A limpet is an aquatic snail
with a shell broadly conical in shape. 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 members of Gastropoda, the group is highly
polyphyletic, meaning that the various lines that we call limpets have
descended independently from different ancestral gastropods. This general
category of conical shell is technically known as "patelliform",
meaning dish-shaped.
Some species of limpet live in fresh water, but by far the majority are saltwater inhabitants.
All members of the large and ancient marine clade Patellogastropoda are limpets, and within that clade the family Patellidae in particular often are called the "true limpets". However, other groups, not in the same family, also are called limpets of one type or another because of the general shapes of their shells. Examples include the Fissurellidae; they are the keyhole limpet family, contained in the clade Vetigastropoda, though many of the members of the Vetigastropoda do not have the morphology of limpets at all.
A study published in the Royal Society journal Interface in 2015 concluded that "the tensile strength of limpet teeth can reach values significantly higher than spider silk, considered to be currently the strongest biological material, and only comparable to the strongest commercial carbon fibres". The material was able to withstand 4.9 GPa. This considerable tensile strength of limpet teeth is attributed to a high mineral volume fraction of reinforcing goethite nanofibres.
True limpets in the family Patellidae live on hard surfaces in the intertidal zone. Unlike barnacles or mussels, true limpets are capable of locomotion instead of being permanently attached to a single spot. However, when they need to resist strong wave action or other disturbances, limpets cling extremely strongly to the hard surface on which they live, using their muscular foot to apply suction combined with the effect of adhesive mucus. It often is very difficult to remove a true limpet from a rock without injuring or killing it.
All "true" limpets are marine and have gills. However, because the adaptive feature of a simple conical shell has repeatedly arisen independently in gastropod evolution, limpets from many different evolutionary lineages occur in widely different environments. Some saltwater limpets, such as Trimusculidae breathe air, and some freshwater limpets are descendents of air-breathing land snails (e.g. the genus Ancylus) whose ancestors had a pallial cavity serving as a lung. In these small freshwater limpets that "lung" underwent secondary adaptation to absorption of dissolved oxygen from water.
The teeth of limpets consist of composite nanostructures with fractions of reinforcing goethite nanofibres within a softer chitin matrix to provide mechanical integrity. A study into the tensile strength of teeth from Patella vulgata found ranges from 3.0 to 6.5 gigapascals (GPa), making them the strongest known biological material, outperforming spider silk. The mineral protein of the limpet teeth can withstand a tensile stress of 4.9 GPa, compared to 4 GPa of spider silk and 0.5 GPa of human teeth. This strength is attributed to a high mineral volume fraction of goethite nanofibres.
As the limpet teeth effectively resist abrasion, corresponding structural design features may be used for novel biomaterials, such as next-generation dental restorations.
Some species of limpet live in fresh water, but by far the majority are saltwater inhabitants.
All members of the large and ancient marine clade Patellogastropoda are limpets, and within that clade the family Patellidae in particular often are called the "true limpets". However, other groups, not in the same family, also are called limpets of one type or another because of the general shapes of their shells. Examples include the Fissurellidae; they are the keyhole limpet family, contained in the clade Vetigastropoda, though many of the members of the Vetigastropoda do not have the morphology of limpets at all.
A study published in the Royal Society journal Interface in 2015 concluded that "the tensile strength of limpet teeth can reach values significantly higher than spider silk, considered to be currently the strongest biological material, and only comparable to the strongest commercial carbon fibres". The material was able to withstand 4.9 GPa. This considerable tensile strength of limpet teeth is attributed to a high mineral volume fraction of reinforcing goethite nanofibres.
Behavior and Ecology
True limpets in the family Patellidae live on hard surfaces in the intertidal zone. Unlike barnacles or mussels, true limpets are capable of locomotion instead of being permanently attached to a single spot. However, when they need to resist strong wave action or other disturbances, limpets cling extremely strongly to the hard surface on which they live, using their muscular foot to apply suction combined with the effect of adhesive mucus. It often is very difficult to remove a true limpet from a rock without injuring or killing it.
All "true" limpets are marine and have gills. However, because the adaptive feature of a simple conical shell has repeatedly arisen independently in gastropod evolution, limpets from many different evolutionary lineages occur in widely different environments. Some saltwater limpets, such as Trimusculidae breathe air, and some freshwater limpets are descendents of air-breathing land snails (e.g. the genus Ancylus) whose ancestors had a pallial cavity serving as a lung. In these small freshwater limpets that "lung" underwent secondary adaptation to absorption of dissolved oxygen from water.
Teeth
The teeth of limpets consist of composite nanostructures with fractions of reinforcing goethite nanofibres within a softer chitin matrix to provide mechanical integrity. A study into the tensile strength of teeth from Patella vulgata found ranges from 3.0 to 6.5 gigapascals (GPa), making them the strongest known biological material, outperforming spider silk. The mineral protein of the limpet teeth can withstand a tensile stress of 4.9 GPa, compared to 4 GPa of spider silk and 0.5 GPa of human teeth. This strength is attributed to a high mineral volume fraction of goethite nanofibres.
As the limpet teeth effectively resist abrasion, corresponding structural design features may be used for novel biomaterials, such as next-generation dental restorations.
The teeth are found on the radula—a rasping tongue which the limpet uses to scrape
from rocks the algae on which it grazes.
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