Limpet
Limpets are a group of aquatic snails with a conical shell shape (patelliform) and a strong, muscular foot.
The basic anatomy of a limpet consists of the usual molluscan organs and systems: The two kidneys are very different in size and location.
The right kidney, however, has taken over the majority of blood filtration and often extends over and around the entire mantle of the animal in a thin, almost-invisible layer.
However, when they need to resist strong wave action or other disturbances, limpets cling extremely firmly to the surfaces on which they live, using their muscular foot to apply suction combined with the effect of adhesive mucus.
In these small freshwater limpets, that "lung" underwent secondary adaptation to allow the absorption of dissolved oxygen from water.
[5] These teeth form via matrix-mediated biomineralization, a cyclic process involving the delivery of iron minerals to reinforce a polymeric chitin matrix.
[4][6] Upon being fully mineralized, the teeth reposition themselves within the radula, allowing limpets to scrape off algae from rock surfaces.
[10] Specifically, this mechanism is associated with the dissolution of iron stored in epithelial cells of the radula to create ferrihydrite ions.
[12] The lack of space leads to the absence of pre-formed compartments within the matrix that control goethite crystal size and shape.
[14] This suggests that the goethite nanofibers serve as effective reinforcement for the collagen matrix and significantly contribute to the load-bearing capabilities of limpet teeth.
[14] Applications of limpet teeth involve structural designs requiring high strength and hardness, such as biomaterials used in next-generation dental restorations.
[14] Measurements taken from the tip of the anterior edge of the tooth show that the teeth can exhibit an elastic modulus of around 140 GPa.
Goethite as a mineral is a relatively soft iron based material,[15] which increases the chance of physical damage to the structure.
[16] The initial event that takes place when the limpet creates a new row of teeth is the creation of the main macromolecular α-chitin component.
[9] The first mineral to be deposited is goethite (α-FeOOH), a soft iron oxide which forms crystals parallel to the chitin fibers.
Iron is consistently most abundant however other metals such as sodium, potassium, calcium, and copper were all shown to be present to varying degrees.
Gastropods that have limpet-like or patelliform shells are found in several different clades: Some species of limpet live in fresh water,[19][20] but these are the exception.
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).
[21] Limpets wander over the surface of the rocks during high tide and tend to return to their favourite spot by following a trail of mucus left whilst grazing.
Over a period of time the edges of the limpet's shell wear a shallow hollow in the rock called a homescar.
[24] Simon Grindle wrote the 1964 illustrated children's book of nonsense poetry The Loving Limpet and Other Peculiarities, said to be "in the great tradition of Edward Lear and Lewis Carroll".
[25] In his book South, Sir Ernest Shackleton relates the stories of his twenty-two men left behind on Elephant Island harvesting limpets from the icy waters on the shore of the Southern Ocean.
Near the end of their four-month stay on the island, as their stocks of seal and penguin meat dwindled, they derived a major portion of their sustenance from limpets.
