True Limpets
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The Patellogastropoda, common name true
limpet Limpets are a group of aquatic snails with a conical gastropod shell, shell shape (patelliform) and a strong, muscular foot. This general category of conical shell is known as "patelliform" (dish-shaped). Existing within the class Gastropoda, ...
s and historically called the Docoglossa, are members of a major
phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
group of marine
gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...
s, treated by experts either as a
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
or as a taxonomic
order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...
. The clade Patellogastropoda is deemed
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
based on phylogenetic analysis.


Taxonomy

Patellogastropoda was proposed by David R. Lindberg, 1986, as an order, and was later included in the subclass
Eogastropoda Eogastropoda was a previously used taxonomic category of snails or gastropods, a subclass which was erected by Ponder and Lindberg in 1997. It was one of two great divisions (subclasses) of the class Gastropoda, the snails. The other subclass of ...
Ponder & Lindberg, 1996.


2005 taxonomy

Bouchet & Rocroi, 2005 designated Patellogastropoda, true limpets, as a clade, rather than as a taxon, but within included superfamilies and families as listed below. Families that are exclusively fossil are indicated with a dagger †: * Superfamily
Patelloidea Patelloidea is a taxonomic superfamily of sea snails or true limpets, marine gastropod molluscs in the subclass Patellogastropoda.WoRMS (2020). Patelloidea Rafinesque, 1815. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=1 ...
** Family
Patellidae Patellidae is a taxonomic family of true limpets, marine gastropod molluscs in the superfamily Patelloidea. (The superfamily Patelloidea should not be confused with the similar-sounding genus of true limpets '' Patelloida'' which is in the ...
* Superfamily Nacelloidea ** Family
Nacellidae Nacellidae is a taxonomic family of sea snails or true limpets, marine gastropod molluscs in the subclass Patellogastropoda. Taxonomy Nacellidae was the only family in the superfamily Nacelloidea as described by Bouchet & Rocroi (2005),. H ...
* Superfamily
Lottioidea Lottioidea is a superfamily of sea snails or limpets, marine gastropod mollusks in the clade Patellogastropoda, the true limpets.MolluscaBase (2018). Lottioidea Gray, 1840. Accessed through: World Register of Marine Species at: http://www.mari ...
** Family
Lottiidae Lottiidae is a family (biology), family of sea snails, specifically true limpets, marine (ocean), marine gastropod mollusks in the superfamily Lottioidea and the clade Patellogastropoda (according to the Taxonomy of the Gastropoda (Bouchet & Rocr ...
** Family
Acmaeidae Acmaeidae is a family of sea snails, specifically true limpets, marine gastropod mollusks in the superfamily Lottioidea and the subclass Patellogastropoda (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). Bouchet, P.; G ...
Forbes, 1850 *** subfamily Acmaeinae Forbes, 1850 *** subfamily Pectinodontinae Pilsbry, 1891 *** subfamily Rhodopetalinae
Lindberg Lindberg is a municipality in the district of Regen in Bavaria in Germany in the immediate neighbourhood of the larger town Zwiesel. Location Lindberg lies in the Danube Forest (''Donau-Wald'') region in the middle of the Bavarian Forest on ...
, 1981 ** Family
Lepetidae Lepetidae is a family (biology), family of sea snails or small, deep-water true limpets, marine (ocean), marine gastropod molluscs in the clade Patellogastropoda the true limpets. Taxonomy This family consists of the two following subfamilies ...
* Superfamily
Neolepetopsoidea Neolepetopsoidea is the name of a taxonomic superfamily which is now considered to be a synonym of Lottioidea. Previously Neolepetopsoidea was considered to be a family of sea snails, marine gastropod mollusks within the clade Patellogastropoda ...
** Family
Neolepetopsidae Neolepetopsidae is a family (biology), family of small deep sea sea snails or true limpets, marine (ocean), marine gastropod mollusks in the subclass Patellogastropoda (according to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), taxono ...
** † Family Daminilidae ** † Family
Lepetopsidae Lepetopsidae is an extinct family of gastropods in the clade Patellogastropoda. This family has no subfamilies. Members of extant family Neolepetopsidae probably developed from Lepetopsidae. McLean J. H. (7 November 1990). "Neolepetopsidae, a n ...
With the exception of calling Patellogastropoda a clade rather than an order, as was previously the case in Ponder and Lindberg, 1997 the taxon has not changed much, differing more in the arrangement of its content rather than in the overall composition. Bouchet and Rocroi omitted Ponder and Lindberg's suborders, and added in the superfamily Neolepetopsoidea.


