vulgata limpets in their natural habitat (here northwestern Galicia). One animal was separated from the rock and turned over to show the underside and muscular foot. Four Patella vulgata limpets in their natural habitat (here northwestern Galicia). One animal was separated from the rock and turned over to show the underside and muscular foot.
Scientific classification
Kingdom: Animalia Phylum: Mollusca Class: Gastropoda Order: Patellogastropoda Lindberg, 1986
Suborders
See text.

Limpet is a very inexact term: it is a word that is commonly applied to a wide variety of different snails (from either marine or freshwater habitats) which have a simple shell which is more or less conical in shape, and which is either not coiled, or appears not to be coiled, in the adult snail.

Most marine limpets have gills, whereas freshwater limpets and a few marine limpets breathe air; all these various kinds are only very distantly related. In other words, the name limpet can be used to describe various unrelated groups of gastropods which have independently evolved a shell of the same basic shape.

This article is specifically about "True limpets", which are marine gastropod mollusks in the order Patellogastropoda, for example, species such as Patella vulgata.

Limpets have flattened, cone-shaped shells, and the majority of species are commonly found adhering strongly to rocks or other hard substrates, looking like little bumps on the surface. In life, many limpet shells are often covered in microscopic growths of green marine algae, which can make them even harder to see, as they can closely ressemble the rock surface itself.

Various different species of true limpets live throughout the intertidal zone, from the high zone (upper littoral zone) to the shallow subtidal, and representatives from the order live on the rocky coasts of all oceans world-wide.

They attach themselves to the substrate using pedal mucus and a muscular "foot". They can locomote using wave-like muscular contractions of the foot when conditions are suitable for them to graze, or they can "clamp down" against the rock surface with very considerable force when necessary, and this ability enables them to remain safely attached, despite the dangerous wave action on exposed rocky shores. The ability to clamp down also seals the shell edge against the rock surface, protecting them from desiccation during low tide, despite their being in full sunlight.

When true limpets are fully clamped down, it is impossible to remove them from the rock using brute force alone, and the limpet will allow itself to be destroyed rather than stop clinging to its rock. This survival strategy has led to the limpet being used as a metaphor for obstinacy or stubbornness.

Most limpets feed by grazing on algae which grows on the rock (or other surfaces) where they live. They scrape up films of algae 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.

In some parts of the world, certain smaller species of true limpet are specialized to live on seagrasses and graze on the microscopic algae which grow there. Other species live on, and graze directly on, the stipes (stalks) of brown algae (kelp).

The majority of limpet species have shells that are less than 3 in (8 cm) in maximum length. However, until quite recently a west Mexican limpet species was known to grow as large as 8 in (20 cm). This species is now in serious danger of extinction, as it is slow to reach maturity, and has suffered from overcollecting, both as a food item, and by shell collectors and dealers.

In Hawaii, limpets are commonly known as 'opihi', and are considered a delicacy. In fact, larger limpet species are, or were historically, cooked and eaten in many different parts of the world.

Homing behaviour

Some species of limpets return to the same spot on the rock known as a "home scar" just before the tide recedes ^[1] . 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, this trail contains pheromones. Other species, notably Lottia gigantea seem to "garden" a patch of algae around their home scar ^[2]. 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, which 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.

Reproduction

Spawning occurs once a year, usually during winter, and is triggered by rough seas which disperse the eggs and sperm. Larvae are pelagic for a couple of weeks before settling onto a hard substrate.^[3]

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

External links

• 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