- For the world’s first commercial wave power device, see Islay LIMPET. For the underwater explosive device, see Limpet mine.
Limpet is a common name applied to aquatic snails with shells broadly conical in shape, rather like the familiar conical Asian hat. The term "limpet" is purely informal, a term of convenience; it refers to any gastropod whose shell has no obvious coiling such as one sees in familiar garden snails or in winkles. Although all limpets are Gastropoda, the group is highly polyphyletic, meaning that the various lines that we call limpets have descended independently from different ancestors. This general category of conical shell is technically known as "patelliform", meaning limpet-shaped. Some species live in fresh water, but most are marine.
The large and ancient marine clade Patellogastropoda includes only limpets, and within that clade the family Patellidae in particular often are called "true limpets", usually together with other families of limpets within that clade. However, other groups, not very closely related, also are called limpets because of the general shape of their shells. Examples include the keyhole limpet family, the Fissurellidae, in the clade Vetigastropoda,
Behaviour and ecology
True limpets in the family Patellidae live on hard surfaces in the intertidal zone. Unlike barnacles or [mussel]]s true limpets are capable of locomotion instead of being permanently attached to a hard surface. However, when they are disturbed or need to resist strong wave action, limpets cling extremely tightly and strongly to the hard surface on which they live, using their muscular foot. It often is very difficult to remove a true limpet a rock without injuring or killing it.
All true limpets are marine and have gills. However, because the feature of a simple conical shell has repeatedly arisen independently in gastropod evolution, limpets from many different evolutionary lineages are found in widely different environments. Some saltwater limpets, such as Trimusculidae breathe air, and some freshwater limpets (e.g. the genus Ancylus) which originally had a pallial lung, are descendents of air-breathing land snails. In the small freshwater limpets the lung has been modified secondarily to be able to absorb oxygen from water.
The common name "limpet" is also used for a number of different (not very closely related) groups of sea snails and freshwater snails (aquatic gastropod mollusks). Thus the common name "limpet" has very little taxonomic significance in and of itself; the name is applied not only to true limpets (the Patellogastropoda), but also to all snails that have a simple shell that is broadly conical in shape, and either is not spirally coiled, or appears not to be coiled in the adult snail. In other words the shell of all limpets is "patelliform", which means the shell is shaped more or less like the shell of most true limpets. The term "false limpets" is used for some (but not all) of the other groups that have a conical shell but are not true limpets.
Thus, the name limpet is used to describe various extremely diverse groups of gastropods that have independently evolved a shell of the same basic shape (see convergent evolution). And although the name "limpet" is given on the basis of a limpet-like or "patelliform" shell, the several groups of snails that have a shell of this type are not at all closely related to one another.
Gastropods that have limpet-like or patelliform shells are found in several different clades:
- Clade Patellogastropoda, example Patellidae, the true limpets, all marine, in five living families and two fossil families
- Clade Vetigastropoda, examples Fissurellidae, (the keyhole limpets and slit limpets), and Lepetelloidea, small deepwater limpets
- Clade Neritimorpha, example Phenacolepadidae, small limpets related to nerites
- Clade Heterobranchia, group Opisthobranchia, example Tylodinidae, the umbrella slugs with a limpet-shaped shell
- Clade Heterobranchia, group Pulmonata, examples Siphonariidae, Latiidae, Trimusculidae, all air-breathing limpets
- The hydrothermal vent limpets – Neomphaloidea and Lepetodriloidea
- The hoof snails - Hipponix and other Hipponicidae
- Slipper snails - Crepidula species, which are sometimes known as slipper limpets
- The pulmonate river and lake limpets - Ancylidae
Most marine limpets have gills, whereas all freshwater limpets and a few marine limpets have a mantle cavity adapted to breathe air and function as a lung (and in some cases again adapted to absorb oxygen from water). All these kinds of snail are only very distantly related.
In culture and literature
The humorous author Edward Lear wrote "Cheer up, as the limpet said to the weeping willow" in one of his letters. Simon Grindle wrote an illustrated book said to be "in the great tradition of Edward Lear and Lewis Carroll" called The Loving Limpet and Other Peculiarities.
- University of Hawaii Educational page from Christopher F. Bird, Dep't of Botany. Photos and detailed information distinguishing the different varieties.
- Lottia gigantea: taxonomy, facts, life cycle, bibliography
- Acmaeidae at the NCBI taxonomy website