2007 taxonomy

Nakano & Ozawa (2007) made many changes in the taxonomy of the Patellogastropoda, based on
molecular phylogeny Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
research: Acmaeidae is a synonym of
Lottiidae Lottiidae is a family (biology), family of sea snails, specifically true limpets, marine (ocean), marine gastropod mollusks in the superfamily Lottioidea and the clade Patellogastropoda (according to the Taxonomy of the Gastropoda (Bouchet & Rocr ...
; Pectinodontinae is elevated to
Pectinodontidae Pectinodontidae is a family (biology), family of sea snails or true limpets, marine (ocean), marine gastropod mollusks in the superfamily Lottioidea, the true limpets.Lottioidea Taxonomy This family was previously ranked as subfamily Pectinodo ...
; new family
Eoacmaeidae ''Eoacmaea'' is a genus of sea snails or true limpets, marine (ocean), marine gastropod mollusks in the subclass Patellogastropoda, the true limpets.MolluscaBase eds. (2020). MolluscaBase. Eoacmaea T. Nakano & Ozawa, 2007. Accessed through: World ...
with the new type genus ''
Eoacmaea ''Eoacmaea'' is a genus of sea snails or true limpets, marine gastropod mollusks in the subclass Patellogastropoda, the true limpets.MolluscaBase eds. (2020). MolluscaBase. Eoacmaea T. Nakano & Ozawa, 2007. Accessed through: World Register of Ma ...
'' is established. A
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
based on sequences of mitochondrial 12S ribosomal RNA,
16S ribosomal RNA 16S ribosomal RNA (or 16 S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome ( SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as 16S ...
and cytochrome-c oxidase I (COI) genes showing phylogenic relations of Patellogastropoda by Nakano & Ozawa (2007) and superfamilies based on
World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive catalogue and list of names of marine organisms. Content The content of the registry is edited and maintained by scien ...
:Gofas, S. (2010). Patellogastropoda. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=382158 on 2010-04-01 Note that the family
Neolepetopsidae Neolepetopsidae is a family (biology), family of small deep sea sea snails or true limpets, marine (ocean), marine gastropod mollusks in the subclass Patellogastropoda (according to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), taxono ...
is not in the cladogram above, because its members were not genetically analyzed by Nakano & Ozawa (2007). However, two Neolepetosidae species ''
Eulepetopsis vitrea ''Eulepetopsis vitrea'' is a species of sea snail, a true limpet, a marine gastropod mollusk in the family Neolepetopsidae, one of the families of true limpets. ''Eulepetopsis vitrea'' is the only species in the genus ''Eulepetopsis''. Descr ...
'' and ''
Paralepetopsis floridensis ''Paralepetopsis floridensis'' is a species of sea snail, a true limpet, a marine gastropod mollusc in the family Neolepetopsidae, one of the families of true limpets. ''Paralepetopsis floridensis'' is the type species in the genus ''Paralepeto ...
'' were previously analyzed by Harasewych & McArthur (2000), who confirmed their placement within Acmaeoidea/Lottioidea based on analysis of partial
18S rDNA 18S ribosomal RNA (abbreviated 18S rRNA) is a part of the ribosomal RNA in eukaryotes. It is a component of the Eukaryotic small ribosomal subunit (40S) and the cytosolic homologue of both the 12S rRNA in mitochondria and the 16S rRNA in plastid ...
. The Daminilidae and
