Limpet

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For the world’s first commercial wave power device, see Islay LIMPET. For the underwater explosive device, see Limpet mine.
The true limpet species Patella vulgata on a rock surface in Wales

Limpet is an unscientific common name which is applied to several different groups of aquatic gastropod mollusks (saltwater and freshwater snails), specifically those where the shell of the adult animal is not, or does not appear to be, spirally coiled. Thus the name is usually applied to any gastropod where the shell is broadly conical in shape, rather like the conical Asian hat. This general category of shell is technically known as "patelliform", meaning limpet-shaped.

The large and ancient marine clade Patellogastropoda is a clade consisting entirely of limpets, and the common name "limpet" is often applied to the family Patellidae, and other families of limpets within that clade. However, numerous other, not very closely related groups, including for example the keyhole limpets, Fissurellidae, in the clade Vetigastropoda, are also called limpets because of the general shape of their shells.

Behaviour and ecology[edit]

True limpets in the family Patellidae live on hard surfaces in the intertidal zone. Although true limpets are not permanently attached to a hard surface like a barnacle, 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. A true limpet will often allow itself to be destroyed rather than give up its hold on a rock.

All of the true limpets are marine and have gills. However, because the feature of a simple conical shell has arisen independently many times in gastropod evolution, limpets from many different evolutionary lineages are found in different environments. There are some saltwater limpets that breathe air (Trimusculidae) and there are freshwater limpets which originally had a pallial lung, being descended from air-breathing land snails (e.g. the freshwater genus Ancylus). In the small freshwater limpets the lung has been secondarily modified to be able to absorb oxygen from water.

Naming[edit]

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.

Phylogeny[edit]

Gastropods that have limpet-like or patelliform shells are found in the following clades:

Other limpets[edit]

The fossil fissurellid or "keyhole limpet", Diodora italica, from the Pliocene of Cyprus

Marine

Freshwater

  • 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[edit]

The limpet has become a metaphor for objects or people who cling stubbornly to something, thus limpet mine.[citation needed]

The humorous author Edward Lear wrote "Cheer up, as the limpet said to the weeping willow" in one of his letters.[1] 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.[2]

References[edit]

  1. ^ Lear, Edward (1907). Letters of Edward Lear. T. Fisher Unwin. p. 165. 
  2. ^ Grindle, Simon; Todd, Alan (illus) (1964). The Loving Limpet and Other Peculiarities. Newcastle: Oriel Press. 

External links[edit]