Lepetopsidae Lepetopsidae is an extinct family of gastropods in the clade Patellogastropoda. This family has no subfamilies. Members of extant family Neolepetopsidae probably developed from Lepetopsidae. McLean J. H. (7 November 1990). "Neolepetopsidae, a n ...
are also not included in the cladogram, because they are exclusively fossil families. All of these three families belong to superfamily
Lottioidea Lottioidea is a superfamily of sea snails or limpets, marine gastropod mollusks in the clade Patellogastropoda, the true limpets.MolluscaBase (2018). Lottioidea Gray, 1840. Accessed through: World Register of Marine Species at: http://www.mari ...
. Actual taxonomy based on data by Nakano & Ozawa (2007) with placement of the three remaining families (Neolepetopsidae, Daminilidae, Lepetopsidae) into Lottioidea is like this: * superfamily Eoacmaeoidea ** family
Eoacmaeidae ''Eoacmaea'' is a genus of sea snails or true limpets, marine (ocean), marine gastropod mollusks in the subclass Patellogastropoda, the true limpets.MolluscaBase eds. (2020). MolluscaBase. Eoacmaea T. Nakano & Ozawa, 2007. Accessed through: World ...
* superfamily Patelloidea ** family
Patellidae Patellidae is a taxonomic family of true limpets, marine gastropod molluscs in the superfamily Patelloidea. (The superfamily Patelloidea should not be confused with the similar-sounding genus of true limpets '' Patelloida'' which is in the ...
* superfamily
Lottioidea Lottioidea is a superfamily of sea snails or limpets, marine gastropod mollusks in the clade Patellogastropoda, the true limpets.MolluscaBase (2018). Lottioidea Gray, 1840. Accessed through: World Register of Marine Species at: http://www.mari ...
** family
Nacellidae Nacellidae is a taxonomic family of sea snails or true limpets, marine gastropod molluscs in the subclass Patellogastropoda. Taxonomy Nacellidae was the only family in the superfamily Nacelloidea as described by Bouchet & Rocroi (2005),. H ...
** family
Lepetidae Lepetidae is a family (biology), family of sea snails or small, deep-water true limpets, marine (ocean), marine gastropod molluscs in the clade Patellogastropoda the true limpets. Taxonomy This family consists of the two following subfamilies ...
** family
Pectinodontidae Pectinodontidae is a family (biology), family of sea snails or true limpets, marine (ocean), marine gastropod mollusks in the superfamily Lottioidea, the true limpets.Lottioidea Taxonomy This family was previously ranked as subfamily Pectinodo ...
** family
Lottiidae Lottiidae is a family (biology), family of sea snails, specifically true limpets, marine (ocean), marine gastropod mollusks in the superfamily Lottioidea and the clade Patellogastropoda (according to the Taxonomy of the Gastropoda (Bouchet & Rocr ...
** family
Neolepetopsidae Neolepetopsidae is a family (biology), family of small deep sea sea snails or true limpets, marine (ocean), marine gastropod mollusks in the subclass Patellogastropoda (according to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), taxono ...
** † family Daminilidae ** † family
Lepetopsidae Lepetopsidae is an extinct family of gastropods in the clade Patellogastropoda. This family has no subfamilies. Members of extant family Neolepetopsidae probably developed from Lepetopsidae. McLean J. H. (7 November 1990). "Neolepetopsidae, a n ...
In 2007, two years following Bouchet & Rocroi, 2005, Tomoyuki Nakano and Tomowo Ozawa referred to the order Patellogastropoda.


Description

Patellogastropoda have flattened, cone-shaped shells, and the majority of species are commonly found adhering strongly to rocks or other hard substrates. Many limpet shells are covered in microscopic growths of green marine algae, which can make them even harder to see, as they can closely resemble the rock surface itself. The substance making up the teeth in the
radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters ...
of limpets is among the strongest biological materials known, with a
tensile strength Ultimate tensile strength (also called UTS, tensile strength, TS, ultimate strength or F_\text in notation) is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials, the ultimate ...
about five times stronger than that of
spider silk Spider silk is a protein fibre or silk spun by spiders. Spiders use silk to make webs or other structures that function as adhesive traps to catch prey, to entangle and restrain prey before biting, to transmit tactile information, or as nest ...
. The teeth are composed of
goethite Goethite (, ) is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the α- polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient t ...
, an iron-based mineral, woven in a particular way into grouped 1μ thick bundles. Many limpets create a home "scar" on the rock to which they always return between tides, the scar provides excellent protection from predators as well as helping to prevent dehydration during low tides. They adhere to the
substratum Substrata, plural of substratum, may refer to: *Earth's substrata, the geologic layering of the Earth *''Hypokeimenon'', sometimes translated as ''substratum'', a concept in metaphysics *Substrata (album), a 1997 ambient music album by Biosphere * ...
via the adhesion/ suction of the stiffened foot against the rock surface to which it bonds each time with a layer of pedal mucus. The majority of limpet species have shells that are less than 3 in (8 cm) in maximum length and many are much smaller.


Anatomy

The true limpets have an internal structure much like that of other members of Mollusca. Their diffuse nervous system is oriented around three principal pairs of
ganglia A ganglion (: ganglia) is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system, this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system, there a ...
—the cerebral, pleural (which are hypoathroid), and pedal—located in the animal's snout and surrounding its esophagus in a ring. The pleural and pedal ganglia each send a nerve cord back through the rest of the body, the pleural nerve cords and the pedal or ventral nerve cords (the latter are embedded in the foot musculature in Patellagastropoda). Just outside the pedal ganglia are each of the two
statocysts The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, crustaceans, and gastropods, A similar structure is also found in ''Xenoturbella''. The ...
(though see ''
Bathyacmaea secunda ''Bathyacmaea nipponica'' is a species of very small (adults are typically about 6 mm in length), deep-sea true limpet, limpet, a marine (ocean), marine gastropod mollusk in the family Pectinodontidae. MolluscaBase eds. (2023). MolluscaBase. ...
'' as an exception to this rule). Like the keyhole limpets, the true limpets have retained both
kidneys In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and right in the retro ...
though in Patellagastropoda the kidneys both lie on the animal's right side and the further right of the two— the "right" kidney— is much larger than the other. The right kidney also has a sponge-like texture whereas the left kidney is essentially a small sac into which hang folds from the sac's walls. They do not have ctenidia, instead obtaining oxygen through a ring of gill lamellae that encircle the mantle just inside the shell edge and from the surface of the roof of the nuchal cavity which is exposed to air when the animal is no longer under water and which is covered in a network of blood vessels all of which eventually carry oxygenated blood and connect to the auricle through a series of veinlets on the animal's left side. Vestigial ctenidia have been adapted into osphradial patches (one on each side of the mantle cavity) with which the animal can "smell". Their low dome-shaped shell is able to withstand the forces of turbulent intertidal water. Inside, the head bears two tentacles, each with a tiny black "eye spot" at its base (limpets can sense light but cannot see images with these eyes). The heart lies within a
pericardium The pericardium (: pericardia), also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong inelastic connective tissue (fibrous pericardium), ...
and is composed of a single (morphologically left) auricle, a single ventricle, and bulbous
aorta The aorta ( ; : aortas or aortae) is the main and largest artery in the human body, originating from the Ventricle (heart), left ventricle of the heart, branching upwards immediately after, and extending down to the abdomen, where it splits at ...
which sends blood to both the anterior and posterior aortae. It lies near the surface of shell on the left, and opposite it on the right are three tubules or "papillae" in a row: that of the left kidney, the anus, and that of the right kidney: all three exit near the same place on the right posterior side inside the mantle cavity. Between these papillae and the heart lies the neural "visceral twist", a nervous condition called streptoneury or chiastoneury, which characterizes many molluscs and all gastropods whose ancient ancestor had an anus located posterior to its head but which now have it positioned much closer because of a change in the arrangement of the shell. In the evolutionary course of the relocation of the anus, the various ganglia posterior to the pleural and pedal ganglia had to conduct a twist— this means, for example, that the
osphradium The osphradium is a pigmented chemosensory epithelium patch in the mantle cavity present in six of the eight extant classes of molluscs (it is absent in the Scaphopoda and Monoplacophora; most Cephalopoda also lack it, but the nautilus has what a ...
on the animal's left side is innervated through the right side of its body and vice versa. The condition is called streptoneury, but the phenomenon is known as torsion. In the Patellogastropoda, the twist is located directly behind (i.e., posterior to) the pleural ganglia; in other closely related groups (e.g., Zeugobranchia, Neritopsina, and
Ampullariidae Ampullariidae, whose members are commonly known as apple snails, is a family of large freshwater snails that includes the mystery snail species. They are aquatic gastropod mollusks with a gill and an operculum. These snails simultaneously h ...
) the twist stretches backwards well into the visceral mass (digestive glands, intestines, gonad, etc.). The digestive gland and interweaving intestine occupy most of the visceral mass behind the head. At the posterior ventral end is the large gonad organ which, when ripe, bursts and empties its gametes into the right kidney from which they are then expelled directly into the surrounding water. One theory of the function of the osphradia is to sense the release of such gametes by other nearby patellogastropods, triggering a corresponding release in any proximate opposite-sex animals of the same species (see diagram for additional anatomic information).


Distribution

Representatives of the true limpets are common inhabitants of rocky shores of all oceans, from tropic to polar regions.


Habitat

Some true limpets live throughout the
intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...
, from the high zone (upper
littoral zone The littoral zone, also called litoral or nearshore, is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely flood ...
) to the shallow subtidal, but other species live in
deep sea The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combination of low tempe ...
and their habitat include
hydrothermal vent Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hot ...
s, whalebone (
baleen Baleen is a filter feeder, filter-feeding system inside the mouths of baleen whales. To use baleen, the whale first opens its mouth underwater to take in water. The whale then pushes the water out, and animals such as krill are filtered by th ...
), whale-fall and sulphide seeps. McLean J. H. (7 November 1990). "Neolepetopsidae, a new docoglossate limpet family from hydrothermal vents and its relevance to patellogastropod evolution". ''
Journal of Zoology The ''Journal of Zoology'' is a scientific journal concerning zoology, the study of animals. It was founded in 1830 by the Zoological Society of London and is published by Wiley-Blackwell. It carries original research papers, which are targeted ...
'', London 222(3): 485–528, plates 1-12. . Neolepetopsidae is on the page 490.
A few species are found in brackish habitats, and one possibly extinct species (Potamacmaea fluviatilis) is known from estuaries and tributaries which drain into the
Bay of Bengal The Bay of Bengal is the northeastern part of the Indian Ocean. Geographically it is positioned between the Indian subcontinent and the Mainland Southeast Asia, Indochinese peninsula, located below the Bengal region. Many South Asian and Southe ...
. They attach themselves to the substrate using pedal
mucus Mucus (, ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both Serous fluid, serous and muc ...
and a
foot The foot (: feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is an organ at the terminal part of the leg made up o ...
. They locomote using wave-like muscular contractions of the foot when conditions are suitable for them to graze. They can also "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 Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. The ...
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 A metaphor is a figure of speech that, for rhetorical effect, directly refers to one thing by mentioning another. It may provide, or obscure, clarity or identify hidden similarities between two different ideas. Metaphors are usually meant to cr ...
for obstinacy or stubbornness.


Life habits


Feeding

Most limpets feed by grazing on
algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
which grows on the rock (or other surfaces) where they live. They scrape up films of algae with a
radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters ...
, 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
seagrass Seagrasses are the only flowering plants which grow in marine (ocean), marine environments. There are about 60 species of fully marine seagrasses which belong to four Family (biology), families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and ...
es and graze on the microscopic algae which grow there. Other species live on, and graze directly on, the stipes (stalks) of brown algae (
kelp Kelps are large brown algae or seaweeds that make up the order (biology), order Laminariales. There are about 30 different genus, genera. Despite its appearance and use of photosynthesis in chloroplasts, kelp is technically not a plant but a str ...
).


Homing behaviour

Some species of limpets return to the same spot on the rock known as a "home scar" just before the tide recedes. 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 them from both predation and desiccation. It is still unclear how limpets find their way back to the same spot each time, but it is thought that they follow pheromones in the mucus left as they move. Other species, notably ''Lottia gigantea'' seem to "garden" a patch of algae around their home scar. They are one of the few invertebrates to exhibit
territoriality In ethology, territory is the sociographical area that an animal consistently defends against conspecific competition (or, occasionally, against animals of other species) using agonistic behaviors or (less commonly) real physical aggression. ...
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.


Predators and other risks

Limpets are preyed upon by a variety of organisms including
starfish Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to ...
, 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 Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. The ...
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.


Reproduction

Spawning occurs once a year, usually during winter, and is triggered by rough seas which disperse the eggs and sperm. Larvae float around for a couple of weeks before settling onto a hard substrate.


Human use

Larger limpet species are, or were historically, cooked and eaten in many different parts of the world. For example, in
Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...
, limpets (''
Cellana ''Cellana'' is a genus of sea snails or limpets, marine gastropod molluscs in the family Nacellidae, the true limpets.WoRMS (2010). Cellana H. Adams, 1869. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accesse ...
'' species) are commonly known as opihi'', and are considered a delicacy; the meat sells for $25 - $42 a pound (454g). In
Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
, limpets are known as ''lapas'' and are also considered to be a delicacy. In
Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
they are also called "lapas" but are so abundant that it's just considered a regular dish. Within Gaelic
Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...
and
Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...
, a limpet is known as a ''báirnach'', and
Martin Martin Martin Martin (Scottish Gaelic: Màrtainn MacGilleMhàrtainn) (–9 October 1718) was a Scotland, Scottish writer best known for his work ''A Description of the Western Islands of Scotland (Martin), A Description of the Western Islands of Scotlan ...
recorded (on Jura) limpets being boiled to use in a substitute for
breast milk Breast milk (sometimes spelled as breastmilk) or mother's milk is milk produced by the mammary glands in the breasts of women. Breast milk is the primary source of nutrition for newborn infants, comprising fats, proteins, carbohydrates, and a var ...
. In
Ulleungdo Ulleungdo (), also spelled Ulreungdo, is a South Korean island east of the Korean Peninsula in the Sea of Japan. It was formerly known as Dagelet Island or Argonaut Island in Europe. Volcanic in origin, the rocky steep-sided island is the top o ...
, a Korean island, limpets are called ''ttagaebi'' () and are used to make ''ttagaebi-
bap BAP or bap may refer to: Food * Bap (bread), a bread roll * Bap (rice dish), of Korea People * Bap Kennedy (1962–2016), Northern Irish singer-songwriter * Bronze Age Pervert, Romanian-American right-wing writer and podcaster Music * BAP (Germa ...
'' (limpet rice) and ''ttagaebi-
kal-guksu ''Kal-guksu'' * () is a Korean noodle dish consisting of handmade, knife-cut wheat flour noodles served in a large bowl with broth and other ingredients. It is traditionally considered a seasonal food, consumed most often in summer. Its name ...
'' (limpet noodle soup)


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{{Taxonbar, from=Q3463993 Gastropod taxonomy